• last year
Every time we brake test a car from 100-0 as part of our performance tests, a lot of you ask why we start braking from above 100km/h. Today Paul Maric explains how we do this testing and why it doesn't matter if you brake from above 100km/h - the results will still be valid.

More information on our data logger: https://www.carexpert.com.au/car-news/this-cheap-gps-device-lets-you-performance-test-your-car-like-a-pro

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#hyundai #performance
Transcript
00:00 G'day everyone, so I thought we'd quickly put a video together just based on some feedback
00:04 that we saw on our video of the Lamborghini Huracan STO.
00:09 You can watch that by clicking up there if you want.
00:12 So in that video we do our brake test and the speedo was reading above 100 km/h.
00:18 I think it was close to 110 km/h when I did the brake test and some of you complained
00:22 that it's not accurate because we're braking well above 100 km/h and I did explain that
00:28 that's not the case and it doesn't really matter when we start braking above 100 km/h
00:33 because our data logger is only logging from 100 km/h through to zero.
00:37 And today I wanted to demonstrate why that's the case and how it works.
00:41 We've got our data logger up here.
00:43 If you do want to find out more about this I've left a link in the description below
00:47 and it'll run you through the app and how it interacts with that.
00:50 But effectively this uses a 10 Hz GPS.
00:53 It's going to be logging our speed when we're driving and the whole idea is that I'm able
00:58 to drive along and it will capture everything from acceleration to braking and that kind
01:03 of thing.
01:04 Now this is accurate to a hundredth of a second and to be honest a 10 Hz GPS isn't going to
01:09 be super super accurate when it comes to braking but it will be accurate enough for us to get
01:14 a good gauge and it's going to be accurate within centimetres as opposed to just metres.
01:18 So today what we're going to do, I'm going to brake from 130 km/h, 110 km/h and then
01:23 100 km/h and I'm going to show you that the braking distance doesn't change between those
01:28 speeds from 100 to zero.
01:31 So we're in our tennis ball, let's go and do our brake from 130 km/h first.
01:39 Okay so here's how this is going to work.
01:40 I've got our access road here.
01:42 I'm going to get this up to 130 and then we're going to stop from the exact same marker from
01:48 our target speeds and then once we're done with all of this I'm going to explain the
01:52 theory about why it doesn't actually make a difference for that 100 to zero time.
01:58 So here comes our brake marker here.
02:00 I'm going to get this at 130, here we go.
02:09 Alrighty so let's have a look at our results here.
02:11 So braking from 130 km/h comes up with a stopping distance of 35.23 metres and 2.6 seconds.
02:22 So remember that number.
02:24 Let's go back now and stop from 110 km/h and what we are doing here as well is we're letting
02:30 the car cool down between each of these runs so that the brakes are in the exact same state.
02:35 So we're going to go park it up, have it sit there for a little bit until everything cools
02:39 down and then we'll come back again for 110 km/h.
02:44 OK so car has cooled down, we'll do our run now for 110 km/h.
02:52 OK here we go.
02:57 I'm glad I haven't eaten yet.
03:02 OK so our brake from 110 km/h, that was a stopping distance of 35.67 metres and a time
03:13 of 2.54 seconds.
03:16 So 35.23 was our first run and then 35.67 was that second run so virtually identical.
03:26 OK cool down finished.
03:28 It's time for our last run.
03:30 This is at just above 100 km/h and for the record the whole reason you have to do it
03:35 above 100 km/h is because the speedo isn't entirely accurate.
03:39 You have to use GPS 100 km/h and we're stopping just above that so we can break through the
03:44 100 km/h zone.
03:45 So I'll explain in a second why all of this will make sense.
03:49 So here we go, 100 km/h stop.
03:53 Alright.
03:54 OK I'm definitely over that.
04:01 So 35.85 metres.
04:05 So there you go, they are all pretty much the exact same.
04:09 Now the reason for that is when you jump on the brakes in a car and you hit the pedal
04:14 as hard as you possibly can, what the car is doing, it's trying to pull the vehicle
04:18 up as fast as it possibly can but it's also trying to not lock the brakes.
04:23 It's then using ABS, so that is locking and unlocking the brakes to bring it just before
04:27 that threshold of where you're getting the tyres locking and you're skidding because
04:32 you don't have control over the car.
04:34 Now as it's doing that your tyres are going to be the friction limit so if you have super
04:38 sticky tyres you're going to be able to stop quicker because you can bring yourself closer
04:41 to that threshold whereas if you have Ranger Raptor tyres for example it's going to take
04:46 much longer to stop because the tyre doesn't have that coefficient of friction.
04:50 Now what's happening is when I hit the brakes from 130 k's an hour we're reaching our maximum
04:55 braking potential and that will run all the way through to zero kilometres an hour.
04:59 So it doesn't really matter if we start braking at 130 or just above 100, we are reaching
05:03 our maximum braking potential almost immediately and then from 100 k's an hour through to zero
05:09 we are braking at that maximum potential through to zero k's an hour.
05:13 Now there are some caveats to that.
05:14 If we were to do 10 brakes in a row obviously you're going to get brake fade if your tyres
05:19 are wearing or are super heating you're going to have issues with stopping but we don't
05:23 have any of those problems because what we do is we accelerate immediately and brake
05:27 straight away.
05:28 We're not doing this multiple times to see what brake fade is like.
05:31 It is just our first stop at the same location and the only variance is then going to be
05:36 the surface whether it's wet or not and we always call that out.
05:38 So hopefully that explains why it doesn't really make a difference what speed we brake
05:42 from and that is why we always have to brake from above 100 k's an hour but whether it's
05:47 100, 110 or even 130 in this case it's not going to affect the validity of our braking
05:52 distance from 100 through to zero which is the number that we quote.
05:56 So hope you enjoyed that.
05:57 If I got anything wrong let me know in the comments section below.
06:00 I think I explained that as best as I possibly can.
06:02 I may have made a mistake so let me know down in the comments section below.

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