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

jaybee

jaybee

jaybee

Soldato
Joined
10 Jul 2008
Posts
8,502
I saw a video on carwow youtube channel where he uses his specialist timing gear (his own words) mounted to the dash board of cars, and then brakes from 100mph down to 0mph to get various braking distance/time stats, including obviously the 60-0 one. He also uses it for acceleration tests.

In one of the vids I was watching (think it was an Audio RS6) Matt says that he is going to test the 60-0 mph brake test times by doing a 100-0 mph (all inclusive) brake test and measuring various times in one single brake test. i.e. He will then get the 100 to 0 time as well as the 60 to 0 time in a single brake test.

In your opinion, would you get the same 60-0 mph brake test time and/or distance by doing either of the below tests, or would they differ? Explain your reasons.

A: You brake from 100 mph down to 0 mph and use the read out from the timing gear that provides your 60-0mph time. i.e. Car is travelling at 100mph before applying brakes until full stop.
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.
 
Last edited:
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.
 
I also guess if the brakes are particularly bad, by starting at 100 instead of 60 you'd have used up some of the capacity and thus it'd be performing worse by the time it has done the 100-60 bit? Though the contrary could also be true, as a bit of heat into them can help. So it could just be different for many reasons?
 
Last edited:
rG-tom said:
I also guess if the brakes are particularly bad, by starting at 100 instead of 60 you'd have used up some of the capacity and thus it'd be performing worse by the time it has done the 100-60 bit? Though the contrary could also be true, as a bit of heat into them can help. So it could just be different for many reasons?
Click to expand...

Yeah. I think there are too many variables to state that you can just use the time from the original test. It's a completely different test. Science teachers would not approve. ;)

My thoughts were that isn't a 100-0 test vs a 60-0 test a bit like a runner doing the 100 meter sprint from static vs having a runup through the start line? The car braking down from 100-0 will enter the 60-0 zone with an already decreasing speed.
But then the counter is that it is unfair because the extra momentum at higher speed has to waste energy killing that down to 60 first.
The conditions are so different.
 
Sirrel Squirrel said:
In the real world the pure 60-0 would be quicker if you factor in driver reaction times but that's not part of the test so I doubt there's a lot in it there.
Click to expand...

Reaction times? The racelogic test gear surely only kicks in when it detects g-force of the driver mashing the brake pedal no? I would have thought human element does not come into it, unless you slightly made the speed higher or lower than the 100 or 60 each time.

I mean to say, you simply mash the pedal and let ABS do its thing. Ok so the road surface and variables may come in and you should average a few tests after cool down if we want to get super strict.
 
Last edited:
jaybee said:
Reaction times? The racelogic test gear surely only kicks in when it detects g-force of the driver mashing the brake pedal no? I would have thought human element does not come into it, unless you slightly made the speed higher or lower than the 100 or 60 each time.

I mean to say, you simply mash the pedal and let ABS do its thing. Ok so the road surface and variables may come in and you should average a few tests after cool down if we want to get super strict.
Click to expand...
Yeah it doesn't that's why I was saying it isn't part of the test but in real life a human's reaction time is quicker at 60 than 100.
 
Sirrel Squirrel said:
Yeah it doesn't that's why I was saying it isn't part of the test but in real life a human's reaction time is quicker at 60 than 100.
Click to expand...
You mean if a human reacts the same in both, you cover more distance going a ton than at 60mph? You could argue reaction times at a ton go up due to increased alertness. ;)
 
Under strictly controlled ideal test conditions, then there will almost certainly be a difference, but - much like MPG values - in the real world there are going to be thousands of other variables at play, all of which will have far more of an effect...

As a way to compare the braking ability of 2 cars - fine, but the figures given are unlikely to reflect normal everyday driving.

TL;DR; it really doesn't matter.
 
Last edited:
Haggisman said:
Under strictly controlled ideal test conditions, then there will almost certainly be a difference, but - much like MPG values - in the real world there are going to be thousands of other variables at play, all of which will have far more of an effect...

As a way to compare the braking ability of 2 cars - fine, but the figures given are unlikely to reflect normal everyday driving.

TL;DR; it really doesn't matter.
Click to expand...

Where do you draw the line on it mattering then? Time it manually with a stop watch and finger in the air guestimate the distance by eye balling it? It's carwow, a youtube channel dedicated to cars where stats are fairly important and discussed a lot.
For the 0-60 we'll just call 2.5 seconds 3 seconds then for example?
 
jaybee said:
Where do you draw the line on it mattering then? Time it manually with a stop watch and finger in the air guestimate the distance by eye balling it?
Click to expand...

As long as it's done consistently so you can compare vehicles then it doesn't really matter - in your example there are obviously the human elements of pushing the stopwatch buttons, and "eyeballing" it, which are going to result in inconsistency, so no, that wouldn't be appropriate.

If car A is measured at 5 seconds under strict lab conditions, and car B is measured at 4 seconds under the same strict lab conditions, then you know car B is 20% quicker at stopping under the same conditions. However, unless you exclusively drive in those strict lab conditions, the actual measurements are somewhat moot.

As I said, it's like MPG measurements. If car A states 40mpg and car B states 50mpg, then that gives you a good idea that car B is ~20% more economical - of course everyone knows you aren't actually going to get 50mpg out of it.
 
Last edited:
DRZ said:
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.
Click to expand...
Agreed


And if you're getting significant brake fade from a single stop from 100mph, then you probably need to have things looked at, or never drive that fast in your car again...
 
Haggisman said:
As long as it's done consistently so you can compare vehicles then it doesn't really matter
Click to expand...

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.
 
Last edited:
bazzabear said:
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.
Click to expand...

To be fair, I haven't watched the video - is he only using this method for this particular car, and doing (or has already done) separate measurements for the other cars being tested?

In which case yes, seems a bit of a stupid way of doing it.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom