I thought I might 'chime' in on this one as well. I think someone in the
group earlier said something along the lines of 'fixing one problem may lead
to another'. In my opinion, I think that this is a distinct possibility in
this case.
I see the merits of the engineering principals in this case to increase the
bending moment of the stub axle. However, care must be exercised, as when we
become focused on eliminating one problem we may, however inadvertently,
induce another problem. This secondary problem may not be immediately
obvious, nor may it prove to be a 'major' problem. This is true, as long as
we understand the full impact and consequences of what we were trying to
originally achieve, and that we are willing to take any secondary problems
that are a consequence.
The issues that I can see with this modification are:-
1. Pre-load and/or zero clearance, is extremely difficult to measure/set
without using some sort of torque gauge set-up. Therefore a consistent
torque setting 'accuracy' cannot be achieved.
2. The risk of excessively pre-loading the hub/bearing assembly is great. If
excessive pre-load is inadvertently applied to the bearings, it will be
detrimental to the life of the bearings/hub unit. Excessive pre-load will
lead to excessive heat through increased operational friction. Excessive
heat will of course oxidise/degrade the lubricant rapidly. Metal-to-metal
contact will occur and if left un-checked, bearing failure/collapse is the
resultant.
3. Every time you change a wheel bearing set you will need to re-shim the
assembly to obtain the correct torque/pre-load.
4. Bearing clearance is the norm in our type of front hub assembly. This is
to accommodate for thermal expansion of the hub. This is typically required
due to the heat generated by the braking components (disk rotor/pads) of the
hub. Also, there is less chance of a bearing failure with an end float
setting as opposed to a pre-load setting.
If this method of increasing the stub axles bending moment is employed to
avoid 'pad knock back', great care should be taken in setting up the hub
assemblies to obtain the 'correct' hub rotational torque which is directly
related to the pre-load. The hub assemblies should be disassembled at a much
lesser frequency than that of a STD hub assembly to replace the lubricant.
As an adjunct to this, I also wondered whether anyone has investigated the
possibility of plumbing in a 3-5 PSI residual pressure valve in the front
line to ensure that the disk pads are kept up against the disk rotors?
Just some of my thoughts.
For those of you who wish further information here is a link
http://www.timken.com/products/bearings/techtips/PDFs/Vol6No3.pdf
Kind Regards
Peter Vucinic
WORKS-4
TR-4
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