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Wheel bearing torque

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bash

bash

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Hi guys

I know this has been covered before, and I am sorry to rehash it, but I finally got to install the new wheel bearings on my friend's 77 MGB roadster over the weekend, and I am a bit
confused by the shim and torque issue. I have only ever done wheel bearings on Triumphs (TR6 and TR7), where the procedure is tighten until wheel stops turning and back off to the next split pin hole.

I saw the article on the Autoist site about leaving out the shims, which makes sense to me, but without any shims in place I am only at maybe 10 lbft torque on the nut to stop the hub turning at all. If I back off to the next split pin hole it turns and all seems fine to my Triumph way of thinking.

What troubles me is that I get no measurable end float as I have it now. I used a dial gauge so even 0.001" should have shown up clearly enough. I packed the inner bearing but not the outer yet - I figured it would be in and out to add shims if I had a problem. Do I need to add a shim just to give some end float? Should I torque up to 40 lbft to make sure the bearings are seated properly or will that ruin them?

There was a single shim in place for the old bearings, but that's probably not relevant because I have a new stub axle and new bearings.

Thanks in advance for any advice.
Alistair
 
You've run into the very reason that you should not leave the shims out of the system. It is impossible to get the correct torque on the hub nuts without them, unless you're VERY lucky.

First, watch this video: https://www.youtube.com/watch?v=RJYIXZtnIiw

Considering it takes only an extra five minutes per wheel, I see no reason whatsoever to leave them out. M.G. was not known for spending money on items they didn't deem absolutely necessary. Considering that fact that this is a life-critical component, I don't understand how anyone can feel good about intentionally leaving pieces out that strengthen the assembly.

As for your question about tightening to 40 lbs/ft, don't do it! If the bearing has too much pre-load on it, you will destroy it in short time and the assembly will fail at speed. The cure is to install a shim or two as necessary to obtain the correct bearing end float.
 
Thanks Steve

I think it just clicked in my mind how the shims work - they hold the smaller part of the bearing further apart to introcude end float. When I put it together last night I went with no shim to find out what size of shim I needed, thinking that the shim took the end float out, but it actually intriduces the end float. Makes sense, and if it is only adds 10 minutes to the front end rebuild (which has already taken a couple of months!) then I might as well do it. Any suggestions what size shims to order so I can do the job without placing several orders or having too many shims left over? Bets place to get them?

Thanks
Alistair
 
The shims not only set the end float, they also take a significant amount of load off the spindles by creating, in a sense, an outer spindle.

You can measure the assembly to see which spacers you need, but it's difficult to be that accurate. Considering how cheap shim are, I would order a set for each side.
 
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