Why 650b?

Why 650b? Well, this for one reason.

Oh, and did I happen to mention gravel?

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10 thoughts on “Why 650b?

  1. Why do you think the slightly smaller wheel makes such a difference on gravel roads? I and understand the effect of the wider tire, tread pattern and corresponding tire pressure. I take it the 650b would be about two inches smaller in diameter than the 700c wheel if my math is correct?

  2. Honestly, there’s not a dramatic difference in wheel diameter from a 700c. I do find that 650b spins up from a stop just a little bit more quickly than a comparably outfitted 700c bike, but even that is negligible to me. To me, the fact that there are supple, wide 650b tires available for bikes specifically designed for the wheel size, with adequate (or more than adequate) clearance for fenders, etc. – well, that is what makes the difference. I’ve only been mildly intrigued by most bikes converted from 700c to 650b because I feel that the builders designing to the 650b size hold all the trump cards. If I could fit a 700 x 38 Compass Barlow Pass tire onto my Boulder, you can be darned sure I’d do it. So to answer your question, why does the smaller wheel make such a difference? I’m inclined to believe 650b is better for the task because it was designed with comfortable, supple tires in mind. The current move toward “All Road” bikes, I think, will up the ante even further. Be sure to read what Jan Heine has to say on this, and if you haven’t already done so take a look at the All Road model he reviews in the current issue of Bicycle Quarterly. There’s some very interesting movement afoot.

  3. Of course, you can be even more of an iconoclast and go with a “true” 26 inch wheel, i.e. 559 mm. Or even be more of an iconoclast than that and go with a 65oA tire, i.e 590 mm. But then you can’t talk about Jan Heine! 😉

    • Unquestionably true! And to be very fair, both of the sizes you mention interest me. I am just tall enough that i’m right on the breaking point between where a builder is comfortable with 650b versus strongly recommending I use a 700c wheelset. I chatted in formally with a builder wants about 26 inch frames and he urged me not to go that route because of my long legs. It’s not so much that I wish to avoid being an iconoclast – because clearly that’s never been the case! – it’s that my body proportions and geometry are better suited to a different size wheel. I think that bike you built-up is especially fascinating.

      • Interesting. Was this same builder who dissuaded you from 26 okay with 650B? Because the outer diameter of a 650x42B and a 26″x2.15″ wheel/tire is effectively the same. I think this is the thing people forget about wheel sizes, esp. the different 26 inch wheel sizes, which both 650A and 650B are part of: while the diameter of the rim is different, the outer diameter of the tire is the same. The best way to see what the hell I’m talking about is this chart:

        And remember that 650 mm converts to 25.6 inches.

        Now since there’s variation in tire sizes to specific wheels (vs. the olden days where you were locked into a particular width) so obviously you can get different outer diameters with both 650B and 26 inch tires. But the underlying original idea is there. So my 26 inch tired “adventure” bike can easily be converted to a 650B wheelset, esp. since I have disc brakes!

  4. zac says:

    don’t laugh, of course I wouldn’t care, but its an oddity, I look for 27 inch rims best and Im alone in that I think. Im spoiled with Super Champs pref. #58 blue labels, shiny as a mirror! Ohh I don’t mind the mothers polish I go thru. They roll like none other. The wheel turns slower thru the air, less egg beater, but thats not it. It the round thing I suppose. Placebo maybe because I can ride such nice pieces cheaply.
    That whole get ride of 27inchers, doest hold because of the Pasela saving the day years back- luckily. And the Pasela its the Only one worth its salt in 2 I’m pretty sure.. I cant push those Marathons because they roll so heavily. 600- 800 grams are you kidding… Im convinced the 27 inch tires roll better personally. But I find my 650s bumpy, maybe its the lower end tires? Of course the wheels are stronger inherently at 650 than 700 and 27 for sure. Its also nice to have a wider tire. But small wheels require very slack head angles. About 1 degree for every inch smaller. The wheelbase has to be longer as tires get smaller, and for some darn reason, gear seems to need to be a tad bigger. yes I know about rollout and true diameter, but they seem to thrive in bigger gears. Im still not sold but now there are good tires so it might be different. I also get super cheap wheelsets because nobody wants 27inch wheels. And I mean Nice stuff!.
    Enjoy, to each his own. I think the 650 bicycles look cool and balanced.
    zac

    • I’ve got dozens of really nice 27 inch wheel sets also, along with a few textured-rim steel anchors. There were some great 27 inch wheels – and you are right: they’re usually dirt cheap because they’re “obsolete.” I used to own a Peugeot P8 with 27s. The frame was Carbolite 103, so not the lightest stuff in the world, but the wheels were outstanding, and paired with nice tires I got an equally outstanding ride from that bike.

  5. zac says:

    i might be interested in your Rigida Steels. You ever see those beautiful cloth rim strips that were woven with a leather grommet? I use to see them but cannot find them. I really like the quality even if they take up a lot of air volume. Thanks

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