Measuring 60-0 mph on carwow using a 100-0 measurement

[Jonnycoupe]

its dealing with a lot more energy for 100mph stop rather than 60mph, double edge sword really, either the pad is working better at the final stage due to heat operating temp or its warm and friction drops off for the feel, ultimately it comes down to the tyre capacity .

 

[MrRockliffe]

Technically no.

Arguably yes.

 

[Tykey]

Hello

Although mines a Dragy rather then Racelogic but still 10hz GPS.

What's your 0-60 using the Dragy?

 

[HangTime]

But that's the whole point. The conjecture from the guy quoted in the OP is that it won't matter even though he isn't doing it consistently. He's doing a test, taking a particular result from it, and saying it's the same as doing a slightly different test.

It's being lazy basically. However if the tester has done enough comparisons of 100-60-0 with 60-0 using a variety of vehicles in a variety of conditions to determine that they give very similar 60-0 times then it's probably OK.

What isn't OK is just assuming they would behave the same and that can you simply infer 60-0 from the 100-0 test. My initial thoughts were the brakes and tyres will be in different states (temperature etc) between the tests, but I don't know to what extent that might impact performance.

in real life a human's reaction time is quicker at 60 than 100.

Do you have any evidence to support this? I'd assume the reaction time would be largely unimpacted by speed, assuming other factors remain the same (i.e. you aren't being bumped around at lot at higher speed and hence take longer to register a danger due to vision instability).

 

[Sirrel Squirrel]

It's being lazy basically. However if the tester has done enough comparisons of 100-60-0 with 60-0 using a variety of vehicles in a variety of conditions to determine that they give very similar 60-0 times then it's probably OK.

What isn't OK is just assuming they would behave the same and that can you simply infer 60-0 from the 100-0 test. My initial thoughts were the brakes and tyres will be in different states (temperature etc) between the tests, but I don't know to what extent that might impact performance.

Do you have any evidence to support this? I'd assume the reaction time would be largely unimpacted by speed, assuming other factors remain the same (i.e. you aren't being bumped around at lot at higher speed and hence take longer to register a danger due to vision instability).

Highway code?

 

[HangTime]

Highway code?

Highway code supports what I'm saying, i.e. apparently they base it on a reaction time of 0.67s for all speeds.

 

[bazzabear]

Highway code?

I don't think you mean that the reaction time is quicker. I think you mean that the same reaction time will mean less distance has been travelled.
Why would you expect someone to react in less time just because they were travelling more slowly?

Anyway, this test completely takes reaction time out of the equation anyway.

 

[ianh]

Just to throw my inexpert hat into the ring with this one - This is my guess:

During a 100-0 run the 60-0 time would be slightly better than doing only a 60-0 test as the brakes, which always better when warm, would've been heated by that initial 40mph scrub off vs a standard 60-0 test. However, back in the real work where the distance also includes the tyres ability to grip the road and not skid, then outside of a testing lab I think it'd make almost no perceptible difference (a few ft maybe).

What's your 0-60 using the Dragy?

"Awful" considering the power at 3.6 seconds.

However, as an excuse my 2008 gearbox was originally designed in the 1980's as a 5 speed without any launch control or similar and my version only has an extra gear added to that very old design for the "new" 6 speed of the late 2000's. Compared to the newest 8-9 speed gearboxes from the same company (ZF) which now have launch control, gear changes within 50ms etc these new boxes are a huge leap in tech which massively improves the 0-60mph of modern cars.

 

[jaybee]

This was the vid I saw. Maybe he does the same test on all the cars, in which case it becomes more valid I suppose if they all use the same "method". EDIT: Seems he does, at least in the Ferrari one he links to in that vid.

 

[kindai]

B: You do a specific 60-0mph brake test to get the time. i.e. Car is travelling at 60mph before applying brakes until full stop.

B, because in the initial bite includes a huge transfer of energy that is absorbed and stored by the suspension and comparing that starting from 60mph and 100mph is comparing apples to oranges.

 

[DRZ]

It depends...

Some (very small) portion of the initial braking effort is given up to compressing the suspension which takes time - albeit quite small. If that is measured somehow and accounted for then sure, else no it isn't quite the same. Without measuring I would expect the difference to be irrelevant in the real world though.

Just to add to this...

Assuming the best available road tyre on a road car, it is almost completely impossible to lock the wheels at 100mph in the dry - most normally-trained drivers have absolutely no hope of locking the wheels at 100mph even if it is damp. If you sustain the maximum possible deceleration, below somewhere around 60mph it'll transition to being able to lock up and below about 20mph if you're really trying to stop, avoiding locking the wheels (or ABS kicking in) requires some finesse. So this test of 60-0 is basically a test of how grippy the tyre is - which for most road tyres is around 1G of deceleration almost no matter the mass of the car. Or, alternatively, a reasonably good test of how good the driver is at bleeding out of the brakes to stay right on that threshold where the ABS wants to cut in.

 

[jaybee]

Just to add to this...

Assuming the best available road tyre on a road car, it is almost completely impossible to lock the wheels at 100mph in the dry - most normally-trained drivers have absolutely no hope of locking the wheels at 100mph even if it is damp. If you sustain the maximum possible deceleration, below somewhere around 60mph it'll transition to being able to lock up and below about 20mph if you're really trying to stop, avoiding locking the wheels (or ABS kicking in) requires some finesse. So this test of 60-0 is basically a test of how grippy the tyre is - which for most road tyres is around 1G of deceleration almost no matter the mass of the car. Or, alternatively, a reasonably good test of how good the driver is at bleeding out of the brakes to stay right on that threshold where the ABS wants to cut in.

