The distance piece and shims must have been the British approach to applying
a more controlled and repeatable preload to the bearings than the "feel"
method used on most cars with tapered roller bearings. It probably does not
make a lot of difference which way it is done unless the bearings are run
very loose or very tight. I put about 35,000 miles with no problems on my
BJ8 after changing bearings and using the same shims that were there for the
old bearing (lack of knowledge and lack of shims). However, after changing
my front hubs I discovered that the shim requirements were quite different
from what I took out of the old hubs. This last time I did it according to
the manual.
Continuing on the discussion about the role of the distance piece (spacer):
I sent the following to the list a couple days ago but never saw it show up.
My argument that the spacer does not strengthen the stub axle to any
appreciable degree is not based on just opinion, but on my education and
experience of the last 38 years as an aircraft structural engineer. A
simple stress model of the axle - nut/bearing/spacer/bearing/spacer stackup
shows that the spacer cannot transmit (relieve) tensile loads from axle
bending to the spacer it sits on, and therefore cannot transmit those loads
into the base of the axle itself. It is the tensile stresses that are
critical to the axle because that is what causes cracking. If the spacer
were welded, bolted, or otherwise rigidly attached to the axle in a way that
could carry tensile loads, that would be a different story. Research all
you want about bearings and you will find the spacer method mentioned as a
way to apply a controlled preload to the bearings to remove excess freeplay;
but nowhere will you find a mention of strengthening axles by doing this.
I do agree that a secondary benefit of the spacer and shims is to load the
inner races of the bearings and reduce the possibility of their turning on
the axle.
Steve Byers
HBJ8L/36666
BJ8 Registry
Havelock, NC USA
-----Original Message-----
From: owner-healeys@autox.team.net
[mailto:owner-healeys@autox.team.net]On Behalf Of Magnus Karlsson
Sent: Wednesday, May 24, 2006 11:08 PM
To: Healey Lista
Subject: Re: Wheel Bearings
One peculiarity about the front wheel bearings is that almost all
other cars with tapered roller beaings do not use any distance piece
or shims. This is also true on early BN2:s, which were designed to
run on exactly the same bearings but without the distance piece and
the shims. On these cars the adjustment is made in the same manner as
most other cars. One tightens the nut to get rid of any slack but not
much enough to get drag. It is actually a much easier way of
adjusting the bearings.
Magnus Karlsson
SWEDEN
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