bump steer and vague steering
 

Ever since I got my '06 S40 it suffered from pretty significant bump steer and on rough roads it seems to make the steering wheel wobble left and right at slower speeds when you let go of the steering wheel. Even though the car still drives straight.

I have replaced the control arms last year and got it properly alligned. I checked all the bearings and wheels for any play which is non existent. It passed the MOT without any remarks.

I'm a little bit clueless but I think the car should drive a lot better than it does now. My mechanic did not find anything either when inspecting the car.

Recently when my S40 had worn inner edges on the front tyres it would so the same.....steering would grab a bit over ridges in the road etc .....all sorted now with new tyres!

I had that really bad on my wife's S40 only last month.

F/R Tyre was excessively worn on the inside edge, got that replaced, tracking adjustment seized (new arms needed) and as soon as that was done it had a really nasty bump steer but like yours drove straight.

Bump seemed to be worse with F/L wheel, got damper checked and there was a 'slight' misting of oil. Didn't seem to feel any different when I pushed down on the L/H or R/H corners but got front dampers replaced (plus mounts) and then problem solved. Plus the difference in ride was also so much improved that I thought the dampers or bushes on my own V50 were shot and had to get them inspected the following week.

If the tires are good I would put my money on the dampers being the culprit.