Took the bike out for a ride in the cool of the evening last night. I was cruising along and I heard this loud sort of "bang","snap" sound and the bike went wobbly. It felt like my rear tire went flat. Thankfully I stopped safely at the side of the road. After a little investigation I found the problem; My rear bearing on the disc side had exploded! So, I got the new bearing today (getting the old one out was a job since there was nothing left of it but the outer race) and I'm looking to install it but I have a couple of questions;
1) What's the purpose of the hollow shaft between the bearings that the axel runs through? As near as I can tell it doesn't seat with the bearings.
2) Is there no flatwasher/shim between the bearing and the rear caliper mount? It seems to me that if the axle is too tight then the round cuff that's on the caliper mount would be applying too much pressure on the center race of the bearing possibly creating the same problem I just suffered from.

if you replace the bearing, replace both of them.
There`s no shim between the brake caliper carrier and the bearing.
There is also no pressure on the inner bearing race as the hollow tube is the bearing spacer inside the rim. If this was missing or replaced by a self made steel tube (maybe one that has not the correct length - I`ve seen that already) the pressure of the tightened axle can damage a bearing.


G.

My tube does not have that offset on the ends. Does that offset slip into the bearings on both sides? If so, what are the measurements on that tube?

Because my bearing was totally destroyed I had no reference of the bearing dimensions except the one from the sprocket side. I ordered a new bearing (from McMaster) based upon the dimensions from the other side. I may actually need two new bearings of correct dimensions along with a new tube!

Most of the center tubes don't have the steps that fit into the inside of the bearing (like the ones shown, but thats what I'm going to do to fit 25mm id bearing onto a 17mm axle for a different set of wheels) That center tub is just a spacer in compression.

Most bikes have the axle ride directly on the inside race of the bearing. When you tighten up the axle, all the torque passes through the caliper mount, inside race of your bearing, center tube, inside race of the next bearing and the spacers and bearing on the sprocket side. Always check that everything spins freely when re-mounting a tire.

The length of the center tube needs to be exactly the same width as the bearing pockets in your hub so that there is no preload on the bearing when installed.

Cheers,

the bearings are SKF 63004-2RS1 / C3 or FAG 63004-2RS
(id 20mm od 42mm width 16mm)

Thanks Paso 750, that's what I bought. However, the tubes you showed in your previous post will not work with 20mm ID bearings. The axle itself is just under 20mm so that leaves no room for the tubes to sleeve in between the axle and the bearing. But, I like that idea. It makes the whole bearing structure correct. I may have to order some new bearings and make that a future project.

Phil should recognize those bearing spacers as they are from a Sport (the ends reduce the id of the bearings from 20mm to the axle`s 17mm). The Paso has one like those on the front and a simple tube on the rear.
I`ve just returned from the garage were I removed the rear bearing spacer from my old rim and it`s
126,2mm /4,97" length
25mm / 0,98" od
20,25mm / 0,797" id

this is roughly the cut through a rear wheel. There are 4 bearing spacers.


G.

Actually, I have never taken apart the stock Sport wheels. My previous bike had SS wheels on it when I got it, and my second one, I haven't removed the wheels yet. But I like the concept. Makes it real easy to remove the bearings. That would explain how Ducati used the same wheels as the Paso on the Sport, but had 17mm axles instead of the 20mm on the Paso. Use the same wheels and bearings, but different spacer tubes. Its a cheap change.

Cheers, Phil

Thanks for the drawing Paso750. The only difference in your drawing to real life is that the wheel core where the spacer runs is tapered. It is larger on the end where the disc is. I guess they do that so that the spacer self centers.

The shaft is the "Distance Piece" part number 037080290, it keeps the correct distance between the bearings. Do you have a copy of TAV.22 page E3 for the wheels and hubs it give you an exploded view of the assembly. Send me an email: ericke2@comcast.net - I can forward a pdf file if you need it.

http://i1158.photobucket.com/albums/p60 ... 1348252518