oversteering

[freelance201]

hi guys,
here are the suspension setup in my car:
front camber: -1.7 degrees
rear camber: -2.5 degrees
front toe: 0 degrees
rear toe: i think its around -.5 degrees
Tein RA: full stiff front, full soft rear with 10/12 kg spring rates
Dali Race Swaybar: full stiff front, full soft rear
SOS strut bar, and NSX-R front chassis
15/16 stock wheels with Kuhmo Ecsta MX
tire pressure: 35 front cold, 32 rear cold
Engine: completely stock


with this setup, I would think my NSX would understeer rather than oversteer.
I was tracking at Pacific Raceway last weekend, and here's few problems I encountered during the day.

1st problem:
the car moves left and right under hard braking (about 140mph-60mph braking).
Turns out the problem is the front toe setting. I had the front toe set at about .5 degree positive which contributed to the problem.
Set the toe to 0 degree and car brakes straight and balanced.

Here comes the second problem that bugs me the most and can't see to find a good solution for it.
the rear end of my car get loose very easily coming out of the corner, the whole car feels just like my friend's 240sx drift car.
Quite uncommon for a MR car.
As a result, I lose lots of confidence coming out of corners. The situation gets worth on tight slow turns, and of course, hairpins.
I already have the Tein RA set up full stiff in front and full soft rear, and dali race sway bar full stiff front full soft rear........the problem got better a bit.....but still exist.

I've read lots of stuff about the stiffer springs on the rear with the Tein RA setup.....and I think I'm gonna order 10kg springs for the rear to see if it makes a big difference.

But here's the question I want to ask you guys.
I'm thinking about replacing the rear Dali race swaybar with the stock ones I took off, but keep the Dali race swaybar in the front.
Do you guys think this is a good compensation for the oversteering?
or is it best that I just replace the front and rear back to stock ones?

thanks lot

 

[ncdogdoc]

Double check your rear toe, make sure that the number you gave is correct. Should be toe in the rear and toe out in the front.

The easiest thing to do is swap the rear bar for the stock bar. I would not change anything but that before your next track day. Then if you are still uncomfortable, try different spring rates.

tires? Not familiar with these. The first event I did on SO3's the rear was owl snot slippery. Once I wore the outside rubber and release compound off, much better. Were they new?

I have never run lower pressures in the rear, so I cannot assume that it would do what you want. I usually run 3-4 pounds lower in the front, even on street tires. HTH.

 

[freelance201]

the tires were brand new.
I did notice the slipperiness of the new tires, but they seem to be fine once they warmed up.
I use to run Toyo T1-S 17/18 with everything I mentioned except the roll bars, and it handled really well. I would say from neutral to mild understeer. Had to change to 15/16 setting due to high budget.
Sorry about the tire pressure thing, I ment 32 for front and 35 rear.
I think the Dali race bars definitely made my car a little tail happy. I would try your advice and swap the rear bar with the stock one and see how it goes on my next track event.
thanks

 

[kenjiMR]

change your TEIN spring rate to 10/10 or 10/8.

 

[freelance201]

alrite...i've decided

i'm gonna swap the rear bar to stock one, and change rear spring rates to 10 kg.....just to make sure there will be no surprises on next event^_^

 

[DangerMoney]

Sounds like this made all the difference:

I use to run Toyo T1-S 17/18 with everything I mentioned except the roll bars, and it handled really well. I would say from neutral to mild understeer. Had to change to 15/16 setting due to high budget.

What were the sizes of the 17/18s and the 15/16's. I'm guessing the width *delta* between 18 rear and 17 front was singnificantly greater than the width *delta* between the 16 rear and the 15 front.

 

[kenjiMR]

I am running almost exactly same set up as you. 10kg/10kg but using 17/18 wheels and Bridgestone S03s.

My alignment:
Front
Camber: 0 degree
Caster: 8.5 degree
Toe: 0.05 (out)

Rear: -1 degree
Toe: -0.03 (in)

Play around with the damper setting. 2low2speed may be able to offer you better damper setting advice.

I was running 4-8 click from full hard last time. FYI, I also have large rear wing which makes the handling characterstics change at speed.

