Brake-testing

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MvM

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Last night I went out and did some acceleration runs with the AP-22 I finally attached to the car.
I also did some brake-test from 100 kph to 0. The car tracked straight, no problem there, but I was a bit dissapointed with the results so maybe it's just the technique I'm using.
Road was dry tarmac, no too rough. Tires are new S03 in front and almost worn-out S02 in the back.
Restults were 2.96 second to stop. That is 41.1 meter from 100 kph or 126 feet from 60 mph.

What I do is that I accelerate to the point the AP22 tells me to start braking, Then I stomp on the brakepedal as hard as I can and let the car and ABS to the rest.
Should I use a different technique to do this.

I've attached a sample run below:

Start Speed 100.0kph
kph s g km
90.0 0.36 0.71 0.009
80.0 0.70 0.86 0.017
70.0 1.00 0.92 0.023
60.0 1.27 1.06 0.028
50.0 1.55 1.01 0.032
40.0 1.80 1.07 0.036
30.0 2.08 1.06 0.038
20.0 2.36 1.05 0.040
10.0 2.65 0.91 0.041
0.0 2.97 0.90 0.042

Peak G: 42.6kph 1.73s 0.035km 1.10g
 
Did you test with cool and hot brakes? Most magazines do both and the difefrence is a couple meters (1-2m).

Over 40m is kind of disappointing, most over 40k$ cars stops in less than 40m today. I am not that surprised, I am one of those that thinks that the NSX stopping power is kind of weak... :(

When I compared to some german cars I felt kind of ashamed (BMW 330 and Audi S3, we did this on a big military parking space this spring... they get 2-3 meters less than the NSX from 100-0kmh :eek: )
 
Hi Gheba,

I did several runs so by the time a was doing the third run the brakes were pretty hot I think.
I think one of my problems is getting the deceleration up fast enough. From the graph and table you can see the NSX can brake well above 1 G but it takes me a while to get there and I therefore I am wondering if I should use a different technique for that. If I can get there quicker the stopping distance would be greatly reduced since the car is still going fast at that point.

The BMW 330 and Audi S3 getting shorter distances might be because the weight of those car is in front so the front tires probably have more grip to start with. With the NSX, at least that's what I think, the weight first has to transfer to the front to get the tires to grip hard.
 
The weight could be the reason. But doesn't the NSX have a weight distribution close to 50-50?
I would imagine that also BMW and Audi for their sporty model do try to achieve equal distribution too.

I am more inclined to think that the NSX brakes, at least the pre '97, are getting quite outadated. And this should not be a big surprise: afterall 10 years are quite a big difference in nowaday tecnology! And in this very case we are not comparing the NSX to Lada or Oldsmobile ;) ...
 
The Audi S3 has 59/41 front/rear weight distribution.
The BMW M3 has a 49/51 f/r distribution. The 330 will have probably the same distri I guess.
For the M3 I have 37.8/36.4 cold/hot meter from 100 kph as reference. For the S3 I have 37.1/37.1 meters for the same specs. Shorter than what I manage to achieve but that might not say much. But then again, I'm not a professinal race-car driver or car-tester.

Maybe it's because of the ABS kicking in. But I think it's more like me not doing something right to achieva the optimal distance. Also, road conditions are very important of course as my tests where done around 23:00 hours. Next is the equipment used which might be different.
 
MvM, when I did the comparison, I think I used the same "technique", or lack of, that you used ;)

Simply press 100% the pedal and wait. The same was done on the BMW and Audi... the difference of 2-3 meters is the same as magazine do get, so I assume there's not a lot that a braking technique could improve.

I used 255 in the rear. Does this improve the stopping distance over OEM? I would say "yes" but any input is welcomed!
 
MvM said:
From the graph and table you can see the NSX can brake well above 1 G but it takes me a while to get there and I therefore I am wondering if I should use a different technique for that.
Click to expand...

Some other things to test while you are at it would be to bleed the brakes and re-test or put in stainless steel lines and re-test.
 
