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MG MGB Technical - Knock off wheel threads

I purchased a 67 MGB for parts. I am an MGA person and I wanted the rear end (3.9) for one of my A's. The car is a parts car that has been stripped of almost everything but the engine trans and rear end. When taking out the rear end I have noticed that the threads on the knock offs are course, not fine like on all of the MGA's that I have. I have heard that the threads are course on the twin cam models but why would they be course on this car. The other B that I have for parts has fine threads on the knock offs. This car was a right hand drive car that was said to come from Australia. Any thoughts on why course threads?
GK George

From 65 i think when the GT come out they changed the hubs to 8tpi to match the GT axle but before that they were 12tpi as the mga was so your axle is a later axle thats all.

Ste
Ste Brown

I believe that they changed the threads when they elimminated the eared knock off. I lived in France for a few years and we had to install the knock offs without ears.
It was a safety thing with the French at that time as I had to remove the spears from my chevrolet Impala front fenders(wings)
Sandy
SANDY SANDERS

Clausager P95 "...from car number 30851 in February 1964, the hub threads were altered from 12 threads per inch to the coarser 8 threads per inch."

So, relatively few MGBs will have the finer threads. The parts car which does have them is very early indeed.

On the eared knock-ons, never in Germany and Switzerland from the start of production (illegal in those places), deleted from some US States from 1965-66 and all of the USA from February 1967. From the start of MK11 production in late 1967 all export cars had octagonal nuts, and they were introduced on home market cars in August 1968 or possibly a little earlier.
Roger T

GK

You parting the engine?
Bruce Cunha

Given the choice between 12 or 8 TPI on my early B racer,
Should I be useing the later or the earlier. Does the later type tighten any better for example ????
R F Murray

Read something believable once that the coarse thread ones are stronger, I think at the thread root. And certainly the coarse ones are less likely to get cross threaded or otherwise FUBARed.

FRM
FR Millmore

Of course it's coarse, as FRM says.

Off topic I suppose but watching Wheeler Dealers working on a Lotus Elan last week I noticed they had the left-hand thread on the left-hand side, i.e. opposite to MGBs. Turns out this is because the Lotus spinner fits inside the wheel hub, not the outside like on the MGB, and everything else with centre-locks, reputedly.
PaulH Solihull

Paul,

I think that there was a bit of leg pulling there.
Possibly the first thing that they thought of, to hide their embarassment.
The Lotus Elan spinner is not inside the hub (see attached image).
And even if it was the self-locking action of a spinner only relates to the direction the wheel is turning.

Mick

M F Anderson

Paul,

I have found what they meant.
The taper on the wheel which mates with the spinner is on the inside of the wheel centre hole, not on the outside of the hole as with the MGB.
See image.
How this results in the left hand thread being on the left hand side is beyond me at the moment.
This requires a bit of investigation!!!

Mick

M F Anderson

It's all about 'precession' and the pressure point between two objects rotating at the same rate moving around the area of contact between them. The reverse effect to a spinning top where the top of the axis describes a circle. Or a spinning plate, shortly before it comes to a halt flat on the floor, starts to rotate. Whilst it's difficult to visualise how the spinner being internal rather than external can reverse the direction it must be so otherwise Elan wheels would be falling off all the time. It was coincidental that the first Elan forum I looked at while investigating this had posts from people saying they had had wheels come loose! It was also rather amusing to read one person totally convinced that in his case it was because he had been accelerating more than braking!! Some better words here http://groups.yahoo.com/group/lotuselan/files/hubs%20and%20nuts.GIF that may (or may not) help but they still get bogged down in acceleration forces which are irrelevant as there are no acceleration forces on the front wheels of either MGB or Elan.

With Elan wheels if the ears on the spinners should happen to hit something as the car is travelling in a forward direction they will tend to come undone, whereas on the MGB (and everything else it seems) they will be tightened still further. Apparently when General Motors first changed from centre-lock wheels to multi-stud wheels they still fitted left-hand threaded studs and nuts to one side.
PaulH Solihull

Chrysler still used left handed studs throughout the '60s, much to the consternation of many owners trying to change a flat tire as well as a novice mechanic. RAY
rjm RAY

This thread was discussed between 18/11/2010 and 20/11/2010

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