Shimming Airhead wheel bearings

[MZRider]

Here's the situation: I'm working on a customer's '76 R90/6 and one of the previous owners has discarded the shims (#2 in the attached diagram) necessary to obtain the correct preload of the wheel bearings. My question is: without any shims whatsoever, how do I determine what thickness of shim I need? Should I buy all the sizes available, swap them in until I find the correct one and then return the remainder (if I can)? Is there an easier way that I'm not thinking of (short of taking the wheels to Bob's and letting them do it)?

I did spend a few minutes this evening on the lathe and turned out a shim which proved to be too wide, it's possible that I could carefully trim a .001" or so at a time off until it's the correct thickness. But, I'm worried that they need to harder than the steel stock I'm using.

Your helpful suggestions would be appreciated.

[pommie john]

If you can make them in a lathe but you're worried about hardness, I'd play around until you make one just the right size, then buy one that size from the shop. ( and a couple either side, just in case something settles).

[Xcuvator]

I don't think the shims are very hard. Duane Ausherman makes and sells small shims to use with the BMW shim, or "wedding band", that he punches out of various thicknesses of shim stock. They are pretty handy to have around. If you aren't in a big hurry you could order some:
http://w6rec.com/duane/bmw/wheel_bearing/index.htm

[mark1305]

Yep, what they said. Although after grinding/welding/modifying/fabricating some Ducati inner spacers in the past (I know, different bearings but same purpose and similar torques to preload properly), they did not appear to be hardened. So I would suspect at the preload/torque/clamping forces needed for the airheads, that mild steel spacers of the proper wall thickness would be fine.

But if in doubt, I'd go with finding the correct length with a series of lathe cuts and trial fits. Then buy the corresponding OEM spacer (+ or - one size either way.

[One Less Harley]

Woody's Wheel works sells sealed bearings to do w/o the shimming if the bearings. Might want to give that a shot

[woody's wheel works]

if you have the expertise and the torque wrenches for ft/lbs and inch/lbs and are doing the wheel install as well as the tapered bearing pre-load..you have a good chance for a good outcome....
it is dependent on accurate bearing pre-load ,,,[circa 9 inch lbs drag at 28ft/lbs for the front and 32ft/lbs on the rear....]

the pickle is that the wheel installer must be able to torque the axle nut to the same value as the person who set up the tapered bearings for this system to work,,,,

i have repaired countless fried tapered bearing set-ups caused more often by over-tightening the axle nuts,,leading to excessive crush,,overheating and seizure/spun races....how many of us have torque wrenches in our tool-kits after all???

[ i was my own victim on my first BMW,,a R75/6,,didn't know anything about torquing axles,,,i went 1,500 miles before the front wheel locked up at 80 in the fast lane of the pennsylvania turnpike...i
that story is chronicled elsewhere in the forum...

not having access to tapered bearings ,,i realized i could convert to sealed ball bearings with a custom spacer,,,,the motorcycle shop to which i had been towed,,,let me use their tools and lathe,,,they stayed behind,,fed me and put me up for the night,,,i've never forgotten the gesture and have reciprocated ever since...]

i had many miles to cogitate over better ways,,,,i put another 60,000 trouble free miles on those ball bearings before i sold it....

the next modification was to the oem way of setting the shims up,,,seeing as to how Harleys use a similar technique and actually had IMHO excessive end-play[ circa .003-.016 as their spec ],,i tightened up the Harley spec to .001-.003'' and all the BMW's to .000''at 50 ft/lbs...i figured that should cover the bases,,and it has...

my track record= .0000 failures,,,,thousands of miles of worry free riding....the harleys handling went from the never ending feeling like you were riding on marbles to precise handling and the BMWs didn't lose any handling while enhancing the safety and longevity of the tapered bearing.

the beauty of the sealed ball-bearing set-up is the ease and lower$$$ of maintenance,,,

OBTW,,i haven't forgotten how to do it the oem way,,it does require an extensive collection of shims or access to them...and the aforementioned torque wrenches for this set-up to work ,,,,truth be told i'm a KISS kind of guy

w

PS,,,it is simpler to get in the ball park by starting out with a longer shim,,tighten things up and then measure the end-play with a dial indicator,,then ya can measure what's in there and adjust accordingly,,OBTW ya don't need the BMW spacer shim & shim holder ,,it is a lot simpler to make a new solid spacer that can be cut down to spec in a lathe,,,trying to make bmw shim replicas is frought with not getting the cuts parallel,,then ya have even worse problems.


