Vibration driving me mad

[fran]

I have a 70 T with reconditioned deep dish Fuchs running 185 70 Vredesteins. I also have regular Fuchs running 205/60.

It happens on both sets of wheels. Definite Vibration in steering wheel and I think elsewhere too.

The problem has always been a vibration at 70 and up. It gets worse the faster you go. Tends to keep me speeds down.

I have had the tires and wheels balanced by different guys/ Porsche shops too. they have been road-force balanced too.

They say the wheels are ok though there are LOTS of weights on them.

What else could be the issue and how can I pin point it?
Where do you take a car to get this diagnosed?
I live north of Boston.

[69Sman]

Have you had the car aligned and corner balanced by a GOOD SHOP?

[fran]

Yes a company in Ct called Musante motorsport did it when I got the car last Sept.
It is too far to go back there about 2.5 hrs.

The car handles well and tracks fine it just vibrates in a straight line about 70 mph.
When I first got the car a assumed it was just a matter of a re-balance, then I thought the rims may be bent.

so i switched to my refurbished Fuchs. there is a shop called autobahn near by. they did the first rebalanced balance and charged a lot.
Perhaps I should go back there....

[blucille]

Check the preload on the front wheel bearings....quick fix.

[t6dpilot]

Yeah, I would go back there and tell them that the wheels should be balanced lug centric, not hub centric. That may be your problem...

[blucille]

I just discovered a BBS wholesaler near me, he has the most incredible tire mounting and balancing machines I've seen in the US....downside is he isn't open to the public, upside is open to offers....I doubled his requested payment, so I'm sure he'd be happy to have me back.

The concept is, he sells new BBS wheels with tires fitted, needs to be sure the wheels are still pristine....so, he buys the best tire mounting gear. No-touch, all hydraulic, no tire irons touching anything, all soft rollers....the stuff you expect to see only in Europe,

Then, for balancing, his current favorite is sonar based, but he's moving to laser based, to check tread depth and plumb of both the tire and wheel....


Pretty awesome stuff.

Lewis

[PStey]

You might want to check if your hub has no run-out. I had similar vibration issues that I ultimately cured by changing the wheel hub.

[fran]

Is there accepted run out measurement? My mechanic said he checked and it was fine.

Fine may not be so fine. t6dpilot mentiond lug centric balancing-can someone enlighten me as to what that is and is it something most shops can do?

[Harvey Weidman]

Fran,
I rule out one thing at a time. First I would check the runout on all of the wheel/tire combos on a front hub (the rear has too much drag to spin freely). Try each and look to see if there is any wheel run out by holding a straight edge near when you spin it. Then inspect the play in all 4 corners. You may need to adjust like Lewis said. Also look at the axles to see if a CV is binding or a bent/damaged axle. Besides wheel/tire combos I have found, loose front bearings, bad CV jopints, bad rear bearing, loose tie rods and many more. The most common vibration is the tire flat spots or bulges. But since both sets do it, I doubt that is the problem. As a last resort I have put the car on a lift that holds up the rear suspension in a driving level and run the assy at road speeds (CV problems showed up quickly).
Hub centric is centering the wheel by the center bore; lug centric is centering the wheel by the lugs. (not too many shops do this anymore)
H

[fran]

Thanks Harvey- The car is at the shop and I have forwarded your message to him. I'll report what we find out. Thanks for the guidance one and all...

Fran