wheel bearings

[hal]

Good evening gentlemen,

How hard is it to change wheel bearing on a 90/6? Haynes recommends to send it away. Not having anyone I trust to send it away to it's a bit hard... And off course it's my daily (and only two wheel) commuter:-(

Story is; on my way home today there was a grinding sound. In the middle of traffic so I took it very gently home (stupid I guess) Removed brake caliper - grinding still there. removed wheel. bearing has a lot of play and there's a grinding sound when rolled.

So, what do you recommend? Guess I'm up to most jobs but special tools and measure tools are a bit low.

Any and all answers would be highly appreciated.
Hal

[chasbmw]

It's not really that difficult, heat and care can be needed. You need to get the preload on the bearing correct, which sometimes requires different sized wedding rings. So it can be a job difficult to turn round in a day if the bike is your only means of transport Look at Duanes site then come back with further queries?

[Airbear]

Morning Hal.
Check out Duane's site - http://www.softcom.net/users/w6rec/duan ... wwheel.htm

Also google Snowbum - he has a different approach, but it is good to get all the info.

I found it challenging initially, getting my head around the 'preload' thing. Persistence and re-reading helped. It's not rocket science and can be done with basic tools. Bearings can be obtained from any bearing supplier. Good luck.

[richard t]

At Ken's rally a few years ago Larry Fix it change out the front bearings on Ladonna's R75/6 in about a hour, that was with the rest of the gang watching and offering comments from time to time, distracting him. We used a heat gun, to heat the hub, and a mic to measure the shims, no other special tools needed

[Ken in Oklahoma]

How hard is it to change wheel bearing on a 90/6? Haynes recommends to send it away. Not having anyone I trust to send it away to it's a bit hard... And off course it's my daily (and only two wheel) commuter:-(

Story is; on my way home today there was a grinding sound. In the middle of traffic so I took it very gently home (stupid I guess) Removed brake caliper - grinding still there. removed wheel. bearing has a lot of play and there's a grinding sound when rolled.

So, what do you recommend? Guess I'm up to most jobs but special tools and measure tools are a bit low.

The advice to read Duane's site about wheel bearings is very good advice. It will be a bit hard to understand, not because Duane writes badly, but because the kind of bearings and the way they are adjusted I've only heard of on BMW motorcycles.

Do you have a Clymer service manual for your bike? Haynes copped out by saying to take it to a BMW dealer. Fat lot of good that would do you today at many BMW dealerships who won't work on airheads. The new big black Clymer book is spendy, but if you're going to be in the airhead business it will eventually be money well spent. The new Clymer book has color wiring diagrams which are a godsend (compared to the black and white diagrams with German notation in the old books).

The first thing you will need to do with your wheel is to remove those chrome hubcaps/seal holders, the ones with four holes in them. Don't do as so many people have done in the past and try to get them off with various kinds of pliers or vice grips. Unless you're lucky and they are loose you'll mar the chrome or screw up the holes in an attempt to loosen them.

That's a tough prescription because now we're talking about a special tool. Maybe your local NAPA or similar store will have a tool that will work. It will probably look like an overgrown circlip remover, but it may work. I made a tool using a piece of 1/4" x 2" x about 1 1/2 ft long strap iron. By carefully measuring the hubcap hole spacing I laid out the pattern on the strap iron. Then, using a 3/16" inch drill I carefully drilled out the four holes. The 3/16 holes are a shade tight for a 10-32 bolt, which is what you want. Four of those bolts with 10-32 nut tightening them to the strap iron, sawed and filed to just the right length will likely loosen a stubborn hubcap.

Now you can get at the bearings. The reason why the bearings felt loose is because BMW employs a unique type of bearing (tapered roller bearing) in lieu of the more common ball bearings. When you tighten down the axle nut you bring the inner races close together. As you tighten the axle nut all the clearance will go away. The bearings would get tighter and tighter if it weren't for the two spacers you will find in the hub which serve to keep the bearings from getting too tight. That is accomplished by a spacer, commonly called a wedding band, which when sized just right will allow the bearings to be squeezed together tight enough but not too tight.

From your description you almost certainly have a bad bearing. Once you have the inner spacer and wedding band out of the way you will need to drift out the outer races from the hub. That hub is aluminum which means you will need to heat it significantly so that enough clearance is generated to allow you to get the outer races out without scrubbing out some of the aluminum.

And when you go to put the new outer races in the hub you will need to heat the hub and have the races cooled down in the freezer. That gives you enough clearance that you won't risk scrubbing the bearing bore with the bearing and creating an aluminum whisker will keep the outer race from bottoming properly.

As often as not I've been able to use the same wedding band that I took out. If it's too thick or too thin you will need to buy one. But which one? They come in small thickness increments. You'll need to make an educated guess. You'll probably want to have some digital calipers or micrometer handy so you will know what you have.

The BMW way of doing the tapered roller bearings, as I said, is unusual. Duane will emphasize that it really is a good system--except so few people seem to understand how it works.

If you are familiar with the tapered roller bearings used on the front spindles of virtually all of the older cars, you will be a long way towards understanding the BMW system. On car spindles you put the new bearings in place and then tightened the axle nut until all of the play went out of the bearings. Then you probably backed off on the nut until you could run a cotter pin through one if the holes in the axle and the castellated nut. The BMW airhead bearings are the same, but they use a spacer between the two inner races to keep you from over tightening the bearings.

Once you do understand the principle, it's all pretty straightforward.

Editing: By the way, those chrome hub caps don't need to be tightened very much when you go to put them back on. The only job they have to do is to hold the seal and top hat bushing in place. If the hubcap were to loosen it would do no harm, except perhaps a bit of grease might get out.

Ken

[hal]

THX! that was very well written and understandable. Bit confused 'bout the wedding band but we'll see

[Major Softie]

THX! that was very well written and understandable. Bit confused 'bout the wedding band but we'll see

It's well explained in Duane's article.

[chasbmw]

The cheap and dirty way of getting the outer chrome covers off, is to use two suitably sized drill bits held in the jaws of a mole wrench. They don't need to be very tight

[Major Softie]

mole wrench

That was a new one for me.

[dougie]

Mole wrench?
Is that a surgical tool?