Vibration

[Adom]

Got a niggling problem with my 96' 993 c2. When driving at over 80 mph, there is a constant vibration coming through the car, not through the steering wheel particularly, more through the seat. This is more noticeable on smoother roads (obviously) and at greater speed (100 +). The car is on original dampers/bushes etc and has covered 64k miles. Most people don't notice it when travelling in the car, but once pointed out, they can feel it too (so I am not going mad), but as this shows, it is not very pronounced.

I have had all the wheels balanced and the rears wheels stripped and re-furbed to check for any run-out abnomalies. Can't think what else it could be as I am no expert, but possibly wheel hub, suspension etc.

Anyone experienced anything similar or have any ideas? Thanks in advance

Adam


Migration info. Legacy thread was 26553

 

[Robertb]

Look in the front few pages of the current GT Purely Porsche (I think)- there are some lot who have a rolling road system which connects directly to the hubs to aid, amongst other things, high speed fault finding. Other than that, can't think of anything except balancing.

Migration info. Legacy thread was 26555

 

[Sean Dudding]

Make sure the wheels were balanced by somebody who knew what they were doing. These wheels are big and heavy and can be hard to balance.

Migration info. Legacy thread was 26558

 

[Adom]

I know exactly what you mean and I have ensured they have been balanced properly. I mostly find that wheel imbalance vibrations occur between approx 60-75 mph, then tail off. In this case it is anything over 80 mph.

Migration info. Legacy thread was 26562

 

[porkapig]

when you had the wheels stripped and refurbed was there any resizing etc done? and did you refit the original tyres? if so this may be your problem as the tyres may have worn unbalanced (doesnt even have to be visible to the eye). i had this on my integrale - took ages to find - all down to one twisted wheel repaired and worn tyre put back on - new set of tyres on sorted it

(unfortunately ended up replacing bushes, rebalancing wheels over and over again etc before looking at the tyre issue)


Migration info. Legacy thread was 26563

 

[Adom]

At the time the tyres were pretty well worn so all were replaced and still the problem remains. Thanks for the suggestions.

Adam


Migration info. Legacy thread was 26564

 

[Used Porsche]

The regulars on Rennlist would all say your shockers are shot to pieces. (they all say 30-40k on the origional Porsche items is about the life expectancy.)
64,000 miles on origional shock absorbers on UK crap roads has to be an area to check. If you have the cash its worth doing it for the handling improvement.

Also the 993 suspension set up should be checked and adjusted for alignment regularly - hence the detailled alignment procedure and printed results you get. Its not just a straight forward job that you have done every 10 years.

Migration info. Legacy thread was 26585

 

[DavidT]

I had a similar problem and it was the brake discs that had gone out of true. Even worse the new ones they fitted were out as well - so it took some time to pinpoint the fault.

I'd get the disc runout checked


Migration info. Legacy thread was 26596

 

[mark pearce]

You sometimes get a similar feeling when the front anti roll bar drop links are starting to wear,

The steering wheel vibrates at 70-90 mph just like the wheels are out of balance,

the drop links are about £25 each and take about 25 mins to fit

Mark Pearce

www.stirlings.co.uk


Migration info. Legacy thread was 26617

 

[Adom]

I suspect the shockers, and will get them replaced when I uprate to factory sports suspension towards the end of the year. In the meantime, it is having a full alignment done today with its minor service.

The discs have all been replaced and the run out checked. I hadn't thought of the drop links, but it not particularly coming through the steering wheel.

Thanks again gentlemen.




Migration info. Legacy thread was 26634

 

[Robertb]

Make sure that they are doing the proper alignment job, ie checking and amending the rear kinematic thingy first;
http://www.autofarm.co.uk/new.php3/Geom.html

Migration info. Legacy thread was 26862

 

[Robert Warner]

I think Autofarm charge £150 for the alignment report plus their hourly labour rate to then fix any problems.

And don't forget that Autofarm can machine brake discs on the car if there is enough life left in them, and this is a repair that they claim can be better than simply fitting new discs.

I have had this machining done elsewhere on a couple of cars, not Porkers, and it has worked well [and saved £3-400 too over the costs of new discs, etc] though before going down this route I always try a few very high speed, very hard stops first as this quite often gets rid of any brake vibration and it is relatively cheap as well as being a bit of fun [check the mirror first though before standing on the anchors!! I once saw a brand new Aston Martin DB5 run straight into the rear of another brand new Aston Martin DB5 because the lead mechanic forgot this basic requirement . . . and the cars hadn't even been registered!]

Also one other key thing with any car is not to apply the handbrake to very hot discs after a blast and then let the car cool down. This is a classic way to warp discs. Park on the level, switch off and leave the car in 1st or reverse gear [or P if auto] until everything is cool before applying the aforementioned parking brake. Common sense really, I know, but it is easy to forget in the excitement of having blown someone into the weeds!

Cheers!

Robert


Migration info. Legacy thread was 27797

 

[JonH]

Just got rid of a similar vibration on my car, after having the wheels balanced by my local OPCs tyre specialist twice and a 4 wheel alignment carried out by Tognola I still had a vibration that got worse over 70mph. Took the the car to Micheldever tyres last week to have 2 new rears fitted using their premier service and also asked them to remove, check and refit the fronts. They did, found no problems with front tyres or wheels and balanced all 4 wheels. The drive home was beautiful - no vibration!

Find a good tyre fitter who knows how to balance wheels properly, its cheap and the most likely cause of the vibration.


Migration info. Legacy thread was 27804

 

[mogsyman]

Intersting because I have had four new tyres fitted to my 03 996 and having had them re-balanced four times (the last using the wheel bolt holes rather than the centre) and there still seems to be vibration through the car at around 50mph and steering wheel wobble at about 75mph.

It does seem to reduce if the car is used on a run and everything gets really warm.


Migration info. Legacy thread was 27913