rubbing 9's

[kiesan]

On my '84 Carerra, did the usual and put my 7's (16" Fuchs) on the front and got 9's for the rear (brand new from Wheel Enhancement). Running the 'yoko ES100 245/45 16" on the rear. Dave at Wheel Enhancement said if I was to have any fitment issues it would be at the front and even then it would only be a matter of rolling the fender lip. Well, no problems on the front BUT the left rear rubs when the suspension compresses. Bummer. It doesn't rub on the fender lip rather it hits the sheet metal dead center in the middle of the wheel well opening about 3" from the fender lip. I am going to ask Wheel Enhancement what they think but any suggestions here? I'm running not quite negative 1 degree camber in the rear (-.85) and the struts (Bilstein Sport) are brand new. Since it is just barely hitting, should I have my friend who owns a good body shop very carefully breath on it with a porta-power for that extra bit of clearance? TIA

[JP911]

If it were me, I would adjust the ride height slightly in the rear rather than start grinding away sheet metal.

[kiesan]

Well, I wasn't thinking of grinding. More like pushing gently. My ride height is just slightly lower than stock but certainly not slammed to the tarmac Fast & Furious style. Was hoping not to have to raise it up any but...

[JP911]

Have you checked the tire pressure? I know it sounds stupid, but if the pressure's too high I would think it would cause the tire to bulge a bit. One other possibility is that your shock in that corner is going bad.

[kiesan]

Just checked the pressure... 32lbs. It has new Bilsteins but now that you mention it it sure seems awfully bouncy in the rear when you push down on the rear bumper cushion thingies. When I say the shocks are new I mean they were installed on the car probably around Spring '02 (new in the box then) but the car did not get driven until about 3 weeks ago. Are 911's supposed to be much easier to compress in the rear because of all the weight there? The front has new struts also and its like a rock when you push on the front bumper compared to the rear.

[89911]

Get that fixed fast! I've seen quite a few track cars that ran tires that rub just were you said. After a couple of times, you'll get blistered paint directly on the opposite of the rubbing. It looks pretty bad and only a repaint will fix. The track guys didn't seem to care. It's a combination of stiff shocks, torsion bars and negative camber that aid in preventing this. I run 245 on 9's on my car and have plenty of room. Your cars height may also need to be checked.

[Silveresrty911S]

I believe your shocks are for the dampening motion (up) not he compresion (down) motion, adjust ride height or stiffer torsion bars come to mind.

[kiesan]

I'm pretty sure that the shocks provide both compression (down) and rebound (up) resistance. The shocks on all my bikes have adjustable compression and when you tighten the screws they sure compress a lot slower. Come to think of it I had adjustable suspension on my '89 Turbo 944 and it would compress (go down) a lot slower if you tightened the screws.

I just went out and bounced up and down on the rear bumper again and it sure feels to me like my 1 1/2 year old new shocks are just along for the ride. After you push down hard the car bounces back up real quick and then it does a little dip down again by itself. I would of thought new Bilsteins would raise slowly and not bounce after the suspension gets back to its static height.

[3.2 CAB]

Hi Kie, I have Bilsteins all the way around on mine, I did your test, just pushing down with my hand, could hardly get any movement at all, and when it did come up it did not go back down again. I would take a look at the shocks, maybe has blown a seal even though it is "new"

[ricwon]

HI kie, If you don't mind my asking, what did you pay for the new 9's from Wheel Enhancement? thanks, ric

[North Coast Cab]

Kie,
I'm running some 8's with 245's and I had basically the same issue. I adjusted slightly the ride height and I installed stiffe t-bars and the problem went away.

John

[masraum]

get more neg camber and/or raise the ride height a tad in the rear. I drive my car daily, so most of my driving is 35-45 through town or freeway, everything here in Houston is straight and flat. I have -1 deg in the front and -1.5 deg in the back, and I still manage to wear my tires evenly with the help of the occasionaly off/on ramp.

[Bob's Flat-Six]

I had a new Bilstein HD in front go bad on me right away. It started leaking, So I would check yours.

