The remarkable evolution of slowing down: No brakes to rim brakes to drum brakes to discs, we convert the energy of movement into heat to slow down. But there is so much detail to discuss! Technical Editor Kevin Cameron and Editor-in-Chief Mark Hoyer talk about braking in detail.
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SportsTranscript
00:00:00Hey, welcome back to the cycle world podcast
00:00:03I'm Mark Hoyer editor-in-chief, and I'm with Kevin Kamin our technical technical editor who you may have heard of
00:00:10Hope he hope he makes it in this business
00:00:15This week's topic is brakes the evolution of brakes where they came from and
00:00:19Everything we've used to slow things down and how we how we've improved so much early brakes
00:00:25well, you know I go back to my minibike and go-kart days and
00:00:30I had an upgrade from just a piece of steel rubbing on the tire with a lever
00:00:35pedal
00:00:37mine mine someone had riveted
00:00:39Canvas too, so I had canvas to sort of maybe help with my braking performance on the rear wheel of my minibike and
00:00:46Go-kart, not bad
00:00:49Not great, not great, but we've used almost everything leather and bands and rim brakes and
00:00:57One learning from
00:00:59Bicycle rim brakes not not me luckily
00:01:02But then get so hot with the friction on the rim that you can you know pop a tire
00:01:09Yep, so heats heats important. You made a great observation Kevin
00:01:13That we take all of these
00:01:16molecular
00:01:18Excitements from combustion and making them act on Pistons and all that
00:01:23There's the molecules the rattle of the molecules making heat to make us go and what do we got to do?
00:01:29Make heat to make us slow
00:01:32Yep
00:01:33So the pads micro weld to the moving disc the welds are stretched ping
00:01:39They break they weld again each time they stretch that piece of disc and let it snap back
00:01:46That is heat
00:01:48molecular vibration in a solid man
00:01:53Is that where we're starting molecules again?
00:01:56Let's talk about asperities. Yeah asperities. Yes. I got we still have asperities fan mail coming in
00:02:03We had an engineer an engineer right and he said he used the word asperities every day in his power drive
00:02:09Shout out to you Joe
00:02:12Power drive AG equipment things like that very precise hydraulic controls and so forth
00:02:19Asperities was part of his daily life as it is everyone's they just don't know it
00:02:27Okay, well where do you want to launch this I want to make a couple of observations about the early motorcycle
00:02:35two main points one is there were a great many ideas for how to slow a vehicle down and
00:02:43you've just
00:02:44reviewed a number of them rim brakes
00:02:47Scraper brakes rubbing on the tire
00:02:51Belt rim brakes of a block of friction material from Herbert Frueds
00:02:56for Odo company
00:02:58the friction material being made out of
00:03:01organic binder horsehair and
00:03:04Who knows what cornflakes possibly, but he started he started a company for Odo still in business anyway
00:03:13lot of ways
00:03:14to
00:03:15slow a vehicle down and
00:03:18the second point was the main point about motorcycles in those early days was to make it go and
00:03:25the idea of having to make it stop is sort of
00:03:28quite secondary
00:03:30So it wasn't until Oh
00:03:33Pretty much into the 20s that it became
00:03:38just as important to stop as it was to go and
00:03:42The type of brake that had prevailed was one that
00:03:47Exposed a hot surface to the bypass to the passing breezes
00:03:53the
00:03:54extra internal expanding drum brake a pair of
00:03:59shoes
00:04:00Faced with friction material were wedged outward by a cam acting on their ends
00:04:07To rub against the internal surface of a shallow drum and the outside of the drum
00:04:14as time passed was
00:04:16Decorated with cooling fins and all sorts of things holes were drilled
00:04:23But
00:04:24It wasn't really until the 1930s that brakes became
00:04:29serious business because if you arrived at the end of the straightaway on your single-cylinder Norton doing
00:04:35125 miles an hour you needed something besides shoe leather
00:04:40and
00:04:41At one point one of the Norton guys went out. He said I'm gonna fix this and he went out and
00:04:49Went out shopping and he came back with several sets of Model T Ford drums. They were eight inches and
00:04:57That's when breaking really got quite serious
00:05:00well, I wanted to pause for
00:05:03Historical context because you said, you know breaking got serious in the 1920s and if we look at the big picture
00:05:10The period between 1900 and 1920 saw a massive change in how human beings moved around
00:05:17If you went to a big city in 1900
00:05:20Your biggest problem was stepping in in
00:05:23Horsedroppings and tons of it were being shoveled out of the city
00:05:26Put put places flies all those things happened and then by the 20s
00:05:31Trucks and cars and things were really happening and by the 30s it was it was cemented
00:05:36So yeah, we we needed to slow down because there were
00:05:39We had invented traffic
00:05:42Just one I just one observation I want to point out is you're not stuck in traffic you are traffic just yes
00:05:51All right, so yeah the world had changed and we needed to stop and that
00:05:55You talked about the drum break and it's sort of
00:05:58rise to
00:05:59primacy utility Model T breaks on your Norton, but
00:06:03You had pointed out a fellow named Elmer Sperry
00:06:08in
00:06:091898 made a disc break. Why didn't they catch on then? There's so much better. I hate I don't hate drums
00:06:16but I don't like I
00:06:20I was so delighted to open the crate
00:06:25of
00:06:25TV2
00:06:27Yamaha Road Racer in 1969 and find that it had that
00:06:32250 millimeter
00:06:34four shoe
00:06:36Four leading shoe front brake on it. I had yearned for such
00:06:44Real in quotes breaks
00:06:46for several years because we I
00:06:50Tried to race a
00:06:51Superhawk and
00:06:53After every practice I had to take the brake shoes out and sand them because the organic binder usually phenolic plastic
00:07:01Rose to the surface my wife called that
00:07:05overheated brake smell
00:07:08Burning pot handles
00:07:11It is you are phenolic. Yeah, I think
00:07:14You know, I've had a few drum brake things in my life
00:07:17I had a 64 Cadillac with four tremendously huge power drum brakes. I mean they were they must have been
00:07:24Probably 12 or more inches in diameter
00:07:28and
00:07:29three inches wide probably
00:07:31And they worked they really really worked quite well if you were just tootling around, but if you really needed to stop, you know
00:07:39You got one and even then if it was a long stop from a high-speed with a
00:07:435,000 pound Cadillac it was brake fade while you wait you just
00:07:48You felt the pedal just you know, same with the velocity coming. Yes. Yeah the velocity, you know
00:07:53I have a 54 velocity in case you didn't know folks. I had a velocity
00:07:58Still have it. It's over there
00:08:00Those you know, those are initial brakes were not the full width hub
00:08:04You know
00:08:04that's the one that people want later is the full width hub so that the width of the hub is all breaking on the inside of
00:08:10The drum and this was just a little watch band as I've said before just about about that wide even possibly narrower than that
00:08:17and
00:08:19Not bad for tooling around but end of a long straightaway really got to get it done
00:08:25Nope, it's not
00:08:27no, those early drums many of them were press formed and
00:08:32Press forming of course puts a lot of stress into the metal and it stays there until it gets hot the next time and then
00:08:40it
00:08:42Relaxes
