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Re: frt wheel bearings

To: TBOLIN@scana.com
Subject: Re: frt wheel bearings
From: Bkitterer <Bkitterer@aol.com>
Date: Thu, 26 Feb 1998 23:44:34 EST
Cc: spridgets@Autox.Team.Net
Reply-to: Bkitterer <Bkitterer@aol.com>
Sender: owner-spridgets@Autox.Team.Net
tim wrote:
>I just received wheel brg kits from moss.  comparing the old with the
>new, there is a difference in the new outboard bearing. while the
>dimensions of the outside diameter and inside diameter are comparable to
>the old bearing, the outer race of the new brg is little more than half
>the width of the inner race, thus exposing the rollers and cage. my
>question is, has anyone else come across this and is this new bearing a
>suitable replacement for the old one?
>thanks to all,

Tim,

I had similar questions and problems when redoing the front bearings on our
car.  The path was long enough that I wrote the following article for our club
newsletter. This is a fairly long article and hope it is not inappropriate for
the news group.  Perhaps it will help.


A Thorny Path With Sprite Front Wheel Bearings

After installing new front wheel bearings on my Sprite recently I was shocked
to find that the wheels wobbled.  Sprites have a “go, no go” ball-bearing
setup for the front hubs.  Basically  you tighten the axle nut down as tight
as it will go.  If you have properly installed the bearings then wheel wobble
indicates that either you have bad bearings or a seriously damaged axle, hub
or king pin.  Since I knew that the latter wasn’t the case, the new bearings
had to be bad.  Now comes some technical stuff.  If you don’t care about it
then jump to the next paragraph.  Sprites use a pair of thrust ball bearings,
two different diameters per axle.  When you tighten it down, the axle castle
nut presses a washer against the inner race of the outer bearing, which in
turn presses against a fixed spacer which presses against the inner race of
the inner bearing which presses against the axle casting.  Whew!!  The hub is
machined with a step that matches the spacer and captures the outer race of
both bearings.  Tightening the axle castle nut (25-65 ft/lbs) just seats the
inner races with the spacer and the axle casting, there is no adjustment that
changes the pressure on the bearings.  The thrust side of both inner and outer
bearings must face the spacer.  Failure to do this can result in bearing
separation and the brake drum and wheel are subject to leaving the car.  A
most unpleasant experience, particularly since it is most likely to occur
while negotiating a turn at speed.

The outer bearings came from Moss Motors (#125-120, $11.95 ea.).  Moss did not
have the inner bearings at that time so I got a set from British Victoria
(#5-749, $14.60 ea.).  I do not think this made any difference because all of
the bearings are FAG of Germany (#7205S.TVP and 7303B.)  These bearings had
been purchased on  combined orders with some other folks so returning them
would be a real pain.  In addition it did not seem to be worth going through
the hassle of returning these bearings in order to get another set just like
them.

After pondering the situation for a while I stopped in at my local Car Quest
dealer, TNT Auto Parts in Encinitas.  These folk have been very helpful and
will take the time to try and find parts for my car.  Well sure enough they
listed ball bearings and roller bearings for the Sprite.  The ball bearings
were very expensive and the roller bearings were reasonable so I decided to
put in roller bearings (#30303 at $19.12 ea and #30205 at $16.09 ea).  Besides
with roller bearings I should be able to adjust the wheel bearing pressure.
It took a day to get the bearings and I happened to be talking to the fellow
at British Masters in Vista.  He suggested leaving the spacer out then you can
adjust the pressure on the bearings.  The world was looking rosy again and I
rushed home with the roller bearings.  Quickly packing all of the bearings
with my new high temperature disk brake axle grease.  I do not know of any
good reason for using high temp grease on this car I just needed some new axle
grease and was feeling extravagant.  (My wife objected to my using a gal
buying a new dress as a simile here)  Because of the taper of the roller
bearings the inner race is slightly offset from the outer race but since I am
not using the center spacer so what.  The bearings were pressed into the hubs
and the hubs onto the car.  On with the washer and castle nut.  Yes I can
adjust the pressure on the bearings so the wheel turns just the way I have
decided it should. - - - Oops, the nut is not far enough on the axle to
install the cotter key.  Well the bearing race does not turn so I can get rid
of the washer and the nut will go on far enough to put in the cotter key.
This works, so on with the calipers, I have disk brakes.  Remember “so what”
back there a ways, well “so what” is that the small offset in the bearing
races have added between the two bearings and moved the hub away from the axle
casting.  Now there is not enough room between the brake disk and the caliper
to install the outer brake pads.  This would also move brake drums out to a
questionable position.

So now what.  After walking around in circles for a while and digging through
old (20 years old) boxes of parts I uncover one unused set of original Ransome
& Marles (R&M) front wheel bearings, #3MJT17 and #34LJT25.  Now I had
something to compare against.  The inner and outer diameters of all of the
bearings matched as did the thickness of the outer race.  This was no real
surprise since these were the proper dimensions to match the axle and hub.  It
is important that the inner race thickness be the same as the outer race as
became apparent with the roller bearings.  However there were several things
different between the FAG and R&M  ball bearings.  The new bearings did not
have a side marked “THRUST”.  Once you look at the bearing construction and
think about how it has to work it is apparent which is the thrust side. But
when the bearing is marked it gives you a warmer feeling knowing that the
bearing has been designed for side loading.  I also noticed that the cage that
contains the ball bearings is made of a black material that resembles plastic
in the FAG bearings.  This cage is made of brass in the R&M bearings.  There
are also some differences in the cross sections of the race’s on the two
bearings.  I do not know if any of this makes any difference.  Because of the
amount of side play and some of the construction in the FAG bearings I wonder
if they are thrust bearings.  I have not located a FAG catalog in order to
check the specifications of these bearings so this is pure speculation on my
part.

Well that was very interesting but I do not have any front wheel bearings.  So
I decided to abandon automotive sources and take the dimensions to an
industrial bearing supplier and see what I could find.  I chose to use KAMAN
Industrial Technologies Corp. and they very quickly identified a set of NSK
thrust ball bearings that matched the specifications.  They also have Timken
roller bearings but I was tired of experimenting.  They got me two pairs of
NSK thrust bearings, #7205BYG at $36.10 ea. and #7303BYG at $18.63 ea.  Other
than not having a side marked thrust, these bearings look almost identical to
the R&M bearings.  This time I only packed one set of bearings and installed
bearings, hub, calipers and brake pads before starting the second wheel.  And
yes the bearings do work and there is no wheel wobble.

It would be nice to know why the FAG bearings didn’t work, anyone have a FAG
catalog?  There are a number of advantages to roller bearings and it would be
nice to know if there are some Timken bearings that will work.   For now there
are front wheels on the car but what a long path it was to get here.



Bob and Ann
60 Sprite



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