Santo,

Find an indy or go back to your HD shop. Do not tell them what you are doing as every HD I have been in swear the 21 will not fit. Even my indy a guy I really trust was not sure until I pulled up and showed him. The guys at the dealer sat and argured with me that a 21 would not fit even though I told them I had it on my bike in the parking lot! I swear I thought the guy was going to continue to disagree looking at it.

Anyway buy the 3/4 bearings and have your shop of choice press them for you. You may need to get new spacers when you are done but I have a good source for them but you will need to get your tire done first and then measure.

Good luck!

 

The bearing sleeve fits tight enough in the hub so that after you press in the bearing...the hole is lined up so you can get the axle in...not a super tight fit.

The purpose of the sleeve is so that there is not lateral pressure on the bearing...it is not designed for it. On the older timkin bearing wheels it also set the free play. On the sealed bearing wheels the spacer has to be longer than the distance between the bearing bores. You cannot cut the spacer shorter than this distance, or it does nothing. On the wheel I was using ....to get the bearing flush would require re-machining the wheel.

 

I'm putting a 19" wheel on a 3/4 axle- gonna change bearings and the spacer--but dont understand the above quote--clarify please why the spacer would be longer than the space between bearings? I thought the bearings have to sit flush with the boss in the wheel-if the spacer is long wouldnt that stop the bearings from sitting flush?

thanks

 

Call Ride Wright Wheels 714-632-8297

 

You are correct. Ideally the internal bearing spacer is exactly the same length as the space between the bearing lands machined into the hub.

For those that don't understand the reason for the spacer, it is so that when you tighten up the axle nut the force is conducted in this order:

face of the axle nut to
swingarm flange to
first axle spacer to
inner race of the first wheel bearing to
bearing spacer to
inner race of second bearing to
second axle spacer to
swingarm flange to
face of the head of axle

This keeps all lateral (side) force off of the bearing's rolling elements.

If the spacer was absent or too short the compressive force from tightening the axle nut would get to the inner race of the bearing from the axle spacer and then, meeting no resistance from the internal bearing spacer, it would push inward on the bearing's rolling elements which would try to move the outer races deeper into the wheel, which it couldn't do since those outer races are pressed into the wheel, against a machined face (bearing land) in the hub.

The same thing would happen from the opposite side.

This lateral (side) load is called "preload". Some bearing require some preload, like angular-contact ball bearings and tapered roller bearings (in car front wheel bearings), but some bearings cannot tolerate any preload at all, like straight roller bearings, or straight ball bearings (as used in motorcycle wheels).

Ideally the internal bearing spacer is exactly the same length as the space between the bearing lands machined into the hub. Generally, they are actually about 1 RCH longer than that distance to assure that no preload exists.

When installing the wheel bearings it is critical to pull the bearings "just flush" with the internal spacer, not tight and not loose. This is the secret to long motorcycle wheel bearing life.

 

The bearings pushed deeper into the hub?

That's weird. The bearing lands should have been the same distance apart as the spacer tube is long.

 

Ah no from experience its a no again.

 

Then why would you have had to cut down the spacer?

or did you cut the outside spacer?

Doh!

 

I ran into this on a 06 Softail. Bought a wheel at a swap meet from an 07. The 25mm 1" bearings were much narrower than the 3/4" bearings on my 06. I woulda had to mill the hub deeper on the wheel designed for the 1" bearing to accommodate the much wider 3/4" bearing. This is what my trusted mechanic told me. This may be different on the rear wheel with the spacer tube.

 

This could be useful.

http://www.gizmology.net/bearings.htm

and

From the above website it seems that the following bearing is what you would need for the 3/4" axle and 15mm wide bearing.

6304-2RS 20 52 15