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MG MGB Technical - Tyre wear on one tyre only?

I'm losing just the outside inch of tread on the front offside tyre of my GT, but at a frantic rate. The tyre is a 185/65R14 on on Minilite-look alloys, at about 28psi. I'm not seeing anything like comparable wear on the nearside tyre.

In my simple world the tracking is the obvious culprit (following abuse by the twenty or more sleeping policemen I have to traverse daily) but I can't understand why both tyres aren't affected?
Steve Postins

Sounds more like camber on the affected wheel than tracking. Have you changed swivel axles recently? If you get one trunnion the wrong way round you will get that effect, but it should be obvious when looking at the wheels. Other problems can affect camber as well.

Tracking is blamed for many things, but all it does is cause *both* wheels to point inwards or outwards the same amount - assuming all other angles on the suspension are the same. Adjust the tracking one side and the amount you have altered it is spread evenly between the two sides. The reason one *should* adjust tracking both sides is to keep the steering wheel aligned correctly, as do9ng just one side will move the rtack off-centre and hence the wheel also. For that reason tracking on its own can't cause a car to pull to one side, that is castor being different between the two wheels.
Paul Hunt 2

It could be that the steering rod balljoint on the offside is loose. -G.
Glenn G

I had a similar thing happen to me on my 74B. The passenger side front tire was wearing a lot more than others on the inner edge. Preasure seemed OK. It turned out that my front lever shock had gotten down on fluid and apparently the tire was bouncing too much. I got some shoch fluid, topped it off, and that seems to have solved the problem. It did occur to the inner edge tho. I hope this helps. Bob
Bob Ekstrand

Thanks for those suggestions. At a glance the trunnions look to be on the right way round but I'm going to find some time to crawl underneath and check things over properly in the next couple of days. I'll report back.
Steve Postins

Is your steering wheel slightly off center to the right? If so, its a tie rod or toe setting issue. If the wheel is centered but the car tends to dart left over bumps, its likely a camber issue, meaning worn or bent parts. It could be as simple as bushing replacement, or be more in-depth and require shock replacement or a kingpin rebuild.
Jeff Schlemmer

Sticking brake?

The kingpin was new about eighteen months ago along with the steering rack and rod-ends. The shocks are Konis, using the old dampers as mounts.

The car drives straight, with the steering wheel centred, and it doesn't pull at all on the straight or dart noticeably over bumps. Thinking about it, there's once or twice been a slightly odd sensation at low speed when braking whilst turning, a bit like the wheels had found a rut and wanted to keep turning into the corner. But then maybe they had found a rut. I've not felt or smelt the brakes sticking but will pay them more attention.

I've had a look under the car and nothing jumped out at me as being wrong. One small point I did note was that the lower trunnion nut tightens further past the holes for the split-pin than I would like; the pin head only fits in the castellation on the nut if it is inserted sideways and I still wanted to tap it towards the nut to be sure. I seem to remember some comment about the sizing of these bolts meaning you can run out of threads before they clamp the trunnion?

A quick look in the archives turned up the suggestion that the kingpin trunnions should have been torqued with car on the ground? I can give it a go but there doesn't look too much room for the wrench so if anyone can confirm that before I do battle I'd appreciate it. Otherwise I guess I'll need to think about the inner wishbone bushes.

Many thanks to all.
Steve Postins

Is the tire cupping? Could be a weak shock.
Try switching the tires front to rear. Does the problem follow the tire? Could be a bad tire.
Lee Bradley

This thread was discussed between 31/01/2008 and 06/02/2008

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