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Spacer lenght for tapered front wheel bearings

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Dan Lockwood Avatar
O'Fallon, MO, USA   USA
In reply to # 3908195 by MG-TC Interesting though this discussion is, it has rather wandered about, and a few misconceptions have crept in...

The original TA/B/C front hubs had BALL bearings, not rollers, and as Steve says, the spacer should be the same length (note correct spelling!) as the distance between the internal hub shoulders. I have measured quite a few, and they are MOL 31mm (1.22" so not a fractional inch equivalent).

The taper-roller bearings do not actually have tapered rollers, instead they are cylindrical but angled between the tapered inner surfaces of the races. So because they work in opposing pairs, they can cope with both longitudinal and radial forces, unlike the ball bearings, which are only designed for radial forces. This is fine if you only consider the static condition with just the weight of the car acting on them, but as soon as you start going round corners, far more forces come into play!

The taper-rollers have an offset of 1.25mm between the inner & outer races, so they will need at least 2.5mm added to the spacer tube. Rather than make special longer spacers, I have always used a 2mm "support" washer, plus thinner shims to set the pre-load. Now there are a lot of opposing opinions on this, but I side with the Timken data book, which plumps for a slight drag, or if you want to measure it, 5-7 lbs. ins. This is the same that I use for taper-roller conversions in the diff. where the same forces are exerted by the crownwheel forcing the pinion sideways and axially.

I always set them up on a hydraulic press, using a dummy spindle which the bearings slide easily onto: the transition from too loose (hub spins freely) to too tight (obvious!) is only a few tenths of a millimeter (my thinnest shims are 0.1mm (4 thou). The idea of making the bearings slide easily onto the spindle (as shown by John Twist) does not make sense from an engineering point of view: the diameters are typically 24.995mm & 19.995mm so they not are quite an interference fit, and any smaller and they would start rocking...

Roger, I'm guilty of using the term roller bearings in the place of ball bearings. But I did use the term tapered bearings for tapered bearings, like your typical Timken style tapered bearings.

I am now a firm believer in using the spacer in this application. It will greatly improve strength of the spindle while under stress.

The spacer and placing the bearings under stress also takes care of, at least in my opinion, the possibility that the inner bearings may be an easy slide on fit to the spindle. With the spacer in place and properly torqued down, effectively the inner bearing races join together and become locked to the spindle. Another bonus of the spacer... smiling smiley

As far as the Timken bearing manual goes, here is a copy from their Manual Tapered Bearing Setting instructions.


Manual methods are frequently used to set bearings on a
variety of equipment with low to moderate volume production
requirements whereby a non- exact, primarily end play, setting
range variation is acceptable. No special tooling, gauges,
charts or fixtures are typically required, but assembler’s skill
and judgment are necessary. For example, in the case of a
conventional truck non-driven wheel with a single adjusting
nut design, manual setting involves tightening the
adjusting nut while rotating the wheel until a slight bind is felt.
Then the adjusting nut is backed off 1/6 to 1/4 turn to the nearest
locking hole or sufficiently to allow the wheel to rotate freely
with some minimal end play. The adjusting nut is then locked in
this position. Skill and judgment are required to determine when
the wheel binds slightly in rotation. The more complicated the
equipment and/or the larger and heavier it is, the greater degree
of skill and judgment required.

For certain complex designs, large equipment or high
production applications, manual setting may be too
troublesome, of inappropriate accuracy and reliability, or too
time consuming. The Timken Company has devised preset
bearing assemblies and automated setting techniques as
alternatives to manual setting.

The Timken site I was on had a picture or two of the standard manual set type bearings that we would use in cars.

Along with several other good examples that would not allow me to use their properties in a thread like this. I also measured a set of Moss tapered bearings that I bought for Midget spindles, they were hard to get the calipers into because of the roller cage, but they are around .030" smaller at the inner end of the rollers, not truly same size over all the length of the roller. I saw many references to cylindrical Timken bearings, I may be wrong, but I believe cylindrical may refer to the rollers in a log or cylindrical shape. But in this case it's a cylindrical style bearing with tapered rollers. How confusing is that... But it really doesn't matter as they are not ball bearings and they're what we use in lieu of ball bearings.

As you said, there are MANY opinions in both camps. I believe that you're having great luck with the way you're setting your tapered hub bearings, but maybe a less experienced person could preload too much and then have an issue. I'll still err on the loose side as that's been a good setup for me for over 55 years now.

I guess the bottom line is USE the spacer on T's and torque the nut accordingly. Use the shims to either preload or set end play, your choice, but do it correctly.

My next project car will have TC spindles and I'll probably upgrade upon assembly to tapered bearings with the spacer and shims with a .002" to .004" end play.

Dan Lockwood
O'Fallon MO

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Edited 1 time(s). Last edit at 2019-03-13 08:31 PM by Dan Lockwood.

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