Rear drum brake alternative.

[Mannyroad]

Hi,
I have an XS650 custom street scrambler which was built up with an Sr500 rear drum brake, presumably because the builder couldn't obtain an XS drum brake. The problem with this setup is that, even with an 18T front sprocket, the bike is under-geared. I've made a 38t rear sprocket, which is the smallest size I can go to due to the config of the SR500 hub, but it's still under geared.
Over here in the UK there isn't a xs650 hub or wheel to be had, so I need to find a plug and play alternative. I believe the TX750 will fit but again, none available in the UK. I can get a MX250 wheel, but with no drum plate. Will the mx250 fit? Is the axle size the same as my SR500 setup? And are there other hubs that will do? Ideally I need a hub with a mount bolt PCs significantly less than 164mm, which is what my SR500 is. Machining a new 33t sprocket from a platewheel.is no problem, so it's just knowing what options are available. Any help here guys?

 

[Jan_P]

Perhaps xs 650 Disc brake in the rear
If a salvage has those parts

 

[Mannyroad]

Thanks for the suggestion, though I'd prefer to stick with a drum brake in the rear. Suits the scrambler style better and I don't want to have to start figuring out calipers and mounts.

 

[5twins]

Are you looking for a spoke or a mag wheel? If spoke, an XS500 wheel can be adapted. It uses the same 20mm axle size as a 650, same sprocket mount as well. You will have to make spacers to fit it though (it's a narrower hub).

 

[Mannyroad]

Thanks 5twins, that's useful to know. The spacers are no problem.

 

[5twins]

For me, the big draw of the 500 wheel is it has a cush drive mounted sprocket. I figured that should ease the strain on those damper springs mounted in the back of the 650 clutch hub .....

 

[Grewth]

For me, the big draw of the 500 wheel is it has a cush drive mounted sprocket. I figured that should ease the strain on those damper springs mounted in the back of the 650 clutch hub .....

View attachment 212826

Ahhh.......Thanks for that, I had no idea about that cush drive hub on a TX/XS 500.
Will the rim and spokes from a 650 lace right up to the 500 drum ?

 

[Mannyroad]

For me, the big draw of the 500 wheel is it has a cush drive mounted sprocket. I figured that should ease the strain on those damper springs mounted in the back of the 650 clutch hub .....

View attachment 212826

Very good point 5twins, though I may have struck lucky in that I may have the chance of getting a full hub with brakes complete from a 75 bike. Sure, no cushion drive but these 500\650\750 hubs are like rocking horse shite, so fingers crossed.

 

[5twins]

Yes, 650 rims and spokes fit. The hub diameter is pretty much the same as is the distance between the spoke flanges. The big issue is the hub is narrower than a 650 one. If you pull it over tight to the left side, the sprocket will align but the rim won't be in line with the front. Move the wheel over to center it and align the rim with the front, and you throw off the sprocket alignment. But the solution is rather simple. You need to move the wheel about 8mm or 5/16", then move the sprocket back that much to re-align it. It just so happens that the sprocket is the perfect thickness and can be used to make all the needed spacers. It has 40 some teeth so is useless for 650 use .....

Only two small ring spacers are needed, one on each side of the hub, I just cut some extras. So, you add one small ring spacer and the sprocket spacer to the left side, and one small ring spacer to the brake (right) side. I welded that one to the 650 spacer .....

 

[Grewth]

Many thanks 5twins, and apologies for the thread hijack.

 

[Mannyroad]

Well, finally sorted out a replacement rear hub for the street scrambler that originally had a SR500 rear hub laced in. That hub forced me to have to use a 38T sprocket (own design) which, with the 18T sprocket up front meant the bike was way under-geared.

Anyway, I sourced and refurbished a Yam MX360 complete hub, which requires a 17mm axle, which is perfect for the Motolana rear swing arm. Machined a 33T platewheel into a rear sprocket to fit the hub, laced the hub into the existing flanged rim (most of the dims for the MX360 hub and the SR500 hub are the same, so rim could be re-used), made a couple of new axle spacers and voila, I've got back pretty close to stock gearing, which gives a great feel to the ride now.

 

[5twins]

Is your axle long enough? It doesn't appear that the nylok portion of the axle nut is reaching the threads.

 

[Kevin Werner]

What is missing... is pics of the bike...

 

[jpdevol]

Is your axle long enough? It doesn't appear that the nylok portion of the axle nut is reaching the threads.

A bit taken off that thick beveled washer on the left would fix that - perhaps.

That Motolana stuff sure looks top-shelf

 

[Mannyroad]

This is the bike guys. The nylon does actually bite ok but I agree that the axle could do with another couple of thread lengths. Good suggestion jpdevol, will certainly look at that, as that washer doesn't need to be quite so thick.

 

[Speakas]

Does anyone know of a spoke wheel with a disc brake alternative that would easily fit?

 

[jpdevol]

Does anyone know of a spoke wheel with a disc brake alternative that would easily fit?

Many possibilities depending on how much custom fabrication you want to get in to.

A couple off-the-shelf hubs ready to lace to various rims ($$$$, or $$$):
https://cognitomoto.com/products/xs650-rear-hub-disc-brake-conversion?variant=21382173377

https://www.mikesxs.net/yamaha-xs650-hub-spoke-wheel-rear-oem-256-25311-00-00.html

 

[Adamc]

This is the bike guys. The nylon does actually bite ok but I agree that the axle could do with another couple of thread lengths. Good suggestion jpdevol, will certainly look at that, as that washer doesn't need to be quite so thick.

Lovely work @Mannyroad, Bike looks a million $$$$ (Or £££££ in Blighty). Has this been in the Calendar?

 

[gggGary]

Needs to be in calendar fersher!
Royal enfield disk spoke rear looks pretty straightforward.
The Suzuki 750/1000 rear disk spoke isn't too bad, but that donor wheel is kinda rare.