Steel 650b fork

[belgiangoth]

Thinking of trying 650b on my current bike. It's Vbrakes, so I think I would need a new fork (no suspension). Is there something I have not thought of?

[Brucey]

er, new frame too? Or modified? How will you get the rear brake to work otherwise?

BTW depending on what you are trying to do, you may be finding a very expensive way of wasting your time.

cheers

[belgiangoth]

Hi brucey,

Expensive and wasting my time seems to be part of the course for me. I have the wheels/tyres and as it's a fixed gear bike I don't need to worry about rear brake. I think I will try and see whether it will work as is with alhongas.
The long story is that I am considering getting a custom bike and then converting my old bike to running 650b and even wider tyres, so that I have a range of bikes and not just two very similar bikes. Thought it would be worth trying the 650b tyres first in case I loved them so much that I wanted to build the next bike around them.
Obviously all options are more expensive than just riding what I got...

[Brucey]

well you need 19mm more drop than with a 700C wheel so a little measuring ought to tell you if you are on the right track or not. There are (crazy, IMHO) folk who ride fixed on the road with no brake; you could try that briefly perhaps?

IMHO there are really only a few reasons for using 650B;

a) you want to put (different) wheels into a frameset that won't accept fatter tyres otherwise
b) you want to use some magical tyre that only fits onto 650B rims
c) you think there is something fundamentally different about a rim size that is about 6% different from 700C size.

If you are thinking of buying new forks then you've failed on a) already.

Item b) is often spoken of but less often acted on, and when it is, it is questionable if there really is much difference.

Item c) is real enough, but might only make much difference when you are accelerating, climbing out of the saddle etc. This is only a tiny fraction of the time for most riders, so can't make much difference in the grand scheme of things, I would have said.

FWIW in your shoes I might lace a hub brake into the rims I wanted to use; but obviously this scheme is only likely to appeal if you can build wheels and you have a hub brake kicking around in the shed....

cheers

[belgiangoth]

Hmmm, hub brake would maybe be cheapest option, though hub, spokes, borrow of trying stand ... I reckon I'd be getting dangerously close to the cost of a fork. No way am I riding without gears.
6% difference in radius would be a 12% difference in inertia. Not sure that it is entirely a good thing, but still I think the inertia of a 23/25-622 is probably as close to a gold standard as possible, so wider tyres should run like a race wheel in smaller diameter.
Maybe.