Vibration - Could my tyres be "going square"

[AndyC]

For some months I have been having trouble with vibrations on my C2S.

I have had the wheels balanced and the situation improves and then reoccurs later. Having left the car for a couple of months over the winter the vibrations this weekend have been particularly bad. It is bad on start up and then as I put a few miles on the vibrations start to reduce.

I am starting to think that the tyres are taking some kind of set. As they become warmer and have spun a bit the effect becomes smaller but neve quite goes away.

The tyres are Bridgestones, around 3 years old. Has anyone else had similar issues or an alternative explanation? I am on the verge of replacing all four tyres but since they are not well worn this is hardly a low cost test to see if I have the correct definition.

Grateful for any feedback / ideas.

Thanks.

Andy

 

[John Maddox]

As I suspect you realise this can be very difficult to diagnose but from your description I tend to go with out of round tyres. If you raise on jack so front wheels off ground - place an object like a hammer head on the floor next to tread and spin the wheel and you should be able to see the amount out of true. Some is to be expected but it will be obvious to you if excessive. While off the ground check for wheel bearing play and suspension joints If it seems ok then try and get tyres balanced on the car. If no improvement then pressure wash the drilled front discs to get the crud out and see if that improves. Does it vibrate more when braking - discs warped? Or corroded back plates. Good luck.

 

[A Ward]

What about swapping wheels and tyres with another 993 owner - that way you can see if it is your tyres that are causing the issue without splashing out nearly £1000? If it goes away then you can put your wheels back on and buy some new tyres...if not then you can start looking at possible mechanical issues that may cause your problem.

 

[lali]

Have you checked the tire pressures?
Failing that I'd go for dirty discs too... Gp through the same procedures you would to bed in a new set if pads, you may have some surface rust on the inside of the disc

I always store the cars with the pressures well above the road pressures to prevent them flattening out. Not much help to you this time but one for next winter..

 

[robslade]

Mine do the same, although it sounds less severe, only occurs at 60mph (annoying that is the speed limit here) and it wears off after 10-15 mins driving. It only started since I shipped the car over to NZ. Not too surprised that 6 weeks in a hot shipping container had some impact... Had them re-balanced several times but if I leave the car for more than a week it comes back. Anyway, since "playing" on the race circuit at the recent international Porsche Parade in Taupo, I will soon need four new tyres, so hopefully that will cure it !
Rob

 

[gm997_1]

Andy

You'd do yourself no harm at all to go back to your tyre balancer and ask him FOC to completely rule out - or rule in - tyre flatspots. Ask him to do it with tyres still on the car if possible, but if not, he'll certainly be able to take each wheel off in turn and spin them up on the balancer to tell you, without correcting it at first, whether the tyre has flatspots or not.

Once you know the verdict, if that's not conclusive, you can at least eliminate flatspots.

While wheel still on the balancer, see for other factors, eg rim is bent, rubber is worn on inside or outside shoulder, rubber is unevenly worn making patches etc etc.
If worn in this way, that can pinpoint mechanical problems, eg track rod control arms worn out on one side or both sides, steering rack worn, shocks worn, etc etc.

Do this for all wheels because up to that point it's all been FOC. Once complete, decide how to proceed further.

Equally, may well be that all this reveals nothing but I think it'll likely be a combination of several factors.

Flatspots and uneven wear highly likely because you can balance a tyre up but then the problem comes back because the tyre contiunues to wear unevenly when on the road.

Also don't forget 4 wheel alignment. It's amazing what an effect out-of-alignment can have if it's not been done in years and the car's been tracked or kerbed or suspension's playing up. The result can be vibrations, uneven tyre wear, shaky steering at certain speed, etc etc.

Maybe this needed too. But don't skimp on that as the majority of kit on the market will only achieve a basic, generic result whereas you need a highly specific one tailored to your car. Get it done using Beissbarth kit for instance, and I wager you'll be well pleased. But only worth your while if you have decent tyres !

Hope that helps.

Graeme

 

[Johnny C]

Robslade... I had the same problem, lots of vibration when I hit 60 and it was worse on certain road surfaces. I replaced the tyres all round and it went away a bit but soon came back. It turned out the steering rack was shot, as soon as that was fixed it went away never to return. Might be worth checking.