Indycam

"When done its fine they just go off after 2-3 weeks?"
"front control arm bushings" ?

chris walrod

I mention this because several of the 993 folks have reported similar issues that were 100% resolved with the installation of replacement control arm bushings. Doesnt make a lot of sense in that its so intermittent. However, very typical symptoms are random steering wheel wobble at various speeds. Also random braking judder at higher speeds.

In this case, I really dont see how having to rebalance wheels/tires weekly is getting at the real cause.

Indycam

I don't see how anything would be improved by a rebalance if it was anything other than a tire .
A rebalance that fixes up worn parts for a week or two makes no sense .
How would a worn part know anything about the rebalance ?
The needing to move the wheel weights .

The test for me is a new set of tires .

chris walrod

Yes, indeed, this recurring problem is a rare one, one that doesnt make a lot of sense which is why one needs to start looking at other possible culprits.

You'd be amazed at how many 964/993 cars I see with failed front lower control arm bushings and the oddball symptoms they present as a result. Some 993's being around the 30K mile mark.

dfinnegan

Any chance there is something inside the tire . . . like some of that fix-a-flat stuff left over that may be shifting around a bit as you drive?

Uber 911

Chaps, I have more news. Car was in the shop last week having rear discs(rotors) fitted and while that was being done the front bushes were checked, ie; jam a tommy bar in the gap between the chassis mount and the arm = no movement, the bushes were replaced 6 months ago to poly ones. Well cars just done 150 miles and the front, under any form of braking, sounds like the 'Mayflower' mid Atlantic! ......and the wheel balance/brake vibration is still there.

Any thoughts?

chris

PS: Tyres were new 6 months ago, Continentals.

Indycam

"sounds like the 'Mayflower' mid Atlantic! "
Eh ?

The test would be another set of tires .

Uber 911

"sounds like the 'Mayflower' mid Atlantic! "
Eh ?

Creeks like a timber boat...

Indycam

Will you try another set of tires ?

Do your tires feel smooth when you run your hand over the tread ?

Colin 90 C2

the creaking is from the poly bushes.
the poly will need constant lubrication to stop the creaking.

If I am reading correctly, your wheels actually lose balance and need rebalancing.
I can't see how any worn parts would make the wheels lose balance.

Computamedic

I've been following this thread with increasing incredulity since it was started. Bringing it back to basic physics it's difficult to imagine how the balance can be affected without some physical change taking place. If there is nothing apparent from the outside of the wheels or tyres it's got to be worth investigating inside.

From my experience, when tyre fitters balance a wheel they usually immediately remove any existing weights before spinning the wheel up on the balancer. They usually refuse to spin it up with the existing weights in place. Is this what happens in this case?? Have they spun the wheel up with the existing weights in place first to confirm the out-of-balance?? Or is it a case where the vibration experienced is ASSUMED to be an out of balance wheel - and the wheel is re-balanced regardless.

The issue of creaking poly bushes is well known and due to insufficient lubrication when they were fitted. Could this be the cause of the vibration?? It's not clear from the previous postings just how much of this problem is proven fact and how much is assumption. It's very obvious there is an on-going problem and I think some additional diagnostic work might be necessary before a solution is found.

Regards

Dave

Uber 911

Dave, your incredulity is only equaled by my frustration...

When the wheels were balanced last time, I had the shop spin them up first and they were out 15-20 gms and non of the previous weights had fallen off, prior to that they were out 5-15gms so there is a discrepancy not an assumption. This time the weights and tyres were marked, as yet I've not had them checked but they feel like they're out - wheel shake >60mph and vibration under braking. I do have access to another set of Cups, very kindly offered by Stan so I'll be trying them to eliminate this problem.

Onto the vibration, interesting the creaking poly bushes are well know.. not to me. I've had poly bushes on three Lancia Integrale Evo's and no creaking. Still, if you recommend they're sufficiently lubricated I'll try that and see the impact. However, I'm surprised that Unit 11 in Warrington, who look after the car, were not aware of this lubrication point, I'll let them know your thoughts.

Computamedic

I can imagine - and my sympathies are with you. The fact is that there MUST be an answer and the more that you do to narrow down the cause must bring you closer to the solution. I'm sure many of the suggestions here must have helped along the way.

The issue of the squeaking poly bushes was mentioned some time ago when Powerflex first produced the bushes for the 964. I suspect much of the potential problem occurs because the original Porsche wishbones are not designed to be re-bushed so the degree of success in re-bushing might depend on the quality of the removal as well as the careful application of lubricant on installation. The noise was one of the early complaints of the Powerflex bushes but the problem seems to have been overcome now.

Good luck with the continued search.

Regards

Dave

boxsey911

Chris, have you found an alternative set of wheels to try out or have I changed my name without knowing?

Colin 90 C2

vibration under braking sounds like warped rotors.

I'm ready to send over my spare set of wheels...