The weight distribution is 42/58 according to the FAQ section (for a 3.2 litre). As for comparing the NSX to heavier cars they would be at a disadvantage because they have a larger mass to stop – this is much more of a disadvantage then the added traction weight gives correct? Another thing since the NSX has more weight in back when you brake the rear weight would transfer forward and perhaps make the weight distribution closer to 50/50 (just a guess)? So then the load during braking would be evened out – maximising the use of the front and rear brakes instead of giving the front brakes more than they can handle? The rear of the car also has wider tyres… Would this not be an advantage over a car with 50/50 weight distribution where during braking the rear weight would transfer forward making it perhaps 60/40 (again just another guess)? Perhaps the 911 could be used as a good example due to the rear engine? Just taking a few guesses here – and perhaps making a complete idiot out of myself in the process… :)
 
Using ABS will not get you the shortest distances. If that is the way the magazines test, then you need to do that for comparison sake.

Since ABS allows a little bit of roll every few milliseconds to retain steering control, it will lengthen total stopping length.

I would say that 1.1g for stopping force is good. The new SO3's may be part of it also, as in my experience, the first 2-300 miles the tires are very squirmy.
 
I doubt weight distribution has much to do with it. My 2000 Audi S4 has huge brakes with an equally huge booster and can really bring the car down to a quick stop. Unfortunately, the setup is so big, it is almost uncontrollable for regular light braking (10% braking) and therefore I have to increase my following distances do to the “touchiness” of the brakes. The new S4’s have a dual-stage booster to help resolve the problem, but Road and Track still complained about the touchiness of the brakes when they tested the car.

I’d take the linear and controllable NSX brakes over the S4 brakes any day (except that day I need the 5ft. less stopping distance). ;)

DanO
 
Using ABS will not get you the shortest distances. . .Since ABS allows a little bit of roll every few milliseconds to retain steering control, it will lengthen total stopping length.
Click to expand...

I think that was your answer. If I hit ABS at the track I've braked too far, missed the turn in point, missed the apex, and cussed myself out. I've noticed that drivers who brake well seem to get to their maximum braking force "right now" and novices, like me, take a tad longer to get there - resulting in longer stopping distances.
 
Found an article that might give some insight...
Sorry for the quality - tough to get the file under 100kb (had to use max compression)
 

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  • weight.jpg
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ky650,

Interesting reading. From the article you posted you would say the NSX should have an advantage over front-heavier cars.
It might be that bigger tires up-front would be one trick to shorten distances (in the dry that is) for the NSX.
For me, one of the steps I will do is bleed the brakes (long overdue I think) and put on new pads in front.

From the table I posted earlier you can see that my deceleration force doesn't reach 1 G after slowing down to 70kph (that's after 1 second). By that time, from the same table, you can see I've already travelled 23 meter, or half my total stopping distance.
Getting that decel-force up to 1 G quicker (say, 0.5 second) would drastically reduce your total distance.

Although this is just a quess, one of the advantages of bigger diameter discs in general is that the calipers apply more torque just because they hang out further from the wheel-center. Maybe because of thay, getting the G-force up to max. might simply be easier for the driver when using bigger discs.
 
I always thought the tires were doing most of the stopping...

Also felt that BBKs were meant to dissipate more heat while extended periods of hard driving such as in racetrack conditions. It really doesn't suprise me that your AP brakes have no better stopping distance since its still your tires doing the stopping work.
 
Originally posted by gheba_nsx
I am more inclined to think that the NSX brakes, at least the pre '97, are getting quite outadated. And this should not be a big surprise: afterall 10 years are quite a big difference in nowaday tecnology!
Click to expand...
Brake technology has hardly changed at all in the past ten years. The big change is the four-channel ABS for which the NSX was a pioneer, and which is now more widely available. But the technology for brakes today is virtually the same as it was ten years ago.

Originally posted by ncdogdoc
Since ABS allows a little bit of roll every few milliseconds to retain steering control, it will lengthen total stopping length.
Click to expand...
That's not the precise reason. It's close, but not entirely accurate.

Stopping length will be minimized using a technique called "threshold braking". This means that the brakes are on the threshold[/b] of locking up, but they are not actually locking up. (Brakes locking up results in the tires sliding.) ABS does not activate during proper threshold braking.

If you use more pressure than needed for proper threshold braking, then the brakes do lock up, the tires slide, and ABS comes on. This sliding is what causes the lengthened distances.
 
Stopping length will be minimized using a technique called "threshold braking". This means that the brakes are on the threshold[/b] of locking up, but they are not actually locking up. (Brakes locking up results in the tires sliding.) ABS does not activate during proper threshold braking
Click to expand...


Even better answer.
 
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