bump steer

cantdecide

Me ol' Dad has a '00 GS300 Sport with rattling and vibrating in the front.

Most of the suspension and brakes have been changed in the front of the car but there has always been rattling on back roads and vibration (which could be slighly buckled 18's).

The bump steer has gotten noticably worse since I drove it last. Outer rod ends are okay, not 100% on the inners but for the symptoms that are there, I'm more suspicious about the rack itself.

Andrewf20

What do you mean by bump steer - that the car pulls to the left or right over bumpy terrain? Are the bushings in good shape? I guess youve already had her up on jacks checking for loose parts?

cantdecide

Andrewf20 wrote: »

What do you mean by bump steer - that the car pulls to the left or right over bumpy terrain? Are the bushings in good shape? I guess youve already had her up on jacks checking for loose parts?

That's it, very bumpy/ shaky steering wheel. Far too much feedback- it would almost jump out ot your hand. Everything Seems to be solid. We've been looking on and off since he's got the car and most of the upper and lower supension arms have been changed along with the brakes carriers and hardware.

Andrewf20

I know large rims with low profile tyres exaggerate this issue & put the suspension under greater stress, and that funny suspension geometry from after market upgrades can increase bump steer, so im wondering if all replacement parts are the same at the standard ones? If the rattling or thumping is still there it could be you bushings are gone. Also, if the toe is out meaning the wheels are more flared out, this can increase bump steer. I reckon an hour on the ramp in a garage to check the toe, caster & camber of the wheels, may point you closer to the cause.

cantdecide

Many thanks Andrew.

I managed to get rid of most of the vibrating and most of the bump steer- How, you ask? The first most obvious thing- Checked his bloomin' tyre pressure. 3 of his wheels were down to 22 PSI (pity there's no emoticons with one fella getting a clip round the ear!).

I gave it the 'turn up the radio' treatment and a great deal (but not all) of the steering feedback was gone but it still has that basic looseness. Rattling noise is just as prevailant as ever unfortunately- it seems to be coming from the centre of the front of the car (does this bolster my steering rack idea?).

Genuine parts only used so far. They are the factory 18's but instead of a 245/ 35, he's put on 245/ 40's which made a significant improvement at the time in ride quality. Having had many cars with many aftermarket wheels of lots of sizes I feel that if there was any negative effects by changing the profile height, it is probably only making existing problems worse.

Andrewf20

Yep 22PSI is not good.

In relation to the steering rack, perhaps raise the car off the ground at the front, hold the steering wheel rigid and get a second person to steer the wheels at the wheels you know what I mean to see if something has broken or loosened as this may affect the toe out. Try rocking the wheels left and right and listen / feel for knocking or slack. Also note that steering racks usually have bushing as well up in the middle of the car which may have failed.