Track questions. Unstable while braking and more.

[NSX-Racer]

I am surprised that nobody has mentioned one of the most common reasons for instability during high speed braking. Check your alignment.

It has been mentioned several times, first in post No. 11. Maybe bad alignment was also a cause for my bad high speed crash back in '97 but it was obviously not possible to check that after the car was totalled :biggrin:

 

[VBNSX]

Biter,

I would completely disagree with doing ANY mods. I also do not think you should replace your shocks at the mileage you describe. The NSX is more then capable completely stock at the level you are driving at. I would do the following:

1. Replace Tires and Check alignment
2. Flush ABS and Complete brake system (DOT4 in main system, DOT3 for ABS)
3. Replace pads (I would use a Cobalt Friction GT Sport, or the like based on your driving experience) and service rear calipers
4. Keep going to driving school

Just an FYI, when my pads are cold, I get some of this too, especially on a cold day.

HTH,
LarryB

agree w/ Larry... i was running on my stockers up through 80k miles and it was still doing ok...

x

 

[titaniumdave]

In addition to everything already mentioned. I am surprised that nobody has mentioned one of the most common reasons for instability during high speed braking. Check your alignment. Not having enough rear toe-in can cause the tail to be unstable. The power oversteer you also described is also a symptom of too little rear toe-in.

Bob

I found removing some toe out from the front helped with my stablity under very hard braking, I am at .1 degree toe out on the front with 2 degrees of camber. I like this balance quite a bit, got rid of the 'hunting' feeling the car had at threshold braking, where the front end felt like every little change in the track surface would pull the car one way or the other. The alignment is critical on these cars, I have found if it is not in the window of what matches your driving style, all the other changes won't add up to the result you are after. Find a good shop which can get you started with an alignment that is close to stock numbers(1991 camber and caster, with the 1997+ toe numbers) once you get the new tires installed, then start to make changes which will suit your driving style. Make only one change at a time and always have the complete alignment checked, front and rear, when one thing is changed, ie. camber increased by .2 degree, check all the settings. I had the alignment changed 4 times to get to the point I am with it, and I am very pleased with the result, took 2 full seasons of messing with it to get here. Time well spent.

I also have the non-compliant clamps on the front end, I notice bumps and potholes through the steering wheel now. The compliant link really damped that out before. I have bushings and toe links on the back, no down side on the driving experience on those parts, just more feedback and being able to sense where the rear end is when you load the car in the corners. All of these parts advantages became more evident when I went to R compound tires.

Another thing to isolate is tire pressures, make sure your pressures are not too high at the end of the session. My street tires will start to act odd in the brake zones as they heat up and have pressures rise toward the end of the session. Check the pressure as soon as you come in, plus try to note if there is a point in the session where things change.

 

[BITeR]

The power oversteer you also described is also a symptom of too little rear toe-in.
Bob

I know this was because of bad tyres in the back. Nothing else.

I am surprised that nobody has mentioned one of the most common reasons for instability during high speed braking. check your alignment

I tend to disagree here. There must be a reason why some trackers are installing non-complience clamps to a perfectly healthy front suspension.

To me that sounds like the car DOES and should have a swirming sensation in stock trim. For those who experience it often (i.e. frequent track driviners) will get rid of the swirming by installing the clamps and reducing some every day comfort. Good for them. Probably not for me.

I really believe I have the answer to my intitial question. I also doubt there is an alignment issue or brakepad issue with my car. (I'll check though) I will also let you all know if the swirming sensation reduces after new tyres are installed.

Thanks for all the help/input and a very interesting discussion. Prime Rocks

 

[1BADNSX]

I know this was because of bad tyres in the back. Nothing else.

I tend to disagree here.

If you know what is causing your maladies, why did you start the thread and ask?

NSX-Racer, I didn’t see any logic based discussion on alignment. It is easy to say “check the alignment”, but it is best supported with cause and effect.

 

[NSX-Racer]

NSX-Racer, I didn’t see any logic based discussion on alignment. It is easy to say “check the alignment”, but it is best supported with cause and effect.

Correct.

 

[BITeR]

If you know what is causing your maladies, why did you start the thread and ask?

I knew the oversteer was caused by bad tyres. That was not really part of the original question, just a comment on how the car was handling with bad tyres.

The thread was really about swirming while braking.

This thread helped me a lot, and also made me more aware of the NSX suspension setup.

 

[BITeR]

A little update here.
I finally installed the new tyres. Bridgestone S02 PP in front and S03 in the back. The unstable braking was fine and so was the oversteer handling. Ride got quite a bit softer with the Bridgestones and the turn in and stiff sidewalls of the OEM Yoko's was much better than the Bridgestones. Didn't think I'd notice it that much, but the difference was very big. Next time I'll consider stock Yokos!

However, I noticed that my left front tyre locked even whith the ALB enganged. I will flush the ABS fluid to see if it solves that problem. Similar issues has been posted.

 

[NSX-Racer]

A little update here.
I finally installed the new tyres. Bridgestone S02 PP in front and S03 in the back. The unstable braking was fine and so was the oversteer handling..

You mean the braking is more stable now, right? BTW: S 02 PP and S 03 are really different tires according to dry and wet grip (yes, I've driven both) - I wouldn't go this "mix way". And of course both have not the "race slick" precision feel of the stock Yokos, as you already experienced.

If you had that "one tire lock" syndrom before I wouldn't wonder that the car was unstable under braking - when one side brakes different than the other you get in trouble with all kinds and brands of tires.