Nitron S/A installed and aligned, oversteer help please...

[OTB]

If any of you can chime in on diagnosing my oversteer problem, I would greatly appreciate it. (this is long, but I tried to include all relevant info)

I recently installed the Nitron single adjustable (525/650 spring rates) setup on my '05 Elise and had it aligned. At my first track day with the Nitrons, I have a really nervous oversteer at the apex and after apex. Turn in feels good, apex and after is way twitchy, and I drifted more times today than I have in the past year. The good news is that the annoying body roll is fixed!

The car is a '05 Elise stock horsepower with Titan QR steering rack, 225/50R15 and 245/40R17 BFG R1 rubber.

I had the alignment guys (in the past and this time also) aim for the following:

Zero front toe, .24 degrees rear toe in per side. Rear camber is -2.0 degrees and front has all shims removed other than abs bracket. Castor is 3.8 (factory spec). Now, perhaps they didn't quite hit these values once everything was tightened down, and that is part of my problem???

With my lss stock supension, this alignment made a neutral steering forgiving machine.

Ride heights are something very close to 112 front, 122 rear.


I ran the fronts at -6 clicks from full hard, and rears at -10 clicks from full hard. The apex and "track out" oversteer was scary, so I went to -12 clicks on the rear. This may have helped a little, but not enough to make any real difference.

Because this instability is happening when I'm already planted in the corner, it seems like it would be alignment or tire pressure related, because the suspension isn't transferring weight very much mid-corner.

With my LSS suspension (and my 15"/17" tires) I found 34 psi front and 35 psi rear hot pressures to work very well. With my new setup, I could lower the rears for more rear grip, but wouldn't lower rear pressure be lotus sacrelidge?

Any pointers on troubleshooting this would be greatly appreciated.

cheers

[ZJChaser]

You can use a lot more rear camber. What sway bar are you running and what is it set to? neutral turn in? what springs rates? elise NA or boosted? Thats a lot of rubber for an NA car.

your ride height depends a lot on your tire diameters and how they compare to stock. make sure they are comparable, if not you need to adjust accordingly. If they are taller then your ride height should be as well, if they are shorter your ride height should be as well. did you measure the ride height with the sport suspension before switching?

edit(addition):

damn I just found all the measurements and typed up a nice response then closed the window before submitting. oops.

I'll try to summarize. you should try switching to the 205/50/15 front tire. right now your front tire is the same diameter as stock and your rear is .7" shorter. That means your car would be sitting almost 9mm lower in the rear than the front with your sport suspension on. to compensate for that right now to get the ride height where you have it you have the rear suspension jacked way up! That can be a major cause of your handling.

the 205/50/15 is .8" shorter than stock and that would work much nicer for keeping a balance. and since you would be running shorter tires you have to remember that you wont be aiming for the same ride height levels. I'd recommend ~ 107 front and 113 rear ride heights if you had the 205/245 setup. That would put your suspension in the same region as 116 front and 122 rear with stock tires(which are the heights I set mine up at to start with and adjust if the track requires it)

I hope that made some sense, I'm sick and heavily medicated so forgive me if its jumbled.

my .02....but thats where I would start. These cars are very sensitive to that balance.

[fitfan]

what spring rates do you have?

my car leaped off the road for zero apparent reason with the nitrons.... not even driving "fast" (like 7/10th). just swaped ends around with zero warning. and i would say would have never happened in any other car at the same speeds - kinda freaky.... feels much more planted 99% of the time - but the 1% of the time is a real confidance burner....

[OTB]

springs are 525/650, stock horsepower, stock swaybar for sport pack non-adjustable, yes a lot of rubber but I've loved this combo!

I didn't measure pre-nitron ride height. Perhaps could compare sidewall heights of stock tires compared to mine, and compensate?

turn in and trailbraking are feeling good, only on the throttle heavy parts of the corners does this oversteer happen. Even on corners that I'm super comfortable with, the apex and track out are not stable like they need to be.

[ZJChaser]

Originally Posted by OTB

springs are 525/650, stock horsepower, stock swaybar for sport pack non-adjustable, yes a lot of rubber but I've loved this combo!

