understeering more than stock?

[Double-J]

hi guys,

i bought my NSX a few months ago from Mike (supergreen125) and was just wondering about the car's handling characteristics. the car was already modded, and as such i cannot compare it to a stock NSX since i haven't driven a stock one in a 'spirited' fashion. i'm hoping you guys can provided some input in this regard (chime in any time as well, Mike).

i understand that from the factory the NSX is tuned for slight understeer. i feel like my car is noticeably understeering, but i can't really tell since i've never driven a stock one. does the setup (described below) promote even more understeer than stock or is it just me not being used to the car (i.e. the steering ratio of the car warrants more steering input than other cars)? it just seems to me that the front end tends to push more under balanced-throttle when driving more agressively during sweeping turns and freeway interchanges/onramps etc., as compared to my daily driver, a slightly-modded Prelude Type SH. i feel more confident driving the Prelude aggressively than the NSX.

here's the suspension setup info from the best of my knowledge:
- eibach springs
- front and rear dali track sway bars (set at the 'default' holes, neutral?)
- NSX Type-R front chassis braces (both bars)
- Kumho Ecsta tires (215/40/17 front, 265/35/18 rear)
- front alignment within factory specs
- rear alignment has -0.2 degrees more camber than factory spec
- Okuyama/Carbing rear strut tower bar

so would the above setup promote more understeer than stock or am i just crazy?

and also a related question, does a car set up for understeer imply that the effects of lift-off oversteer are diminished? i.e. can i steer the car with throttle (more to widen turn, ease off throttle to tighten turn) without compromising rear-end grip that would result into a spin? since this is my first NSX i admit i've been rather paranoid reading various forum posts about spins from lifting the throttle, so when i take turns, believe me my lead foot stays planted. am i just a wee bit too paranoid?

 

[nsxtasy]

I don't know about understeer. However, if the "Kumho Ecsta" tires you are referring to are the Kumho Ecsta Supra 712 (Kumho sells many tires under the Ecsta name), then this may be part of your problem. The Ecsta Supra 712 is a budget tire, whose performance is not on a par with the best tires around, such as the Bridgestone Potenza S-03 to cite one example. The fact that the tires are not all that grippy may turn a slight tendency to understeer into a major one.

You may want to check out this topic, in which another owner using the Kumho Ecsta Supra 712 tires also complains about handling problems.

I would suggest replacing the tires with some really good ones (such as the Bridgestone SO-3 or the Goodyear Eagle F1 GS-D3) as a first step, before doing anything else (partly because it sounds like you've got most of the other possibilities covered). One thing you might do, if you do replace the tires, is consider going with 255/35-18 in the rear instead of 265/35-18, just to get closer to the stock front-to-rear "stagger" and reduce the chances that that is causing any additional understeer.

Oh, and one other thing you didn't mention is checking and playing with the tire pressures. The Acura-recommended 33F/40R is a good starting point, and even after adjusting to your preference you will probably remain somewhere around 32-34 front and 36-40 rear.

The NSX should NOT understeer less than a Prelude...

 

[ncdogdoc]

I agree with Ken regarding the tires.

I would suspect that the NSX has a slower steering rack than the Prelude SH, but as I have never driven the Prelude, I cannot comment directly. The NSX rack feels slow at most street speeds to me. I think this is because at speed a quick rack could induce snap oversteer. (Do not ask me why I think this)

You can throttle steer the car very easily. But remember, use baby steps. Being mid-engined, the NSX is a quick change artist, especially with drop throttle.

You can always try tightening the rear bar or loosening the front bar to see if that does not make the rear more lively.

 

[Yellow Rose]

You can always try tightening the rear bar or loosening the front bar to see if that does not make the rear more lively.

Isn't this backwards? I thought that the end of the car which is "stiffer" will be the dominant, in terms of over-understeer. If that is the case, making the rear bar stiffer will further amplify the understeer, no? To further illustrate this point, the RealTime #42 NSX has no rear bar at all.

Regarding the 215 front tires, in my humble opinion they are too narrow. The rear tires are "overpowering" the fronts, resulting in the push.

 

[ScienceofSpeed]

Everything described on your mod list will keep the car fairly neutral with the exception of the Dali Racing track sway bars. Although these stabalizer bars are advertised as the "best since they are the thickest", this is untrue. The stabalizer bars act to limit load transfer from corner to corner using torsional force. This is great for driver confidence as body roll and weight transfer is decreased. However, if the torsional force is too great, the benefits of an independent suspension are eliminated, limiting turn-in response, inside tire traction, and stability on rough surfaces.