00:08:43Into a shape that won't stop your bike
00:08:46so
00:08:48Not only did the drums
00:08:50Open up like this. I'm making a he's making a cone a cone shape
00:08:56They're opening up because the side of the drum is
00:08:58Material it's the side plate and that it's gonna hold
00:09:01The inner part of the drum and then the the outside is gonna bloom like a flower that the side where that you know
00:09:07All the mechanics go in the open top of the bowl
00:09:09So to speak it just goes in and it opened it blooms like a flower under heat and as Kevin pointed out
00:09:14That press form break, you know, you take this material that might be if it's rolled. It's nice and flat and then you
00:09:22Gang you stick it into a thing and it's just got all kinds of different
00:09:26Stress areas at a molecular level
00:09:29That are just waiting to express themselves as you said with heat
00:09:34That's why we do stress stress reliefs and and so forth heat. I visited the shop of Mac McConney north of Boston
00:09:42in the
00:09:43middle 60s and there was
00:09:46Jess Thomas who was a well-known American racer in a certain era and
00:09:52He was standing talking to Mac
00:09:56The proprietor and saying you mean this whole thing is cast-iron. No wonder. It's so heavy
00:10:04but they made those cast-iron drums because they could
00:10:09Restress relieve the casting and have a break that would continue to work even when it was quite hot
00:10:15So that was a step. Yeah poured to form, you know, it it it was up poured
00:10:22into a bowl and mold and then machined where you needed it to be machined and and the way you went and that was a
00:10:28step away from
00:10:31Boeing
00:10:33Yes, so
00:10:38In the late 1930s the Germans were the pioneers of the full-width hub they
00:10:44earlier the break drum had been like a
00:10:48Six-inch ashtray or a pie plate
00:10:52that was bolted to one face of the front spool hub and the backing plate was
00:10:59with the shoes was
00:11:01rode inside of this and
00:11:05Vincent
00:11:06Built their front break as a dual drum. It had two of these pie plates one on either side of the hub
00:11:15In hopes of having more
00:11:17braking power to go with their large v-twin engine and
00:11:22the Germans
00:11:24Who had come through?
00:11:28Bismarck's system of higher technical education
00:11:33Looked at the thing and said why don't we make the drum the full width and lace the spokes onto the drum flanges?
00:11:42not bolt us all together out of lots of little foolish pieces and
00:11:47That was a great step forward and the tremendous break drum drum brakes of the
00:11:551960s on racing motorcycles that some among us revere to this day because of their
00:12:03Extreme nature and their mechanical beauty
00:12:09Eventually people were using three different friction materials on each shoe
00:12:15these
00:12:17Leading shoe is a shoe that
00:12:20Is self servo acting inside the drum the rotation of the wheel
00:12:26adds to the pressure
00:12:28pressing the shoe against the drum so you don't want to put the ultimate friction material out at the tip where the
00:12:38The multiplying effect is large so they had to they step this so that
00:12:42They could avoid the problem of having so much self servo action that the brake would not
00:12:49Release when you let go of the lever
00:12:51That's been known to happen
00:12:54so it was a sort of a
00:12:58High wire act and getting that to work just right and the drum brake
00:13:04soldiered on in automobiles and production motorcycles and
00:13:08Meanwhile in auto racing in 1953
00:13:14Jaguar won the Le Mans 24-hour race with Dunlop disc brakes and
00:13:22I remember the description was that the here were the
00:13:26Mercedes cars with the big flap that opened up lifted up behind the driver an air brake and
00:13:33They had tremendous finned drum brakes
00:13:36And the Jaguar would come whizzing past them on the approach to the corner the
00:13:42Mercedes drivers devoting himself to forcing the pedal to the floor and
00:13:49This Jaguar comes by still on full throttle brakes violently once darts around the corner and is gone and
00:13:57People just looked at that and they said well that's over with
00:14:01progress
00:14:04Progress
00:14:06Happened right now, and they had been putting trying out disc brakes on aircraft
00:14:13the f8f
00:14:15Bearcat didn't make it to World War two as a carrier fighter, but
00:14:21It was given disc brakes
00:14:23And the great thing about disc brakes is that since the friction material is being pressed against the disc from both sides
00:14:31There's no escape
00:14:33The disc can't get away. It can't warp away
00:14:39Subject to some
00:14:46Explanation later, but yeah, there are rules
00:14:48Yes, the thing that the thing that was that was so wonderful in 72. I brought my
00:14:56homemade
00:14:57750 Kawasaki triple down to Daytona with one of those 250 millimeter Fontana brakes so beautiful
00:15:05so useless and
00:15:07every lap lose a hundred feet into turn one on to the disc brake equipped bikes and
00:15:14The disc brake couldn't come into its own until the slick tire became
00:15:20generally used from
00:15:221974 onward so you had all this wonderful grip from the tire and you had a disc brake
00:15:29that could
00:15:31Absorb that energy without warping fading, etc
00:15:36so
00:15:38that was a that was a period of rapid evolution 1969 Honda came out with the
00:15:45CB750 that had a disc brake on it and
00:15:48Supposedly the background to that was that
00:15:52Yoshio Harada
00:15:53who was big wheel on CB750 had spent time in the US and had seen a
00:16:01Lockhart
00:16:03Disc brake might have been for as a part of a spindle stopper system for machine tools. I'm not sure
00:16:10Someone had adapted it to a motorcycle. It also happened on the East Coast with
00:16:15a
00:16:17Different make of caliper. It was Bo Brinker that did that. He was a bull taco guy, but
00:16:23Mr. Harada saw these things and
00:16:28Thought
00:16:29this is
00:16:30We must have this. Yeah, and so he went to mr. Honda and he said
00:16:37now
00:16:39We're planning to put drum brakes on this motorcycle, but here is a better idea
00:16:44What must we do and mr. Honda said disc brake on the front drum brake on the back
00:16:50cover your bets
00:16:53so that was the start of disc brakes on motors on production motorcycles in that same year or
00:17:00maybe beginning in
00:17:031968 the late great Peter Williams
00:17:10Adapted formula car
00:17:12Disc brakes to his Arter matchless
00:17:16G50
00:17:18called wagon wheels that also had cast wheels and
00:17:23Showed that this was a
00:17:26Substantial advance over the drum brakes that had been used previously
00:17:31Now bear in mind that one reason for the drum brake
00:17:35Being successful was was hard for water to get inside of it
00:17:41It wasn't going to just fill up with water
00:17:45External contracting band rim brakes. All of those brakes were subject to loss of grip from water
00:17:53But
00:17:55Eventually, of course they began to make pad materials that could deal with water, but that came later
00:18:02well, I wanted to go back to
00:18:04drum brakes and kind of talk about the
00:18:07Fundamental operation since we we kind of sped by into discs and that transition
00:18:15Your typical drum brake of the you know, the 50s in your tryout for whatever it was a single leading shoe and
00:18:22So you'd have a drum, you know of your your drum. That's you know pie plate or you know spring-form pan
00:18:29for your cheesecake
00:18:31Yes, and you'd have you'd have that and then the mechanics would go in and you'd have a single
00:18:36A cable would come down. It would pull a lever arm and it would twist a cam
00:18:41Inside and the ends of those shoes would be expanded on the same end
