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PostPosted: Mon May 13, 2013 9:00 pm 
Gold Trader
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Joined: Mon Jan 15, 2007 11:40 am
Posts: 3002
Having been thinking about it for ages, and finally being inspired by TGR's mixte restorations, I'm thinking of doing something similiar. I still don't have a bike or frame, but before I buy one I'd like to know about wheel sizes... 700C or 26" would be easiest, but I've seen that many bikes of this type (mixtes / step through type frames) come with 650 size wheels. I'm aware of the difference between the sizes, but what I don't know about is parts availability... isn't 650B the "new" mtb craze? What about the other three? Which one will give me the largest selection of rims and tyres? I won't be needing anything amazing, but would like to know that I can choose from a reasonable selection of rims, tyres, and possibly mudguards. I don't want to buy an old bike to restore, and then find that the wheel size is completely out of date and I can't get parts!

thanks, Andy


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PostPosted: Mon May 13, 2013 9:45 pm 
rBoTM Winner
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Joined: Wed Dec 12, 2012 10:18 pm
Posts: 2373
Location: California
The 650B tire was, and still is, the preferred size of Randonneuring and so the choice is pretty good. Although after reading the short para graph on the link below I am already questioning this very response


http://www.rivbike.com/650B-Tires-s/111.htm


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PostPosted: Mon May 13, 2013 11:55 pm 
Dirt Disciple

Joined: Fri Mar 30, 2012 12:23 am
Posts: 70
I had the same interest a few months ago but found that 650B are pretty difficult to find. Basically I only found them at a resonable price on one online french shop. In the end I forgot about it. If you find anything interesting please post here.


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PostPosted: Tue May 14, 2013 8:25 pm 
retrobike rider
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Joined: Tue Jan 29, 2008 11:04 pm
Posts: 1802
Location: A wretched hive of scum and villainy...
These days 700c is still the most widely available range of tyres and rims for general touring/trekking.
But if your frame just won't fit a 700c/622mm set-up...

--650A: 590mm bead seat: A lot of old mixte and roadster bikes would have been 650A, or 26 x 1 3/8" as it's better known in the UK. Not much choice of tyres these days, rims almost non-existent. I'd steer clear unless you prize originality.
--650B: 584mm bead seat: lots of 28-40mm road tyres with enough tread for a bit of rough. Still pretty niche, with a lot of whitewall 'Eroica/Porteur/Rene Herse' stuff around, though there are plenty decent mountainbike tyres arriving, but they wouldn't fit a road frame. This size is definitely growing in popularity on both the MTB and touring fronts with rims and mudguards available too.
--650C: 571mm bead seat: the next size down from our 700C wheels. Pretty much dead in adult bikes, restricted to under 23mm tyres and tubs these days, although they do still have a solid following in racing handcycles. Tyres and rims restricted to racing bike widths.

So, a Mixte frame originally built for the dead/dying old UK size 650A/26 1 3/8"/590mm built for a 28mm tyre (646mm OD) could be replaced with previously-dead-but-now-rising-again French 650B/584mm wheels and slightly fatter 32mm tyres with only a small adjustment to the brake block...3mm down and some nice hammered aluminium mudguards. Just watch the frame width between the forks & stays.

A summary of sizing for clarity; the best size guide is the bead seat diameter (ETRTO). Assuming you're not thinking of tubular tyres, this is the diameter of the seat in the rim where the tyre sits, not the outside rim diameter (which is about 12mm larger). Add 2x the tyre width to this number to give a rough estimate of the overall wheel size to check clearances, brake drop etc.

All the best,


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PostPosted: Tue May 14, 2013 8:37 pm 
Gold Trader
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Joined: Mon Jan 15, 2007 11:40 am
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Thanks, lots of useful info there! I hope to find a frame for either 700C or 26" (mtb) wheels. But it looks like if i do need to go to 650-something, then 650B is the way to go.


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PostPosted: Wed May 15, 2013 11:17 am 
Old School Hero
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Joined: Tue Nov 09, 2010 10:31 am
Posts: 224
Location: Christchurch, Lew Zealand
650c is tricky
I have an old 650c Zunow frame that I'd like to sell but, I know that no one will want it because of the wheel size

At work we have a carbon Jamis TT bike with 650c wheels that will probably still be on the shop floor on the day of the apocalypse


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