bump steer

[kelnic]

i have recently purchased a FC holden and being the first FC i have driven i would like to know if the FC's are common to wander around over the road? eg bumps in the road or different types of road surfaces/camber?

[EffCee]

Hi kelnic

Before that can be answered we need to know what tyres you have fitted to the car. Is the front end standard or has it been modified? Crossplys are notorious for following all the ridges in the road commonly known as tramlining. Radial tyres dont suffer from this, unless the ruts are quite deep.

Secondly how are your tyres wearing? Are there any signs of scuffing or irregular wear patterns on the tyres. Are the tyres at the correct pressure? Scuffing tyres may mean that the wheels are out of alignment.

Thirdly check you sterring linkages for any signs of wear. Have someone rock the steering wheel while you inspect the steering components. Start at the pitman arm first, then the idler arm and then the tie rod ends. If any part has movement then it requires replacing. If no movement is found raise the vehicle off the ground, placing suitable stands underneath the vehicle and with your hands in the 12 O'Clock and 6 O'Clock position rock the front wheels check for wheel bearing play and kingpin play. Adjust or replace wheel bearings if movement is found or replace the kingpins if movement is found there.

Fourth When you drive on the road what sort of camber is there. It is common if there is a fair bit of camber for a car to drift to the left if you let go of the steering wheel. If you were to cross to the opposite side of the road and the car were to drift to the right then you could put it down to the road camber. However if you turn to the left or right, and the steering wheel doesn't return to the centre and it feels that it wants to pull the way that you have just turned ie after turning to the left it wants to pull left or after turning to the right it wants to pull right then there will be a steering component that is seized or binding. I have found Kingpins seized and idlers arms that have have become so close to seizing that it has been extremely difficult to turn them. In this case it is a matter of raising the vehicle up on a jack, placing suitable stands underneath the car and moving the tyres from side to side. In some cases you will not be able to do this. From that point on it is a matter of disconnect components to find out what is seized and upon finding the seized component repairing or replacing the component.

I hope that this helps

Keith F4

[Glenn 'Stinky' Stankevicius]

What Keith said, these cars are all pretty old now and even with radial tyres worn out steering components will let the car wander (not bump steer).

[pedro]

Good answer Keith, you covered pretty well everything, I'd just like to add when you lift the car up to check for play make sure you put the jack or stand under the front wishbone, if you put it under the body the wheel will hang down against the stops and you won't feel any play
                                                   Pedro F4+

[KFH]

A steering specialist friend of mine mentioned to me recently that another problem that can cause steering wander is the mounting rubbers between the sub frame and front end assembly. If these are old and spongy or anyway deteriorated they should be replaced.

Keith

[FB_MAD]

I find most times that bump steer only becomes a problem when lowering cars as the tie rod arm arc becomes neutral or reversed somewhat after lowering.In the case of rear steering linkage ( original Holden ) setup ( after lowering ),the arc tends to want to pull the wheel to toe out on bump and front setup ( ie front mount rack and pinion )seems to tend to want to pull the wheel to toe in on bump.

In standard height suspension the tie rod arc under movement tends to move to neutral and gives you toe in under travel.

It's been 18 years since I've work in wheel alignment so hope my memory isn't failing me on what I've written above happy to be corrected on anything I've written if it's wrong

I've just lowered my FB sedan 2 1/2 inches at the front ( original kingpin front end ) and I'm not suffering from bump steer.Had to cut and reshape bump rubbers to get some suspension travel though.


Only problem I have is steering wander due to wear or adjustment needed.Either adjustment or steering box rebuild will ease that.

Seems like your problem ( at least part of it ) is due to steering box wear.If worn and or needing adjustment, the  car will have wandery steering and you will always be correcting it.And if steering geometry is out ( as Effcee describes ) then that also adds to your wandering woes and could be a big contibutor to the problem.

Effcee's description of how to check your front end is very good and I'd be checking the front end for wear as he has described.

[kelnic]

thanks for the very helpful advice. i had a quick look underneath tonight and i think found the cause of the problem.looks like a few cold nights in the shed replacing steering components.when i drove the car i would keep the wheel steady and when i went through bump/uneven surface in the road it would go in either direction and yes the car has radial tyres and the front end is standard.