Front axle thrust bearing

G

gacannon

Junior Member
In rebuilding a model A front end, I asked myself why the thrust bearing is on the top instead of the bottom? It sits under the top of the king pin where the brake actuator shaft fits.

On most spindles, the thrust bearing is on the bottom where the axle will sit with its weight.

What is the proper procedure for shimming the spindle? Does the king pin locking pin act to pre-load the thrust bearing?

Why is it on top and not the bottom?

That is the only thing I can think of.

Don't know the right way to set it up. Want to get it right to reduce friction and make the steering as best it can be.

Bob gacannon
 
Think of it like this: The front of the car is essentially hanging from the king pins, which themselves are held up by the thrust bearings, which are held up by the spindles. You add shims as necessary to ensure that the axle is not too low and rubbing on the lower part of the spindle.

As for why they did not put the bearing at the bottom, that is a good question...

Doug
 
If the spindles are worn, shim under the bearing so the top swivel part of the bearing doesn't ride on the spindle causing hard steering.
 
I can see wear on the spindle bearing houseings which contain the king pin bearings. Obviously it has sat hard against the lower block for a while. I can see that the king pin is locked in place in the axle so yes, the weight is hung on the top of the spindle. Makes sense now.

Bearings were installed improperly with grease holes not in place and grease fittings missing. Got all that fixed up and reamed out.

I was planning on cutting custom shims on the lathe to take up for some wear on the spindle bearing housings. I think I see the picture now. Seeing the picture is what its all about. Knowing how to approach it.

I had many model A's in my younger years. Only in my older years do I question things more. Back the, it was just getting it running again so I could drive it and have fun. Its interesting now to investigate things a bit further and possibly do a better job repairing things. I am not a show car kind of guy, can not afford it, but I still like running around in them.

Thanks for the input, its appreciated much. I will tackle assembly tomorrow with a better insight now.

Bob Gacannon
 
They make shims that go on top the spindles. The idea is you do not want any up and down movement with the spindle as that will affect the brakes.

I suggest you check your wheel bearing to spindle fit. Many spindles have significant wear in this area.

For future reference, it is much better to hone the bushings to fit. Reaming will leave high spots that will wear smooth quickly. This will make for slightly loose bushings right off. Honing will stay tight for a long time.
 
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