While the very thick stabalizer bars may be ideal for a race car running with wide sticky tires and on a very smooth track surface, it's not the same for a street car with street tires.

I'd recommend at least trying the factory stabalizer bars, and seeing what the difference is.

Cheers,
-- Chris

 

[sjs]

Isn't this backwards? I thought that the end of the car which is "stiffer" will be the dominant, in terms of over-understeer. If that is the case, making the rear bar stiffer will further amplify the understeer, no? To further illustrate this point, the RealTime #42 NSX has no rear bar at all.

It may seem counter intuitive but as a rule of thumb, stiffer front = understeer and stiffer rear = oversteer. As for #42, they may have balanced via springs rather than bars.

 

[sjs]

I agree with Andy and Ken that the rear tires are likely adding to the problem, and with Chris that the race bars are too much for a car not capable of pulling the G's to bend them. Start by moving the front bar to full soft (longest effective arms). If that's too much, soften the rears, not enough, switch back to stock if you have them. If things are back to normal but you want less lean then get some mild but adjustable street/track bars.

 

[W]

What wheels are you using, oem? I've noticed a lot of NSX's with smaller offsets in the rear wheels. That could contribute to the understeer feeling. You may want to check your alignment.

 

[NSX/MR2]

I don't know about understeer. However, if the "Kumho Ecsta" tires you are referring to are the Kumho Ecsta Supra 712 (Kumho sells many tires under the Ecsta name), then this may be part of your problem. The Ecsta Supra 712 is a budget tire, whose performance is not on a par with the best tires around, such as the Bridgestone Potenza S-03 to cite one example. The fact that the tires are not all that grippy may turn a slight tendency to understeer into a major one.

You may want to check out this topic, in which another owner using the Kumho Ecsta Supra 712 tires also complains about handling problems.

I would suggest replacing the tires with some really good ones (such as the Bridgestone SO-3 or the Goodyear Eagle F1 GS-D3) as a first step, before doing anything else (partly because it sounds like you've got most of the other possibilities covered). One thing you might do, if you do replace the tires, is consider going with 255/35-18 in the rear instead of 265/35-18, just to get closer to the stock front-to-rear "stagger" and reduce the chances that that is causing any additional understeer.

Oh, and one other thing you didn't mention is checking and playing with the tire pressures. The Acura-recommended 33F/40R is a good starting point, and even after adjusting to your preference you will probably remain somewhere around 32-34 front and 36-40 rear.

The NSX should NOT understeer less than a Prelude...

So better tires do increase grippiness?

 

[nsxtasy]

So better tires do increase grippiness?

Yes... they increase grip. But I'm not sure that grippiness is a word.

 

[sjs]

So better tires do increase grippiness?

Needless to say, it depends on your definition on "better". If to you it means longer-lasting, or run-flat, low noise, comfort, or cool looking then probably not. But of course "better' could also be about how they respond at the limit, not just the maximum lateral G's they produce. Here I generally mean best overall dry performance as it might translate to lap times, though some would include wet grip in the equation.

 

[Double-J]

thanks guys, i appreciate the help. i'll first try to do as chris and sjs suggest, by adjusting the swaybars first since this would be the most economical option.

i suspect the tires have something to do with it as well, so when i need new tires i'll ditch the Kumhos (yes ken, they are the Supra 712) for grippier tires and see what effect that will have.

fyi my wheels are volk gt-p 17x8 front and 18x10 rear. the rears have a big lip on them, so i assume the offset is pretty low, hence increasing the rear track width. what effect does changing the front and rear track width have on over/understeer?

 

[W]

I think your aftermarket wheels are the source of your added understeer characteristics. If you ever get a chance, try out a set of oem 16/17 wheels. Maybe someone will lend you a set at a track day.

Edit: Increasing the rear track width will increase understeer. I went from aftermarket 16/17's (wider rear track width to fill the wheel wells) back to oem. The difference is night and day. The car is now very light on its feet. I suspect that your wide front wheels make it more difficult to steer, thus requiring more turn in effort.

 

[NSXDreamer2]

By the way, I'm using Kumho's MX tires... Even though it's not as good as the S03, it's half the price of any comparable "Max Performance" tires on the market.

So far I had more than 5000 miles on my 91, even though I haven't tracked the car, it does see some aggresive drivings... on both wet and dry weather, also cold weather like 30's...

It's worth a try on them.

 

[polar]

was searching topic regarding dali swaybar and found this topic,
Just wanna share my experience.

