Track questions. Unstable while braking and more.

[BITeR]

Hey NSX trackers.

I need som input on a few issues regarding driving on the track.

I took my NSX to a local track yesterday and the car didn't handle as good as I believe it should.

First, in the hardest braking zone, from about 110-70 mph (straight) the ABS activates for a few seconds, and the car seemes a little unstable, moving a little side to side. Nothing scary, but I feel I have to pay attention. Is the ABS supposed to behave like this. If not, what can I do? I know it's a 4 wheel independent ABS system, so maybe this is normal. (It may be relatet to the other question below)

Second, my tyres are 7 years old (yeah, flame me on this one, I got them on a used set of rims. New ones on order..) and do not have much grip left, the back less than the front. Can that explain the first issue? I.e. while braking, the back is actually loosing grip before the front?
Tyres are Yoko A022s.

Third. My setup is stock, both wheel, tyres and suspension. I assume dampers are stock from 91. My only has 35000 miles, but should I change the dampers? I really don't know if they are worn. Would Bilstein improve over stock handling anyways, assuming fresh dampers on both setups?

I did have a lot of fun despite the issues above. Because the rears were shot, I got to experience the NSX from it's worst side, oversteer de-luxe! Man I had to work hard to keep the rear in check. Even hard neutral cornering, the car would break loose in the back, and power oversteer in every turn. Scary, but also fun. For fast driving I do prefer understeer. I got beat by a lot of slower cars so next time I'll be more prepared. Help me.

cheers
Biter.

 

[NSX-Racer]

ABS behaviour depends a bit on the model year - was refined over the years - but: Yes, that sounds familiar to me. Of course it gets worse with bad tires but generally the NSX tends to be tailhappy with stock suspension when you brake hard from high speeds (I totalled my first NSX because of this behaviour).

That has something to do with the weight distribution and the amount of brake diving. Stiffer shocks and springs can reduce this. Or: Apply the initial braking a bit more tender from high speeds.

 

[BITeR]

ABS behaviour depends a bit on the model year - was refined over the years -

Is there any way to update this by re-programming the ABS computer? Should be a patching regime on cars too, like thay have on computer software.

Will the Bilsteins alone help this? Or do the springs need stiffening too?

Thanks for the other tip. I'll try that. I do tend to smash the brake hard, because I know I'll need all the stopping power there is on that straight.

 

[NSX-Racer]

I have no clue about reprogramming, sorry.
Bilsteins alone will help a bit but not much. I have even still a lot of brake diving with Bilsteins and Eibach Pro Kit springs with race slicks of course. With less grippier tires (like my Bridgestone S-03s) I have not much diving but the car is less stable under braking than with slicks - don't ask me about the physics behind that - maybe some expert could chime in.

 

[Hrant]

Under heavy braking, especially if the road/track surface is not smooth/even, the car will tend to be at a loss as to which way it wants to pull because of changes in caster and toe. Comptech offers a non-compliant clamp which helps to reduce such changes.

http://www.comptechusa.com/store/16040.html

I have one and it seems to help.

 

[ncdogdoc]

Get rid of those old tires!!!!!!

Follow the advice on braking methodology. Smooth is the key

Your rear tires were probably losing grip quicker than the fronts, leading to more of a squirm than you liked. That is part of my guess. The rest has been covered above.

 

[Ojas]

Tires!

Compared to other tires I have used, it seems like the stock tires loose much more of their grip as they approach the end of their life - even when it’s perfectly dry. I agree with ncdogdoc: Replace the tires before you start messing with other things.

 

[docjohn]

Get thee new tires and while your at it new shocks,if you like stock ride,if not have fun researching your spring/shock aftermarket options :wink:

 

[BITeR]

Under heavy braking, especially if the road/track surface is not smooth/even, the car will tend to be at a loss as to which way it wants to pull because of changes in caster and toe. Comptech offers a non-compliant clamp which helps to reduce such changes.

http://www.comptechusa.com/store/16040.html

I have one and it seems to help.

From the Comptech site:
"The Front Non-Compliance Clamp for the NSX prevents unwanted caster and toe changes during braking, which may cause unstable or unpredictable handling when entering turns after heavy braking.
The Clamp holds the front factory compliance link in place, not allowing it to flex backward during braking.
By adding this upgrade to your NSX, you will maintain caster and toe alignent under braking, keeping the car stable and predictable."

This is exactly what I'm experiencing, now the question is if this behavior is ok, and not dangerous for me or the car. Has this behavior been changed on later models or is it really a good behavior? I feel more comfortable now that I see the car is supposed to handel like this. Any downside to the comptech Clamps?

And yes, you're all welcome to flame me on the old tyres.... new ones on order. At least I know what it's like do drive a totally oversteer MR car.

 

[BITeR]

Did some more research on the topic.

Looks like there are 3 "upgrades" available to reduce dynamic change in toe.