I didn't measure pre-nitron ride height. Perhaps could compare sidewall heights of stock tires compared to mine, and compensate?

turn in and trailbraking are feeling good, only on the throttle heavy parts of the corners does this oversteer happen. Even on corners that I'm super comfortable with, the apex and track out are not stable like they need to be.

not sure if you replied before my edit to my first post or not but your car was previously sitting nose high with this setup and very heavily loading the rears(I imagine it was very stable in the rear). To reach your 10mm in rake you have to compensate for the 9mm of "negative rake"? That means your rear suspension is sitting 19mm higher now compared to the front than it was before. The car will not transfer weight to the rears nearly as well. Especially combining that with the much stiffer springs.

[xtn]

I'm not doing the math, but I'm guess perhaps you need a touch more rear toe-in.

During turn-in you probably have the rear unloaded, causing it to droop, in turn causing rear toe-in and therefor increasing the stability at that end of the car.

But during accelerations the rear end is squatting down and possible going toe-out.

Just an idea is all,
xtn

[R Motorsports]

I would raise the front by 5mm, which is about 1/4 inch. That should help with the oversteering issue and it doesn't hurt to have more clearance. Whatever you do, adjust one thing at a time and make sure you write everything down. That way you can always go back. Good luck.

[carl]

You need more rear C go to -2.6 in the rear.Max out the front -1 take out the abs bracket or better get a set of SHinoos V2 arms and run -2.2 in the front. stiffen the front bar one hole. Plus re check the toe it sounds like the rear maybe too much. I remember checking Eddies car and it had 1/2" of toe in the back and they told him he was in spec. Remember to much toe feels the same as not enough the tires are going sideways and not tracking..Shinoo is coming out with a simple repeatable extreamly accurate toe gauge that measusres front or rear toe from the rims not the tire.You will be able to take it to the track and takes less the 1 minute to check toe no BS.. Simular to what the indy teams use. I bought one it 1987 but there not made any more. carl

[holmz]

Start with the dampers on full soft and get the steady state turning adjusted (start with the roll bar).

If you sway bar is not large enough (or too large), you will not achieve the steady state performance.

If it can go around and around left and right - then move on.

[AZReason]

Is the only thing you changed is the shocks/springs (and resulting ride height)?

I know you wrote that you have the same suspension settings, are they the same tires? If those size tires worked with the LSS then you should be able to get them to work with the nitrons.

Make sure you only change one thing at a time.

The rear toe you posted does not mention direction. Make sure you have toe in and not toe out. Otherwise the rear is very twitchy with toe out.

With stiffer springs/shocks the car should have less body roll and be less forgiving.

The only other thing I could offer is to drop the rear tire pressure if your toe is correct. The BFG R1's sidewall does not roll over easily, so you can probably drop the rear pressure and not have too much of a problem.

[robb373]

Here is my advice:

Take a setup guy or someone who has experience to the track with you. Don't start making changes given from the virtual world. Not that these guys don't know what they are saying (many of them are VERY qualified) but your ride heights, settings and communication might not be correct or so many things can be screwy with the car.

It is best to evaluate the causes with the physical car in front of you and on track....

another point...

it could be a few different things right now, but just to let you know how I would rule out shocks is to turn the rear full hard in this situation and see the results and then full soft. This will give you a determination of the value of shock adjustment and allow you to better understand the use of adjustment. then you can back down from there.

tire temps are good too.

good luck!

[Slipstreamer]

Easiest fix:

Increase front damper settings from 6 to 9 (while retaining rears at 10); or front to 11 (rears at 12). Tire pressures might be a little stiff too.

Simple reason--when your front suspension is a lot softer than your rear, the balance of the car is easily upset by the front end letting the front end dive and allow the rear to come around. Try it.

[fzust]

I am sure whoever sold you the shocks can give you good setup advice based on their racing experience. BWR does.

[fzust]

So reading through this is looks like you are OK on corner entry/trail braking. Mid-corner I.E. limit of adhesion & neutral throttle(sweeper) is OK. Only corner exit when you apply power the back end wants to step out?

Soften the rear compression some, say 25% at a time to see if that helps.

Sometimes too much front rebound limits weight transfer to the rear. If the rear compression doesn't fix it, try the front rebound. All the while look for how this affects other parts of the corner.

