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MG MGB Technical - Differential offset - 74 MGB

I have a 1974 mgb roadster and it appears that the rear axle/diff is offset toward the LH side of the car by about 1 inch. I have been told that this is not uncommon due to manufacturing tolerances and ageing jigs but I am not yet convinced. The car is otherwise very straight with no apparent previous accident damage. I am interested to hear if this is common and if there is any way to fix this.
Colin Gibbs

I think it is fairly common to a greater or lesser degree its just that most people wont have noticed unless fitting wider tyres which foul the wheelarch on one side. I dont think it is ageing jigs as I have a 1964 car and there is a noticable difference.
An inch difference between left and right tyres and the wheelarch lip, equates to the rear axle being half this distance, ie half an inch off centre.
It could be that the mounts welded to the axle are half an inch off centre and not necessarily the cars chassis or axle/spring mounts.
I dont think there is any easy cure, however if it makes no difference to the way the car drives I dont think you need to be too concerned.
R J Collier

Hi Colin

Bugged me also when I did my restoration, but when I eyed up another 10 or so cars in the workshop, mine being only an inch out seemed like a good one!
End result, I didnt worry about it and enjoy the sunny days
Ed Braclik

Seems like most midgets are the same. I think it was one way of "centering" the pinion to reduce prop shaft angle rather than having the axle housings and half shafts different lengths. Certainly a lot cheaper to produce this way.
Bill Young

I think if you took alot of body measurements you might find that it is not so much the axle that is offset as the rear bodywork. Quite likely a mixture of the 2.

Once I used a plumb line to mark key points, such as suspension mountings, on my garage floor. While the diagonals were not perfect, they were much closer than the wheel/outer arch measurements implied.

So as Ed and Robert have already said, don't worry about it.
David Witham

Colin, if you have replaced the rear springs they may be the cause of some of the offset. The mounting eyes at the ends of the springs are not in line with the leaves, they are twisted. The factory springs have some twist but the replacements are worse. Check in the archives under springs.
John H

This thread was discussed on 30/01/2007

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