1. non complience suspension beam
2. non complience toe links
3. non complience pivot clamps (from this thread)

1. and 2. help to stabalise the rear, and 3. the front.

Now, would it help just to do the 3rd option?
1. and 2. seemes to be a more pricey job.
If I only adjust the front, will the rear get worse?

Going off topic, so I'll post another thread in main forum with this last post.

 

[Ojas]

Don’t get the clamps yet

This is exactly what I'm experiencing, now the question is if this behavior is ok, and not dangerous for me or the car.

The behavior may be the same as described on Comptech’s site, but that does not mean that the clamp will solve your problem. The problem you had is not normal. If I were you, I would not even worry about the clamp until you tried your car out after the new tires. While you’re having the tires mounted, you may also want to have the alignment checked.

Has this behavior been changed on later models or is it really a good behavior?

If you are asking if the compliance pivot has changed, I don’t think so. The compliance pivot is actually a cool bit of hardware designed to work with the rest of the suspension system to maintain the geometry of the suspension. Unless you are a hardcore track guy (I think several folks who have posted above definitely are) with modified suspension and the unwanted geometry changes are holding you back at the track, I’m not sure the benefits of the clamp are even worth giving up the function it serves.

Any downside to the comptech Clamps?

Yes. You will effectively disable the function of the compliance pivot. You can read more about it in the Technical Information and Development History book, page 36.

 

[2slow2speed]

From the Comptech site:
"The Front Non-Compliance Clamp for the NSX prevents unwanted caster and toe changes during braking, which may cause unstable or unpredictable handling when entering turns after heavy braking.
The Clamp holds the front factory compliance link in place, not allowing it to flex backward during braking.
By adding this upgrade to your NSX, you will maintain caster and toe alignent under braking, keeping the car stable and predictable."

This is exactly what I'm experiencing, now the question is if this behavior is ok, and not dangerous for me or the car. Has this behavior been changed on later models or is it really a good behavior? I feel more comfortable now that I see the car is supposed to handel like this. Any downside to the comptech Clamps?

And yes, you're all welcome to flame me on the old tyres.... new ones on order. At least I know what it's like do drive a totally oversteer MR car.

From my own personal experience, the ride quality will become harsher, you will feel a bit more feedback on the steering wheel when you go over bumps, etc. It's worthwhile only if you plan to track your NSX often. The front suspension has not changed between the various years.

 

[BITeR]

Re: Don’t get the clamps yet

The behavior may be the same as described on Comptech’s site, but that does not mean that the clamp will solve your problem. The problem you had is not normal. If I were you, I would not even worry about the clamp until you tried your car out after the new tires. While you’re having the tires mounted, you may also want to have the alignment checked.

Yes. You will effectively disable the function of the compliance pivot. You can read more about it in the Technical Information and Development History book, page 36.

Yes, new tyres first. However I've had better tyres than I have now, and have done some hard stops with them too, as well as in the rain, and the exerience is the same. Just didn't bother to really question why the car was like that. Bad tyres probably aplifies the effect some, but like I said, nothing scary for me.

I think my explaination might be a little different than the one on the Comptech site, but when I read their description and did a search here, I felt that it described my "problem" perfectly. Now I know I don't have a problem.

Thanks for pointing out the book reference. It sure helps. I'll do more reserch to see if the non complience part(s) is for me.

 

[Hrant]

The comments above are all valid.

I forgot to mention that besides your tires being old, did you pick a lot of marbles from the track? I have noticed that even when the track pavement/surface is clean, if I have picked rubber pieces, marbles from the track with hot tires/lap, this WILL affect the kickback you get in the steering from heavy braking.

As others noted, the clamp will help with toe and caster pull/push but it won't correct the changed balanced of the wheel/tire from debris ........... I have not noticed much change in street driving with the clamp perhaps because I also installed the Type R bars as well as running full stiff Comptech sway bars on the front, so I keep them on all the time. But compared to OEM set-up, yes there is substantial differnece in how the car handles now; more of a GTS than Touring feel of the 98-T. If you run OEM 16/17 wheels/tires with no spacers, the clamps may touch the tire on full lock.

But I would not jump to doing the clamps. I recommend you transition into your mods one step at a time; the clamps would be down the list in priorities.

YMMV

 

[OLDE GUY]

Unstable while braking and more.

I don't think that the stock NSX is inherently unstable under braking if you have good quality tires, a good alignment and good brakes and rotors. I have tracked my NSX stock and decelerated from 120 - 130+ MPH many times without experiencing instability. I would check these issues first before I investigated the non-compliance gear - which I have by the way, along with the NSX type R suspension.

You should be able to drive a stock NSX on the track very fast; and corner and brake without difficulties. Do the obvious first before getting into the exotic fixes. Don't forget that Arton Senna thought that the NSX was a wonderful handling sports car - STOCK!

