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Advise on suspension tweaks to settle rear

Joined
20 October 2015
Messages
145
I've been autoxing my '95 for a year now. Done a bunch of events, well over 100 runs at this point. I'm looking to really dial down some oversteer and get some more confidence in the car to drive it at its limit without getting the rear swinging out so often.

Tires:
225/45r17 front- 255/40r17 rear Bridgestone re71r's.

Current alignment is:
Front Camber -2.1* (maxed with factory adjustment)
Front Caster +9.0/9.3* (maxed out positive)
Front Total Toe at 0

Rear Camber -2.5*
Rear Total Toe 0.15*

Suspension is:
OTS Koni Sports
Ground Control coilovers- 650# front 550# rear
I have Dali 1" front bar on. I've ran 1" Dali rear bar on full soft. I have the stock rear bar and also have a 19mm rear bar(yet to test).

On stock bars, the car pushed a good amount. Tested stock front bar with 1" rear bar on full stiff, lots of oversteer, too much. Threw on 1" front bar, much better, but still a lot of oversteer. Still ran with both 1" front/rear bars and near full stiff and near full soft on shocks for a while, never feeling confident in the car. Comical in the rain. Then ran 1" front on full stiff and stock rear bar. A good bit better, but still plenty of snappy oversteer esp on quick transitions. Still not as confident as I'd like to be. Today I tried out 1" front on full stiff with NO rear bar. Noticeable more push on sweepers, still able to throttle oversteer on exit, little more confident but feels a bit wallowy in the rear. Have not yet tried the 19mm rear bar.

I think ideally I'd like to run the stock or 19mm bar. But, I'll need to tweak elsewhere so it isn't so snappy. If I go more toe-in(positive) on the rear, will that help reduce oversteer?
 
Have you tried just lowering pressure on the rear tire? For me I feel having about .5 to 1 psi less in the rear, when the tires are hot, helps with having a bit more rear traction. With the tires pressure equal all around the rear end feels greasier.

I'm usually at 32-33psi in the front and 31.5-32.5 psi in the rear.
 
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I run around 28f and 26r for tires. 26 is the lowest in the rear I could go before rolling over the sidewalls.
 
try running slight - front toe...increase rear toe abit...keep front shocks stiff ,rear full soft, keep rear oem bar...try 275 rear tires....consider rear non compliance bushing/toe links...be less aggressive with throttle/brakes on transitions....use an s2000:biggrin:
 
I hate to throw more parts at your car but i'll just speak from experience. I'm not trying to hype up any particular parts per say but since you're certainly more experienced at AutoX than I am I'm assuming you've addressed all the low hanging fruit like alignment and tire pressure.

I've been able to dial out a lot of the "snap" oversteer and converted it into a slow roll in my car. The biggest culprit in aiding that was the JRZ dampers. They unload weight so much slower, have a ton of droop travel, and are much more predictable it's become such a joy to drive and to Hoon around in. I'm happy to post my suspension settings if you care but mine vs. yours would be just tweaks. It's become so much fun to drive that the heavy steering feel has really become quite apparent. It takes a lot of effort to countersteer sometimes OR I just need to grow bigger guns.

BTW, A lot of folks on here like to remove the rear sway bar. I'm actually considering more rear bar to induce even more oversteer to add to the fun factor but since adding the OS Giken LSD the rear of the car has become so much planted in accel and decel. It's a hoot.
 
oh and keep your roof on.....
 
Id try your other rear bars first even on full soft that 1" seems like A LOT of bar.
[MENTION=20915]RYU[/MENTION] ive got big rear sway bars in storage if you wanna try them.
 
try running slight - front toe...increase rear toe abit...keep front shocks stiff ,rear full soft, keep rear oem bar...try 275 rear tires....consider rear non compliance bushing/toe links...be less aggressive with throttle/brakes on transitions....use an s2000:biggrin:

I've been getting near perfect tire wear with the alignment I currently have. But, after some more research and info, it seems like I could use some more rear toe-in to help get the car more towards understeer. I may double the rear total toe-in and see where that gets me. For now I'll be sticking with the 255 rear tires as that's the widest a Bridgestone re71r comes in for 17" wheel. Believe me, I have to tip-toe the car through certain transitions. On corner exit I also feel like I just can't be as aggressive and I'm waiting where I feel like I should be on throttle. Just can't or else the rear end will slide out.

I hate to throw more parts at your car but i'll just speak from experience. I'm not trying to hype up any particular parts per say but since you're certainly more experienced at AutoX than I am I'm assuming you've addressed all the low hanging fruit like alignment and tire pressure.

I've been able to dial out a lot of the "snap" oversteer and converted it into a slow roll in my car. The biggest culprit in aiding that was the JRZ dampers. They unload weight so much slower, have a ton of droop travel, and are much more predictable it's become such a joy to drive and to Hoon around in. I'm happy to post my suspension settings if you care but mine vs. yours would be just tweaks. It's become so much fun to drive that the heavy steering feel has really become quite apparent. It takes a lot of effort to countersteer sometimes OR I just need to grow bigger guns.

BTW, A lot of folks on here like to remove the rear sway bar. I'm actually considering more rear bar to induce even more oversteer to add to the fun factor but since adding the OS Giken LSD the rear of the car has become so much planted in accel and decel. It's a hoot.

Certainly the Koni's are not the best option, but they work well and provide a good ride. I'd prefer to stick with them for a while. I think running without a rear bar, particularly for a track day, may be better. I don't mind losing a bit more weight off the back and for a track situation, I'd prefer controllable understeer vs snap oversteer in a car like this. I can get away with a loose car for autox.. Going for more rear toe-in to see if that will induce a bit more understeer, and then if it's too much, I can go to stock or larger rear bar to tune it better.

oh and keep your roof on.....

