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MG MGB Technical - rear axle offset

The rear axle offset on my MGB is about 1 1/2" and although it drives perfectly well, it does look odd from the rear with the n/s spinner fully visible and the o/s spinner not visible.
Has anyone corrected this very odd situation and if so, can you please give me some advice on how to do it or conversely who can do it for me.
Thanks
R.W. Homer

This has been discussed over and over again. It is not "a very odd situation" as you put it". You tend not to see it on cars made in the first few years of production, but it is extremely common on cars from the late 60s onwards. I think the general agreement is that the axle is more or less central in relation to the engine/gearbox, but that the rear body components are out of line. I suppose it happened as the press tools wore out. As the eye sees mostly the body, and expects it to be straight, the impression registered by the brain is that the axle is not central.

I say more or less, because these cars were not built to fine tolerances and a quarter inch here and there is to be expected. If all the quarter inches occur on one side then the car looks out of line. Most people just live with it. It's one of the quirks of owning an old car.
Mike Howlett

My '72 Roadster has an offset to the LHS (rear view) of about 15mm. Caused no end of problems when I fitted some alloys with thicker centre bosses as the LH tyre could touch the wheel arch when turning right at speed. All sorted now with new rear 1/2 wings.
1 1/2" does seem rather a lot to be explained away by worn out press tools. Has the car had a rear shunt and/or a rear rebuild?
Richard Coombs

1 1/2" is a huge amount from any cause, unless you mean 3/4" in one side and the same out the other. But then again if one spinner is visible and the other not it is a lot! I can't really see how one tyre isn't fouling the arch when standing still, unless perhaps it is a rubber bumper. As well as the causes mentioned the springs could also have a sideways arch, apart from that there is little room for manouvere in how the axle and springs are assembled to the body.
PaulH Solihull

Before you do anything drastic, take you car for tracking. This often done these days by a jig which also confirms 4 wheel alignment., i.e., whether the rear wheels are "following" the fronts!
Allan Reeling

As Paul says, an excessive sideways arch on the rear springs can exacerbate the problem. A set of new springs made my 10mm offset into a 20+mm offset. I reinstalled the original springs to make sure I was not imagining it and I wasn't.
Unfortunately there are varying qualities in the rear springs available even from reputable suppliers.
Ian Buckley

Another interesting thing to check is to see how central the tailshaft is in the tunnel. Mine was biased to the left by the same amount the wheel was closer to the outside of the wheelarch.
Ian Buckley

An interesting alternative datum, Ian. But again, it's how the spring/axle junction aligns with the chassis rails that are most important, and whether the rear wheels follow the fronts or not as Allan says.
PaulH Solihull

I think you need to take some more measurments to be sure. With my old B I was concerned that it was not straight so I painted the garage floor white in certain key places and then used a plumb line to mark the position of important points. Once the car was wheeled out of the way it was easy to take measurements and establish where the problems were. The points in the workshop manual alignment diagram are a good start but I used many other points as well. More is better as you will not get the car back in the same place a second time.
David Witham

i had a similar problem with my 68 gt. i measured the axle mounts and one side was half an inch further in than the other, i used a spacer to compensate.
A P New

Where did you put the spacer AP?
Richard Coombs

Because this topic comes up from time to time I thought I'd offer (for what it may be worth) measurements off my roadster to add to our collective data base.

The car was assembled in Australia from CKD components around June/July 1969. I have no way of accurately telling the manufacture date of the body but the casting dates on the (original) block and gear casing are October 1968. Assuming some degree of consistency between assembly of block/gearbox and the body in the UK, I presume the latter is a late 68 assembly.

Two prior owners, first '69 to '71, second '71 to 2001. Papers and service file dating back to registration in 69 came with the car and I am confident it has never been involved in an accident.

Wire wheel axle, octagonal locking nuts. Measures taken of overhang of the nut face centres to the outer face of the rear guard at the edge of the wheel arch, in the vertical line of wheel centres.

LHS 5.5mm

RHS 3.5mm

So, a left bias of 2mm.

From the rear view the car has a very slight amount of the expected drivers-side dip, RHD. I'm not sure what effect levelling the car might have on these measurements.

I believe these cars were assembled here on a locally made body jig - supposedly the one re-discovered and now used by Heritage in making the current body shells in the UK. Local assembly of these CKD cars ceased late in 1972 so the jig would not have been worn beyond that date.

I note other contributor's remarks regarding wear and tear on UK body jigs and the contribution of accident damage and repair quality to this issue.

Regards
Roger
Roger T

"I believe these cars were assembled here on a locally made body jig - supposedly the one re-discovered and now used by Heritage in making the current body shells in the UK"

Are you sure about that? My understanding is that all the *shells* were assembled in the UK, then shipped out to Oz with a kit of parts for the *car* to be assembled. It seems very unlikely that the tons of parts used to construct the shell would have been shipped to the UK when production finished, when there would already have been a full set in the UK. Again my understanding is that the Heritage jigs were the UK jigs 'put out to grass' (literally).
PaulH Solihull

This thread was discussed between 21/02/2011 and 06/03/2011

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