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MG TD TF 1500 - Camber angle?
|The near side/offside(US), front tyre of my TD shows excessive wear on the outside edge.|
The pressures are correct, and so it would seemed to be caused by an incorrect camber angle, but since this does not appear to be adjustable, has anyone got any suggestions please?
|Mike, if one front tire is wearing excessivley on one edge, I would check the toe in of the front tires. Caster/cameber is not adjustable. Toe In should be zero and is set with the tie rods on each side.|
|I have experienced exactly the same thing on the right front tyre of my MGB, which has a practically identical front suspension. I suspect the reason was a bad shock absorber, but am not sure yet. If wrong toe-in adjustment was the cause I would think both front tyres would be worn?|
|Thanks Jim and Tore,|
Tore, I have refurbished shocks on the front, so I think I can eliminate that possibility. (that was one of the reasons for refurbishing them).
Jim, I think that you may be right and the reason for posing the question here was to check if anyone else thought so too. I can't see any other reason for the wear other than tracking. The only problem is that wouldn't the tracking have to be way off on the side in question, and I mean way way off, to produce this type of partial wear?
Caster and Camber is adjustable with shims beneath the shock base. The rotate the base of the shock and move the pivot point of the stearing knuckle accordingly. See image.
Also, I believe Torre is right. The incorrect toe-in would affect both tires as the stearing would 'center' toe-in or toe-out.
I can see that shims at the front of the shock would alter the camber angle to a more correct position for me. Are these stock shims from Moss? And would you know what sizes they come in and how the correct size is chosen?
If the tracking on the front wheel on one side was 'out' wouldn't that have the effect of scrubbing the tyre on its edge as it tried to steer towards the car?
If the other wheel was 'correct' then at speed wouldn't it just run true?
I may be wrong, but I donīt think it is possible for one front wheel to run straight and the other to steer towards the car. The sideways friction of both tyres are the same, so the effect of this would be to turn the car in the direction the scrubbing wheel is pointing. To keep the car going in a straight line, I believe both wheels must be in the same angle in relation to the direction of speed. Or am I wrong???
Phew - that was difficult to express in English!
You are right but --and that is a thing to check, the steering arms on both sides must be of the same lenght. It is easier for a lazy mechanic to just adjust one side to get correct toe-in, but that can give your symtoms.
|Regarding Toe-in or Toe-out:|
Suppose you purposely set up your steering with the steering wheel centered and zero toe-in. The car tracks straight and evenly. Then, because you like experiemnts, you decide to adjust the Right Tire to toe-in .10 inch by turning in the steering arm, while leaving the Left Tire alone, and the steering wheel centered. When you drive the car, the steering wheel will turn toward the toe-in and both tires will run with about .05 inch toe-in. You can try turning the steering wheel to the left to re-center it, but in fact the car will now turn to the left, away from the toe-in.
Suppose you purposely readjusted the steering with the steering wheel centered and zero toe-in. The car tracks straight and evenly. Again, because you like to experiment, you decide to adjust the Right Tire to toe-out .10 inch by turning out the steering arm, while leaving the Left Tire alone, and the steering wheel centered. When you drive the car now, the steering wheel will turn away from the toe-out and both tires will run with about .05 inch of toe-out. You can try turning the steering wheel to the right to center it, but in fact the car will now turn to the right, toward the toe-out.
To complicate things, the steering geometry is such on a car that in order to turn, the wheel on the inside of a turn always has to have a tighter angle then the wheel on the outside of a turn. This is accompished by moving the steering pivot on the front steering arm outboard compared to the king pin axis. If you center the wheels and draw a line from the steering arm pivots through their king pin axis and extend them to the rear axle, the lines will intersect at the center of the rear axle.
Finally, I've never seen shims advertised, but if after a wheel alignment and caster and camber check as described in the manual, It should be relatively easy with geometry to calculate the thickness of shims needed to correct the caster and camber by carefully measuring lengths of the suspension.
I hope this helps,
This thread was discussed between 22/03/2008 and 23/03/2008
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