Steering wobble?

[Adrian Southgate]

I have had the wheels balanced on the Sierra but I am still getting quite a wobble between 35 an 40 mph.

TCA ball joints seem fine, TRE's seem fine, bushes seem ok. Its not affected by braking as I have tried applying the brakes while holding the speed constant with the throttle so I'm ruling out disc balance and run out issues.

The only other thing I can think of is the play in the actual steering rack internals which I was advised about at the MOT.

Can I have your thoughts please gents?

[Big Vern]

Was trying to reply yesterday when the ning server put a rod out!

Geometry wont cause wheel wobble, nor will caster or tracking! £45 racks are pants they're not overhaulled or recon'd they just get the TR arm nut wrenched up (which usually finished off the plastic cup) then resprayed and new gaiters fitted. To rebuild a rack properly will cost that just in parts! 

Ade, Define exactly what you mean by wheel wobble - Does the steering wheel vibrate 'side to side' OR is the direction of the vehicle affected by a pothole or deviation in the road.

If the vehicle is 'weaving' it could just be tram lining as Pete Clayton suggested which is the side effect of Carlos Fandango superwide wheels

Poor Geometry will contribute to tram lining - I had assumed when you siad wheel wobble the steering wheen was getting a shimmy on at speed.

[Adrian Southgate]

The steering wheel shakes as if one of the front wheels is undone.

Geometry is definitely a factor though as I adjusted the track rod ends on one side lunchtime and it has diminished a little. Its a side to side wobble and its quite hard to initiate a turn but once the wheel is past 90 degrees its easier.

I will get out of work early enough tomorrow to have the geometry checked on the way home. They will soon spot where the 'loose' bit is happening when its got fangly laser thingys hanging off it.

[Adrian Southgate]

The saga continues.

I'm off to ATS to play with lasers. had the whole lot in bits all day after nearly crashing this morning. I'll post the exact findings up later as they can do a print out and I can scan it.

[Adrian Southgate]

Well that certainly improved things.

So I know things are certainly not straight under the car now. Some of the numbers seem a little odd for a rwd, live axle car but I suppose being a Dutton it's never going to be perfect. It was quite a bit out as you can see definitely had the wobble before it went in and no wobble when it came out, There was a miniscule amount of play in one of the wheel bearings but enough to produce an audible noise when moved top/bottom on the jack. Nipped that up and set off. wheel shook all the way there until I slowed down so that hadn't fixed it. 20 minutes later I was bombing up and down the road outside trying to make it wobble without success, good job well done I think. 

The setup for the machine was for an unladen escort van circa 1975 as it was the closest I could get to weight and size.

[Big Vern]

So the wheel wobble was related to whatever was loose that gave you the extra neg camber on the NSF. Was that the top mount?

Rear axle looks bent as well :-o

[Adrian Southgate]

Between one sheet and the other nothing was moved apart from the track rod ends.

As far as I know there isn't any other adjustment that can be made unless you have adjustable TCA's which I don't.

Its a 40 year old axle, I don't think its ever been absolutely straight. :-)

[Big Vern]

The axle looks to be bent, probably due to a hard life but with those rear toe values, you have an amount of rear steer.

Between the before and after the front NS camber changed. This could only happen if something is amiss. Since adjusting the toe on from the extra toe in you put on the other night back to reasonable values cannot reasonably explain the disapperance of the wobble one must presume something was loose that has got tightened during setting up the alignment.

I must have done close to 1000 alignment set ups on literally 100's of cars with some really wild settings as part of suspension development and ride and handling assesments on a state of the art alignment rig but I've never managed to introduce a wobble nor use alignment adjustment to get rid of one!

[Dave Adams]

my rear axle has very similar readings as does a second live axle i have...they are built with a little camber and toe-in from the factory. ade has a similar problem to me in that he has a little "thrust" on the axle (his is to the right mine is to the left) this can be adjusted out but it can be bigger on standard cars from new and be within tolerance.

[Dave Adams]

when i worked at a BMW accident repair shop you would not believe how wide the tolerances were on some cars....probably why rubber bushes are so popular

[Dave Taylor]

No wonder there're no jobs left in the UK you've had them all Dave, was that you tonight on Strictly take 2?

[Big Vern]

Escort geometry spec for the production vehicle has zero for rear toe and camber. Guess the axles are more easily bent than I had thought.

Most production cars have quite wide tolerances for susp. Geo, thats why I had to set cars with some pretty mad geo to assess the effects and to determine what is considered safe for the general public :-o  Set the car to tight tolerances and a huge difference it the way the car handles can be achieved :-)

[3a038xvsl2h4u]

I should have spotted this thread sooner. My sierra has a vibration at the exact same speed but appears to be on the back rather than the front. Does that help at all? I tried swapping wheels around and it made no difference, I was starting to wonder if the new prop I have is a little out of balance?