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MG MGA - Wire wheel over tightening spline issue.

I have just had the front wire wheels off a car that I have recently acquired and found that the internal splines on the wheel hub have knurled a pattern into the wheel adaptor at the base of the taper (see photo attached). I assume this is from over tigthening in the past or from not enough relief at the base of the taper when the adaptors were machined. This car had previously lost a wheel competing in a hillclimb - maybe this was the cause? Has anyone else had this problem? (The wheel hub looks fine).
Mike


Mike Ellsmore

Not sure you can "overtighten" a wire wheel?

I always belt mine with the hammer for all I am worth! :) This look like the inner taper is incorrectly machined?
Bob Turbo Midget England

The contact zone on the majority of the taper looks okay. I used a round file and cleaned up the knurl marks giving a little more relief at the bottom of the taper. (The brown stuff isn't rust - anti-sieze paste)!
Mike

Mike Ellsmore

Mike -
It's not from overtightening, rather from running loose. The wheel wears the taper, and the wheel's splines cut into the axle taper. There will also be corresponding wear on the wheel, in particular a high ridge around the periphery of the wheel hub where the axle hub taper ends, although this depends on whether the wheels have been changed about. Either wheels or hubs that have wear should have the high spots taken off, since fitting parts that have not worn in together will leave the wheel sitting on little high spots, which will flatten out, leaving the wheel loose again. Then it wears more, until the wheel falls off!
See the thread <"hub angles" RH Davidson> on the MGB tech board for more discussion.

FRM
FR Millmore

I tighten my wires with the wheels on the ground using a heavy home made lead hammer (melted lead job)fairly tightly but I've heard different views on how tight the spinner should be. One view is that historically the spinners were put on with a couple good wacks of the hammer and no more. This suggests that the splines are doing most of the work in transmitting the torque to the road. The other view is that the spinners are put on very tightly to create as much friction between the shoulder of the hub and its mating surface with the wheel. I lean towards the latter approach so make sure that the only grease applied is a little on the splines and thread. If the wheel starts rocking on the splines it can be the beginning of the end for both wheel and spline. Good wheels and splines have squared off tops not made pointed by deformation.
J H Cole

JH-
I should have mentioned that the wear on the tapers is also a result of long-term use without adequate lubrication. The wear mechanism is "fretting corrosion". This happens when there is slight motion between close fitting parts that are not lubricated. It is what produces the characteristic red staining and the peculiar dark but high polished look of the worn surfaces. Both colours are forms of iron oxide, and both are excellent abrasives, and when you get them powdered in a joint you have trouble. It consumes a lot of metal, and is deadly to splines as well as tapers. The same thing can be seen around loose standard lug nuts, where it additionally results in wheel failure from fatigue.

The grease on the tapers also acts as a seal to keep water and dirt out of the joint. I have taken thousands of wheels off & on, (sometimes with a torch) and I can tell you that unlubricated parts are evil and soon dead.

Every book I've ever seen tells you to grease the splines, threads, and tapers - do it!

FRM
FR Millmore

Thanks FRM - I understand and agree running loose would have allowed the wheel to rock in and out on cornering causing the indentations. Interestingly there was no deformation on the wheel hub - perhaps the hub material is harder than the adaptor.
Mike
Mike Ellsmore

Mike, but if you grease the taper there will be no frictional contribution to transmitting the torque. I've never quite understood the process here if reliance is totally on the splines. If this is the case the wheel/ hub relantionship should be a machine fit if not even an interference fit almost like half shafts but even with a new assembly there is a small amount of slack with the wheel until the spinners are done up tight. I still think that without friction there will always that small 'click' as one drives away or reverses. Do you remember the days when owners would play around with silver paper on the splines to take up the slack?
J H Cole

I agree with JHC there should be no movement whatsoever between the wheel and hub, so therefore the taper will NOT wear irrespective of whether or not it has lubrication. The tapers have 2 functions, the first to hold the wheel the second and most important is they centralise the wheel onto the hub in much the same way as do the wheel/lug nuts on conventional wheels.
As can be seen wheel/lug nuts are also tapered and fit into tapered holes (male and female tapers), these do NOT need grease but rely on friction to remain tight. If they become loose then you DO get the red staining that everyone knows is a sign of a LOOSE nut and the remedy is not grease but is tighten the darn thing up!
IMO

That said a bit of grease ought to stop water ingress, but I do not know of any taper that has grease applied.
Steering joints etc! Mini flywheel to crank!
Robert (Bob) Midget Turbo

This thread was discussed on 06/02/2010

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