Yabo

Replaced:
Front Rotors ($160)
Inner and outer / Driver and passenger tie rods ($120)
Track ball joint kit from rennbay after trying standard kit that failed ($60+$200)
Lubricated and exercised calipers, seemed fine
Both side front wheel bearings

painted my wheels. It did this prior to tie rods, ball joints, painting wheels, etc and after so I tend to think it's something unrelated.

just got an alignment today, $60 more...

Feels pretty much fine until about 60-65 MPH, then by 75 it shakes the steering wheel like hell, and at about 85-90 it is completely gone... Then slowing down from 90, 85 its fine, 80 its fine, 75, its back and stays till 85 or 90 again.

Pretty much running out of things to replace. Tires were new last summer and were mounted and balanced by a reputable shop. Tires are almost worn out but still have a mm or two before the wear bars.

Passenger side control arm bushing at the crossmember looks like it is old, but i can't get any movement out of it so I don't want to spend another 60 on that yet without some diagnosing..

Any ideas?

V2Rocket

The balance could have been thrown off; I had my wheels balanced when I had new tires put on, but about 6 months later the steering wheel was vibrating like crazy; turns out some of the weights on one of the wheels had come off and unbalanced the setup.

Yabo

I'll swap wheels front to back again.. but i am pretty sure I've done that and it's done no good. Would find it hard to believe both front and back are out of balance too.

Wouldnt wheel out of balance show up more throughout the speed range?

75ohm

Here come the tire experts, me excluded...

What kind of tires are you running?

Yabo

BFGoodrich G-Force sports

Antonio951

Devon I know EXACLY the frustration your feeling. You just explained the same exact thing my car is doing. I replaced the tires, brakes, alignment and last week I replaced the steering rack(old one was leaking) & inner/outer tie rods. I have had the front tires balanced 3 or 4 times after replacing the tires and they only have 500 miles on them. The old tires did the same thing, at 60-65 the steering wheel shakes like crazy, nothing before and nothing after. Sometimes however its not there, it’s perfect at 60-65 but then I gain speed and slow down to 65 and it starts again. I have not replaced the ball joints and believe they are original. A guy at a Porsche dealership said it could be my spacers so im going to try to take those off, if that’s what the problem is im buying different wheels because I hate that shake at 60mph!

jtsporsche

well you have sweet wheels. so if thats the problem, what ya gonna do with'em?

schwank

Just bought a 951 with the same problem above 60 only. The tires were only maybe 6 months old. It seemed to come from the right front, so I took that wheel to the local shop and it was WAY out of balance. PErhaps some weights came off, but they reweighted it and now the car is fine.

Yabo

Antonio's story scares me.. Sounds like mine. What else could it be? MAYBE struts? but even then it seems weird on a perfectly flat road.. Although 60-70ish might be the natural resonance for the front spring weight and it's just sending it crazy if theres not a good shock to dampen it? My shocks FEEL good, but they are KYB gas ajust with about 2 years on them ( i put them on new).

931guru

kyb shocks that are two years old are worn out shocks.

billthe3

I vote tires out of balance. My car did exactly the same thing at the same speeds, got the tires balanced, problem went away. Its not like it's uncommon for tires to get unbalanced, just have them checked. Why start rebuilding the entire suspension when it may be something as simple as that?

75ohm

Knock yourselves out guys!

http://en.wikipedia.org/wiki/Tire_Uniformity

Trucho-951

This 60 mph to 75 mph vibration or "shimmy" as the alingment guys call it, seems to plague 951's. Mine had it real bad when I bought mine two years ago. I did a google search and found out that it was very common problem. I've since changed many, many parts (control arms, tie rod ends, upgraded to 968 castor blocks, new wheels, have gone thru many sets of tires, upgraded springs, new koni yellows struts, upgraded rear torsion bars and struts, etc.) trying to solve the problem and have only succeded to minimize it.

The car runs great at the race track, but the shimmy, although barely detectable, is still there at normal freeway speeds. I've come to believe that the 951's have some instrinsic greometric flaw in their suspension design (perhaps not enough caster 3 deg max), something that makes the wheels undergo bad harmonics at or near 60 to 70 mph. I sort of envision it as the problem the front wheels of shopping carts have when pushed too fast that they shake violently back and forth.

As an aside (I'm just thinking outloud here), but this instrinsic suspension problem might be the reason that 951's chew up ball joints so quickly. I mean, I've never heard of other cars going through lower ball joints as fast as the 951's seem to, even guys with aftermaket lower control arms continue breaking front pins, or stressing lower control arms in other ways. Hmmm....

Devon, if you have flat spotted a tire, either from locking up during a hard breaking manuver or maybe the car has sat too long in the same spot, then the tire flat spot could also be causing the shimmy. Good luck.

billthe3

Triple post ftw!

Yabo

It sucks if it is an intristic suspension design issue.. because it makes the car feel like crap.