[AD18]

Originally Posted by therealdb1

Are you sure it did not do this before you replaced the tyres?

From memory I don't think you have had this car long, have you?

It could be a drive train problem that you have only noticed since the new tyres went on so they get the blame.

No no, I've had it for about 3 years now. There was definitely no shaking before.
Your other comment on type of place that did the fitting is true though, granted I did not buy from the most reputable shop and the fitters...well..lets not go there. But thats why I then took it to my local indy who I trust for balancing and alignment, but shaking was still there at 70mph.
Went back to tyre shop to tell them and they didn't really care, took the rears off, rebalanced them (thats the third time now) and sent me on my way. I won't be going there again.

Originally Posted by m20b25

I have exactly same problem after swapping from run flats. Smooth as butter then hit 70 and get vibration through the floor and seat. Braking and corners don’t make a difference and it disappears around 100.

I’ve changed all front bushes and ball joints. New tyres all round, new dampers, springs, top mounts and bump stops. Didn’t just change these to fix the problem, it all needed doing anyway.

Thinking it’s drive train related: guino, gearbox & engine mounts (gearstick bounces a bit over bumps)

Yeah, same experience as you, but oddly seems to now be more at 80 than 70. I need to go for a long drive to properly feel it. Mine got noticeably worse the higher the speed from 70 on the quick test run I did do.
Overall ride is much improved, just need to get rid of this vibration and then it'll be a very nice ride.

[therealdb1]

Originally Posted by Donnie2000

You can see the extreme wear and marking on the sidewall of the tyre.

If you are cornering on the side walls no wonder you have understeer!

What pressure do you run in the fronts?

[Donnie2000]

Originally Posted by therealdb1

If you are cornering on the side walls no wonder you have understeer!

What pressure do you run in the fronts?

Exactly. And its on the very edge of the tyres because of the almost zero camber and I'm guessing the really soft bushing in the upper control arm doesn't help. M3 control arms have helped a lot.
Was worse at 36psi, better at 40psi. But still understeer until m3 arms. And no the old arms weren't worn out. 50k on them. I guess the heavyish 6 cyl engine up front doesn't help with only a 225 tyre.

[Donnie2000]

All I'm saying is taking off the rfts exposed other problems and I supposed because the car was set up with run flats in the first place. However if you are just looking for a softer ride then standard tyres will give that!