PPS,,you should really ask these questions over here,,,
http://www.advrider.com/forums/showthread.php?t=145899
i

[supershaft]

I like your PS woody.

I shim wheels with the axle in a vise and a easily made spacer so the the axle nut loads the bearings. I use a torque wrench to tighten the nut to spec but that is only to insure that the axle is tight enough that being any tighter won't effect bearing adjustment. I adjust the preload by feel. If done right, that bearing spacer stack will not crush with any reasonable amount of torque put on it. I have been around airheads for a long time and if properly set up wheel bearings depended on torquing them to the exact torque that they were set up at BMW would have gone out of business a long time ago for making bikes that won't roll. The axle nut is not the bearing adjuster. That is the whole essence of the adjustable stack! With the stack adjusted right, the axle nut can from then on be tightened enough to way too much and not effect the bearing adjustment at all. The axle nuts have been over tightened by hand all the time for decades. That is when they are adjusted right to start with.

All that being said. I would convert tapered bearings to sealed ball bearing in an instant!

[Rob Farmer]

Start with a 6.8mm shim. Virtually all the shims I've fitted have been somewhere round there.

You just need something like this to get the torque right http://www.uni-max.co.uk/torque-scre...nm-28pc-set/d/ along with an adapter to allow a wheel nut sized socket to fit and a 2.3" long tube to to fit over the spindle and allow the nut to pull down on the bearing. The acceptable range for the torque is 1.5 to 4.5 N/m. Ideally 3N/m

This is my set up

Pre set torque drivers were 99p each on ebay, the hand adjustable driver was £10 again on ebay.



Calibrated gauge to set up the pre set drivers though to be honest I hardly ever use them since I picked up the hand adjustable one.



The whole set up came to less than having the dealer fit and torque a set of wheels bearings and shims for me.

Here's BMW's explanation

[R12Battletub]

Cycleworks sells a kit with a bunch of very thin shims in it. They are used in conjunction with the "tube" spacer to get things to the right spec; no need to buy a pile of the tubes in various sizes.

[El Hombre]

Originally Posted by woody's wheel works

if you have the expertise and the torque wrenches for ft/lbs and inch/lbs and are doing the wheel install as well as the tapered bearing pre-load..you have a good chance for a good outcome....
it is dependent on accurate bearing pre-load ,,,[circa 9 inch lbs drag at 28ft/lbs for the front and 32ft/lbs on the rear....]

the pickle is that the wheel installer must be able to torque the axle nut to the same value as the person who set up the tapered bearings for this system to work,,,,

i have repaired countless fried tapered bearing set-ups caused more often by over-tightening the axle nuts,,leading to excessive crush,,overheating and seizure/spun races....how many of us have torque wrenches in our tool-kits after all???

[ i was my own victim on my first BMW,,a R75/6,,didn't know anything about torquing axles,,,i went 1,500 miles before the front wheel locked up at 80 in the fast lane of the pennsylvania turnpike...i
that story is chronicled elsewhere in the forum...

not having access to tapered bearings ,,i realized i could convert to sealed ball bearings with a custom spacer,,,,the motorcycle shop to which i had been towed,,,let me use their tools and lathe,,,they stayed behind,,fed me and put me up for the night,,,i've never forgotten the gesture and have reciprocated ever since...]

i had many miles to cogitate over better ways,,,,i put another 60,000 trouble free miles on those ball bearings before i sold it....

