Help needed - 325Ci with the shakes

[TheGremlin]

Hope someone can help me out ....

Recently purchased a 325Ci (06 plate) - all fine until I get to 70 (ish) on the motorway when a very noticeable vibration starts coming through the seat. I'm told that it stops when you get past 85 - but I'm guessing that the BiB wouldn't think me not wanting to have my kidneys liquified is a good excuse for speeding.

I've had all the wheel alignment checked and all the suspension bushes (even replaced a couple just in case) but the problem's still there.

Any other thoughts/ideas ?

[E30M3SE]

You say nothing about having had the wheels balanced, have they been, also check you do not have directional tyres mounted the wrong way round, failing that, prop shaft and or prop bearing.

Edited by E30M3SE on Tuesday 30th June 13:09

[D5SPM]

Have you had the wheels balanced? As I would normally associate a vibration at certain speeds with this especially if it goes away over a certain speed.

As I found out it may not fix it the first time it took me 3 attempts before it went away, each time the wheels were balanced it would last a few days before it returned, still think it is a set of crap tyres (on my part)

Edited by D5SPM on Tuesday 30th June 13:15

Edited by D5SPM on Tuesday 30th June 13:16

[TheGremlin]

Sorry - yes wheel balancing done, and tyres checked.

Luckily bought through a BMW stealership - so all under warranty. Good job prop shaft/bearings sounds expensive

[asbo]

Is it a high mileage?

The infamous BMW shimmy can be attributed to a number of things, including those you've mentioned, but also things like worn top-mounts. However, given the age of the car, I'd think this unlikely, unless it's doen a rather high mileage.

[CypherP]

Might sound like a stupid point, but have you checked the inside and outside tyre walls for defects? On a couple of occasions, i've had pretty serious judders from a defect tyre doing 70 on the m/way, and when ive pulled up and checked all tyres, i've found a bulbous part of the tyre wall.

May be worth a check if you haven't already. It's a long shot, but thought i'd point that out from experience with 'cheaper' tyres.

[TheEnd]

from the seat suggests the rear, front wheel shakes are felt through the steering wheel.
the 70mph shake you can drive through to the other side tends to suggest wheels, so maybe a buckled alloy?