Not to bump old threads, but this seemed the best place to tap the knowledge.

I'm looking at getting a new (to me) bike-really looking at a project frame to learn on-and love the idea of 650b. I started riding my 3 speed around and love the feel of smaller wheels.

Finding decent quality vintage steel in this town seems a bit tough. I've found 2 bikes so far that may work. Saw a Nishiki Sport today at the Co-op with 27" wheels and a busted rear axel. It's just a bit tall on me. Wondering how well 27" to 650b would work? I've seen a few on here.

I may find the measurement guides for the conversion and go back at the next open shop to see if it would work. Don't know if it will drop it enough, though.

here's my conversion, 1988 Schwinn Tempo
 

Just finished this weekend. Only modifications needed were the wheels, obviously, and the brakes, also obviously. I used Tektro 556 and I went with Velocity Twin Hollows with Deore hubs and straight gauge. Had to spread the rear triangle as per Sheldon's (may he RIP) instructions. worked like a charm. I'm posting because I couldn't find info about a Tempo conversion anywhere else. For those who are interested, convert away, there's limited but adequate clearance at the chain stays for Col de la Vies and it works fine.

Sorry, the title didn't post. This is a 1988 Schwinn Tempo that I converted to 650b. Hopefully anyone looking for info on a Schwinn Tempo conversion will now be able to find this.

It typically requires a long reach brake. 80s road bikes are good 650B conversion candidates. You'd have to install a brake with longer reach if you are sizing down from a 27" or 700C bicycle. In practice, it presents no real problem and a mid-sized Panaracer Col De La Vie 38" tire is equivalent to a 19" 700C tire. The medium width tread makes its useful for all around commuter tasks.

27" to 650b should work very well. 27" inch wheels are 630mm in diameter whereas 700c wheels are 622mm. You'd only need 4 more mm of reach from the brakes to convert from 27" than you'd need to convert from 700c. Tektro R556s have something like 55 mm to 73mm in reach. If you're riding a 27" bike that uses short reach brakes (39mm to 49mm) the Tektros should work OK with the pads all the way at the bottom of the calipers.

One other issue that might crop up is the axle width on the rear triangle of a 27" wheeled bike. Most 27" bikes were built for 126mm wide axles. Most 650b wheels, at least the prebuilt ones, come with 135mm wide Deore MTB hubs. You'll probably have to spread your rear triangle to accomodate them unless you build a set of wheels with 130mm hubs. LIke I said in my post, it's surprisingly easy to do if you follow the directions on Sheldon Brown's site.

I suspect the part of the reason that you didn't find anything about a conversion on the Schwinn is that there aren't any fender braze ons. Most guys are looking to put fenders on when they do the conversion. I have that same model Tempo and considered it for a conversion, but ended up choosing a Centurion that had the fender mounts.

my LBS says that they have had a boom in interest about this conversion. I saw a nice bike in there getting 650b. Previously it had thin 700c.

Old mtb frames have either 130 or 135mm so no need to spread. Make for better conversions too if the aim is to carry loads. Often the stock brake can be used. If you can't adjust the brakepads high enough you should be able to lengthened the slot with a file, even though some tend to replace them with Tektro Oryx cantis instead.

I had no idea wheelchairs were 650A. Economically, it would make more sense to use the 650A because of the bigger base of potential customers. I guess it's a lot more romantic to use tires from a bygone French stantdard than a wheelchair.:(

I'm thinking exactly the opposite. It's hard enough to find brakes with long enough reach going from 27" to 700C. Now add another 4mm and it becomes even harder. Basically you're going from 630mm to 584mm. That's 46mm in dia or a difference of 23mm smaller in the radius. That's almost a full inch, 25.4mm

Well 650 is 26 x 1 3/8" which aren't the widest tires. I had a 3 speed for a while with that tire size and it was OK, but I can see where people would want the wider tires. Isn't the point of 650b conversions mainly to help re-purpose old road frames to be better commuters with wider tires and fenders?

Quick search shows Schawlbe, Panracer and Michelin all make 650a. Seems like there is some good quality out there.

cs1,
Not "the opposite". It's a matter of math and depends solely on the brake reach on the 27" wheeled bike. If the 27" bike uses 39mm-49mm short reach brakes, the Tektro R556 should work fine. The Tektros have a reach from 55mm-73mm. Using your own figures, lets assume that the 27" bike used the short reach brakes with pads dropped all the way down to 49mm. If you switch to 650b, you'll need an extra 23mm of reach. What's 23mm plus 49mm? 72mm. The Tektro R556s should have just enough room (up to 73mm). If the 27" bike used brakes with a reach longer than 49mm, then the R556s wouldn't work and you'd need a longer brake, most likely an old centerpull.
soma2x

You're probably right murphjam. No fender mounts. My back got soaked this weekend riding around the block in the rain and I could have used fenders. I gave up on fenders for other reasons, the rattle annoyed me and the stays also tend to bend a bit when I put my bike on the rack. Then I have to straighten the stays and make sure they don't hit my tires... Also, I prefer the look without the fenders.

1mm of reach is dangerously close IMO. I always thought is was stretch to go from 27" to 700C.

