WR250 1987 - Rear Brake Shoes Cutting into the hub

Marty, are the rear hubs the same for the 83 CR and XC500s? What Is the difference?

2 toughts
first I assume you are not using CR brake shoes, as they are wider
second the one spring you have on the back of the shoes, is it hittingnthe bosses on the backing plate?
if it is it will push the shoes out

I have been looking at my cr 500 which has the floating brake arm and my wr that I am putting together that has the brake aluminium stay (as does the xc): the wr and xc have the flush internal brake backing plate and the swinging arm fork that has the tab for the aluminium brake stay and the other tab for the chain cover. The cr with the floating brake arm has a backing plate that sits out and over a ridge on the hub. So the cr hub is different to the wr and xc hub. The brake shoes are different for the two hubs.

The parts manuals are not always helpful for the back wheels when seeing the difference between rear hubs for 1981 1982 and 1983. I am looking at the HVA manuals. The summary picture page 1 for 1981 shows a different rear wheel than the breakdown on the page it refers to. As Marty has pointed out despite the wr and xc with fixed brake arms having a different hub and shoes to the cr that has the floating brake arm ....the left spacers should be the same.

My problem is that I have a rear hub that has the internal flush backing plate ....it also has the bigger flange on the left side of the hub like 82 and 83 have but it has a spacer coming out of the left of the hub only allowing space for an 18mm additional spacer not the 31mm spacer all 83 and 82s should have. I think I must have the wrong rear hub .....if it was only a spacer problem that would be easy but the rim does not seem to sit in the middle of the swinging arm it tends to sit right of middle but the sprocket lines up with the front sprocket correctly so I cant push it left.

My swinging arm gap without the hub is 200mm. The hub with built in spacers on the backing plate and left of hub is 182mm. What was the length of the 1981 hub left spacer? Anyone have an 81 year bike?

Hope it all makes sense what the problem is?

I can take a look after I get home later

Chris, the 83 CR and XC rear hubs are not the same due to the rear brake. The Cr's have the floating type rear brake and the XC does not.

Marty

You can remove that short spacer from the left side and just add the one piece long spacer. Or install the other half (outboard side) of the two piece spacer. You have only the inboard side of the two spacer set.

Hope this helps
Marty

Does this help ?

Pic 2

Pic 3

Yes thanks it helps your pictures show the same arrangement as the one my 83 cr.

My 83 wr appears to have the same left big flange on the hub but has a smaller room for a spacer on the non brake side which I think was used on the 81 or earlier wr bikes. It is smaller due to another spacer in the hub already. So as Marty suggests I can just use a smaller spacer or replace the spacer with just one bigger one. The spacer on the brake side is smaller than the cr it is 5mm....the cr is 10mm.

My wheel does not sit in the middle of the swinging arm though so maybe the wheel re spoking has caused that problem?

See picture

Brake side

Large flange on rim with small spacer in hub

So Marty what you're saying is that the brake itself is different but the hub spoke pattern is the same and the same size is that correct I bought spokes for mine I think I bought them for a CR I'm hoping I'll be okay

Yes, the spokes are the same, 83-88 rear wheels all have the same spokes size and pattern.

Marty

Guys. The most common problems are that people use a 25 wide shoe where a 30mm shoe should be - or that the brake plate is bent (usually because of bush/bearing wear on the crossers, or because a 25mm shoe has been fitted at some time previously). If the brake plate is bent - it is scrap. You can mig weld a washer onto the cam end of the brake cam to keep shoes from running out of square. Some bike manufacturers did this in the old days. It is a worthy upgrade.

Also, often people have used an earlier wheel (25mm shoe version) in a bike that was designed for the 30mm shoes. This often but not always ends in disaster. It is important that if a bike has been used with a bent brake plate - that you look carefully at the brake surface to see it is not worn in a way that will encourage the shoes to mis-align. If in doubt. Buy an new hub or wheel or get it skimmed and use oversize linings....


Andy.