 

[VBNSX]

I know what you're talking about.. with the bit of instability... but when i focused more I looked back and found that:

1. tires were getting junky
and
2. I gave the most tiny of movements in the wheel when stopping.. (focus was drifting).. causing the tail to become just a tad

kinda curious.. how much track time experience have you had?

x

 

[docjohn]

I have tracked my car often with stock brakes and bbk without the pivot clamp and did'nt experience what you describe.Now that I have the clamps I can tell you that it won't fix your problem,the changes I feel are very subtle,so don't think a clamp is going to fix things :smile:

 

[NSX-Racer]

Mmmh - BITeR, I just watched another thread about "downshifting to deccelerate" and asks me if that could be part of the problem. When you brake with clutch engaged the rear wheels can get an additional brake impulse by the engine and may block (even with ABS) which makes the car unstable

You may try braking from high speeds with clutch disengaged and see if it gets better.

 

[BITeR]

Re: Unstable while braking and more.

Make certain that your NSX is properly aligned, that you have high quality sport tires and that your brake rotors and pads are good before you get into other fixes.

Last alignment was 2 years ago. From what I can remember it was like this then too. Brakepads and rotors are not worn at all, unless pads go bad after 13 years, since mine are stock.

You should be able to drive a stock NSX on the track very fast; and corner and brake without difficulties. Do the obvious first before getting into the exotic fixes. Don't forget that Arton Senna thought that the NSX was a wonderful handling sports car - STOCK!

I know That's why I want to keep my car mostly stock. Even if the instability "feeling" is there, now I know that the car was designed to allow changes in the suspension.
It's important to stress that the instability feeling is not severe, and not scary in any way. The car goes straight while braking.

 

[BITeR]

I know what you're talking about.. with the bit of instability... but when i focused more I looked back and found that:

1. tires were getting junky
and
2. I gave the most tiny of movements in the wheel when stopping.. (focus was drifting).. causing the tail to become just a tad

kinda curious.. how much track time experience have you had?

x

Good points here. I've already concluded that the tyres probably amplifies the geometry adjustments made by the suspension. Like I said before, I wasn't aware of the stock suspension setup that can explain this kind of feeling.

My track experience with the NSX is only 2 years, 3-4 non timed trackdays a year, and a couple of autocross sessions. Prior to the NSX, I've tracked my Integra Type R for 2 years, same amount. I have pushed the NSX to it's limits, especially in the slow sections, where loss of grip is not scary at all. That's why I track the car, to learn my and the cars limits.
Just never bothered too much about the swirming sensation until a friend of mine asked me what it was. Then I started worrying Worried no more I am... (as Yoda would say)

 

[BITeR]

Mmmh - BITeR, I just watched another thread about "downshifting to deccelerate" and asks me if that could be part of the problem. When you brake with clutch engaged the rear wheels can get an additional brake impulse by the engine and may block (even with ABS) which makes the car unstable

You may try braking from high speeds with clutch disengaged and see if it gets better.

This is a very interesting comment.
I askend one of the track/triving instructors last year, wheather to brake hard with or without the clutch pedal to the floor. He most definatly told me to just brake and keep the car in gear. Your suggestion is to keep it out of gear while braking hard (i.e. clutch pedal to the floor)?
Can you post the link to that thread. Can't find it.

 

[Peter Mills]

Re: Unstable while braking and more.

BITer:
Have you taken the rear wheels off and looked at the brake pads? The instability could be caused by the rear brakes not performing properly.
The NSX is set up with brake bias favoring the rear wheels, so under heavy braking the rear will be "light" and hop or bounce.
When you brake are you braking in a straight line and then shifting after ALL THE BRAKING IS DONE or are you braking, shifting and braking again. If you are doing the latter then the problem is created by you. You are transfering the weight to the front, then back to nuetral then back to the front, causing a see-saw effect. Very slight but the NSX will react accordingly.
Also check your rear brakes to make sure they are not binding. Jack up the rear so both wheels can turn. With the car in gear and with the E-brake and engine off, see if your can move the rear wheels. They both should move 1/2" to 3/4". If one doesn't move at all, then you need to adjust the rear brake piston to release the pad.
If you can get your car on a lift, check all the bolts in the rear beam and suspension members. Torque to correct Ft Lbs or Newton Meters. Do not over torque as all these pieces are aluminum and can be damaged or stripped.
What PSI do you have in your tires when you track your NSX?
Please keep us advised as to your progress.

]Last alignment was 2 years ago. From what I can remember it was like this then too. Brakepads and rotors are not worn at all, unless pads go bad after 13 years, since mine are stock. [/B]

I know That's why I want to keep my car mostly stock. Even if the instability "feeling" is there, now I know that the car was designed to allow changes in the suspension.
It's important to stress that the instability feeling is not severe, and not scary in any way. The car goes straight while braking.

 

[1BADNSX]

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

 

[Larry Bastanza]

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

 

[NSX-Racer]

Can you post the link to that thread. Can't find it.

it's here but has not much do with your issue, it just gave me the idea.