oversteer at track

[L8apex32]

Just got back from a DE at Heartland Park. Car ran great, over all. However, Houston, we have oversteer.

I realize that this can be caused by a number of easy to fix/control things so let me try to explain that these common issues have been accounted for. For instance, my alignment is as close to factory specs as I could get it. I have slightly too much negative camber in front and slightly less caster - but otherwise, front and back are in spec. The tire pressure is right - I was running Avon track tires - forget the name. Anyway, that stuff is fine and normal and the car was quite fast. It was just had a little too much oversteer.

I do have Dali adjustable sway bars. These are the ones where the rear is adjustable and the front is not (from several yeras back). I went to full soft in back on the sway bars. I also stiffened my front shocks and left the rear shocks at full soft. This helped some. But, I still have too much oversteer.

One option is to purchase a stiffer front sway bar - or even just another whole set.

Or, I could go with stiffer springs all around. If I go that way, wouldn't I want to lower the car, too? But, if I go lower, I'll get more negative camber - which is already a little too much.

I hear some people go with the NSX-R suspension. What does that get you?
Any ideas as to spring/sway bar combos that you like? What about going lower and getting more negative camber? Is that a problem?

Any ideas would be great. Thanks.

 

[Batoutahell]

Hey thanks for the ride on Sunday! I always start with the simplist adjustments before I look at changing parts. What are your alignment settings? Do you possibly have toe out in the rear that can be dialed out to correct your oversteer? Did you adjust your tire pressures at all?

 

[dquarasr2]

Hey thanks for the ride on Sunday! I always start with the simplist adjustments before I look at changing parts. What are your alignment settings? Do you possibly have toe out in the rear that can be dialed out to correct your oversteer? Did you adjust your tire pressures at all?

What kind of oversteer? Power-on oversteer? Corner entry oversteer? All the way around?

I had a similar problem that I posted some months ago. I found that by modifying technique, finishing braking fairly early and rolling on the throttle as I turned in to plant the rear, then progressively feeding throttle at the apex and beyond, actually resulting in the rear being very planted (and on some corners experiencing some mild understeer).

Also, alignment settings, while "in spec" can still be less than optimal. Bat mentions rear toe. Also, you mentioned that your fronts have slightly more negative camber than "spec". If you have more camber in the front than the rear it could account for better grip in the front ( = oversteer).

Post your alignment specs, and be introspective on your technique.

 

[Ponyboy]

Just got back from a DE at Heartland Park. Car ran great, over all. However, Houston, we have oversteer.

Post of your full specs (alignment, tires and sizes) and the condition of the oversteer. I'm supposing it's corner entry but would like to know for sure...

 

[L8apex32]

My alignment, as I said before, is very close to the factory settings. Here are the numbers, just to be complete.

Front:
camber: -0.8 -0.8
caster: 7.2 7.2
toe: -1.4 -1.5

Rear:
camber: -1.5 -1.6
toe: 1.5 1.6

As for how it feels, it does not feel that much like oversteer at turn in. In fact, it feels much more like oversteer on the throttle, even part throttle.

Turn 3, for instance, is a carousel where you have to pick up the throttle part way around. It will easily oversteer in 3rd in the carousel.

Similarly, coming out of tight corners, in 2nd gear, it really wants to spin the
tires. (My engine is stock and old.)

Compared to my mid-engine race car, it feels good, come to think of it, in braking and turn in, just not with any throttle.

There is another concern I have that may be related. Sometimes, in street use, under street acceleration, the TCS light will flash on/off. This is usually after an upshift and at low rpms.

On thought I had was, what if the limited slip wasn't limited anymore and only one wheel got traction? This would have one tire spin (burn out) and the other not... but this doesn't occur at low power usage and is quite obvious when it happens. Also, I tried a straight line "burn out" and did leave two black marks. Still, I wonder if, perhaps, the transaxle is giving more power to the right rear under acceleration. The track I was at did not have many tight right turns... always to the left. Hmmm.

 

[Batoutahell]

Hmm, I don't see anything unusual with your alignment settings.

I have an idea what might be happening, at least in the carousel. Your suspension is fully loaded going into and mid-way through the banked carousel. You start rolling onto the throttle while you're still on the banking. As you approach the exit, and applying more throttle, the camber of the carousel goes away as the track flattens out. All of a sudden, your right suspension is becoming slightly unloaded and your right tires are losing a little bit of grip, all while you are applying heavier throttle towards the exit. These conditions will induce oversteer.

I would have to walk the track again to be sure, but I seem to recall that the carousel starts to lose its camber about 2/3 of the way through the turn. Does that marker seem to coincide with when you felt the back end get loose?