 

[Tank]

I think you're on the right track. I would say increase the toe-in in the rear but if you're already at .50 degrees that's more than enough and you're problably eating tires like mad at this setting. The only thing I would add is increase you rear tire pressures.

I just went from the T1-Ss to the Escta MXs and I find them to be quite comparable. Although I would run T1-Ss in the rain over any other tire.

t

 

[polar]

hey freelance

I just took my car to pacific raceway again today, and I was running my cousin's kumho MX today. at the last track event I was running the stock yoko's, and I can tell you that, no matter how I play around with the pressure on the MX, it just never felt as good as the yoko's.
maybe these MXs are still pretty new, but I've encounter same problem as you do, 135 to 60mph the steering wheel really moves left and right, (I think it's the track surface rather than the tires, athought I've experienced longer braking distance/less stable with the MX) , and I had a hard time getting traction at turn 5B and 6 today, where I had no problem all day last week.
Last week I really had fun when I was running the yoko's and today I had to fight with understeer/oversteer all day long.

 

[freelance201]

yeah, I'm running 205/50/15 and 225/50/16 for the stock tires, but I was running 215/40/17 front and 265/35/18 on the rear with the Toyo T1-S.
That's quite a big of a change right there.
I don't want to jump into conclusions that Kuhmo MX are inferior than Toyo T1-S b/c I did not have a chance to run MX on 17/18 settings.
I did ran Bridgestone SO2s with 17/18 setting, but that's without any suspension upgrades except H&R lowering springs on stock shocks. The car seems to have quite a big of body roll and nose dive under hard braking....but no matter what you do, the rear end just won't brake it lose.....it understeers quite a lot.

Hey Polar,
I'm glad you went to Pacific Raceway again, fun track isn't it?
I did have the same problem as you did at PR during the hard braking zone going into turn 2....my car goes from left to right and right to left....which is quite scary consider its around 140mph.
Collan from Speedware told me it was the front toe setting, and corrected the problem by making the front toe close to 0 degree, and the problem was solved.
and True that I had to fight getting my car to stick on turn 5B and 6 too and I did not have the problem with the T1-S.
However, Kuhmo MX will last hella of a lot longer than the T1-S.
My T1-S got mangled after just one event with dual drivers. The Kuhmo MX is still pretty good after two days of hard driving with dual drivers. Although I do not know what the tread wear for those two tires but probably in low 200s.

I might consider trying Yoko AO22 since they were designed primarily for the NSX and I've heard a lot of good things about it......that's only if I can find it since Yoko don't produce them anymore.

 

[freelance201]

hey Kenji,
does the rear wing only works during high speed corners, or does it work pretty well on slow sharp turns (around 45 to 60 mph turns)? and which rear wing do you think works the best?
thanks

 

[Andrie Hartanto]

I am running almost exactly same set up as you. 10kg/10kg but using 17/18 wheels and Bridgestone S03s.

My alignment:
Front
Camber: 0 degree
Caster: 8.5 degree
Toe: 0.05 (out)

Rear: -1 degree
Toe: -0.03 (in)

Play around with the damper setting. 2low2speed may be able to offer you better damper setting advice.

I was running 4-8 click from full hard last time. FYI, I also have large rear wing which makes the handling characterstics change at speed.

check your number again. Totally out of whack. There is no way you can run only -1 degree in the rear with suspension that low. Same with the front.

 

[freelance201]

i just noticed that my caster is around 9.8 degrees.
I wonder if this has anything to do with the handling problem i'm having b/c my caster seems a bit high compare to others.

 

[kenjiMR]

check your number again. Totally out of whack. There is no way you can run only -1 degree in the rear with suspension that low. Same with the front.

Andrie is right. After looking at those notes, it is from my old suspension setup. Please ignore.

 

[polar]

I might consider trying Yoko AO22 since they were designed primarily for the NSX and I've heard a lot of good things about it......that's only if I can find it since Yoko don't produce them anymore.

