Re: Why splines wear

John Souders (frodo4(at)ix.netcom.com)
Fri, 21 Jun 1996 14:02:47 -0700


You wrote: >
>
>OK, I have been thinking about this. (The unspoken conclusion is that
>what follows is a gem, if I have been thinking about it.) No matter
how >tight the hub is, torque is transmitted from the brakes and engine
through >a series of inclined planes (the splines) in contact. There will be a
>component of force radially, tending to expand the wheel hub. If
there is >a slight expansion of the wheel hub, which seems likely, the two
inclined >planes will slip a bit relative to each other, causing wear.
>
>Having the hub very tight should minimize wear, by preventing sideways

>slippage and by helping to transmit torque from the axle to the wheel.
>Probably doesn't eliminate it completely, thought.
>
Regardless of the radial expansion, the splines are not a perfect fit. There will, by definition, be a LITTLE (fraction of a whatever) clearence between the splines when new. So, at each acceleration and braking the wheel is capable of rocking a little. The rocking will hammer the splines, and slowly the gaps between the splines will increase, causing more hammering. The snowball is now rolling.

Tightening the wheel beyond a certain point really does not prevent this, as the force is normally transmitted via the splines. Tightening attempts to cause some of the torque to be transmitted via the friction between the ends of the wheel hub and the axle (which I doubt really happens), but does not tighten the splines. Tightening a taper joint helps, but these splines are not tapered (are they???).

There may be something in tightening beyond normal, as it causes the wheel to remain centered around the axle (ends of hub are tapered), but I doubt this prevents wear.

Thats my one cents worth. Now lets get the real answer from an expert.

John - Alpine IV