How close are your wheel clearances???

david914 · 07-08-2004, 07:19 PM

OK. After what seemed like an eternity at work today, I raced home, loaded my new Dunlops and 7 and 8 by sixteen inch Fuchs in the SUV and bolted for the tire store to get everything mounted and balanced. Been waiting for this moment for a long time! At any rate, got everything back home, pulled out the floor jack, air hose, impact wrench, torque wrench, etc. and went to town. Got everything mounted, spit polished the wheels, and took her for a shakedown cruise...

Well... shakedown is a pretty accurate term in this case. As I get up to speed (60+ mph), the wheel starts to shimmy. The shimmy seemed to be speed dependant, worse at some speeds than others, but not necessarily linear with an increase in speed. Good thing the tire store included free lifetime balancing. Guess I'll have to take it back for some "tweeking". Not sure they put their best guy on the balance machine...

At any rate, I digress. As I drove around, I noticed a "rubbing" sound that happened each time I made a sharp right turn. Pulled off into a parking lot and took a closer look. What I found was that the left front tire is very close to the front edge of the fender lip and the valance. The tire was actually hitting the lip of the valance where it wraps around into the fenderwell. When I got home, I took the handle of a hammer and carefully bent this lip inward slightly and took it for another drive around the block. It seems to be OK now, but I was surprised at how close things are. My SC seems to have a bit more room between the tire and the front lip of the fenderwell.

To cut to the chase, how close are your tires to your fenders? I am running Dunlop SP8000's, 205/55-16 fronts and 225/50-16 rears on 7 and 8 inch Fuchs with 911 offset. I need some encouragement!

BTW, it was dark when I got done. I'll take some pics tomorrow.

singpilot · 07-08-2004, 07:24 PM

I run the same setup on my SC. Did you move up from 15's? The changes and shimmying might be balance, but might also be the changes in alignment from the changes in geometry you introduced with the new sizes and widths. If the check of the balance does not cure the shaking, it is time for an alignment. And yes, the tires can be close on an SC with 16's depending on ride height and widths.

1973911s · 07-08-2004, 07:25 PM

I am running 7 and 8 with the same size tires, and my car is low. I do get rubbing when I hit a curb to fast.

Is there a chance you put the wrong tires on the wrong rims, or the wrong tires up front?

How low is your car?

Hope this helps

Michael

david914 · 07:32 PM

I had the stock 6 & 7 by sixteen inch Fuchs on there already. I forgot to mention, this is on the '86 Carrera. You may have something there with the alignment. I bet the toe is out a bit now. Guess I'll have to have that checked.

The car is at European ride height. Tires are mounted on the right rims (first thing I checked when I picked them up).

CJFusco · CJFusco's Garage

"How close are your wheel clearances??? "

pretty damned close... no rubbing though.

ted · ted's Garage

1/8 inch side clearance from tires to fenders.
245/40/17 fronts and 275/40/17 rears.
There should be a way to get your's to fit?
Why the wobble? Wheel bent, not balanced or loose?

Eagledriver · 07-08-2004, 08:34 PM

They only need enough room to not rub. You'll hear them if they rub. I had to roll the front fenders and shave the rear fenders to stop the rubs.

-Andy

david914 · 07-09-2004, 04:13 AM

OK. After having read your suggestions and gotten a good nights sleep, I drove to work this morning paying close attention to when and how the shimmy happens. I'm pretty convinced at this point that the problem is the alignment. Since I've just widened the track, my guess is the toe is now biased outward. If I go into a turn, the shimmy stops. The handling is a little twitchy as well.

Noel · 07-09-2004, 04:26 AM

The toe should not change just from installing a new set of wheels. Make sure all of your lugs are tight first. If that is not it, then it is balancing if it wasn't doing it before.

dickster · 07-09-2004, 05:05 AM

Quote:

Did you move up from 15's? The changes and shimmying might be balance, but might also be the changes in alignment from the changes in geometry you introduced with the new sizes and widths. If the check of the balance does not cure the shaking, it is time for an alignment

mmmm, i'm not sure about that advice - changing wheels and tyres does not affect alignment.

david914 · 07-09-2004, 05:38 AM

OK, I think I may have found my trouble. Just had a thought and went outside to try something. I grabbed each front wheel and gave it a shake. My passenger side has what feels like a loose wheel bearing ( I get a very slight "thunk-thunk" if I grab the top of the tire and push-pull). That would explain the intermittent nature of the problem and how it seems to improve when turning (getting more side load on the bearings). What d'ya think? My only concern is that I didn't notice it with the 6's on the front before. I guess the larger rims may just be accentuating the problem.

singpilot · 07-09-2004, 05:54 AM

Quote:

Originally posted by dickster
mmmm, i'm not sure about that advice - changing wheels and tyres does not affect alignment.

hmmmm.