The other point where I guess you're spinning the rears is T6, the tight left-hander. Everyone loses traction there because the track is very bumpy at the exit. There's a dip about 6" from the edge of the track at the exit where your tires finally bite, but it's easy to lose the back end there due to the bumps. My TCS would activate every time at T6.

 

[L8apex32]

What you are saying is fine and true, but the extent to which I'm getting oversteer is the problem. Also, a gradual transition from braking to coasting to throttle should increase understeer as weight is transferred to the rear.

If we ignore turn 3 just so we can ignore camber changes in the track, we can consider turn 14 (or whatever number it is these days) going to the front straight. This is a basic, flat turn, just greater than 90 degrees. I should not have huge oversteer well past the apex. I should be able to transition to WOT as I unwind the wheel, and pick up some understeer. But that doesn't occur like it should. Too much oversteer.

A well balanced car should be capable of some trailbraking at turn entry, be able to turn very sharply at mid corner (not have too much under or oversteer here) and be able to accelerate hard out of the corner (leading to some understeer at turn exit). Currently, I'm not complaining about turn in or mid-corner, but do have problems at turn exit.

Thanks for continued ideas and suggestions.

One path I'm taking to investigate is to check the differential (limited slip). It is an easy check with the torque wrench to see if it is working correctly and I'll report that when I get a chance to test.

 

[docjohn]

If I can trust your judgment that you are not too early and agressive with the throttle then I bet your rear tire pressures were too high and you were running on the centers of those avons.Did you take acurate hot pressures in the hot pits?

 

[HPower3]

l8apex32, I know you said your tire pressures are right but would you mind telling me what your front and rear pressures are that you're using?

 

[stuntman]

If you are getting the wrong outputs from the car, you are probably giving it the wrong inputs.

Weight transfer - grip where their is weight on the car (ie. Braking - more grip on front, accelerating, more grip on the rear). -keep these in mind when driving and utilize them to get the right outputs from the car.

 

[L8apex32]

If I can trust your judgment that you are not too early and agressive with the throttle then I bet your rear tire pressures were too high and you were running on the centers of those avons.Did you take acurate hot pressures in the hot pits?

I not only took pressure, but tire temps. I ended up with 34 or 35 front and 37 or so rear tire pressure (PSI).

I used tire temp gauge to ensure and even temperature across the tire.

(It may be interesting to know that I had oversteer my first two sessions... when the tire pressure was still low. I think I started at 28 or 30 psi front and about 2 more in the rear. For session 2, they were higher. By session 3, when I had changed my rear sway bar to full soft, I was at the 34 front, 37 rear, give or take.)

 

[L8apex32]

l8apex32, I know you said your tire pressures are right but would you mind telling me what your front and rear pressures are that you're using?

At peak, in pits, it was 35 front and 37 or 38 rear.

 

[docjohn]

For toyo ra1 those rear pressures are fine,you should check with avon or other drivers who use them to see what pressures are optimal.most r tires are sloppy until up to optimal pressure,but it sounds like it probably is not your tire pressure.

 

[dquarasr2]

A few other thoughts and things to consider.

This is a gross generalization, so use it as such, however, the more the grip, the more toward understeer, and conversely, the less the grip, the more toward oversteer.

That said, what was the track surface like? Cold out? Warm? Green track after just having been "cleaned" by rainfall?

And what of the Avons? Where they new? Had they been scrubbed in, heat cycled at least once? Sticker tires (brand-new) tend to be "greasy" until they've been heat cycled once across, say 24 hours.

Other than that, the only thing I can think of is that the rears were pressured a tad high, and they were crowning, but if you say the temps were even across the tire, then maybe that's not it.

This is fairly puzzling. So many reason this could be happening.

Please don't take this the wrong way, but you're not a "wheel-whipper", are you? I would think not based on the amount of experience and knowledge you seem to have. Sorry if I'm barking up the wrong tree, but sometimes if you're too aggressive with turn-in, and the fronts are actually biting, the rear sometimes might not want to cooperate. I'll assume this is not the case, though, but I thought I'd ask.

And re-reading this entire thread, it sounds an awful like my situation. After I modified my technique and pretty much gave up on doing any trailbraking, using weight transfer to the rear as I was starting to turn in, the car settled down a bunch. Before that it was always wanting to be "up on its haunches", the rear never settled, always feeling like it want to step out, and sometimes actually doing so. I had to really exaggerate completing my braking early and transfering the weight before I was happy. And as others have pointed out, I'm on 80k mile OEM shocks, which are probably toast.

Anyways, continued good luck in chasing this down, and of course, if you do hit upon a solution, please let us know!

 

[Larry Bastanza]

What are your tire temps?
NEVER too much negative with track tires.
What suspension/spring rates?
What sway bars?
Do you have hard bushings and toe links?