[OTB]

I'll start with a lower rear ride height on these same tire sizes to see if that gets me somewhere. I've been so happy with the 225/245 widths, that I won't change that unless I find a dead end.

Yes, rear toe is toed in, and yes these are the same tires I've been running with LSS coilovers.

My first step will be raising the front 5mm. This is consistent with comments from ZJ and R Motorsports.

Also, I'll use the extremes of damping adjustment to feel the effect as Robb suggests.

Thanks!

[robb373]

Originally Posted by OTB

I'll start with a lower rear ride height on these same tire sizes to see if that gets me somewhere. I've been so happy with the 225/245 widths, that I won't change that unless I find a dead end.

Yes, rear toe is toed in, and yes these are the same tires I've been running with LSS coilovers.

My first step will be raising the front 5mm. This is consistent with comments from ZJ and R Motorsports.

Also, I'll use the extremes of damping adjustment to feel the effect as Robb suggests.

Thanks!

just $.02 more cents from me...

on an N/A car the 225 fronts are a lot. My fastest times in my N/A elise were with 205 front and 225 REAR

also, where are you measuring your ride heights from? I use the tub rails closest to the center of each wheel.

good luck! and remember to have fun with it as that's what it is all about!

[OTB]

Going by factory claimed measurements:

LSS tires are 23.6" diameter front and 24.9" rear.

My 225/50R15 and 245/40R17 are 23.6" front (sweet!) and 24.2 rear.

So theoretically the rear sits .35" (9mm) lower than LSS tires.

Independent of tire size, don't I still want approx 10mm of rake in ride height?

BTW my front sway is stock non-adjustable.

thanks again

[robb373]

Originally Posted by OTB

Going by factory claimed measurements:

LSS tires are 23.6" diameter front and 24.9" rear.

My 225/50R15 and 245/40R17 are 23.6" front (sweet!) and 24.2 rear.

So theoretically the rear sits .35" (9mm) lower than LSS tires.

Independent of tire size, don't I still want approx 10mm of rake in ride height?

BTW my front sway is stock non-adjustable.

thanks again

sorry, I meant "big" as in WIDE and will slow you down with drag, possibly also creating a greater sensitivity adjusting out oversteer

I have 5"mm of rake and car is perfect. I also use an easily repeatable measure of bottom of rim to fender of car once I got my height perfect. This takes out tire pressure differences as well as uneven ground.

[OTB]

So, I dialed in a combination that works, but I'd like find a way to go lower in the future.

Basically, due to my 225/245 combo, I actually dialed in approx 5mm higher front than rear. I also ended up adding a touch more front camber by removing the ABS brackets. This got the car back to predictable, neutral steering at the limit, even in the big sweepers that were scaring me with the oversteer.

Unfortunately, the rear ride height is as low as it can go with just a touch of spring preload when the car is up in the air. I play with the curbing alot, so I really don't want to use an unloaded spring (when off the ground), and the single adjustables don't come with lock rings, just one ring.

So, the car is handling great, body roll is gone, steering is neutral, I just wish I could keep the same rake (or anti-rake) and lower the front and rear by equal amounts. Is a helper sping (at least rear and maybe front) the answer to go lower without rattling springs when up in the air?

I didn't have the tools to measure ride height at the track, only tools to measure change in front height. However, the ride height is high. something like 135 front 130 rear.

cheers!

[robb373]

Originally Posted by OTB

I didn't have the tools to measure ride height at the track, only tools to measure change in front height. However, the ride height is high. something like 135 front 130 rear.

cheers!

My F250 might be lower than that!

are you measuring under the tub rails closest to the hubs?

Are you in love with those wide front tires? It seems that those tires are the reason your are up so high. The rear can definetly come down with those tires and should, but you are going to need the front down.

If the tires are the reason that you are high in front, then those tires are the only reason you are not under steering being lower in the rear and you are losing all benefit you think you are getting from them due to the loss in setup on the rest of the car.

At this point I would be sure that if you went to a 205 front, and dropped 7mm in back and 17mm in front (117f, 123r), you will be going much faster and utilizing the car set more.

just my advice

good luck