mtmann

Hey, that gives me an idea. I just picked up a pretty cherry 83 Trek 400 that I'm thinking would make a fine 650b conversion. My questions - and excuse me if any have been answered elsewhere.

First, are there any issues in converting from 27 inch wheels to 650b that are not covered in the 700-650b discussions?

Second, are 650b wheels spaced for a 126 rearend fairly easy to find?

Third, I've got access to a couple good used parts stores and can probably find Mafac Racers (though Raids have proven elusive - and have you seen what they go for on ebay) or diacompe whatevers. What do folks recommend? Thanks.

nlerner

You need an additional 4mm of reach going from 27" to 650B as compared to 700c conversions. That's usually lots of reach, more than Mafac Racer brakes will offer. I did a 630mm to 584mm conversion recently and ended up using old Weinmann calipers that had 81mm of reach. You can usually find brakes with that kind of reach made for BMX bikes (or a pair of Mafac Raids).

Most new wheelsets will be for 130 or 135mm spacing, so you can either cold set your frame or swap the axle if it's a hub that'll allow that.

Neal

mtmann

Hope I'm not hijacking this thread as I don't yet have a conversion to show off. I checked on freewebs.com and compared their numbers with the Trek 400. They recommend 371mm as the maximum distance from axel to brake bridge and this bike is about 368 (center-center). At 320mm from axel the inside chainstay width is about 44-45 mm, so I think I'm good. Will Mafac Racers work with those dimensions? If not, what are the Weinmann model I should look for if I can't find Raids? The bike WILL have fenders - either Honjos or Blumels. I will keep the rear at 126 spacing, and probably have a wheel built on a freewheel hub running a 7-speed freewheel (If I can't find one). Then my choice will be drop bars and downtube shifting, or go with moustache and bar-ends. Hmmm.

nlerner

I don't think the Mafac Racers will give you enough reach. As far as those Weinmann 810s, there's a set on eBay right now: https://cgi.ebay.com/1960s-SCHWINN-ST...QQcmdZViewItem

They're not beautiful calipers, but they'll do the job (and with polishing will look pretty good).

Neal

nlerner

Here's a recent conversion for me: a 1978 Raleigh Competition GS w/ Sun CR18 650B rims, Col de la Vie tires, long-reach GB Sport brakes, Belleri bars, Nitto Technomic stem, Tektro R200 brake levers, SunTour bar-end shifters, TA Pro-3 crankset, Campy NR mechs, Velo-Orange 650B alloy fenders. To get enough tire clearance on the back, I have the axle pulled to the very back of the dropouts, and that amazingly allows the Campy derailer to work with the 32-tooth freewheel cog.

Neal

joaos

No exactly vintage but is 650B. Fixed Gear (61 gear inches), Caloi 10 frame (70 or 80?). 650x45B Wheels (Here in Brazil, 650B is the commonest size. The Caloi 10 originaly is 27").

hhabca

Nice bike! 650B is the commonest size in Brazil? Can you walk into a bike store and buy rims and tires without special ordering them?

kpug505

Ya! What gives? Might be time for a vacation.......I could probably pay for it with some extra luggage on the return trip! The exchange rate is pretty good isn't it? Maybe you could make a nice chunk of change on the side by selling the 650b goodness on eBay?

hhabca

ya, that's what I was thinking. I wonder what the prices are like - they might be pretty high if the rims and tires are imported from Japan.

joaos

(first of all, excuse me my poor english)

Yes, is easy to find on popular bike shops (but in the touristic places is not as easy, the most bike shops there sell imported bikes - and tires - to upper classes).

But there are no much widths to choice, I know only 40mm (Pirelli "Selo Branco", 40-584), 45mm (Pirelli "Manga Turbo" 47-584) and 50mm (Pirelli "Manga Turbo" 54-584). See https://www.pirelli.com.br/pt_BR/brow...alogo_BIKE.pdf. There are also other brands (I dont know what tire widths), but the best slick tires are Pirelli, indubitably. The name most used here is 26 1.1/2.

The "barra forte" or "barra circular" are theses bikes (there are thousands in all places here, and all uses 650B):




Maybe the Pirelli ( https://www.pirelli.com.br/web/motorc...e/default.page ) sells to exterior. The Vzan (rim manufacturer. its rims are very much good), also have site https://www.vzan.com.br/loja/produtos...subcategoria=6.

politicalgeek

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.

soma2x

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.

soma2x

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.

NormanF

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.

soma2x

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.

murphjam

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.

unterhausen

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.

fenderbender

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.

cs1

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.

cs1

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

politicalgeek

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.

soma2x

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

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.

cs1

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

murphjam

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.