Width of disc rear wheel ?

[jmcgowan]

Can anyone tell me the precise width of the rear wheel hub on a disc brake equipped special ? I need the width WITHOUT the sprocket or brake disc mounted.
I'd like to see if I can make my own conversion kit to put a front wheel on back (a la omars)
Thanks

 

[Travis]

I think you'll need more information than that. I don't think each side spacer will be the same so if someone tells you how wide it is and you make two equal spacers to make up for the difference, your sprocket and rotor offsets will be off.

I just sold a rear disc wheel otherwise I'd be able to help you out.

 

[crash]

 

[jmcgowan]

I'm gonna buy a sprocket and rotor, I just don't want to buy a whole wheel because then I'll have 2 rear wheels I'm not gonna use. Once I know the width, I can measure the bolt circles on the rotor and sprocket. I'm gonna try and just use the stock sprocket bolt spacing by doing two of the same pattern (think of a universal 5 lug wheel for a car). One bolt circle for the sprocket to bolt to the spacer, and one bolt circle for the spacer to bolt to the wheel.

 

[mule]

Remove the sprocket and rotor from the wheel you already have, the dimensions are right there for the taking. Some of this stuff you need to do on your own! Then you'll know it'll fit YOUR bike.

 

[Travis]

jmcgowan, I'm still not sure exactly what you're talking about, but this should help http://www.xs650.com/forum/showthread.php?p=2355#post2355

 

[jmcgowan]

Remove the sprocket and rotor from the wheel you already have, the dimensions are right there for the taking. Some of this stuff you need to do on your own! Then you'll know it'll fit YOUR bike.

My current rear wheel is a spoked drum.

 

[jmcgowan]

jmcgowan, I'm still not sure exactly what you're talking about, but this should help http://www.xs650.com/forum/showthread.php?p=2355#post2355

BRILLIANT ! that's exactly what I need

 

[mule]

If you plan on using a stock front hub and a stock sprocket, mount the hub in the center of the swing arm and get a dimension from your stock rear hub (drum) to get a measurement for the sprocket alignment. Hint: The sprocket will need to be the same distance from the chain adjuster regardless of what hub you use.

Assuming you're still concerned about weight savings, don't try to adapt a stock XS650 rear disc brake assy as they weigh a ton. Go with something off a late model dirtbike. The disc can be anywhere you want it so long as it doesn't hit the shock on the right side and the caliper doesn't hit the spokes.

Finally, just make your spacer/bearing adapters to fill the gap between the hub and these two components. Use the largest bearings you can get to fit and move the bearings as far outboard as possible. 2nd Hint: A 650 front hub is probably the least desireable hub you could use for a 650 rear hub application. Its too small and narrow even though there is already someone making a kit for it. Doesn't make it right. If it was an acceptable application, Yamaha would have jumped right on it 30 years ago!

A cheaper, smarter, lighter way to go is to just buy a used Barnes Q/C type wheel and adapt the disc of your choice. Sprockets can be easily changed and any size is available new or used. Thats why they been used in racing and have stood up to extreme use for 40 years. Nobody uses an XS650 front hub to build up a rear racing wheel! Not even on a 250!

 

[Travis]

Mule, a lot of good info there. I'm not sure if jmcgowan is using a spoke wheel though. He might be trying to get the 19" mag on the back, but as we already discussed in another thread, it will weigh more than a spoke wheel.

I think you might have talked me into the Barnes style hub for my project with 23's even though it won’t be used in any manner that would need the stronger wheel. Since you sent me that information through email I've been trying to figure out what I'm going to do. For your tracker projects with that style of rear hub, are you using 4" or 5" hubs? Do they determine that measurement off the overall width of the hub without the spacers or is that the flange width? Finally, what size spacer do you use on the sprocket side to get the offset close? The spacers come in pretty standard sizes don’t they?

 

[mule]

That all depends on budget. If you are buying new, get a 5" A&A type or Kosman. If used, about all you'll find is a standard Barnes type at 4". What you might also try is a YZ, RM, KX, CR motorcrosser rear hub which is wide, spoked, disc AND light! Might just do the trick! I have a used wide Kosman that needs bearing carriers made if you're interested.

Standard sprocket spacing? I've measured it a jillion times, but haven't kept a record of it. Damn!

Gowan should buy the Omar kit and be done with it. Much less hassle in the long run I'd say.

 

[jmcgowan]

Gowan should buy the Omar kit and be done with it. Much less hassle in the long run I'd say.

What's the fun in that ? I can't justify spending 300 bucks for a couple pieces of aluminum I can make myself.

I'm not super concerned about weight reduction, just removing the extraneous stuff. I'm not gonna spend ridiculous sums of cash.

That said, I might just go the RD400 rear wheel route, seems much easier and provides a wider choice in tires.

PS- jmcgowan as in Joe McGowan. people butcher or misspell my last name daily.

 

[Travis]

Mule, I thought about using a dirt bike hub like one from a YZ450f, but they just don't look that good. The barnes style is much more appealing to me.