00:18:45So one side would have a self-servo effect and the other would be the opposite
00:18:50anti self-servo
00:18:53and you could do things to make those effective, you know people would lace their wheel and
00:18:58Then skim the drum and their you know, German submarine gap bed lathe
00:19:03Kevin Cameron
00:19:06Gap bed lathe just means you can take out the bed and you could put a big wheel in and spin it around and then
00:19:11Get your tool in there and you know cut a drum round and then you could surface your shoes
00:19:16In a similar fashion so that the whole thing would touch the drum that you wouldn't have the art of farm contact
00:19:23Yeah, you're arcing the shoe to meet the drum, but it was still you know
00:19:28One servo one anti servo and they were okay, but they didn't work that great
00:19:34Double leading shoe
00:19:36Would then be two shoes and you would pivot
00:19:40So that both you would pivot on opposite ends and there were two cams
00:19:44Yeah, two cams so you'd have a cable that came down and then you got Oh linkage linkage
00:19:49It would go across the outside of the drum and it would operate the cams and you'd have to carefully adjust that and and do
00:19:56Everything to make it perfect for your race or your day-to-day, whatever you're doing and then for leading shoe brakes
00:20:03Which you know kind of well, I'm you said there was even six leading shoe
00:20:07You said one Italian outfit decided to just march on in the direction. They were going it's like the pictures of seven eight valve
00:20:16Yamaha cylinder heads when they were yes few plugs and they had valves everywhere as they were exploring
00:20:21How many how much valve area can we fit into a cylinder and what good is it and we found out for is just fine
00:20:27of course
00:20:29and for leading shoes are really that was probably the
00:20:33The pinnacle of the of the drum and then in that case you had linkages on both sides and you had four four shoes inside
00:20:40the drum and
00:20:41All kinds of things to adjust and maybe two cables going on. Yes. Yeah
00:20:46And you had to make sure all that was tip-top, you know yet you really to get maximum even
00:20:53braking force
00:20:54You had to adjust that stuff perfectly you pointed out something really great about
00:20:59Great big drum. So the drums grew to fill the wheel practically spokes went from you know, seven inches or
00:21:06Something to two little tiny stubs that kind of connected the rim very closely to this huge drum in the middle of the wheel
00:21:13I've got a box in the shop a little short like three inch two inch spokes little tiny things and
00:21:21You know making the hub out of the brake was was was a great leap forward that was a great leap forward but also
00:21:29You're putting the heat into the hub itself and then you've got tiny little spokes that don't have a lot of spring to them
00:21:34so what you're doing when you're lacing this, you know, the longer the spoke is the percentage of change of stretch is
00:21:42Let's say you have more to work with on a long spoke but in a short spoke you put it under tension
00:21:47There isn't a lot of stretch to it because it's just this long
00:21:5010% say just call it 10% 10% of 2 inches or 10% of 10 inches is a big difference
00:21:57So you'd lace your wheel up and you would everything to be perfect to be be straight and the spoke tension would be perfect and
00:22:04Then you just hammer it, you know into turn one and what would happen, you know?
00:22:08like at by the fourth lap or fifth lap the drum would grow and
00:22:13Wobble would happen your your rim would no longer be be straight. Yeah
00:22:19Yeah crazy, I mean I I'm I feel I feel good about disc brakes I do
00:22:28I love a beautiful drum brake and you can make them work pretty well and people are racing with them in Arma and
00:22:33people are racing with them in Arma and and having fun and you know, we like them on vintage bikes because they you know, typically
00:22:39your your uh
00:22:41your drum brake on you know, your british motorcycle doesn't have brake fluid which thank you because
00:22:47Bleeding, you know, it's enough to keep up with batteries on on these things but also to bleed holes in your shirt
00:22:54Yeah, so
00:22:56Oh, yeah brake fluid always tell you could always tell the setup kid in any motorcycle shop because he was wearing a t-shirt
00:23:04With holes all over. Yeah
00:23:06Yeah, brake
00:23:09Absolutely
00:23:11And brake fluid will strip your paint and and um and dye your uh, or or bleach your shirt
00:23:16So you can take the color right out of a lot of clothing with some brake fluid
00:23:19It's a great soap in small quantities with some hot water. You can actually
00:23:23Clean a few things with that, but uh, we digress
00:23:27So yeah, it was uh drums were okay, but um, you know glad to move on
00:23:33And move on they did
00:23:34uh honda's first system, uh, the caliper swung on a pivot
00:23:40so that as the pads wore the caliper sort of swung it had a piston on one side and
00:23:48no piston on the others which meant that
00:23:50Uh as the shoes wore down the the caliper would would swing
00:23:56And that system
00:23:57Didn't last. Um, it was a sort of a first try affair
00:24:02um
00:24:04Kawasaki had uh
00:24:06A system with pistons on one side yamaha went to their cast iron caliper that came out on
00:24:13rds in the 70s
00:24:16Um, it had pistons on both sides and that caliper could be mounted rigidly to uh bosses on the fork legs
00:24:24so
00:24:26That was something of of an improvement, but those cast iron calipers weighed four and a half pounds
00:24:35Yeah, that's something well you talked about jaguar disc brakes and you know
00:24:38I've spent a little bit of time working on those and um, yeah, so
00:24:43You know what we have now are incredible like the brembo machine tools that they use to do these, you know
00:24:49Super exotic stylemas and and all that
00:24:52They they a lot of times will have a single piece and they stick the machine tool up and it goes out and it machines
00:24:58The bore so you have a caliper that's a single piece and even if they're bolted together
00:25:02they're these great big aluminum things or whatever material they're using and they bolt them together with great big bolts and
00:25:09It's a it's beautiful and it's quite rigid
00:25:12and um
00:25:14The early dunlop disc brakes on jaguars was a cast iron, uh bridge
00:25:19So it was like a a horseshoe but lengthened so to speak
00:25:23It went over and then with four relatively small the bolt heads on them are seven sixteenths
00:25:29Uh four relatively small bolts on either side is the piston half that bolts to that with tiny little bolts
00:25:37Oh and you know like on it. Yeah and on it and then you stick this uh
00:25:41Kind of fig newton sized um
00:25:43Food analogy. Thank you
00:25:45A fig newton sized pad with a little slot in it so that it would also retract from the piston
00:25:52The seals were in a weird spot too. The seals weren't in the bore. The seals were on the piston
00:25:57All kinds of problems. Uh, they they did work. Okay. I spent a lot of time making my factory jaguar e-type brakes work
00:26:03as as well as they possibly could
00:26:06and uh what you would get is
00:26:09You say you're doing 100 miles an hour
00:26:12and you're coming up to a corner and you
00:26:14First apply the brakes and say 20 percent you 20 percent braking force as you're squeezing down
00:26:21You think wow, these are really good
00:26:23The car slows and then you get to a point where you're adding a lot of force and the caliper
00:26:29Starts to deform and all those four tiny bolts that are holding the pistons are going
00:26:34What are you doing?