Are you under the impression anyone does anything other than mash the brake pedal as hard as possible in an emergency stop on UK roads? Even "better" drivers with sports cars are still just mashing the pedal. 0.01 % of people will do better than ABS by cadence braking, or trying to depress the pedal just enough to be braking but not entering ABS kicking in.

 

[DRZ]

Are you under the impression anyone does anything other than mash the brake pedal as hard as possible in an emergency stop on UK roads? Even "better" drivers with sports cars are still just mashing the pedal. 0.01 % of people will do better than ABS by cadence braking, or trying to depress the pedal just enough to be braking but not entering ABS kicking in.

I'm saying that 99% of people who only trained to pass their driving test get nowhere close to braking as hard as they could do, even when faced with certain death. If you were to plot a graph of brake pedal pressure vs time for that group of people, it'd have a fairly shallow slope up to a peak of maybe 70% of what the brakes can do until the speed comes down to the point that ABS kicks in.

When you've had some proper tuition you find you get to 90-95% of the maximum stopping power within a fraction of a second and can hold it there. 0.01% of people aren't cadence braking to "beat" ABS - cadence braking in almost every circumstance is worse than ABS. What you CAN do though is feel the tread of the tyre starting to reach the limit of deformation (this is quite a pronounced feeling) and then its a dance between your braking foot, the tread blocks in the tyre and the ABS pump which at this point is audibly priming (and can easily be felt through the pedal). The goal is to keep the tread right at the limit and get out of the brake pedal enough as the car slows through 30/20/10mph without ABS kicking in. You'll take 10 car lengths off your stopping distance from 100mph vs the method you're taught to pass your test.

That exercise is the very first exercise you'll do on just about every single high performance driving course worth the cost. The instructors want to know you can stop the car properly before they teach you how to make it go faster.

 

[Tykey]

"Awful" considering the power at 3.6 seconds.

However, as an excuse my 2008 gearbox was originally designed in the 1980's as a 5 speed without any launch control or similar and my version only has an extra gear added to that very old design for the "new" 6 speed of the late 2000's. Compared to the newest 8-9 speed gearboxes from the same company (ZF) which now have launch control, gear changes within 50ms etc these new boxes are a huge leap in tech which massively improves the 0-60mph of modern cars.

Still very quick but yeh i bet with with a more modern box it'd be under 3.

 

[theone8181]

Out of interest why is the op interested, is that what you base the purchase if a car on, its emergency stop distance .

 

[jaybee]

Out of interest why is the op interested, is that what you base the purchase if a car on, its emergency stop distance .

I thought OCUK motors forum might like the technical discussion on it. No I would not base stopping distance on any purchase decision.

 

[mjt]

My issue with these tests is the acceleration - he uses the manufacturer's claimed 0-62 time and then tests 0-60..

 

[nicRob]

Just to add to this...

Assuming the best available road tyre on a road car, it is almost completely impossible to lock the wheels at 100mph in the dry - most normally-trained drivers have absolutely no hope of locking the wheels at 100mph even if it is damp. If you sustain the maximum possible deceleration, below somewhere around 60mph it'll transition to being able to lock up and below about 20mph if you're really trying to stop, avoiding locking the wheels (or ABS kicking in) requires some finesse. So this test of 60-0 is basically a test of how grippy the tyre is - which for most road tyres is around 1G of deceleration almost no matter the mass of the car. Or, alternatively, a reasonably good test of how good the driver is at bleeding out of the brakes to stay right on that threshold where the ABS wants to cut in.

Used to be able to get ABS kicking in at >100 on Eagle F1s in my Fiat Coupe when the Carbotech pads had some temperature in, they had some bite!

Got plenty of brake test data at work, will see if I can find anything from around 100-0 and 60-0 in the same car to see how the 60-0 is impacted. Generally for our testing we'll accelerate up to about 70, lift off and then full braking at mid 60s, so that the car is in full braking by the time it's at 60. Will be pretty much constantly in ABS from around that speed down, but the best braking distances I've got is always when just staying out of ABS and balancing on the edge of grip. 1-1.1g is the usual limit at this speed as you say.

 

[m4rmite]

I like car wow however personal bias does eek into his opinions when compared against stats.
Hyundai n30 60-0 braking distance was 35m, matt said that was pretty good for a hot hatch.
Mg5ev did 60-0 braking and the distance was 35m, he described it as "meh" if I remember right.

Back on topic, we all know rs6 drivers never do a100 or 60-0 brake in real life.

They just plough into the nearest hedge/ wall

 

[theone8181]

I like car wow however personal bias does eek into his opinions when compared against stats.
Hyundai n30 60-0 braking distance was 35m, matt said that was pretty good for a hot hatch.
Mg5ev did 60-0 braking and the distance was 35m, he described it as "meh" if I remember right.

Back on topic, we all know rs6 drivers never do a100 or 60-0 brake in real life.

They just plough into the nearest hedge/ wall

Naa, everybody else has to brake around them. I'd of thought that the difference between 100-0 (using 60-0 out of that) and 60-0 is going to be a tiny difference, possibly similar to testing with different level of fuel or a heavier driver. I reckon you could do it 5 times and get a spread that covers both measurements. I'm not sure if they normally declare what tyres as that going to have a massive difference.