the next modification was to the oem way of setting the shims up,,,seeing as to how Harleys use a similar technique and actually had IMHO excessive end-play[ circa .003-.016 as their spec ],,i tightened up the Harley spec to .001-.003'' and all the BMW's to .000''at 50 ft/lbs...i figured that should cover the bases,,and it has...

my track record= .0000 failures,,,,thousands of miles of worry free riding....the harleys handling went from the never ending feeling like you were riding on marbles to precise handling and the BMWs didn't lose any handling while enhancing the safety and longevity of the tapered bearing.

the beauty of the sealed ball-bearing set-up is the ease and lower$$$ of maintenance,,,

OBTW,,i haven't forgotten how to do it the oem way,,it does require an extensive collection of shims or access to them...and the aforementioned torque wrenches for this set-up to work ,,,,truth be told i'm a KISS kind of guy

w

PS,,,it is simpler to get in the ball park by starting out with a longer shim,,tighten things up and then measure the end-play with a dial indicator,,then ya can measure what's in there and adjust accordingly,,OBTW ya don't need the BMW spacer shim & shim holder ,,it is a lot simpler to make a new solid spacer that can be cut down to spec in a lathe,,,trying to make bmw shim replicas is frought with not getting the cuts parallel,,then ya have even worse problems.


PPS,,you should really ask these questions over here,,,
http://www.advrider.com/forums/showthread.php?t=145899
i

I was wondering about dumping the tapered bearings and going to ball. Four 6203 bearings are on order. I have the lathe and measuring tools to make a custom spacer. I looked at your thread, you mentioned the spacer is .010" longer than the hub flanges are apart. Any particular reason for that?

[gplane]

Originally Posted by Xcuvator

I don't think the shims are very hard. Duane Ausherman makes and sells small shims to use with the BMW shim, or "wedding band", that he punches out of various thicknesses of shim stock. They are pretty handy to have around. If you aren't in a big hurry you could order some:
http://w6rec.com/duane/bmw/wheel_bearing/index.htm

Read Duane's article. Well worth the time. I don't know if Duane still sells the shims, but I think Cycle Works or Bench Mark Works does.

[supershaft]

Originally Posted by gplane

Read Duane's article. Well worth the time. I don't know if Duane still sells the shims, but I think Cycle Works or Bench Mark Works does.

Dealerships still sell most of them I believe.

From reading that article myself and reading what others get from that article, I think it gets people treating the axle nut as if it were a bearing adjuster. He says it doesn't but then it does. He says that his article doesn't say to do that but then he recommends running the axle nut loose or it will bind the bearings. Not if they are adjusted right! IMO, he is setting up people that tighten axle nuts like they should be tightened for bearing failure. It's self fulfilling if you think about it.

[woody's wheel works]

Originally Posted by El Hombre

I was wondering about dumping the tapered bearings and going to ball. Four 6203 bearings are on order. I have the lathe and measuring tools to make a custom spacer. I looked at your thread, you mentioned the spacer is .010" longer than the hub flanges are apart. Any particular reason for that?

sure is elhombre et al,,,

we want that extra length to insure that the inner races will not be compressed /bind against the outer races...when tightening the axle

hence the rule of thumb in the industry is to make the inner spacer .010'' longer when made of steel and .020'' longer when made of aluminum[usually 6061-T6]

woody

[nella]

I haven't had any problem making these shims out of mild steel on a lathe.

[El Hombre]

Originally Posted by woody's wheel works

sure is elhombre et al,,,

we want that extra length to insure that the inner races will not be compressed /bind against the outer races..

hence the rule of thumb in the industry is to make the inner spacer .010'' longer when made of steel and .020'' longer when made of aluminum[usually 6061-T6]

woody

Thanks for the quick reply, I thought it might have something to do with pinching the bearings. Have you noticed any difference in the name brand SKF, etc. and the cheaper ones? I ordered two of the SKF for the back wheel, and going to try two of the cheaper ones up front.