00:26:35And it just it just kind of the feel they're okay, I mean they're they're certainly
00:26:39They're heat durable, you know, you can do that over and over again. It's just that um
00:26:45You know making the rest of the components very rigid
00:26:49As we as we've seen with motorcycles going to a radial
00:26:52Master cylinder where you're squeezing against the handlebar. You're not
00:26:56Doing it through a lever that's pushing
00:26:59Uh in the same plane as the handle or along the same, uh axis as the handlebar
00:27:04And then putting um, you know
00:27:06super titanic
00:27:08Brake lines on there that don't deform at all like a rubber brake line is going
00:27:12It's inflating a little bit no matter what you do kind of you put that braided line and then you have a caliper
00:27:18That is knock out and then what you get is your force
00:27:22You're feeling the you're feeling the pads squeezing on the disc and as you pointed out
00:27:26The disc has nowhere to go when it's being squeezed from either side
00:27:30And then you got really impeccable feel and what we've done, you know what Brembo has done and
00:27:36principally Brembo with the racing operations, you know, there was a press introduction for the
00:27:42Aprilia
00:27:43Mille
00:27:45factory at Mugello circa 2003
00:27:49Those brakes it was the first time I'd experienced brakes of that caliber and I was riding Mugello
00:27:55Which is a good place to have good brakes
00:27:57and um
00:27:59There's a chicane at the top
00:28:01And I went through the chicane and I got a much better drive than I had ever before
00:28:05in my learning of the track and I was like, oh that was fantastic and then you're
00:28:10You're going toward that downhill section
00:28:13And I was like, oh my you know, I really was going in pretty hot. So I hit the brakes and I lifted the back
00:28:20Just like like very quickly pivoted up and uh, and I was like, oh no, but I still needed to slow down
00:28:27and
00:28:28It was a it was that step in modulation the ability to release
00:28:33And still be braking hard
00:28:35Not release and then try to start braking again, but release and allow the bike to come back down to reduce. Yeah
00:28:42reduce without going
00:28:44that that you could at
00:28:47Enough braking force to lift the back of the motorcycle then modulate it to keep braking hard
00:28:52But let the thing get back down so that you could
00:28:55Hey make the corner
00:28:58so
00:28:59It was great. I mean, it's just it's it's beautiful the way uh
00:29:02and it also as you point out tires, you know the way that um
00:29:07I had a I had a time travel moment at at my arma experience at barber, you know racing
00:29:13twin front discs on a 1972 bmw with 75 70 75 horsepower
00:29:19really reliable
00:29:20uh repeatable braking never
00:29:23Lever never changed for me through four days of practice and racing lever never changed good good old brakes
00:29:29And and very good, you know vintage race tires are using these these connies. Um with a race compound
00:29:36Narrow 90, you know 90 90 something at the front, you know, uh
00:29:41perfectly great
00:29:43Well, I just what I want to do is finish is going to then getting on a bmw m1000 rr, you know
00:29:49book ending the super bike era
00:29:52What an ass kicker I mean
00:29:56Phenomenal
00:29:58Lifting the rear wheel going into charlotte's just lifting the rear wheel going. Oh, yeah. Okay. This is what we're doing
00:30:04um, then the fatigue that that also brought because the forces are so much higher but um
00:30:10You know slick tires 17s, you know full race rubber
00:30:14um
00:30:15Yeah, phenomenal change. Yeah
00:30:18well on the way
00:30:20to
00:30:22the successful present day in
00:30:25metal brake discs
00:30:27uh, there were some
00:30:30uh difficulties
00:30:32uh when super bikes
00:30:35Uh, the old the 1000 cc sit-up super bikes became a big deal
00:30:40uh from
00:30:4276 onward 76 through 81
00:30:4682
00:30:47um, they had trouble with
00:30:50Disc warpage and
00:30:53uh
00:30:57Gary mathers at kawasaki decided that they would
00:31:02Have
00:31:03cast iron discs made and they would grind them flat
00:31:07And stress relieve them and grind them flat and stress relieve them until they finally got
00:31:13discs of the desired dimensions
00:31:16That would absorb the heat without going all funny
00:31:20That was one thing
00:31:23on the other hand, uh, my rider rich schlachter and I went to loudon in 78 and
00:31:30Loudon has 10 turns in 1.6 miles. So
00:31:34There's a lot of
00:31:35The engine is just basically
00:31:38Turning the brake discs so that the brakes can be can get a hard time
00:31:42And they did what happened was that
00:31:48The brakes would become very hot
00:31:51And they would stretch their rigid bolted connection to the hub
00:31:58the aluminum hub
00:32:00Permanently, they would yield yield it and then when the disc cooled
00:32:06The hub would be too big and the disc would be too small and so it would have to go out of flat
00:32:12And in doing so it pushed the pads back in the calipers
00:32:17Always a bad time. Yes at a bad time
00:32:22And
00:32:23uh
00:32:25I got out the
00:32:26The 12 inch straight edge and laid it across the disc. You could see it right away. It was just cone shaped
00:32:33It was bad and it wasn't all between the disc and the carrier either
00:32:37It was also within the disc because what was happening is
00:32:41The heat enters a disc more rapidly where the velocity is highest namely at the od
00:32:47More rapidly than at the id of the friction track and those yamaha pads were two inches in diameter
00:32:54So there was a large radius difference
00:32:56Well, that was the that was a big that was a big deal
00:32:59Radially the friction area matched the pads and as you say it was like a two inches and so the speed at the inside
00:33:06Much lower than the speed at the outside
00:33:09So and and then the coning the heat because it's hotter where it's going faster there's more friction
00:33:16And there are various strategies which you know, go ahead you tell us tell us how you fixed that
00:33:22Um
00:33:23With my with my heart in my throat because nobody likes to mess with brake discs
00:33:29Just as nobody likes to mess with gearboxes
00:33:32I went home. I drove home
00:33:3490 miles that evening and I
00:33:38uh
00:33:42Drilled or sawed radial slots in the disc and they immediately became flat again
00:33:49Because I had relieved that hoop stress
00:33:53And at the end of the
00:33:55Saw slots. I drilled a round hole so that the radius would be large enough that the
00:34:01The metal wouldn't say to itself
00:34:03Hmm that cracking is a great idea. I wonder what we could do with that. Let's go give it a try
00:34:10and
00:34:11uh
00:34:12That's called stop drilling a crack. It's a familiar technique when you don't have enough parts
00:34:19but uh
00:34:21then I beveled the edges of the saw cuts and
00:34:24uh
00:34:26Brought the disc back and in first practice
00:34:28He had wonderful brakes
00:34:31And they stayed that way
00:34:33well
00:34:34What was happening of course was the tires were getting better brakes were getting better
00:34:40uh, the rate of heating going into the discs was just
00:34:45Uh extraordinary and what came next was narrower discs
00:34:52Carried flexibly on their hubs by means of um, driving pegs
00:35:00uh little spools
00:35:03Slots all sorts of things to allow the disc to grow without having to pull the carrier with it
00:35:11So, uh, that's why modern disc brakes have narrow pad tracks
00:35:19Because that minimizes the velocity difference between the id and the od of the pad track
00:35:24so that the
00:35:26Uh non-uniform heating does not cone the disc much
00:35:31and uh
00:35:32The flexible mounting the floating
00:35:35disc mounting
00:35:36Um is now universal. You don't see any rigid mounted discs anymore
00:35:42It just it's not up to the work
00:35:46So, um
00:35:48in a way when
00:35:49Uh pads that were two inches in diameter because they they saw that they had to go to a narrower
00:35:55Uh pad track and in fact a long a long narrow pad because you're adding
