Hi all....

I'm relatively new to the performance tuning on my car so bear with me on this. I was on a spirited drive this morning with my some work buddies (driving impressive hardware I might add: 2001 Turbo Carrera, Ferrari 360, NSX) While my car did quite well given the competition, I noticed a tremendous tendency toward oversteer, with a very twitchy rear end. My suspension is stock except for OZ COMP wheels with Yoko AVS intermediate tires (front 17X8 w/ 235-45 rear 17X10 w/265-40). My motor is mildly modded (intake, DP, CatBack).

Given my tire combination, I'd expect a bit of understeer. Decreasing my rear tire pressure as low as 28psi didn't seem to help much (35 front 28-35 rear) Now I understand the 93 had a relatively stiff rear antisway bar. Do you think this is the issue? Should I start by getting a stiffer front bar? Are my tires at fault? Driving style? I'd like to get a coilover setup at some point....maybe i should get stiffer front springs???

Maybe some of you tuning gurus can help.

Thanks in advance....

Fabian

 

Hi, I grew up in Saratoga and went to Bellarmine. Nice to know there's some more Gatons out there. I would suggest getting a front sway bar in that case as well as replacing your stock suspension with adjustables if you haven't.

You can really increase the performance if you get some lightweight forged wheels as well, both in acceleration and handling.

I'd like to meet up with you guys at some time. We try to have meets every month or two, so please add your name to my BBQ list in the west section. And we can all get together.

Where abouts in Gatos? I used to live on Sobey Road off Quito and Hwy. 9. Hope to see ya.

Rishie

 

Rishie....

I'm right in downtown Los Gatos, on Pennsylvania Avenue. I didn't grow up here but moved to the area for school and ended up staying. I'd love to connect with you for some drives....I'm not sure how to get on the list you mentioned though. We can communicate by email if you'd like.

When I put the OZ's on I was not really interested in the performance issues. As time has gone on however my emphasis has changed. I will be looking into new wheels at some point, but I think I may do some suspension upgrades at the same time/ or first.

Thanks....talk to you soon

Fabian

 

I am in Los Altos.

I have a pretty good setup that I can share with u.

I have been in several FD with various tire size and all i can say is that larger is not always better. there are weight and unsprung wieght issues as well as alignment.

I know of a good alignment shop - Wheel works in sunnyvale 408-969-1700 ONLY have craig do ur work. he did mines and i love it.

He has many years of race car experience.

 

From your post, your car is definitely setup for understeer, and I'm surprised to read that your rear-end is twitchy.

There could be other causes.

It could be that your rear tires are just plain cold, and take more time to heat up (they are 30 mm wider than the fronts!), or perhaps the rear tires never heated up to temp during your run through the twisties.

If you trail-brake deep into the turns, you will definitely induce oversteer, even if your car is setup to understeer. I actually use this type of driving style to get my car turned into a corner, while maintaining as much speed as possible (of course with enough oversteer, your rear tires should eventually heat up and stick more)!

You could also check into your rear suspension bushings. If they're excessevely worn, this could explain the rear-end twitchiness, at least that was my experience before I finally replaced my rear suspension bushings recently. The oversteer, was almost a "snap-oversteer", not a progressive rear-end drift. The "snap-oversteer" really caught me by surprise many times out on track, but I eventually learned how to drive my car with crappy rear bushings. I just had to be faster with dialing in more opposite steering lock!

As for your rear sway bars, you might check to see if they're set to their stiffest setting. If they are, try the softer setting to dial in some understeer.

IMHO, it's hard to judge what your car is actually doing just from spirited street driving experience. Testing the car's suspension and tire setup can only be done properly on a closed road racing circuit. On a related note, the only way to generate accurate testing data is for the driver to turn very, very consistent laptimes--usually within 0.4 to 0.6 seconds each lap! At least this has been my experience, testing my own setup at Putnam Park Road Course. The guys I had along to help me gather testing data, complimented me on my ability to turn such consistent laptimes. It really helped them make better decisions on what to adjust next!

Good luck, and have a great 2002!

 

sleepR1

Thanks for the post. I agree that it may be a tire temperature problem on the street, since things got somewhat better as the day progressed. I guess measuring tire temps (if done correctly) may be informative. Is there a source for appropriate tire temps for individual brand/model tires?

Is there a way of checking the rear bushings short of simply replacing them? "Snap"oversteer is a perfect description of the problem, very sudden and requiring large opposite lock inputs. Trail-braking was certainly out of the question.

I didn't realize my stock rear sway bar is adjustable. I should check that.

I'm planning some track time in February....but I would like to not waste a lot of track time tuning out problems I may be able to "ballpark" before getting there

Thanks again for the really helpful post.

Fabian

 

Oops, I didn't read your post thoroughly. Your stock rear sway bar is NON-adjustable. Sorry! At least that eliminates a variable If you don't trail-brake into turns, then that leaves us with the tire temps and rear suspension bushings. If the grip got better as the trip progressed, BUT the oversteer didn't go away, then that leaves the rear suspension bushings, as the likely culprit for your oversteer problem. If it's a "snap-oversteer", then it's looking more like your rear suspension bushings.

A sure way to tell is to put the car on a lift, or jack up the rear end until the rear tires are completely off of the ground and the suspension is at its longest stroke. Note that it's much safe to to this on a lift! With the rear wheels off of the ground, push up on the rear tires. There should be no play at all when you push up on the rear wheels/tires. If you hear a thug, thug, or feel any play, then chances are your rear suspension bushings need replacement.

