Explaining how we brake test cars from 100-0...

CarExpert

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  We review every new car on the market, bust car myths, cover the latest car tech and answer your burning questions.  Whether you need new car advice, purchase validation or simply love learning more about new cars and technology, we are your car experts.  Subscribe to Car Expert: https://www.youtube.com/channel/UC7DvMhvy3H7ntEgn9n3xQcQ?sub_confirmation=1  You'll find us dropping new video content three times a week. If you'd like to ask a question about one of our videos, simply leave us a comment. If you'd like to give us any feedback on our content, feel free to email us, or alternatively, hit us up on social media.  Finally, we want this channel to grow with your support and feedback. If there's anything you don't like or would like to see us change, we'd love to hear from you!  Follow us on social media to see what we're up to and to ask any questions!  CarExpert: Facebook: https://www.facebook.com/CarExpertAus Twitter: https://www.twitter.com/CarExpertAus Instagram: https://www.instagram.com/carexpert.com.au  Paul Maric: Facebook: https://www.facebook.com/PaulMaric Twitter: https://www.twitter.com/PaulMaric Instagram: https://www.instagram.com/PaulMaric  #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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