Shimming Airhead wheel bearings

[Wirespokes]

Originally Posted by El Hombre

I don't know how they do it down under, but up here we lean the bike into a corner. And that puts the bearings directly inline with the load. In a car, rip thru a turn and you feel your ass wanting to slide sideways on the seat. Do the same on a bike, it just pushes you harder into the saddle. But when you antipodian's come up here, you seem to pick up the leaning in turns thang pretty good; Mladin, et al.

I seem to agree with John, but can't really explain why. It does appear to me that with traction (in a turn) gripping the side of the tire, forces are trying to tilt the wheel in the swingarm, or forks. That's why braced swingarms and fork braces were such a hot item in the older bikes.

To me, that translates as a sideways force on the bearings.

[pommie john]

Originally Posted by El Hombre

I don't know how they do it down under, but up here we lean the bike into a corner. And that puts the bearings directly inline with the load. In a car, rip thru a turn and you feel your ass wanting to slide sideways on the seat. Do the same on a bike, it just pushes you harder into the saddle. But when you antipodian's come up here, you seem to pick up the leaning in turns thang pretty good; Mladin, et al.

And how do you lean the bike into the corner? By exerting a twisting force on the front wheel which side loads the bearings.

Also, when you are leaned over, sure, the force is in direct line with the bearings...so long as you ride on a billiard table. Any bumps and undulations on the road are going to be exerting side loadings on the wheel bearings.

[pommie john]

Originally Posted by Wirespokes

I seem to agree with John, but can't really explain why. It does appear to me that with traction (in a turn) gripping the side of the tire, forces are trying to tilt the wheel in the swingarm, or forks. That's why braced swingarms and fork braces were such a hot item in the older bikes.

To me, that translates as a sideways force on the bearings.

Another good point.

When leaned right over, the contact patch of the tyre is no longer in the centre line of the wheel, so again lateral forces are applied to the bearings.

[Beemerboff]

My G/S has a rough front bearing, waiting for a shim kit and greaser from Cycleworks.

I thought about 6203s balls, and dug into it a bit.

According to some of the stuff I read the hubs with roller bearings had a tighter fit on the bearings - which discouraged me a bit - has anyone any practical experience with these hubs and can confirm if this is correct, and if it is required

And is there any reason why I couldn't use the Cycleworks shim kit to position the inner race on the ball bearings - I dont have the wheel apart yet and dont know the setup, but according to what I have read the spacer on ball hubs is curved to match the bearings , but I dont know if this is really necessary.

[mark1305]

And with regard to angular loadings on the bearings when leaning and turning, don't forget the tremendous gyroscopic forces exerted every time the wheels are forced to change direction. I've tried the old high school science class experiment where you stand on a swivel platform holding a just a mere bicycle wheel out at arms length. Someone spins it and when you try to tilt it, you start swiveling around. Strong forces for just a bicycle wheel. Add the extra mass of a moto tire, rim, brakes..... whew!

Oh yeah, back to the topic a little. I've also had decent service from NSN brand bearings, although I think they are a cut below top quality like SKF or FAG.

[supershaft]

Of course there is some side loading on bikes. Street bikes have more than dirt bikes. How much? All I know for sure is that it isn't too much for sealed ball bearings. They work perfectly. Do tapered roller bearings take more axial load than ball bearings? Of course but why use them when that much load isn't there to start with. How do I know that much load isn't there? Because sealed ball bearings work perfectly. I guess ball bearings can take more axial load than some think by the looks of things?

[El Hombre]

Originally Posted by Beemerboff

My G/S has a rough front bearing, waiting for a shim kit and greaser from Cycleworks.

I thought about 6203s balls, and dug into it a bit.

According to some of the stuff I read the hubs with roller bearings had a tighter fit on the bearings - which discouraged me a bit - has anyone any practical experience with these hubs and can confirm if this is correct, and if it is required

And is there any reason why I couldn't use the Cycleworks shim kit to position the inner race on the ball bearings - I dont have the wheel apart yet and dont know the setup, but according to what I have read the spacer on ball hubs is curved to match the bearings , but I dont know if this is really necessary.

Both style of bearings are 40mm od. From what I've measured over the years, it'll be 40mm +or- a ten thousandth.

The only reason I can think why the end of the spacer is anything but flat, is to have a counterbore. Where the bottom of the counterbore is where the spacer contacts the inner race and the spacer is maybe .010-.020" longer. Bored big enough so it will slip over the inner race diameter and prevent the spacer from falling down into the hub when you pull the axle.

My Bonneville has ball bearing hubs, the spacer falls down and I have to fish it back into alignment before the axle can go it. PITA.

[supershaft]

I still can't tell what you guys are talking about. Some ball bearing spacers have recesses so that it is easier to get a puller under the bearing. Is that it?

[mark1305]

Echoing Supershaft, I never came across a spacer with anything but flat ends in 3 sets of Ducati wheels and 2 sets of F650 wheels. However, the spacers put maybe 2-3 thou preload on the inner races when the bearings were seated properly which was just enough to hold it in place when pulling the axle out or putting it back in. And just enough "give" to be able to reach in and shift the spacer out of alignment to use a long drift and drive the far side bearing out. The Ducati spacers had one slot cut to accomodate a long screwdriver or similar tool reaching through from the opposite side to drive that bearing out first, remove the spacer, then knock the remaining bearing out. I took a very long thin screwdriver that never got any use and curved to blade to one side edgewise. Then I ground the tip at a slight angle to help it stay seated in the slot and on the bearing to get that first one out.

But chamfered or cupped ends on spacers - haven't run across that yet.

[MZRider]

Wow! Look what I've started! Damn troublemaker...

Thanks to those who responded to my initial query. Managed to turn a "wedding ring" of proper length out on the lathe and already have the wheel bearings repacked and everything reassembled. The tapered roller bearings and necessary shimming are old hat to me - 90% of my work is "Loopframe" Guzzis which use a similar setup. No wedding ring there though, just a stack of shims to get clearances correct. Much simplier and more robust than the Airhead design IMO.

[Houseoffubar]

I've come to a conclusion while reading this thread! I think the main reason I am enjoying ADV forum (old's Cool, at least) is that there are a lot of opinions here, but not a lot of dummies!
I don't know everything, by a long shot, but it is actually pretty rare to learn much reading a lot of forums out there. That is not the case here, you guys are some fart smellers! Thanks for some good info

[Beemerboff]

MZRider, how do you set/measure the preload on Guzzi wheel bearings - I am assuming that you dont measure rotating resistance with a spring balance like BMW recommend.

[El Hombre]

Originally Posted by Beemerboff

MZRider, how do you set/measure the preload on Guzzi wheel bearings - I am assuming that you dont measure rotating resistance with a spring balance like BMW recommend.

If it's a tapered roller bearing, probably the same way it's done on an airhead. Install the wheel, while you're tightening the axle nut, push and pull the wheel, feeling for slop. If the axle nut pulls up tight, and there's just a little slop/wiggle out at the tire, it's OK. Lots of slop when the nuts tight, you need to put a shorter wedding ring in there. No slop at all, wedding ring is too short and you need a longer one.

The slop is barely perceptible, just some movement. Easier if you have it up on the centerstand.