If you widened the stance (centerline of the track), or increased the rolling circumferance of the tire / wheel combination, you have changed the geometry of the alignment. Remember, not just straight line, but turning.

After several of these over the years, a re-alignment always cures whatever ills I introduced by doing one or both of these things. After making sure pressures, out of rounds, out of true, wheel bearings, tie rod ends, ball joints, and bushings are up to snuff.

Paulporsche · 07-09-2004, 06:11 AM

Let us know if tightening the wheel bearing helped.

If it doesn't, try jacking up the front, have someone hold the steering wheel, and try moving the tire at the 3 and 9 o'clock positions. This will tell you if your tie rod ends are bad.

Paul

dickster · 07-09-2004, 06:17 AM

Quote:

If you widened the stance (centerline of the track), or increased the rolling circumferance of the tire / wheel combination, you have changed the geometry of the alignment.

hmmmmm, ok i'm listening

what settings are effected?

i'm thinking - camber, no, caster, no, toe, no..........

or am i missing something?

Jdub · 07-09-2004, 06:26 AM

Has anyone mentioned if the wheels were balanced correctly on the rims? You might revisit that.

An alignment, if you cannot recall having had one done, is a must. Also, consider rolling the lips of the front flares anyways, just for good measure.

John

david914 · 07-09-2004, 06:40 AM

The guy that I purchased the car from had it aligned not long ago. Besides, it felt perfect (and I mean PERFECT) prior to swapping wheels. Not one vibration, shimmy, nice and tight. I'm confused about the wheel balance. If it was wheel balance, wouldn't it vibrate all the time and just get worse with an increase in speed?

911ctS · 07-09-2004, 11:58 AM

Quote:

Originally posted by david914
The guy that I purchased the car from had it aligned not long ago. Besides, it felt perfect (and I mean PERFECT) prior to swapping wheels. Not one vibration, shimmy, nice and tight. I'm confused about the wheel balance. If it was wheel balance, wouldn't it vibrate all the time and just get worse with an increase in speed?

It seems wierd but static imbalances tend to be most noticeable at a particular speed range. For ex. 55-65mph. Not sure why but sometimes if you go faster than that speed range they become less noticeable. Maybe its some type of cancelation in forces or vibrations when spinning below or above the plagued speed range.

As for the alignment debate, I think the setting effected by wider/narrower tires is the scrub radius. (the imaginary line drawn down through your strut and where it meets the contact patch of your tire) The offset of the wheel is the determining factor in this.

braddb_82SC · 07-09-2004, 12:49 PM

I ran into the same rubbing problem when I switched from Dunlop SP8000's to Kumho's. There was no alignment done at the time so I assume the rubbing was due to differences in tire manufacture's offsets. Your problem surprises me, as you switched TO Dunlop SP8000's and had a problem. I had assumed Dunlop's ran narrow.

-Brad

david914 · 07-09-2004, 02:08 PM

Yeah, I was surprised not only by the fact that it rubbed, but also WHERE it rubbed. Seems that I recall that the driver's side historically has been where people have the problems. I've also been told that the differences between cars is attributable to the fact that they were hand built. Part of the mystique I guess...

Well, I'm home now. Gonna grab some dinner and head outside and jack 'er up. The passenger side wheel bearing seems a bit loose, so I'm going to check/tighten both sides. The PO had told me that the front bearings had just been repacked, so there's a good chance that they may have just settled in and need snugging up. I'll let you all know shortly... (plus some pics as promised)

Bill Verburg · Bill Verburg's Garage

The drivers side fender/bumper seam is a common interference point, there is a shelf there that collects debris that juts out perpendicular to the fender . I just grind it down till it's no longer an issue.