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-   -   Suspension question (http://www.bimmerfest.com/forums/showthread.php?t=9349)

daven 07-13-2002 09:05 PM

Suspension question
 
I'm driving a 99 Z3 2.8l coupe with 17" wheels.

Suspensionwise I upgraded the OEM shocks to Bilstein Sport shocks last fall to correct severe body roll at the track. So much so that I wore through the plastic wheel well cover on the front passenger side. Seemed to work great. Went to NHIS after the upgrade and the roll went away. This spring before a session at Lime Rock, I discovered much to my dismay that both my upper and lower ball joints were shot with only 11,000 miles. (Public transportation commute and little free time = low mileage.) Dealer replaced them under warranty and replaced the rear sway bar links that were under an owner requested recall.

I've been to Lime Rock twice this year and noticed no severe body girations - with the exception of 1 spin coming out of Big Bend last time

Today while changing my oil, I noticed that I have worn through the plastic wheel well cover on the front driver's side and can feel where it has been rubbed on the passenger side.

Any ideas? I lose my warranty in September, so it'll be going in to the dealer for a look see by their experts, but I trust you guys more.

Would upgraded sway bars help? I'd like to leave the springs to last; Boston roads suck and even with stock springs and the Bilsteins the ride can get a little rough.

Thanks in advance

scottn2retro 07-13-2002 09:21 PM

Hi daven -

Are the 17" wheels from factory or standard for your car or did you upgrade from 16"? If you upgraded, did you go to a tire size that was the same outside tire diameter as the factory tires?

daven 07-14-2002 07:01 AM

Maybe this is the answer?
 
The wheels are aftermarket upgrades and are 8 x 17 rather than stock 7.5 x 17. (So much for Tirerack saying they will fit perfectly) Tires are
stock 225/45 R17.

If this is the problem, is there a fix?

Thanks Scott
:banghead:

scottn2retro 07-14-2002 01:31 PM

should not be a probelm . . .
 
It's definitely possible to upgrade wheels and tires and keep the same (or close enough) outside diameter of the tire.

The suspension geometry is designed for a certain tire diameter, so if someone were to increase or decrease the tire diameter enough with no other changes, then the suspension geometry changes and could account for things like bushings wearing out prematurely.

That doesn't seem to be the problem in your case. Your car already had 17's and I don't think a half inch increase on the wheels with the same tire size would make too much of a difference. The wider wheel should allow you later to go to a wider tire with a lower aspect ratio (in your case 45 down to 40) and keep the same overall tire diameter.


Any other suspension gurus out there got any ideas?

Pinecone 07-14-2002 04:25 PM

One thing is to compare offset on the sheels. If the wheel has the extra width in the wrong place, it could lead to wear also.

Sway bars could help. They would reduce roll during steady state cornering.

You might also contact H&R or another spring manufacturer about higher rate springs, but with stock ride height. This would make the ride firmer though, but without the added problem of lower ground clearance.


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