650B wheels

[I Want Sachs?]

Can I use MTB 26" wheels in place of 650B? I thought 650B is slightly smaller than 700c and usually on 135 rear spacing hubs, is that correct?

[dauwhe]

The issue is brakes--can you adjust your brake pads enough to hit the rim?

Rim diameter is 559mm for MTB, 584mm for 650B, and 622mm for 700C. So if bike was designed for 650B, you'd need to move brake pads down (584-559)/2 or 12.5mm in order to use 26" wheels. Bottom bracket would also be lower by this amount (depending on tires, of course) which could also be an issue.

Dave

[palincss]

Can I use MTB 26" wheels in place of 650B? I thought 650B is slightly smaller than 700c and usually on 135 rear spacing hubs, is that correct?

650B aka 584 is 19mm smaller radius than 700C aka 622. MTB 26" aka 559 is 31.5mm smaller in radius than 700C, and 12.5mm smaller in radius than 650B.

With any conversion, you have to deal with issues of changes in brake reach (assuming you are using rim brakes) and changes in bottom bracket height. To some extent, bottom bracket height changes in practice are often minimized because of the difference in size of the tires.

In most cases, you'd do a 650B conversion on a bike with limited clearance in order to gain room for wider tires and fenders. Since a 700Cx20 wheel and tire combination is about the same outside diameter as a 650Bx38 wheel and tire combination, you may end up switching out a 700Cx23 wheel for a 650BX38 wheel and lose only 2 or 3 mm of bottom bracket height.

Typically you'd need 19mm longer brake reach going from 700C to 650B. If you wanted to go from 700C to 559, you'd need a whopping 31.5mm additional brake reach (and good luck with that).

You can build 650B wheels on hubs of any rear spacing. All mine are on 135mm hubs, but I'm sure most of dbrk's are on 120mm wide hubs.

[I Want Sachs?]

Thanks. That information is helpful. I am trying to see if I can get a bike like Kogswell P/R and use my MTB wheels that I have lying around. I guess I will need to check if Kogswell brake mount will allow such shift towards center.

[palincss]

Thanks. That information is helpful. I am trying to see if I can get a bike like Kogswell P/R and use my MTB wheels that I have lying around. I guess I will need to check if Kogswell brake mount will allow such shift towards center.

Just about every Kogswell P/R but mine (a first-generation kustard-colored model) has cantilever brake mounts. I doubt you'll get 12.5mm downward pad adjustment on a canti brake. Even if you decided to remove the canti studs, you're still not home free: my P/R has Mafac RAID centerpulls, which provide 80mm reach, and I'm using it all.

Sell the MTB wheels, get proper 650B wheels, atmo.

[dauwhe]

I'd email Kogswell and ask what might be done. I think he might be making 559 forks that might work on a P/R. Don't know if there's a 559 version of the P/R itself in the works; but you might be able to move the canti studs.

Dave

[J.Greene]

My buddy just converted to 650b. He is much slower now. Discuss!

JG

[Frankwurst]

Call Matthew at Kogswell. I talked to him awhile back and he is pretty big on 26" wheels. I believe he has P/R's built for 26 inchers. He's very plesant, full of opinions (as we all are) and I'm sure would be glad to help you out. :beer:

[dbrk]

All the relevant issues about brake reach and clearance have, I think, been covered. When you add the tire size, even the smaller 30mm tires, on 650B rims the overall size often very closely matches a 700c with 25c or 28c tires. So the issue is not overall diameter but brakes to rim. When you go down to 559mm/26" the reach issue becomes more significant ---and relevant numbers have been covered.

I have 650B bikes with 120mm (Rene Herse), 123.5mm (Alex Singer), 128mm (Mariposa), and 130mm (Mariposa) rear spacings. The in-between sizes allow going to different wheels and gearing without compromise to the chainline or stretching the rear too much or squeezing too much.

dbrk

[tys]

I've gotten faster since converting to 650B!
Kogswell makes the P/R in 26"/559, but currently only in the 59cm size (Matthew's size, mine too!)

tys