00:36:00You know, we're doing the six piston calipers and stuff
00:36:03so you're you're trying to get the you're trying to get the area for the pistons just as you would put four valves in a
00:36:08cylinder you've got
00:36:10You want a very long pad and it's uh, you're going to get that by adding
00:36:14Pistons so the diameter of the piston can match
00:36:18This narrow braking area and then you're just distributing
00:36:21You're just distributing it along the radius to make your brakes work pretty darn good
00:36:27and then of course, um
00:36:29the initial pad materials were
00:36:32uh
00:36:33So-called organic which means that they might have bits of metal in them
00:36:38um
00:36:41Or ceramic
00:36:43Powder or various stuff like that, but it was all bound together by organic
00:36:49uh resin namely, um
00:36:55The same stuff that they make pot handles out of which is why
00:36:59when you get organic
00:37:01Uh brake pads or shoes extremely hot. They smell like some a pot on the kitchen stove has boiled dry
00:37:09and that um
00:37:12Resin
00:37:13Is starting to give off gas
00:37:16And of course the gas is another thing the gas forms a layer between the pad the friction pad and the friction surface
00:37:24So you squeeze really hard
00:37:27It's that gas comes boiling out of the organic material and
00:37:32You don't have very good brakes if you're trying
00:37:35for ultimates
00:37:36So that's where we got
00:37:38sintered metal
00:37:39or sintered
00:37:41uh ceramic pads
00:37:43the sintered metal is
00:37:45Uh sort of like what you can see on certain ducati clutch plates you look at them you say oh
00:37:51It's copper on there
00:37:53and then you get out your little magnifier and you look and it it looks like
00:37:56Lots of little copper chunks that are somehow magically held together
00:38:01It was powder, but it's been heated to the point that the little chunks are just
00:38:06sticking together they're just
00:38:09uh bonded to one another
00:38:11and that um
00:38:13Metal can make a wonderful friction material
00:38:17The same thing with ceramic the ceramic stuff which is also sintered
00:38:22uh
00:38:24It's supposed to just shrug off rain. Don't don't need to worry about rain because that awful scratchy pad material is is going to
00:38:32Uh reach the disc and do the job. Well, what about um, so you're talking about the gases
00:38:38Um, what about giving them some place to go?
00:38:40Is that what was that the meaning of cross drilling your rotors putting lots of little swiss cheese holes?
00:38:46There was a lot of theory put forward on that but the original reason
00:38:51um
00:38:54Kawasaki's discs were seven millimeters thick and they were really heavy
00:39:00so
00:39:01uh
00:39:03Steve Whitelock who was a vonda hamels mechanic
00:39:06saw that
00:39:07Indy cars had
00:39:09All kinds of holes drilled in their discs. So he went over to dan gurney's shop
00:39:13The late great dan gurney
00:39:16um
00:39:18who
00:39:19Dan who loved to build things including his uh
00:39:24Strange feet forward
00:39:27alligator motorcycles
00:39:29Whitelock went over there and they came up with a drilling pattern and they filled that
00:39:34Those kawasaki discs with half inch holes made them a lot lighter
00:39:38Lightness was their original
00:39:41goal
00:39:42but people had started drilling holes in race car discs because of this
00:39:47gas problem or
00:39:49theoretically a problem
00:39:52And since that time there have been all sorts of hole patterns and curlicues and wavy shapes
00:39:59um, I would recommend
00:40:02well
00:40:03mike baldwin said
00:40:05I choose my tires by walking over and seeing what's on the podium
00:40:10And I would commend that to uh
00:40:15People who want their brakes to work exceptionally well try stuff
00:40:20Use what works
00:40:22And
00:40:26Now of course racing has moved on
00:40:28Moto gp has moved on from metal discs
00:40:32to the carbon carbon discs that first
00:40:36appeared on aircraft brakes
00:40:39The first c5 transport plane, I think had beryllium
00:40:44brakes
00:40:45uh
00:40:46Wow, what's that smell?
00:40:48Don't yeah, beryllium is not healthy and it's and uh
00:40:54Then they they converted over to this carbon carbon material and which is basically
00:41:02um a preform
00:41:04Of carbon fibers which have incredible tensile strength
00:41:08Now remember that old time friction material had
00:41:12Asbestos fibers in it that was to hold the material together the resin bonded it all into a hole
00:41:19But the fibers were there to give it tensile strength so that it didn't just crumble away
00:41:24So you've got this carbon fiber preform
00:41:28And they fill it with organic material and it goes into an oven
00:41:32and
00:41:34The organic filler
00:41:37Uh gradually sort of
00:41:41Calcines away until what's left is carbon free carbon
00:41:46And then they repeat the process as many times as necessary to achieve
00:41:52The density they want and the reason they call it carbon carbon is that it's carbon fiber
00:42:00filled with carbon
00:42:02The preform is impregnated with carbon so that you get a solid part
00:42:08and
00:42:09um
00:42:11When our
00:42:12our friend
00:42:14uh, gandalfi who worked for brembo took me on a
00:42:18a tour
00:42:19He opened up boxes and took out
00:42:22Carbon brake discs handed me one
00:42:24It was my fingers after that were covered with with black stuff just as if i'd cleaned out the pencil sharpener
00:42:32and
00:42:34Those
00:42:36Discs in moto gp are now
00:42:39nearing their limit
00:42:41On the racetracks such as motegi where the braking
00:42:45uh
00:42:46load is
00:42:48Tremendously great
00:42:50even the largest discs
00:42:53355 millimeters
00:42:55That moto gp
00:42:57Has a standard size is 320 340
00:43:00355
00:43:02They're becoming uh marginal and some of you will have seen the recent photo of
00:43:09um
00:43:10Mark marquez's front discs
00:43:14in in raw daylight
00:43:17Glowing red. This is not a subtle effect like turn off the lights. You can see it glowing
00:43:23this is just
00:43:24Too much of a muchness what you would like is that the brake disc should operate between 250 centigrade
00:43:32and 850 centigrade
00:43:34But clearly on some tracks they are exceeding that upper limit
00:43:40and
00:43:41not sure what
00:43:43the result will be but
00:43:45One of the things that has been tried
00:43:48Is moving the fork legs farther apart by making wider steering head crowns
00:43:53So the discs can be moved
00:43:57Out from behind the tires wind shadow
00:44:00So that there's a higher velocity of air passing over the disc to cool them
00:44:05but
00:44:06How far does that go? Another thing that they've done is to extend the disc material inward from the pad track
00:44:14in the form of lots of little
00:44:16Uh fingers, it's it's all sawed
00:44:19Radially to produce a lot of surface area. Those are
00:44:23the discs
00:44:24Cooling fins. Oh my mountain bike brakes have those my shimano. My shimano brakes have little inserts in them. They're wavy
00:44:33Yeah, well my road bike does too for that matter. I got I got them on both
00:44:37But yeah, because those are you know, you're with a bicycle
00:44:40it's it's motorcycling taken to an extreme because you're dealing with a you know, my my bicycle weighs maybe
00:44:4719 pounds
00:44:49And so that you know, and it's got to rely on my pitiful wattage
00:44:53And my great also my great weight, you know 220 pounds with very low wattage output
00:44:59So we're trying to make it light and strong and reliable
00:45:02And so yeah, we have those
00:45:04Those wavy things on our brakes and they do work great. They are great brakes. I'd never go back to rim brakes on a bicycle
00:45:11No rim brakes
00:45:14Although honda did
00:45:17resort to them in
00:45:201965 with one of their
00:45:2350 cc twin grand prix bikes
00:45:26uh had rim brakes
00:45:29and
00:45:32I think
00:45:33I haven't seen other examples of that same sort, but that was bringing back an idea from the early days when
00:45:40Bicycles had rim brakes and people thought well, why don't we try them on motorcycles then?
