Porsche Enthusiasts Club Forum

Hi
if it's not your tires, and you are not getting any vibration through the steering I would highly suspect one of the rear suspension bushes has had it. Given that you are feeling it through the chassis, and particularly if you can feel it through the seat, the primary suspects would be in order:-
1. the torsion bar tube to chassis bushes. As these bolt to the chassis if failed they will send a lot more road vibration / chatter into the car.
2. The big donut spring plate bushes. When failed or worn will allow the cap section over the torsion bar to contact the carrier flange, again transmitting more chatter and vibration through to the chassis

3. There is a banner shaped 'wing' that comes out and up from the torsion bar carrier, on the end of it is a mount / bush the bolts into the chassis near the top bolt of the shock absorber. It has a metal L shaped plate and block of rubber with a V shape that sits on top of the banner bar. The rubber can persih and the metal rusts resulting in the two separating.

thanks for the info guys

I have just tried reducing the tyre pressures by 6psi all round, there is a noticeable improvement, I've only driven around town a short distance so far... I'll see how it is tomorrow when I deliver my daughter's wedding dress ready for the weekend, that's a motorway trip and one particular part has been very rough of late so I should get a good idea if the ride has indeed improved...fingers crossed..

Pete

I hear what you're saying and if we were talking another marque such as Ford I'd agree....in fact my boys who are fast Ford fans with highly modified cars one of which has more power than mine then yes....things will and do break. However we are talking Porsche and more importantly we are talking 951...these cars are very much over engineered with much learned from their foray at Le Mans....These chassis's can take far more than 400bhp as many have proved...my car has been modified in some form or another for most of my ownership of 18+ years. I have an awful lot of experience in modified 951's now...if there is a mechanical issue it will be more likely down to age rather than abuse. But yes something could break if I mess up a gear change for example...I did destroy my original transmission in such a way..today I have the later 89 box which is a lot stronger than my old 86 box was.

Regards

Pete

NB:..hmm the post that this was answering seems to have disappeared....i'll leave my reply in case anyone else is thinking the same....cheers guys...

A small but important update...my son has just been home to unload his gear from holiday and get ready for the wedding tomorrow, he took a very quick look at the tyres, in fact from a distance he could see a difference in colour around the centre circumference...he pointed it out to me but alas I struggle to see dark things due to laser surgery. He then got me to run my hand around the circumference of the centre portion, remember these are directional tyres so have a defined centre, well let's just say that it was like running my hand over the Himalayas....there is a noticeable number of high spots like castellations and the tyre is rock hard. He has said all along that it's the tyres, I have been leaning that way myself in recent days as stated earlier, I'm now nearly convinced that it's the tyres and the tyres only....I will try to get a new set asap, my son is going to check availability and price next week for me....

fingers crossed

Pete

fingers crossed

Me, a garage & a warranty company once changed both rear wheel bearings on my Alfa 75 because of a wheel bearing noise. All of us had checked the not very old, perfect looking Goodyear tyres. At the garage was their chief tech & the manager.
This wasn't a cheap job, I seem to remember around £190 per side in 1995. It didn't fix the wheel bearing noise so I lived with it. A year later I renewed the tyres, the noise went instantly. Rechecked tyres with tyre man, nope couldn't see anything at all.

A severe vibration at speed on my old Maxi was caused by a blister the size of a duck egg on the inner sidewall. "Can't balance that mate!"