A-Z of checking/replacing wheel bearings

[kiwidave]

I can't take the credit for this, the basis of this full rundown came from a couple of mechanics
across the pond, and I have edited it based on my own experiences.

It's actually a fairly simple job that gets quicker with practise. If I've made any obvious errors,
then apologies, just correct me and then we all have a useful and correct resource.


Have your Harley manual ready for cross-reference, now read on:


Parts needed: wheel bearing grease, two new oil seals per wheel. New bearings
and races only if the bearings are worn out. At less than 10,000 miles they should not be,
but that depends on care/riding climate of previous owner.
A good guide is to inspect, repack or repair with every tyre change.


Tools:

torque wrench, plus usual sockets, etc to remove axle nuts...

and a non-metric dial gauge indicator
http://www.machinemart.co.uk/product.asp?p=040218075
mounted on a magnetic stand
http://www.machinemart.co.uk/product.asp?p=040217200

(these for example only, I got both off ebay for £15 total!)


Your mission: The wheel spacer (without, but more usually WITH shims) will - with the axle nut fully torqued -
be just the right length so that the roller bearings ride *just off* the outer races pressed into the wheel hub.

If the spacer is too short and/or you do not add enough shims, when you crank down on the axle nut
the bearings will be forced hard into the outer races, prompting extreme wear and the possibility of seizure.

If the spacer is too long and/or you have too many shims, when you tighten the axle nut,
the wheel is effectively loose. This won't be hard to spot! Not least while you are riding......


Procedure:

Pull the wheel off.

You can feel bad wheel bearings by putting the axle back through the hub, and use a couple
sockets to space off the axle so you can put the axle nut back on and tighten it. Then turn the axle and feel. It
should turn with no perceived roughness at all. If you don't change them you will pretty soon hear them on the road
- and that is a definite warning.


Disassemble, remembering to put the left bearing back in the left race, etc, if it can be reused.

Clean everything, including the bearings.
DO NOT SPIN the bearings with compressed air. you WILL damage them.

Once everything is clean and dry, inspect for mechanical damage.
Rust is immediately apparent, even before cleaning. Check the outer
race (wedged inside the wheel hub) for tell-tale
lines where the rollers have actually removed material from the race.
Also look for any impressions of debris, metallic or otherwise, in the
inside surface of the outer race.

A slight 'wear' pattern on the surface of the roller bearing or the outer race is fine,
but nothing that you could feel by running your fingernail over it.


Roll the clean, dry bearing on the inner race with your hand, and feel for
any roughness. The rollers should turn easily and freely on the inner
race, with no roughness.

If there is any doubt about the condition of the bearing, REPLACE IT.
You MUST replace the entire bearing, not just the inner race with rollers,
or just the outer race.

The bearings are a standard Timken product, and can be found at any
bearing supply house (numbers are onsite elsewhere). Or, take the old bearing with you,
so there will be no doubt you get the right onest.
MUCH cheaper than buying them from Harley shop. They willl sell you oil seals too, again take old one with you.
Harley do not make bearings and seals, just sell other manufacturers' at exorbitant prices.


If you need to replace the bearings first you have to remove the outer races pressed into the wheel hub.
On some wheels you can use a drift i.e. a long screwdriver (not your favourite one!), old chisel,
narrow flat bar, to drive them out.
On some wheels there is no 'lip' that gives you a pry point from the other side.
So then you take the wheel to your local backstreet garage and get them to
weld a bead across the race, the heat means they drop out pretty easily.

Do NOT pound at the wheel with a drift getting nowhere. The aluminum wheel hub is soft, and the
outer race is hardened steel - guess which one gets damaged if something goes wrong?

When inserting the new outer race, freeze it for a few hours or overnight and when ready to insert it,
head the hub with a hot air gun. This freezing contracts the bearing race and the heat can expand
the hub a little, just enough to make the job easier.

There are fancy tools available, but really, if you are careful you can press-fit the new outer race
by placing the OLD race upside down on it, then a block of wood, then judicious use of hammer.
MAKE SURE that it is going in square, all the way down the the lip in the hub (on most models, check manual)

Oh yes, use a light film of grease or copper grease on the outer rim of the new race, that helps slide it in too.

Then you have to reassemble the axle with new bearings but WITHOUT any grease.
This screws up critical endplay measuring.

Put the wheel in a vice or lay it across two crates/ small tables, etc,....any position where the axle
can go through and be reached without interference.

Place one new bearing inner race (with rollers) all the way down the axle, fattest side near axle head,
then spacer, then any shims that were on then push the axle up through the wheel until the new bearing
on the bottom of axle sits in its place against the new race on the bottom or 'other' side.

Then place the other inner race down the axle into its race facing you, then use bits of pipe, old sockets, etc, to take
up the play that the swingarm would normally account for.