00:45:45as long as the power was low and
00:45:49There was no consumer protection
00:45:52They were a viable
00:45:54product
00:45:55well, you might end up with a
00:45:58A lighter wheel because with a conventional front disc brake
00:46:02it's
00:46:03Your force is coming in at your 300 millimeters or whatever it is 320
00:46:08Yeah, it's got to go down to the hub
00:46:09So that has to be strong to put the the braking force into the hub
00:46:14And then it has to go all the way back out through the spokes
00:46:17And out to the rim so whatever those spokes may be whether they're wire spokes or they're cast spokes they are spokes
00:46:23and um, so you had to you had to make a wheel structurally capable of taking that braking force and
00:46:30That was really one of eric buell's. Uh
00:46:33religious
00:46:35Adherations, you know, like well
00:46:40Eric is wonderful because he
00:46:44He doesn't give up easily
00:46:47and
00:46:48He'll keep on with an idea that everyone else is kind of going
00:46:53Man, can we just go home and get some dinner?
00:46:57um
00:46:58But sometimes you discover something useful that way by just being very persistent and nobody nobody can question eric on that
00:47:06uh score because
00:47:08He was able to survive that relationship with harley davidson for years
00:47:13and they with their
00:47:16tradition of tradition
00:47:18Were not easily dragged kicking and screaming into the latter half of the 20th century by eric
00:47:25But he kept at it
00:47:28And of course his system
00:47:32Was basically to say we're not going to use the rim
00:47:36as the
00:47:38Friction member we're going to mount
00:47:42the disc a large disc
00:47:44On the rim
00:47:47And then we're going to have an inverted caliper that fits inside of that
00:47:52large ring disc
00:47:54Now we'll only need one brake disc and it's at a very large radius. So its brake torque is high
00:48:01And these are all points in its favor as is its velocity
00:48:06Yes, the velocity is high
00:48:08Because it's farther from the center
00:48:10but um
00:48:13One of his former employees sort of
00:48:17winked to me after one of uh after a
00:48:21lecture delivered on the subject of um
00:48:25How good this single rim brake was?
00:48:28and he took me aside later and said
00:48:31It's actually a really good brake on the street
00:48:35It's only when you go super bike racing
00:48:38That uh, you need something more
00:48:41And
00:48:44So it's one of those
00:48:46Yeah when they're doing
00:48:48Yeah, when they were racing with hero and all that, um, they were having a tremendous problem with pads and it took them a long time
00:48:5511 25 era
00:48:58There was they had a I want to say an eight piston
00:49:01It was the big the big caliper. It's kind of the next evolution of that front brake
00:49:06and it
00:49:08Itself had some sort of self servo effect to it
00:49:11And um in testing, you know, we were testing it. I think I was testing it
00:49:16Oh versus an 848 or something we were at streets of willow and um
00:49:23It was a challenge breaking it down to the apex because you would make your brake application
00:49:28and as you were coming down to the apex it would
00:49:32Basically apply more braking force on your behalf
00:49:35So you would you just say you're pulling with 13 pounds or
00:49:3912 pounds or one pound whatever you're squeezing your brake lever at
00:49:43if you held that perfectly as you might
00:49:46Try aspire to yes
00:49:48um as you're going and you're releasing
00:49:52As you're trading cornering for braking you're releasing the brake so that you can turn more
00:49:58Because you only have so much traction and you're using it more to turn and less to brake
00:50:02The brake would continue to brake harder even as you were releasing
00:50:07And it made it
00:50:09that's a you know, everyone has a different tolerance for
00:50:13the
00:50:14Feeling that you have trail braking don kane
00:50:17Was really really is really really good at trail braking like his ability to
00:50:22Get it into a corner. Like if you want to find out where don kane smokes me and everybody else
00:50:27It's transitions between it's the transition between upright and apex and he was a
00:50:33Devil at the apex as well like his lean angle and speed at the apex was
00:50:37very high
00:50:39More than other riders and that transition
00:50:42Period where you're you are trading that cornering so to have a brake be inconsistent
00:50:47Well, it was consistent, but it was unexpected and hard to control. Yeah, it just consistently would do that and they worked on pad compounds and
00:50:55Blah blah blah
00:50:57and once they
00:50:58kind of reformed into ebr
00:51:01those were pretty good, but then
00:51:04You know the grinding process of this tremendous big disc. That's you know, the diameter of the wheel
00:51:10we had uh
00:51:12we had a brake disc on our test bike that was missed ground and and uh at the track it started to vibrate and
00:51:19Was uh, there were a lot of challenges to it in any case
00:51:21So that that rate it was a good street break at that point ebr we got the new wheel
00:51:26They shipped us a new wheel and we put it on that. Um,
00:51:291190
00:51:31and
00:51:31It was a really nice street break. It really was but as you said in racing and you know when they had it that hero
00:51:38They were smoking pads before the race was over. Here's the here's the reason behind it and that is
00:51:45That you're essentially saying okay
00:51:48The motorcycle is approaching turn one at x speed and
00:51:53uh, we can figure out what its kinetic energy is
00:51:58At that point you're about to apply the brakes
00:52:01Then you break down to the corner insertion speed and you figure out what the kinetic energy is at that point
00:52:07a much lesser kinetic energy
00:52:10And you subtract the one from the other to get the amount of energy that you're going to dump into the brake
00:52:17Now
00:52:19The lighter the total disc mass the higher the brake temperature will rise during that energy dump
00:52:27whether you're breaking for turn one at daytona or or wherever it is and
00:52:34It's very clever to try to make a lighter assembly
00:52:38Or one that steers more easily
00:52:42Those are admirable
00:52:44goals
00:52:46It's like when yamaha adopted adler's idea of a crankshaft mounted clutch
00:52:53Oh, well, this will be great because we can make the plate smaller
00:52:57because
00:52:59Now the clutch is turning at engine speed rather than at gearbox input speed
00:53:04So everything can be made smaller, but then you could only make one really hot start because all that energy of clutch slip
00:53:11would heat that
00:53:13Little stack of five miniature clutch plates. It looked like they were made for a motorcycle with a 30 inch wheelbase
00:53:20and they
00:53:22Plates warped and cracked they turned blue the friction material came off
00:53:27It wasn't a good design
00:53:29Well, they they messed with it with the yzf600
00:53:32With which they called the thundercat
00:53:35Circa 98 97
00:53:38And they changed the primary ratio and they spun it faster so they could