I think tire rack still sells them, but they're not cheap, even at wholesale price, they're nearly 200 dollar each for the rear, my friend can get good deal on them, let me know if you wanna get them. Another friend of mine who's gonna host a lapping day at PR on July 8th , and his shop is dealer of toyo tires, I think i'm gonna order a set of Toyo RA1 from them. If you want the pricing of these tires, I can ask them for you, I know they're doing a group buy right now.
Are you still planning to go to the one this sunday at PIR? I'm still thinking about it, since it is such a good deal, if I'm going I'll head down on saturday and stay over for a night, let me know if you're going so maybe we can carpool down there.
did you ever got my PM?

 

[freelance201]

hi Polar,
sorry I normally don't check PMs, but you can always reach me at my email at [email protected]
I don't think I can go this sunday, b/c I'm still waiting for my brake rotors and brake pads..which should come in about a week.
My front rotors are cracked pretty pretty bad to the point where driving on street is dangerous.....lots of pulsation.
Are you going to the lapping day at PIR that you mentioned?
I'm very intersted in that one. it would be great if we can all go down there together.

I'm not looking to buy tires right now, I'm gonna destroy those MX before I get another set of tire.

 

[titaniumdave]

I Just put a set of Kumho MX tires on today. First impression was they are sloppy feeling in the rear, checked the tire pressure and the shop had set all the tires at 35 PSI. I put the rears up to 39 and dropped the fronts to 33 and I think that should help the issue. I am going to get some high speed driving in this weekend and I am looking forward to seeing how these feel.

I won't get a chance to track them till next month, but I will report my impressions on Portland IR.

 

[Hrant]

Please, be safe and avoid high speed driving on new tires for at least 300-500 miles. It takes that long for them to settle and lose all that oil residue built in the tires. And even then, test it before assuming they are ready. You have a CTSC so I would be extra cautious!

The sloppy feeling may be in part due to the tire pressure but perhaps equally due to the fact that they are still not broken in.

 

[titaniumdave]

Hrant,
Thanks for the warning. I get to start with a good bit of freeway driving which should be perfect for scubbing the release compound. As with any change I make, I test in little steps, and never more than 7 tenths on the open road. Save the real testing for the track!

 

[NSXDreamer2]

my experience is that I couldn't feel the difference in the Street driving, I actually went and drive a small stretch of winding road and I can feel there's barely difference on grip... (compare to my wider 17/17 set up, same tires though).

I will jump on the band wagon stating that the Kumho is not as good as the Stock Yokohama. I guess it's that the tread design is not as important as the tire warmed up at the track... the internal design and the tire compound became much more important...

Both me and polar didn't like the Kumho MX when compared to stock Yokohama (even though I liked the mx on my 17's, but I was running less aggressive last time and the tire already had at least 7000 miles on 'em) I'm trying to see if that was because of the tire tread being too tall, so I will stick with the Kumho for a while until I totally wear them out.

 

[freelance201]

yea, I agree with you on this one NSXDreamer2.
I think how good the tire is depends on the compound that its made of and its tread wear rating......that is when the track is dry.
As for the tread design itself, I think most of them are designed to direct water out on rainy days......which makes tread design more important than what its made of.....but only in wet conditions.
correct me if i'm wrong

 

[NSXDreamer2]

you are not wrong...

but I just have to add that the tread design also contributing the noise level and ride comfort... which I guess none of us Track rat wannabe cares

 

[freelance201]

Exactly!!!!

 

[apapada]

which makes tread design more important than what its made of.....but only in wet conditions.
correct me if i'm wrong

I'm not going to say you are wrong, just that your statement is incorrect.
Although truth is that tread design is important for wet conditions, it is incorrect to say that tread design becomes more important than "what it's made of". Reason being is that the tread design is there to help get rid of the water so that "what it's made of" is able to meet the road surface and generate grip. The "what's is made of" is always the most important as that's what generates the grip in a tire, not the tread design. I have tested slick tires in wet conditions and one is incorrect to think that they do not generate grip because they have no tread design. They generate as much grip overall as a tire with "tread design" but they are extremely binary with regards to grip, they are not forgiving and very difficult to drive on. My lap times were however similar (actually a tiny bit faster with the slicks)

 

[apapada]

Re: you are not wrong...

but I just have to add that the tread design also contributing the noise level and ride comfort

not ride comfort (unless you do include the noise in " ride comfort" which it seems to me you didn't)