Hand-tighten the axle nut against the axle washer, so you are drawing
the inner bearing (with rollers) towards the internal spacer. As you tighten,
keep checking the end play by hand. Push-pull on the axle, You should be able to move
the axle back and forth (or up and down, depending on how wheel lies), with a distinct clicking sound,
as you tighten the nut. If the end play goes away, STOP! Further tightening will
damage the bearings by forcing the rollers really hard up against the outer races.

Add shims, then carry on.

Once the nut is fully hand-tight, and you still have end-play, tighten
the nut, in several steps, with a torque wrench. Make sure you
always have some end-play as you tighten. (You will have to hold
one end of the axle with a box-end or socket wrench while you
tighten the axle nut.) Tighten until you have reached the specified
torque for your wheel (front and rear are different, as are different
model years). The wheel should spin freely and you should feel some play.

At this point, with the axle nut fully torqued, and still some detectable
end-play, you can measure it. The critical bit!

Reach for your dial gauge indicator on its magnetic base
(there's a picture of this and the specs, in the manual.

Clamp or place the magnetic base on the disc (this is why I do this with wheel lying down
on Workmate or crates) and mount the dial indicator so its measuring tip is just hitting the
end of the axle without any reading. Then push/pull the axle repeatedly to get a consistent endplay
reading. Try not to rotate the axle as its tip is not usually very flat, and rotation will give a false reading.

Check your manual for desired reading. If you need shims, get the shims from the dealership
(no easier source, I've tried). They are made in thicknesses of .002, .004, .008, .016, and .032
but dealerships generally just carry one of the smaller sizes and you add 1,2, or 3 to suit.

Adding shims INCREASES end play; removing shims DECREASES end play.
Torquing the axle pulls the bearings together until the inner races (with rollers) are riding on the centre
spacer/shims *just off* the outer races pressed into the hub.

Endplay on many models is set between .004 inch to .018inch, aim for the tight side.
If you do have the maximum of .018 inches or more with just the
stepped shim washer (if fitted) or inner spacer in place, the inner spacer is too long,
and must be shortened. Get out the grinder!

To repeat, too much endplay, the bike will wobble like hell. Too little, the rollers
will be damaged in no time.

Without end play there would be no film of lube to prevent metal to
metal contact and wheel bearings would be destroyed in short order.

Once end play is set on a new set of bearings, wear just increases the amount of end play.
But if bearings are kept properly cleaned and lubed the wear is insignificant, so end play should not
increase by any large amount

When endplay has been set to spec, disassemble the wheel
bearings from the wheel. Grease EVERYTHING, including axle, inner spacer, shims, and
outer race. The inner race/roller assembly must be "packed" with grease.
This can be done by hand. If you want to go fancy, you can buy a packing tool.

The important part of packing the bearings is that all the air spaces between rollers be filled with
grease, with no air voids. Also, on the new wheel oil seals, fill the
inner cavity of the seal with grease, and be sure there is a light
film of grease on the inner lip of each seal.

Use wheel bearing grease for all this, not just any old goo.

Re-assemble bearings, spacer, shims ... it doesn't really matter which end of the spacer the shims go on.

Once the inner bearing is in place, put some additional
grease over the bearing, then insert the wheel oil seal. Some
seals go flush, others are positioned a specified distance
below the wheel surface. Again, check your manual for the
specs. And pay attention to right and left; the dimensions
can be different. Carefully use hammer and old outer race or socket to carefully place
the seal SQUARE in hub.

Run the axle through the new set-up to clear out to get a good run through the new grease
and check alignment. CAREFUL not to poke out the new roller bearings on to the floor (see below).

Remove the axle, and clean up any grease that may have
gotten where you don't want it. Pay particular attention to the
brake disc(s). Clean both sides with brake cleaner on a rag
or paper towel. The last place you want grease is on those
discs. Once everything is clean, you are finished with the
bearings. Mount the new tire, and replace the wheel on the bike.


USE A TORQUE WRENCH to tighten the axle nut. If you do it
by feel, 9 guys out of 10 will overtighten the nut. And
in doing so, crush that cheep-ass mild steel spacer, which
will reduce the bearing end play to zero, or even preload
them. Then you are riding for a fall.

At this point, you should be done. There now, wasn't that easy?

****One last point to remember: if you drop a bearing on your garage floor, don't use it.
The experts will tell you that it *will* be damaged, even if you can't see any obvious problems,
and it's life will be shortened. Take care - it's very easy to do when placing/removing to add shims.

***Props to Harley email Digest gurus Jan Otto (Colorado) and Ratbike John (California).
They taught me all this stuff that the manual doesnt explain quite so adequately.


Further reading::

http://www.timken.com/products/bearings/techtips.asp