LarryB

 

[titaniumdave]

What are your tire temps?
NEVER too much negative with track tires.
What suspension/spring rates?
What sway bars?
Do you have hard bushings and toe links?

LarryB

I agree with Larry, Mono-balls in the rear beam and rigid toe links will help tons!!!
PM if you need a set...
More sway in the front helps too.

This is a no brainer, but you do have the TCS off??

 

[L8apex32]

What are your tire temps?
NEVER too much negative with track tires.
What suspension/spring rates?
What sway bars?
Do you have hard bushings and toe links?

LarryB

Hey, Larry.
Springs are stock, I have Dali street sway bars.
I have stock (and old) busings and toe links.

I checked my tie rod ends and found no wiggle.

 

[L8apex32]

I agree with Larry, Mono-balls in the rear beam and rigid toe links will help tons!!!
PM if you need a set...
More sway in the front helps too.

This is a no brainer, but you do have the TCS off??

I'll PM you about mono-balls and various toe links.

Since going softer (sway bar) in the rear did help, if I can't figure anything out as being broken, I'll go with stiffer sway bars (particularly in the front).

I do drive with TCS off. I experience the oversteer mostly in power-on situations as I recall.

 

[L8apex32]

Well, I'm baack and still have oversteer that I'd like to clear up.

The two main causes I can think of are a bad LSD and bad sway bar combination.

First, as far as the LSD, I checked it before my last event. Although it is below the designed specs (37 ft-lbs instead of 43-101 ft-lbs), I thought more about it. A bad LSD lets the inside tire spin (unloaded) and does not cause oversteer. Even if my LSD is weak its neither giving up grip nor causing oversteer.

My other thought was sway bars because I have changed them. I said before I have Dali street but in reading some old emails in the FAQ of mine (my initials are BSD btw), I see that I actually tried the street and race versions from Dali and kept the race ones. For what its worth, its the race ones I have now.

Since then I've been thinking, hmmm, could the Dali race bars have too much rear sway bar and be causing this oversteer? I also read that many people are switching from upgraded front/rear combos to upgraded in front only. So, I tried going to stock in back and keeping the Dali track in front.
This reduced my problem a lot. But, it is puzzling. How can increasing the front sway bar not just cause more understeer than stock? And, how can I have oversteer with a stiffer front bar???

That got me to looking and I found a link on the relative stiffness of various sway bars:
http://daliracing.com/v666-5/catalog/suspension/more_sway_race1.cfm?swaybar=race

I notice that this page shows bar stiffnesses relative to stock. What it really needs to show is stiffness in the front bar relative to the back bar for each pair. Excel is good for this. Here are some numbers:
stock: 1.29
Dali street race: 1.00
Dali street race front / stock rear: 2.59

With my current set up, I should have HUGE understeer. But, I don't.

I know my rear toe is slightly reduced and I know Acura designed rear toe in to help prevent oversteer, but I only reduced it a little.

Tell me this, in my race car, and in my high-torque Mustang in previous days, you can nail the throttle in the turns and the weight transfer to the rear causes understeer and not have any trouble with power-on oversteer. Plus, although I haven't driven an NSX in years on the track (until recently), my car could NOT have had this much oversteer before... could it???

When you are in a sweeping turn at maximum turn, can't you just squeeze on the gas and go?

(Normally I drive on track with TCS off but I left it on last event to help with this problem.)

I really have to figure this out. Now its bugging me.
Thanks for the help.

PS: A question for you if you track your car and care to help. What springs and sway bars are you using (a) and (b) can you apply throttle in mid turn and easily cause oversteer (or the TCS light to come on if you use it)?

For me, the answers are:
a) stock springs, dali front race and stock rear sway bar
b) yes

 

[titaniumdave]

Turn the TCS off.

You may find the whole issue is a combination of the weak LDS and the TSC shutting down your throttle as you accelerate out of the turn.

Stiffer springs all the around will help, and lowering the car.

As stated by myself and Larry B., rigid toe links WITH stiffer beam bushings will help reduce dynamic alignment change in the rear end too, that sounds like a portion of your issue too.

 

[stuntman]

www.skipbarber.com

 

[latzke]

As titaniumdave reaffirmed, keep TCS off.

As far as alignment, you mention your rear toe is "slightly" decreased. IMO your toe out in front and toe in in rear are more than slightly out of spec. You might try dead in the middle of the 93+ spec as a starting point (-3.5mm in front and 4mm in rear)...and don't be afraid to increase the rear if you don't mind the trade off between handling and tire wear. Actually, sans the rigid toe links I might suggest the 91-92 rear toe spec of 6mm as that will help hide the compliance.