Bad rear suspension bushings are common on higher-mileage FDs. I've been dealing with my bad rear bushings for 20,000 miles, but finally had them replaced a few weeks ago (92,000 miles on the odo).

There are no upgrades for the rear suspension bushings. The parts are metal ball joints with rubber seals. The ball joints are what fail over time, thus necessitating replacement. You'll need to do all the ball joints--upper and lower control arms, trailing arms, etc. It's a major job. Parts alone cost me $315 plus taxes and shipping, and that's WITH my Mazda Comp member discount. A proficient FD suspension tech should be able to do the job in about 2 hours (1 hour each side). If the tech has never done the job, count on 4 hours of labor. Advanced Import Motorsports' Technical Director, Paul D'Angelo did my rear bushing job. He goes by "PaulyDee" on this forum. Check out my AIM links in my sig if you'd like to contact Paul directly. Tell him I sent you!

One more thing. You'll need to get your wheels RE-aligned AFTER the rear suspension bushing replacement job has been completed.

Good luck!

 

I didn't address your tire temp question. I use Hoosier R3S03 road race tires for track duty. Hoosier offers quite a bit of info on their website regarding tire temps (see my sig for more information on Hoosier tires). In my case the R3S03s have an optimum temp range of 180 to 200 F. The last time I tested (Dec 15), the temps never got higher than 118 F, so obviously there's more stick to be had on a warmer day!

If you're running the AVS Intermediates on the track, then you'll need to contact Yokohama's technical department on optimum tire temps. I can tell you that street tires (non R-compound) tires have a much lower optimum heat range than R-compound tires, and that range is much tighter than an R-compound tire's heat range.

I guess you could just use your sense of touch? If the tire tread feels tacky after your run through the mountains, you can be sure that you're getting some heat generated in the tires

Best of luck in the coming year!

 

Do you know what the alignment numbers are ? Maybe you not running enough Toe ?

 

Fabian, Manny's comments are right on... assuming you've checked the basics: worn rear tires, bad alignment (toe-out), etc. i'd say you have a rear suspension issue, most likely rear bushings. Bad Toe Link bushings will cause snap over-steer - one of the reasons people upgrade to M2's competition Toe links.

Anyway, I have a set of stock Toe Links and Trailing arms with bushings in place... about 20K miles of use. You can have them for a lunch...

I'm in Los Altos...
zeemr@yahoo.com

-Azeem

 

The SSR Comps I took off of your hands, matched with 245/45-17 and 275/40-17 Hoosier R3S03s are a potent combination. I've turned my fastest laptimes @Putnam Park 2 weeks ago, with ambient temps in the low and mid 30s F! My suspension/wheel guys tell me I'll knock another 2 seconds off my hotlap times just from warmer weather! I was surprised how little understeer there was with 1 inch wider tires in back. I changed my driving style, and took advantage of the greater stick in back. I plan to replace my tired stock twin turbos with '99 J-spec twins, and hope to take advantage of the J-spec units' faster spool-up time. I'm told the J-spec units make boost at 2500 rpm, while the stockers make boost at 2800 rpm.

Anyhow, I'm very happy with the SSRs you sold me, and appreciated the care you took in packaging them to make the trip from the left-coast to America's heartland without any damage from the ham-fisted UPS folks.

Fabian, if you buy something from, Azeem, you can be assured of the quality of the part, and the care he'll take in sending the part to you in good shape.

Good luck!

 

foko,

I didn't read through all the responses, but if even one of your rear shocks are worn you will experience unusually strong oversteer. The rear tires won't be able to grip. And with the size of the tires in the back and your tire preasure up on the front you should be fine. Have a garage test your rear shocks.

About the bushings. You probably wouldn't notice THAT big of a difference with a stock suspension. Upgrade for sure, it makes the car that much more enjoyable. But make it your last suspension upgrade to REALLY feel the stability.

good luck

 

I noticed that your tires are a different size on front/rear. I can't speak from experience with my FD, but on my FC, tire sizes have to be picked carefully...

I went from the stock 205/55 on all four wheels to:

205/55 16 Front
225/45 16 Back

This made my car a deathtrap. At first when entering a corner, it would seem pretty neutral or understeer some... then as you applied a little more steering angle, the rear end would very suddenly snap around. It was pretty scary to drive like this.

I replaced the 55 profile fronts with some 205/45 16 and the car felt much safer.

People seem to mix and match more on the FD and get away with it... but that's just something to think about. Changing the tire sizes front relative to back changes the roll stiffness too... This affects your balance!

Good Luck, let us know!

Brian

87 TII
93 R1

 

I had similar problem with "throttle off" oversteer. Keep on the throttle through the turns and it will stay planted. Also Do the ROb RObinette Sway Bar bushing Mod. I did it and it made a difference. For like 12 bucks! He replaces all the FRONT sway bar bushings with Poly ones. Its easy and its cheap and it works.

 

thanks for all the advise....i'm looking into it and will keep you all informed.

thanks again

fabian

 

I agree with the others that street driving is not the best way to judge if your car really tends toward oversteer. There could be several things in your driving style that are provoking oversteer.

All the things Manny and the others mentioned are possible mechanical causes you can have checked out at low cost.

One last thing to file away for future reference is that decreasing your rear tire pressure INcreases the tendency to oversteer. Suggest you keep F/R tire pressures the same for normal driving.

 

damn u guys write alot
just kidding

 

...regarding your oversteer problem? Just curious if you resolved the issue?

 

unfortunately i've been held up by other projects...so no news at this point.

still on the to do list though.

fabian