Vibration at speed

[alanmac]

Has anyone had any problems with vibrations at speeds over 90? I have a 996 C4 tip and am getting noticable vibrations and the front nose feels a little unstable above 90.

[dazren]

Check tyre pressures and be honest with yourself, have hits any potholes or bounced any of the tyres on kerbs? Check the tyre wear.

Next stage is to get a geometry check, once you are happy with the above.

DAZ

>> Edited by dazren on Tuesday 11th May 19:53

[clubsport]

Agreed check the tyre presure first off.
Next on the list is to check the wheel balancing, ideally thy should be done every 5k miles as tyres weardown.. Ensure you get a dynamic wheel balance where they balance the wheel on the rim and near the hub..call around to get this facility (not normally found at kwikfit). Not expensive my local tyre fitters charge 6 quid a rim.
I get this done twice a year and always notice a big difference.

If you still have problems then move on to a geometry check, correct laser alignment costs 150-200 sheets, so spend the small money first.

[Cyrus1971]

in my experience of driving at least a few 996's they all vibrate mildly between 85 - 100 mph. My 99TT does - figure it is just a characteristic of the car at this speed. Have heard the same from other 996 owners too and reading this thread confirms it.

[911nutter]

alan,

i had a similar problem myself...

www.pistonheads.co.uk/gassing/topic.asp?f=48&h=&t=95549

for all responses i obtained. bottom line - took it to the dealer and they sorted it out. now it's fine...

[alanmac]

Thanks all. I have only just got the car so do not know how many pot holes were hit etc!! The tyre tread is a bit uneven on the NSF tyre with a spread of 4mm on the outer edge, 5mm in the middle and 3mm on the inside edge. The other wheels have either 5mm or 6mm across the tyre. I had an OPC check done before I bought the car but they never highlighted this as being a problem. I will check the pressures next.

[john m]

Unlikely but worth a quick check; occassionally you can get something hanging off into the slipstream (loose front spoiler I can remember a couple of time) which vibrates aerodynamically.
If tyres aren't 'round', wheels may not be either. And even the brakes can be out of balance.
Your OPC should be able to track it down.

[paulmon]

I had the very same problem with my 993 C4S. It was fine until about 80MPH and then the whole of the cabin would start shaking, I took it back to the dealer who had the balancing done. Got the car back and it was still the same. When I took the car back to the dealer they said that the company they use had not been doing the balancing properly so they did it themseleves and it was perfect.

P