I've got the car since november and it came with 17/18 BBS LM with Bridgestone S03 225/255 tires, otherwise the car is bone stock. with the aftermarket wheels setup, I'm experiencing more understeer than either stock wheels w/stock yoko tires or stock wheels with Kumho MX tires. both on street and track.
So I agree with "W" that your understeering issue could be caused by your aftermarket wheels.

 

[THonda]

was searching topic regarding dali swaybar and found this topic,
Just wanna share my experience.

I've got the car since november and it came with 17/18 BBS LM with Bridgestone S03 225/255 tires, otherwise the car is bone stock. with the aftermarket wheels setup, I'm experiencing more understeer than either stock wheels w/stock yoko tires or stock wheels with Kumho MX tires. both on street and track.
So I agree with "W" that your understeering issue could be caused by your aftermarket wheels.

totally off topic, but do you have more pictures of your car? thanks

 

[polar]

totally off topic, but do you have more pictures of your car? thanks

http://www.nsxprime.com/photopost/showgallery.php?cat=500&ppuser=8390

Notice that you were asking for wheels advise the other day, The BBS LM is a classy piece, and the look never gets old, but the design of it limited the Big Brake kit selection.

 

[nsx1164]

F/R width ratio influences grip ratio ?

Regarding the 215 front tires, in my humble opinion they are too narrow. The rear tires are "overpowering" the fronts, resulting in the push.

I think its your front/rear (F/R) width ratio (215 F vs 265 R) and the grip differential F/R that causes increased oversteer. At least compared to the OE spec tires.

FWIW, I ran two back-to-back events at my local "handling" track in SW Michigan a few seasons ago. First one with 215F/275R (Toyo T1-S Proxes) ; second one with 235F/275R (Yoko AVS Sport), with similar max-perf street tires in both events. In the WET, the 215/275 had noticeably more push than the 235/275.

 

[W]

http://www.nsxprime.com/photopost/showgallery.php?cat=500&ppuser=8390

Notice that you were asking for wheels advise the other day, The BBS LM is a classy piece, and the look never gets old, but the design of it limited the Big Brake kit selection.

I agree, your wheels are very classy.

 

[NSXDreamer2]

http://www.nsxprime.com/photopost/showgallery.php?cat=500&ppuser=8390

Notice that you were asking for wheels advise the other day, The BBS LM is a classy piece, and the look never gets old, but the design of it limited the Big Brake kit selection.

yeah, the wheel is so classy that it actually blind polar and forced him to buy the car even though he knew for sure the car had mis-matched paint on doors and fenders...

 

[polar]

yeah, the wheel is so classy that it actually blind polar and forced him to buy the car even though he knew for sure the car had mis-matched paint on doors and fenders...

LM ownz you!!!!!!!!!

 

[titaniumdave]

(Regarding the 215 front tires, in my humble opinion they are too narrow. The rear tires are "overpowering" the fronts, resulting in the push.)

I found simular results by going from a 265/40-17 to a 255/40-17 on the rear of my car. I feel the balance is improved and the car seems friendlier when cornering hard, especially when pushing hard enough to get the car to drift. I can't clear bigger tires in the front, so I went smaller in the back.

I am running the Kumho MX tires and am reasonably impressed, I look forward to getting them on the track the end of this month. I would say getting grippier tires on the car makes more difference than anything else you can do.

 

[ballistic]

Here are some other ways to get the car more balanced / or less understeer
1 Decrease front camber. cheapest and best response go to -.3 to -.5 untill you find the balance.
2 Increase rear camber. You said you had -.2 rear put it back to stock.
The more neg camber you put in both ends, the more grip you will pick up in cornering and it will be quite a noticable gain. The only downside of this is more wear on the insides of the tire. If you go to extremes the car may get darty under braking and have slighty less braking ability do the fact that less tire is on the road in a straight line.

 

[SexyRed]

Do you want the nsx to be a little understeer?

My setup:
koni eibach combo. Koni set in middle setting.
Front Dali Street/Track sway bar. Rear oem sway bar.
Front tires 215/40/17 Dunlop Sp 9000. Rear 285/35/18 Bridge SO3.
What do you recommend to do with front sway bar to get balance?

Do I need to add the rear Dali street/track bar?

TIA.

Danny

 

[titaniumdave]

Balance?

SexyRed,
Replace your front Dunlops with the SO-3's like you have on the rear. Getting tires with the same grip will do more for the balance of the car, then you can start to sort out the sway bars and shock settings.