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MG MGB Technical - Rear end sag
|I purchased a '74 mgb roadster awhile back and the left rear corner is lower than the right by 1 1/2' TO 2" measuring from the trim line. All springs were replaced by the previous owner and the rear springs still have the Moss sticker on them. With the rear off the ground the front is level and the front springs under compression measure the same. The # of leafs are the same. I have tried loosening the shackles and repositioning the axle. The car is straight and never in an accident. I am at my wits end short of removing the rear springs and checking the arc. Has anyone had a problem with the Moss springs? |
|You are right to suspect the spring but there are a couple of other check before you take them off. Firstly check out the front spring hanger - pull uo the carpet behind the seat first - is the deck in good good order ?|
Then have a look at the axle tube again - it has a castle section welded on and that provides a locating seat for the spring - is the axle in the right position - finally at the rear - is the shacklebolt in the correct position. Yes springs do sag and sometimes sag unevenly - don't be surprised if that is the problem.
|First of all measurements should be taken from the wheel centre to the trim, not the ground. Second have a look at the spring shackle angle on each side.As a cart spring compresses it gets longer, the shackle is there to allow this, with equal loading (not entirely possible on a B) and matching springs, the shackles should assume more or less the same angle of deflection. You can get a good idea of the spring sag by using a piece of string from one eye to the other, either over a pit etc., or with the dif jacked up. Also look in the boot at the rear chassis leg, the floor on either side and the rear valance, heavy corrosion here could give the unevenness you describe. But getting decent replacement leaf springs is a problem,as recounted many times on these pages.|
|A problem at one front corner can cause a measurement difference at the diagonally opposite rear corner. This can be removed from the equation by supporting the front under the chassis rails or cross-member - assuming the chassis as a whole isn't twisted.|
This thread was discussed between 28/02/2011 and 06/03/2011
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