Shaky Steering Wheel

[pjmoody]

I have a 99 S-type 3l auto, and I've noticed that my steering wheel tends develop a shake about between 75mph and 85mph. It seems to be worse or better depending on the surface and camber of the service.

It's been to a Jag garage for a check up and they haven't mention anything to do with the suspension.

I thought it might be tyre pressures so was going to do it on the way home, but don't have the manual, does anyone know what they should be?

Thanks

Peter

[Zad]

Okay, I know that the only link is that Ford own Jaguar, but..

This used to happen on Sierras, right on the motorway "sweet" spot when you are cruising along in normal traffic. Ford denied it was a problem and said it was unbalanced wheels. However, no matter how well the wheels were balanced, it never went away. Anyway, a few years ago I decided to treat my elderly XR4x4 to some poly bushes instead of the standard Ford fall-apart-in-2-years control arm bushes. Hey presto, no more violent steering wheel shaking. It still vibrates slightly on some surfaces but the amplitude is way down and is no longer in the "OMG this things going to fall apart" league (ok, it is, but that's due to it's age rather than anything). So it may be worth investing in some heavier duty bushes in whatever the vulnerable joint is.

[GavinPearson]

Tyre pressures are 26 front 28 rear, for both 16 and 17 inch wheels, for max comfort below 100 mph. If you exceed 100 mph you go up to 32 f 34 r. I would use the lower pressures for all road use in the UK.

Regarding the tyre and steering wheel shake, there are some fixes.

1. There is a rear subframe bush that damps noise noticeably at the speeds you mention.
2. There are lower front control arm bushings that take a lot the vibration out, plus they noticeably improve the ride over ridges in the road.
3. There is a high inertia steering wheel that damps out the oscillating motion when side to side imbalance is out of phase.
4. If you have flat spots on the tyres you can drive them out by running at the low pressures for about an hour at motorway speeds, then inflate the tyres to 34 all round, drive through a car wash to cool the tyres down, then drive around 5 miles to settle the tyre.
5. There is a procedure to balance the tyres and remount that optimises the vehicle. Get the flat spots out first or it could make the situation worse.