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MG MGB Technical - rear axle kicks to the right!?

All bushings are new within the last year or so. While I was replacing the rear shocks (actually my son was, its his now) we saw that the rear drivers tire had been rubbing the inner side (right side) of the fender well. There is a gap, nearly the same as the other side. I think the rear axle is kicking to the right when we take a foot off the gas or possibly when accelerating from a stop? Unknown, so we shifted the axle slightly to the left, about 1/2". What could cause this?
kids1

The rear axle is located by its relationship to the rear springs. If the U bolts holding the rear axle to the springs are not tight, it can allow the rear axle to shift, something which can be felt as it is happening. You will also feel the car moving to one side as this happens.

Your comment about, "so we shifted the axle slightly to the left, about 1/2" is what concerns me. This should not be possible if everything is in good condition and bolted together properly. At least it was not on any of the four axles I have worked on over the last few years.

Les
Les Bengtson

Do to the questionalble quality of springs and for that matter the variations in the tolerances during welding of the body it is quite common that the rear end is slightly off center. Rare is the car with equal spacing from tire to wheel well in the rear
John H

I have found that a broken center pin ( the bolt that holds the spring together ) can do the same thing

Bob
BOB FISHER

I should have been more clear. We loosened the Ubolts alot while the car was in the air. Then we slid the axle to the left and tightened the bolts back down. The center pins are still there and seem to be centered.

Can the axle be moving sideways when the car accelerates or decelerates? If the leafs have slack between them (they have the thin plastic film), won't that allow the axle to shift sideways as though the leaves act like a hammock.
kids1

There is a sheet metal piece under the U-bolt. If it is cracked it can allow a small shift. I had one like that, and all the tightening of the U-bolt was in vain until I found the cracked piece.
werner haussmann

What size tyres on what size/style of rim on what model?
Roger T

'Rear axle steering', which is what you seem to be describing, is usually caused by loose or broken U-bolts.

What Les and Bob say still applies, if you slacken the U-bolts you should only be able to move the axle a fraction of an inch side to side, there should be a peg on top of the springs which locates in a hole in the spring pad. No way should you be able to move it 1/2".

Given their length and the fact that only the longest spring locates 'positively' relative to the body (and even that has some movement side to side with the shackle and rubber bushes) cornering forces are bound to move the axle and hence tyres within the arches. With the correct axles, hubs, wheels and panel alignment there should be no rubbing, but with different parts there can be. The interleaving has no effect on this either way, the strength of plastic being minimal relative to the leaves of the spring. the ends of the three longer leaves should be tied with brackets round the whole spring, which reduces how much the overall spring can 'bow' sideways, but doesn't eliminate it altogether.

Rare indeed is the car with equal spacing, but that is almost always due to panel alignment even on unmolested cars, and very rarely due to axle, springs, chassis rails or anything else.
Paul Hunt 2

How are the rubber spring pads in between the upper and lower plates on the axle? These can cause a shift to one side on aceleration, and a shift back on de-celeration, can drive you nuts and its such a simple solution --just hadnt seen it mentioned in this thread.
Gil Price

I agree with Paul's theory.
"there should be a peg on top of the springs which locates in a hole in the spring pad. No way should you be able to move it 1/2"."
This peg must be broken off allowingthe axel to slide relative to the spring pad and plates.

Best regards,
Doug
DT Toms

There is a threaded stud that sticks down from the springs and goes thru the hole in the pad and it has a nut on it. If I loosen the nuts on the Ubolts, the axle can move seperately from the spring pad. On top of the axle, is a curved (half pipe) guide for the Ubolts. It too slides with the springs if I loosen the Ubolts. Its the axle sandwiched between these items that I can't seem to locate in its proper place.
kids1

The half-pipe *will* slide, it comes off altogether. Gill makes a good point, I had forgotten that. I think there is a cylindrical flange on the rubber that fits between the peg on the spring and the hole in the seat. With the pad missing maybe the spring would move as much as you say. It should be a cylindrical, flat-topped peg for location, not a threaded stud and nut, that should be on the other side of the spring.
Paul Hunt 2

This thread was discussed between 13/04/2007 and 16/04/2007

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