00:53:44Make the clutch diameter smaller and it was a pretty good clutch, but you could put a lot of heat into it
00:53:48Yeah, and it couldn't take it
00:53:50Well, this is this is the same the reverse problem
00:53:54uh happens with
00:53:56With the brake if you don't have enough mass in the brake the temperature can go very high
00:54:03and
00:54:04You can deal with that if you have friction material that can handle it and the if the disc material is
00:54:10Not warping or developing hard spots at that temperature, but some engineering may be required
00:54:18the other thing is that
00:54:20Yamaha had a problem with clutch starts sometime
00:54:25In the first decade of this century
00:54:29and they did
00:54:30Exhaustive testing of friction material until they found a friction material that whose grip did not increase with temperature
00:54:38and what you were talking about the brake continuing to
00:54:41To break harder and harder while you're trying to break less
00:54:46could very well be a case of
00:54:48a positive friction friction versus temperature coefficient
00:54:53The hotter it gets the more grip it has and when you try to make a clutch that works that way
00:54:59You're going to have a sudden wheelie
00:55:02And have to release and you've lost the start. Oh, they're they're all in turn one and i'm sitting back here
00:55:08I think i'll read the book
00:55:10so
00:55:11um
00:55:13Again, these are details that engineers will
00:55:16Have to open the handbook of chemistry and physics and call up their favorite friction material suppliers and start a testing program
00:55:25Well something we've completely taken for granted during this entire conversation is as brake hydraulics brake seals
00:55:32I mean we talked about hydraulics a little bit, but we did not talk about
00:55:35brake seals in the caliper
00:55:38talked about molecular welding of pad material to the disc and stretching it and then letting go and re-welding and
00:55:45Yep, that's uh, that's amazing. But the rubber seals there's a lot of disco
00:55:50Well called magic a lot of magic happening with the rubber seals because um that fineness of control
00:56:00Possibly has a great relationship to how the seals are acting how they grow the thing is the thing that you want is, uh
00:56:08That the pads should retract slightly so that they aren't causing drag and fric and horsepower loss
00:56:15While the motorcycle is rolling with the brakes
00:56:19Released so you want some tiny amount of pad retraction
00:56:25But you also want you also want the ability
00:56:29For the for the pistons to advance
00:56:32to compensate for
00:56:34pad wear
00:56:36And what was found was that the surface finish
00:56:40of the bores in the caliper
00:56:44was
00:56:45an important determining factor here that
00:56:48With enough texture the piston would sit there and retract nicely
00:56:56and
00:56:57Gradually the lever would come down a little bit because the pad was wearing away and then suddenly the lever would come back
00:57:04What did that mean? It meant that the pads had advanced they had overcome that grip
00:57:10that the seal had on the on the texture of the surface and
00:57:13Yeah
00:57:14They had moved inward a little bit and now they could sit there
00:57:19Testing data real real life. Uh triumph. I want to say trophy 1200 way back, you know, the early like 95
00:57:27I believe it was I believe it was a trophy 1200. Uh, the brake lever over time
00:57:33Would just get softer and be farther
00:57:36Uh farther from engaging the pads so you had to pull the lever farther
00:57:40And I complained about this in my road test
00:57:43Back in cycle news and I said, oh this this happens
00:57:46And I took it back to the guy who was doing the prep and he was a very detail oriented guy
00:57:51a really good mechanic and
00:57:54you know, he was doing the right job for his personality and
00:57:58Jetting carburetors and all the stuff that he was doing and he said oh here
00:58:03And he goes over to the brake lever and he puts a squeeze on it and he just squeezes it like he's holding the brake
00:58:08Lever with both hands squeezing it
00:58:12And he does that for 15 seconds and he's like here check and
00:58:16He was advancing the pads
00:58:17He was forcing the pads and the seals to get back into these just do that every once in a while. I'm like
00:58:23That's great
00:58:24But can't we design around this so that I don't have to do that, you know
00:58:27like i'm all for making things difficult in life, trust me, but um
00:58:32Yeah, let's just fix that the opposite of that was honda
00:58:36I think it was 954. So the cbr 954 rr
00:58:41Uh, it was that or the 929
00:58:44They put a coating
00:58:46On the pistons like a low friction coating on the pistons to help with brake feel and etc
00:58:53and um
00:58:54What we found is that it also made them more prone to knock back
00:58:58Knock back being like a little bit of wobble in the front wheel
00:59:01and the brake, you know, the pads are are
00:59:04Uh
00:59:05Are getting shaken back and forth and just a little wobble on the 954
00:59:10A little would make the the pistons. I think it was 954
00:59:15Don't quote me
00:59:17but it was
00:59:18It was of that era. It was sort of like
00:59:202002 ish three four or somewhere around there
00:59:24And uh, yeah, the pads would just the pistons would knock back easier because they had some you know, I don't know
00:59:30Butter teflon something low friction on them
00:59:34yeah, and uh
00:59:35It would give you a surprise going into the next corner because then you had to
00:59:38You know push the pistons back to where you needed them to be to make a hydraulic pressure
00:59:44Yeah
00:59:45Well, it was a problem. Um with some of the 600 sport bikes
00:59:51that uh, if you went over a bunch of
00:59:54ripples that
00:59:57Stress while the motorcycle was leaned over
01:00:00the front tire the front wheel might
01:00:03Rock back and forth
01:00:05Between the fork legs and in doing so the brake disc would push the pads back
01:00:12And then you'd arrive at the next corner and the brake lever would come so far in that your heart would be
01:00:19um in your mouth
01:00:20Yeah, i was talking about deflection of the axle a little spindly little tiny weak-ass axles
01:00:27allowing the the wheel the
01:00:29The whole fork simulator side to side yeah the tilt
01:00:33and this is why uh
01:00:35First of all gp bikes got great big front axles 25 millimeter hollow axles in the front whereas in the past
01:00:44uh 14 and 17 millimeter axles had been
01:00:48considered normal and perfectly satisfactory
01:00:51but
01:00:53With motorcycles things creep up on you and you've got all this tire grip that keeps
01:00:58It
01:00:59Working away at the problem of let's really shake up this motorcycle. Let's put forces through it for which it was never designed
01:01:08Maybe if not this year next year, we'll get their attention. Well, that's and
01:01:12More engineering is required again
01:01:15Which is what's beautiful about the progression of technologies you say like, oh, why don't we just take disc brakes back to?