I have the Sports in the rear with 26mm T-bars and I'm low at under 24" in the rear.

I havn't had any rubbing with the 9's I just put back there, And have done just about every kind of driving.

You shouldn't be getting any bounce like you mentioned in your suspension, so that's your problem. I would check the shocks and add a stiffer torsion bar.

The 26 mm bars have worked well for me with the stock SC bars up front. TRE recommended the set up and it's been great for the street.
The profile of the tire your running will play a role too. My SO3's give me good clearance in the rear.

Also, I am running neg. camber too of 1.2 front and 1.5 rear

Merry Christmas

[kiesan]

Thanks to all for the helpful info. I think I'm going to try more negative camber in the rear. Come to think of it, I had the car aligned when the 7's (225/50) were back there. I only dialed in -.85 degrees and my guess is that when I bolted on wider rims and tires I have even less than that now. I'm also going to get another opinion on the shocks... it just feels too squishy for having fresh Bilstein yellows in there. Was also thinking of going to a stiffer torsion bar. What is a good one for aggressive street use while still maintaining a decent ride? Are the hollow ones that much lighter? TIA

[techweenie]

Stock is 24.1 in the rear, I believe, but I've been happy with 26/27mm bars on that type car. I don't believe in going too stiff with torsion bars for street or dual-use driving.

The tire really shouldn't be rubbing, but Porsches do vary a little bit in body measurements. You should be over -1 degree negative in the rear. Maybe -1.5 for spirited street driving.

Good luck!

[Mike Feinstein]

Definately upgrade your t-bars. Think about your driving requirements first. If you like a firm but comfortable ride, I'm very happy with 29's in the back and 22's up front. If you auto-x or DE, you'll be glad you did it. I run 9's in the back and my car is pretty low (23.75 rear ride height) with no rubbing whatsoever. I don't use Bilsteins so I can't comment, but I know Koni Sports (yellow) don't allow any bouncing at all.

If it doesn't work, I'll gladly take those yucky old 9's off your hands!

Good luck,

[kiesan]

22's and 29's... sounds like a good compromise. Are the hollow ones that much lighter or better?

[Jdub]

Kie:

You want to stand back and think about this for a minute so that you spend your money most effectively.

Several NorthWest guys, including myself, Paul, and a few others are rebuilding thier suspensions this winter. Now I am not saying you ought to do the same, but the problem you have has a central cause in the suspension, and if you are going to touch one thing, well, you are looking at "while I am in there" thinking.

For example, if you are going to pull the rear tbars, you ought to just go ahead and spend the $40.00 for fresh Neatrix bushings. Certainly the sag of old bushings is contributing to your current situation. Once you get these two things taken care of, you are going to realize the benefits of the 9"ers.

Whether you decide to also go into the rear swingarm bushings, sway bar bushings, and drop links is up to you. But once you get in there, you begin to realize that a 25-year old suspension will show wear in ways you never noticed because none of us drove these cars when new.

I have a set of 7/9"ers and I promised myself they wouldn't go on until I had replaced the bushings, the tbar, the bearings, and regreased my CVs. I felt pretty sure that once I had performed "due diligence" on the peripherals, I would benefit the most from the increased traction (and conversely the strain the larger wheels put on the back end).

So I guess I'm thinking out loud here, but if you have the money to do so, consider upgrading the tbars to SwayAWays, non-hollow, and saving any difference in money to apply to other areas of the suspension that might bring you car back to near-original specs.

John

[kiesan]

I wonder... if I were to replace the missing lower left shock mounting bolt would my tire rubbing problem get any better?

Someone shoot me.

On the other hand, is there any reason to remove or loosen that bolt during an alignment?

[911pcars]

If that missing lower shock mount bolt is for a high pressure gas shock (Bilstein, Koni sports), then not having the shock connected will affect the ride height slightly.

Otherwise, the shock is there to control suspension oscillation, not control ride height or rear wheel alignment.

Sherwood
http://members.rennlist.org/911pcars