While PonybBoy asked for tire sizes, I don't see them listed. I made the mistake once, when getting R-compound tires, of getting them too wide in the front as compared to the rear. I think I increased both by 20 millimeters, so the ratio didn't change much and shouldn't have been a big deal...but the feel certainly did change (and not in a way I appreciated). I ended up keeping the wider rears and buying another set of front tires (in stock width).

RE the LSD it sounds like you have a pre-97 differential, in which case the LSD isn't the greatest when turning. Sure, you can break both tires loose and leave marks in a straight line...but my experience is you'll spin the inside tire when weight is shifted in a turn and you provide enough power. You could increase the preset torque in the diff to R specs (change collar to thinner type-r version, add spring plate), but that can have it's own disadvantages (more preset torque means the rear will oppose turning more because the tires are more opposed to operating at different speeds) so probably not where I'd start changing things (plus opening the tranny isn't cheap).

 

[L8apex32]

Turn the TCS off.

You may find the whole issue is a combination of the weak LDS and the TSC shutting down your throttle as you accelerate out of the turn.

Stiffer springs all the around will help, and lowering the car.

As stated by myself and Larry B., rigid toe links WITH stiffer beam bushings will help reduce dynamic alignment change in the rear end too, that sounds like a portion of your issue too.

With TCS off, it spins the tires way too much on the slow turns. I had it off in my first event of the year but left it on for the more recent one.

I will look into toe links and the bushings.

 

[L8apex32]

As titaniumdave reaffirmed, keep TCS off.

As far as alignment, you mention your rear toe is "slightly" decreased. IMO your toe out in front and toe in in rear are more than slightly out of spec. You might try dead in the middle of the 93+ spec as a starting point (-3.5mm in front and 4mm in rear)...and don't be afraid to increase the rear if you don't mind the trade off between handling and tire wear. Actually, sans the rigid toe links I might suggest the 91-92 rear toe spec of 6mm as that will help hide the compliance.

While PonybBoy asked for tire sizes, I don't see them listed. I made the mistake once, when getting R-compound tires, of getting them too wide in the front as compared to the rear. I think I increased both by 20 millimeters, so the ratio didn't change much and shouldn't have been a big deal...but the feel certainly did change (and not in a way I appreciated). I ended up keeping the wider rears and buying another set of front tires (in stock width).

RE the LSD it sounds like you have a pre-97 differential, in which case the LSD isn't the greatest when turning. Sure, you can break both tires loose and leave marks in a straight line...but my experience is you'll spin the inside tire when weight is shifted in a turn and you provide enough power. You could increase the preset torque in the diff to R specs (change collar to thinner type-r version, add spring plate), but that can have it's own disadvantages (more preset torque means the rear will oppose turning more because the tires are more opposed to operating at different speeds) so probably not where I'd start changing things (plus opening the tranny isn't cheap).

As far as alignment, my alignment sheet from the dealer says the rear toe specification is 1.5mm to 2.5mm. I'm at 1.5 and 1.6 which is in range.

Are you saying that the rear toe spec for a 1992 NSX is 6mm? On each side or total?

I'm a 1992 so I have a pre-1992 LSD I think. Although my tranny was replaced about then by Acura. I don't spin the rear tire... I spin both, in the turns.

I use the stock tires sizes (205 front, 225 rear.) I agree, changing tire sizes could cause big issues like this.

I will look into rear toe links. I assume Dali or SOS has them?

Thanks for your ideas.

 

[latzke]

With TCS off, it spins the tires way too much on the slow turns.

Seeing this comment I'm inclined to think the oversteer problem might not be related to some issue with the car's setup...but to your modulation of the throttle (i.e. too much too soon / too much for the situation).

Are you saying that the rear toe spec for a 1992 NSX is 6mm?

Yes, and yes, that is a lot of toe. It was changed to 4mm in 1993 as complaints (and law suits over) tire wear apparently lead Honda to the conclusion that a different compromise between handing and tire wear would maximize owner satisfaction (and/or minimize class-action law suits). There is nothing different between your 1992 and the 1993 that would warrant different alignment settings...picking between these (and others outside these specs) are matters of preference - compomises between various goals. If you want handling...the 91-92 are decent specs (developed with Senna's input) and the 93+ are a decent compromise.

More alignment info here: http://www.nsxprime.com/FAQ/TireWheel/alignment.htm

That does list the toe setting as "total toe" so I guess it is additive between sides...in which case it's not as bad as I thought. Your 3.1mm would be at the very low end of the 93+ rear spec (outside the low end of the 91-92 spec by 1.9mm). -2.9mm is within the -3.5mm (+/-1mm) for the front.