01:01:231950 and put them on a manx. Well, nope
01:01:26Because all you're going to do is lock the front and beer down or you're going to flex the fork so much that you know
01:01:32I mean
01:01:33That's the that's the beauty of what you were saying about mark marquez making his brake discs glow
01:01:39It's we found the limit again
01:01:42We're all that's what's great about racing because it just forces all we're pushing
01:01:47Yeah, we got to rush around this track over and over again and see who can do it faster
01:01:53and
01:01:54and people keep figuring things out and the riders keep
01:01:57You know you get a good rider you take you know, it takes someone like me
01:02:01and I go from a 75 horse bmw to 190 horse bmw with
01:02:0650 years of technology 55 years of of technology behind it and I spent the last four days
01:02:13getting my g-forces and my
01:02:16Brake feel and my feel for the contact patches all tuned up for a 75 horse 1972 motorcycle
01:02:22It takes me a really long time to recalibrate I still knocked off, you know, eight or ten seconds over my lap times
01:02:28From the old bike to the new bike. Yeah, but it is hard work and you get somebody like a marquez who is
01:02:34Or any of those guys
01:02:36moto america riders like immediately
01:02:40Immediately like oh, yeah, these brakes are better and I I get
01:02:45This lap time or you give them a tire like watching
01:02:48Even
01:02:50I saw the limit of nicky hayden's talent the first time he got a
01:02:54During the dunlop, you know when you could run any tire you want
01:02:58Yeah, jim allen gave him a qualifying tire when he was early in his career
01:03:03and he'd never had a really killer quote like the really good ones that last like
01:03:07A lap and a half like you get an out lap and you get you you have to go right away
01:03:12Because it's gone the next lap
01:03:14You know where you can just turn the throttle it's like woolen socks they go shrinking by
01:03:19Yeah, and he tire goes aging past
01:03:22I saw nicky hayden walking through the pit
01:03:25With this his pie-eyed walking toward jim allen and jim allen said let me guess
01:03:30By the time you figured out how good it was it was gone and he's like, yeah
01:03:35Well, he didn't make that mistake again. It took him. That was the only session
01:03:39He just but he only had a lap and a half
01:03:42And I it took you know someone like me, I mean i'll never you know, I mean i'll never take it to the
01:03:48next degree, um or to anywhere close to those guys, but you take a marquez and he's
01:03:53He's found the limit of the best
01:03:56breaks in the world
01:03:58Yep
01:03:59on last year's ducati
01:04:01yes, so
01:04:03it's uh, it's beautiful it really is so it is and ultimately what you're looking at is
01:04:10a trying to make a ratio the best ratio you can between the force at the lever and the g's of
01:04:17deceleration that you get from the bicycle
01:04:20and
01:04:21That can be it's it's a good way to to
01:04:25quantify
01:04:26uh how
01:04:28Well the system works and I tried
01:04:31using smaller master cylinders and
01:04:33Eventually, I just got to a point where the springiness of everything in the system made the lever too bouncy
01:04:40And I had to give that up
01:04:42but uh
01:04:44brembo's
01:04:45moto gp and world superbike calipers are designed using
01:04:50A finite element analysis to put the metal where it can do the most good those calipers weigh one
01:04:57pound each
01:05:00And
01:05:01They're they're good
01:05:04They are stiff and the lines are stiff
01:05:07Uh, you were telling me about honda saying oh we like to put the rubber lines on because
01:05:14The rider can feel the motion the movement of the lever i'm breaking
01:05:19Fairly hard now i'm breaking harder
01:05:21this was
01:05:22um
01:05:24Something that happened with early versions of the f-16 fighter had had a side stick
01:05:30And the original concept was that the stick would be immovable
01:05:34And the system would measure how hard you were pushing it in whatever direction
01:05:39but pilots
01:05:41Did not adapt to that. They liked to have some movement. They wanted to feel the stick move
01:05:47That helped them to gauge how much effort they were putting into the uh stick
01:05:53so
01:05:53uh this concept of production bikes having
01:05:57softer lines
01:05:59May have a basis in fact
01:06:01Uh for racing it's important that everything in the system be
01:06:06pretty rock solid
01:06:09And shall we pass over the uh terrible problems of bleeding brake systems
01:06:16The ultimate is of course when when you're in the midst of this and you've ruined the paint job and you've ruined your clothes
01:06:23And you've got brake fluid all over the floor
01:06:27And you're saying to yourself i'm going to build a swimming pool and fill it with brake fluid
01:06:32Then i'm going to take all this stuff down in that swimming pool holding my breath mind you
01:06:38And i'm going to assemble a system with no air in it
01:06:44Actually, it's possible to do it without the swimming pool, but it can
01:06:47Present problems. Well, yeah, I mean, I mean you could take a the nice thing with a
01:06:52Motorcycle front brake system is it really isn't that I mean
01:06:56For your average race bike. It's not complicated if you truly needed to take it completely off the bike
01:07:02And then you could put the calipers at the top
01:07:04You could hold the calipers up
01:07:06And you could bench bleed and get your air out the top and that'd be one way of solving the problem
01:07:11Another piece of sheet metal in each caliper to uh, you know, get the air out
01:07:16Caliper to um, yeah take the place of the disc. Yeah, that works you could do that. Um, the one of the other solution
01:07:25Yeah, one of the other solutions that I don't like is
01:07:28Bleeding from the bottom if you have an immaculately clean system
01:07:32You can force fluid in from the bottom and fill the master cylinder
01:07:38From the bottom so you put it in in the caliper
01:07:41But since I work on a lot of really crusty old garbage
01:07:44What you want to do is get the garbage out
01:07:47So I usually drain I don't if I have a hydraulic seal
01:07:51If I have no air basically no air in the system
01:07:54And I just want to renew that I will get a bulb syringe or I will get my you know
01:08:00Vacuum thingy bob and I will vacuum out the reservoir and I will fill it with fresh fluid
01:08:06No air this way and then I will bleed it until clear fluid comes out and i'll do that again until I don't get any
01:08:13Trash, you know any visible trash coming out and yeah
01:08:16That's but boy starting starting from broken lines and air, you know
01:08:21I just I tend to rely on on gravity for to do the first round for me. It's just fill it up
01:08:27Open the bleeder and just kind of stand by have a cup of coffee
01:08:31Wait for it to drip drip drip drip drip and you can get you can get a long way with gravity bleeding on cars, too
01:08:37cars in in my pickup truck
01:08:43Well, thanks for listening folks, uh, we're putting the brakes on the show. Oh, ow, sorry. Ah,
01:08:49Terrible terrible lawyer. Don't do that
01:08:52We appreciate you listening. Um
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