Roof stays for events lol

Id try your other rear bars first even on full soft that 1" seems like A LOT of bar.
@RYU ive got big rear sway bars in storage if you wanna try them.

The 1" proved to be a lot of bar. Figure if I do use a bar it'll be stock or the 19mm. I have wondering if I'd be able to make a smaller than stock(17mm) rear bar. The 19mm rear bar I have is such a stupid simple design, if I knew it was built the way it is, I would have just made my own. I just don't know how small of a bar I could safely get away with. Will need to research that a bit.
 
You're unfortunately having to work-around a less than ideal tire width ratio there, although I've run 255 rears on my car (with 215fronts) and had good regional-level AX success you probably would want a 265-275 to balance the rear with a 225 up front. I gather the Re71R is the hotness this year, and none of the others are competitive (RS3, etc)?

I think you'd be on the right track, as others have suggested, dialing in a smidge of toe-in at the rear which should gain you some stability during higher-speed transitions. Obviously you don't want to go too far with anything since you still want the car to be able to rotate on/off throttle when you want it to, but just do it predictably. That with a smaller bar and maybe slowing down the rear dampers (assuming adjustable?) should get you somewhere.

I don't see any issues with even the basic single-adjustable koni setup. I managed to dial the snap out of an MR2 turbo in (old) BS trim with just a big front bar and tire-pressure/damping changes.

I suppose that brings me to my other solution: go buy an MR2 Turbo, run that bastard in stock/street tire class, then come back to the NSX. After that, anything that happens at the rear of the NSX will seem like slow motion, lol :)
 
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1" on the rear is extremely aggressive for most applications.

Your tire pressures also seem a bit on the low side. Have you tried running low-mid 30 psi?

Measuring from the ground to the front and rear jack points, what is your ride height front and rear?
 
Figured I'd update for answers. I ended up changing the rear toe-in. I doubled it from 0.15* to 0.30*. I ran 2 back to back autox's afterwards, 12 runs total on large and technical courses. First 4 runs I ran with no rear swaybar. I immediately noticed more understeer. Great! Actually what I wanted. So I knew I was on the right track. For the next 4 runs, I put on my 19mm rear swaybar on the middle setting. Started to feel good. With some minor shock tweaks, I was able to get the car right where I wanted. Just enough oversteer to rotate comfortably and have some confidence in the car.

I just got home from NSXPO and I did 3 sessions on Sebring. I left everything exactly the same as I ran for my autox runs. It felt really really good on the track. I was worried the higher speed corner entries/exits would upset the car and get me loose, but never once did I feel uneasy. I felt very comfortable on track(big thanks to iRacing!), could toss the car around and felt amazing. Sebring is known for being rough, and it was bumpy, but surprisingly the Koni/GC 650f/550r held up really well. Little rough, but no problems.

You're unfortunately having to work-around a less than ideal tire width ratio there, although I've run 255 rears on my car (with 215fronts) and had good regional-level AX success you probably would want a 265-275 to balance the rear with a 225 up front. I gather the Re71R is the hotness this year, and none of the others are competitive (RS3, etc)?

I think you'd be on the right track, as others have suggested, dialing in a smidge of toe-in at the rear which should gain you some stability during higher-speed transitions. Obviously you don't want to go too far with anything since you still want the car to be able to rotate on/off throttle when you want it to, but just do it predictably. That with a smaller bar and maybe slowing down the rear dampers (assuming adjustable?) should get you somewhere.

I don't see any issues with even the basic single-adjustable koni setup. I managed to dial the snap out of an MR2 turbo in (old) BS trim with just a big front bar and tire-pressure/damping changes.

I suppose that brings me to my other solution: go buy an MR2 Turbo, run that bastard in stock/street tire class, then come back to the NSX. After that, anything that happens at the rear of the NSX will seem like slow motion, lol :)

I don't think I would gain much going to a 265, maybe a 275, but I am also limited on options since I prefer to run 17" wheels all around. Bridgestone RE71'rs completely blew away everything else. Some people still like the BFG Rival S for certain cars/modifications, but the vast majority are running 71r's. Everything else is old news.

1" on the rear is extremely aggressive for most applications.

Your tire pressures also seem a bit on the low side. Have you tried running low-mid 30 psi?

Measuring from the ground to the front and rear jack points, what is your ride height front and rear?

Yup, I more than likely won't run a 1" bar again. With everything else how it is, I think either stock rear bar or my current 19mm rear bar is just fine. Tire pressures are good. The RE71'rs tend to run very low on most cars/setups. at 27psi in the front, I am getting perfect tire wear. It is a bit high up front as far as roll over is concerned, but if I go lower than I will get more oversteer(which I was trying to dial out). At 26psi in the rear, I have again perfect tire wear and perfect roll over on the edges of the tire. In my '91 Civic Si I run RE71'rs at around 25f and 28r. Most people I know with these tires run them under 30psi unless maybe if they're in a stock class in a certain car.

I can't remember the height via jack points. All I know is the ride height measurement is a bit funky since I have an oversized front tire. The suspension itself sits pretty low, but the tall tire makes the body still sit relatively higher. Compared to the stock cars I saw at NSXPO, my car is just slightly lower in the front, but obviously have no tire/fender gap.
 
Glad to hear the car is handling better to your liking. It would be very beneficial to know your ride heights. Take a tape measure and measure from the ground to the bottom of the front and rear jack tabs under the frame rail.

You should really invest and learn how to use a PROBE-Type tire Pyrometer. That's the best way to dial in your camber, toe, swaybar, and spring rates, since it tells you how the tire is working and where it's generating grip and heat far better than looking at tread wear and roll over.
 
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