I also like the look better without the fenders, but I also like to have the option of putting them on if I want to. I used the sheldon fender nuts to make it easy to take them on and off. It's funny because I posted my conversion without the fenders and one of the guys likes them better with the fenders.

oh my. how'd you paint the fenders? something about the simple beauty of this one just got me, even more than some of the flashier bikes posted on here so often. i had to catch my breath. thanks for sharing.

Edit: looks like the photos don't show in the quotation. See the very first post of the thread for reference.

The prelude was a step or two up from the le tour in the schwinn lineup. I have an 86' prelude here that has 700c weinmann double walls stock, and I imagine the Le Tour of that era had 27' single wall araya rims.

cs1,
I suppose 1mm is cutting it pretty close. I'm also not so sure that most 27" bikes would use short reach brakes anyway. I think short reach brakes got popular along with 700c wheels. I'm just saying it depends on the existing brake.

I finally had a chance to test ride and take some pics of my PX-10 650B conversion. It sports Grand Bois Hetre 42mm tires, Rigida 650B rims and Campy NR hubs, Stronglight 99 crankset w/ 45-32 rings, 14-28t SunTour 5-speed rear cluster, Shimano Crane RD and Dura Ace FD, SunTour bar-end shifters w/ Campy hoods, Dia Compe 750 brakes (I needed 710mm reach) w/ Kool Stop Continental pads, Lyotard Berthet pedals w/ Christophe toe clips and V-O sew-your-own leathers, AVA stem, Belleri bars and Mafac levers, Nashbar cork tape w/ lots of shellac, original Simplex seatpost and Ideale 90 saddle. I have a set of hammered alloy fenders, an eBay find from Belgium, but haven't had time to fit them. One advantage of converting this frame is that it's a tad too large for me, so lowering it makes it work fine. A smooth rider so far.

Neal

http://lh5.ggpht.com/_GmYBBzTzcVQ/Sb...PX10_650B1.jpg

http://lh5.ggpht.com/_GmYBBzTzcVQ/Sb.../PX10_650B2.jp

http://lh6.ggpht.com/_GmYBBzTzcVQ/Sb...PX10_650B3.jpg

Neal,

The Pug looks great! I am really interested to here your impressions of those tires. They look to be the same size as a set of Conti Town & Country tries I picked up recently for a mountain bike project. What is the max PSI on them?

Thanks, Brian. I'm running those tires around 50 psi, which feels right (I had that wheelset on another bike that was one of my commuters all fall). At first, I was running them too hard, which made me really doubt the many folks extolling their virtues, but after some break in and loss of some psi, they felt much better. My test ride on the PX10 felt very good--rolls over everything without feeling draggy. There are bike builders designing bikes around those particular tires, so something good must be going on.

Neal

Yep. It can lower the standover height of a larger making it safely usable by a smaller rider. Looks
like a cool set of original parts on your PX-10. If you decide to turn it into a porteur/ranonneur bike
it would look awesome! I'm saving the Grand Bois Hetre 42mm tires for an MTB. I'm running Panaracer
Col De La Vie on mine because it seems to look more or less correct for a 650B commuter.

I have a 2007 Kogswell, which I've set up as my dedicated porteur: Col de la vie tires, albatross bars and bar-end shifters, cheap Nashbar front rack and a basket zip tied to it. I'll likely get the Kogswell porteur rack when it eventually/hopefully gets produced. I also use it to haul my trailer for large grocery store runs. The PX-10 will be for longer rides.

Neal

Looks cool! What is the BB height after the conversion? Most of the older bikes that I've considered for conversion have had a very high bb to start with.

It's at the pushing-it range: about 25.4cm. I'd probably be better off with 165mm crankarms, but I used what I had, and in my initial ride, I didn't have any pedal strike problems or feel like the BB was too low. Guess I'm not going to be using this one for mountain biking!

Neal

I like it, in spite of the bizarre bar angle.

Great bikes! It's got me thinking about doing a 650B conversion, too. But I have a couple questions:
1. Where do you get 650B rims in the US? Finding tires seems to be no problem, but a quick check on the internet turned up very little in the way of rims. CTA in Australia seems to offer the most choices (including the nice retro-style Glider), but shipping must be expensive. Other than that, about all I see is the Weinmann ZAC-19 at Velo-Orange. Where can you get Sun CR-18's?
2. What fender sizes are most compatible? Would fenders for 26" wheels work?

You can order rims & tires here:
http://www.vintagebicyclepress.com/componentoffer.html

When I built my 650b bike I used a NOS set of Bluemels Airlite alloy fenders That were made for 26" wheels...

Any bike shop should be able to order Velocity Synergy 650B rims for you. I have 3 650B wheelsets with them - very nice rims.

I hear the Sun CR18s are slightly too big making it an absolute bear to put on tires. If you want a cheap set, a complete set of Velocity Twin Hollow wheels with straight guage spokes and Deore hubs can be had for less than $160, including shipping (check ebikestop). Yes, they're single-wall (gasp) and four ounces heavier per wheel than the Synergys (gasp again) but they seem really solid, they look good enough and they spin just fine.