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MG MGB Technical - rear axle alignment

hi all,
the rear axle on my cgt is about 1 inch further over to the nearside than the other. is it as simple as loosening of the u bolts and sliding it across or are there likely problems i could come across.
thanks bob.
Bob Taylor

This is extremely common on both MGBs and MGCs. I think it is more likely due to the rear wings not being equally shaped on either side. I wouldn't try to slide the axle over - I'm not even sure it can be done. Even if you could do it, you would proably find you upset the handling.

I suggest you read the piece titled "Alignment" on Paul Hunt's web site. here's the link.
Mike Howlett

There is hardly any scope for sliding the axle across as it is positively located on the springs. An inch is quite a bit, usually they are more like half an inch (and always to the same side apart from a single claim I read). You may be able to get it a bit better by slackening the U-bolt nuts with the car on its wheels, then giving the body a good hard shove to the near-side while the nuts are tightened. It can also be caused by springs being warped sideways for some reason (look along their length from the back), or structural damage from an accident, or following rear wing replacement.

Bob, As has been said misalignment such as this is quite usual, 1" is slightly more unusual. As Paul indicated, apart from some of it being a chassis inaccuracy, springs are another common problem. If you're up for taking the springs off, check out any sideways curve. You may be able to improve things, if they are curved, by having then re-sett.
I have a 4 link conversion on the rear of my V8. When I put the set up on I aligned the axle lines parallel, then got the prop shaft exactly central in the tunnel. But a four wheel alignment session showed the axle to be 10mm off-set. When shifted over the difference in handling was really obvious. I might add this is a car which has never been pranged, so this misalignment came about because of Pressed Steel Fisher poor assembly.
Allan Reeling

I had this issue and never knew it until suddenly wider tires rubbed on one side. I took it to several mechanics. One refused to correct it. The other didn't see a problem rewelding the saddles on the rear axle.

After being fixed 75K miles ago I haven't noticed any handling issues. This is a photo of what it looked like prior to being fixed.

I can't find the photo of the axle off center, unfortunately.

"The other didn't see a problem rewelding the saddles on the rear axle."

That may well centre the tyres between the arches but almost certainly will move the rear tyres out of line with the fronts and the car will crab - unless the chassis rails or springs are bent.

Mine has always had a 1/2" offset, despite two axles and three sets of springs (changed or other reasons). I took a series lateral, longitudinal and diagonal measurements from drop-lines and found everything squared up i.e. the rear wheels were correctly tracking the fronts. The narrower gap on the left is despite that outer wing bulging out compared to the right, as in the attached. Look at the gap between the tops of the 'actual' and reflected spirit levels, and the angles of the reflected ones The spirit level was up against the end of the wire-wheel hub in both cases.

With wire wheel conversion hubs on a stud wheel axle the near-side tyre rubbed very badly, even as 165s. A pukka wire-wheel axle reduced that to just occasionally on a sudden sharp turn when fully laden, but since fitting 175s it is more noticeable again.


Very interesting comment. I did have the whole car checked for alignment of unichassis and front/rear wheels after doing this from a chassis specialist. Years ago the car was T-Boned the one and only time I lent it to someone. I wanted to be certain everything was straight. They didn't find any issues. I didn't notice a difference. Guess if I lived closer and you had the time, I'd have you drive it.

Mine, too, has this all too common syndrome. Tried loosening U-Bolts etc to no avail. Plus, not helped by having 195/70 tyres, but remedied with a bit of judicious scissor jacking of wheel arches both sides, but more of course on UK nearside. I wonder if they cured it on the BMH shells?
Peter Allen

" I wonder if they cured it on the BMH shells? "
I doubt it. The new shells don't seem to be made any better than the originals were, except that they are better protected against corrosion. I also use 195 section tyres on my GT V8 conversion, but I built the rear wheel arches and rear wings myself so they are even on each side. Then I fitted Hoyle independent rear suspension which keeps the wheels in total control, so there is no contact even under the hardest cornering. There is a video somewhere on Youtube where the camera is under the back end of an AH 3000 pointing at the axle while the car is driving. It is quite alarming to see how much the axle moves about, paricularly sideways, because of the leaf springs.
Mike Howlett

BMH shells??? I've rebuilt 2 cars on BMH shells. Woefully inaccurate, whether any worse than the originals I couldn't say. As i said above my '73 V8 is 10mm out. Accuracy probably declined later on in production as the jig locations became more worn.
Allan Reeling

I seem to remember someone in Oz saying theirs were the same, even though they made their own body shells. Surely MG jigs and presses, though.

"camera is under the back end of an AH 3000 pointing at the axle while the car is driving"

Not sure there is much sideways movement visible at that camera angle though, even in the squealy bits, its more like the axle pivoting about the prop-shaft line in bends i.e. roll.

This thread was discussed between 29/01/2017 and 31/01/2017

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