Thursday, August 12, 2010

650B Schwinn World Sport

It's not done yet -- not even close. But today I received the 650B wheelset I bought to try out with Juli's Schwinn, and it's official -- the bike will be built up as a 650B.

The wheels are basic, but perfectly serviceable. They've got inexpensive Deore hubs laced to inexpensive Weinmann ZAC19 rims. Hubs, skewers and rims are black, and spokes and braking surfaces are shiny, and it's a combination I think works pretty well. They won't knock anyone's socks off, but they should perform well for as long as Juli needs them.

The bike was built for 27" wheels, but it will support this smaller wheel size just fine. At the rear, the brake bridge is well-placed (if shabbily welded) for this conversion, allowing a Dia-Compe 750 centerpull to reach comfortably to the rims while using only about half of their adjustment range. The long and dorky fork, on the other hand, requires all of the available reach, which you can kind of see in the photo. Honestly, I was surprised by that, because it's not uncommon for the rear triangle to use up more brake reach than the fork -- my own Schwinn Sports Tourer is that way, for instance. Some older 10-speeds even used different brake sizes at either end -- a Weinmann or Dia-Compe 610 up front and a 750 in back. But that's OK -- the fork is coming off anyway, in favor of a 700C lugged fork (in chrome), and that will no doubt take an inch or so out of the fork legs -- a 650B wheel might even work with a shorter-reach 610 brake after that swap.

Swapping the fork is going to drop the bottom bracket a bit more than the wheel swap alone, and also steepen the head and seat tube angles. The angles they look pretty relaxed as it is, so I don't think the bike will be flighty or anything, but I'm a little concerned about bottom bracket height. Juli is running a 165 crank, so there probably won't be a problem, but I'll have to pay some attention to that, and will hold off on buying tires until I've had a chance to measure things out with the new fork. A little extra loft through a poofier tire might be called for, there. She's already had a pedal-grounding crash on her Fuji, so she understands the perils of pedaling through corners, but I don't want to handicap her with too little clearance, either.

It will be quite a while before the bike is ready to ride, though. I can still do a little work here and there, but most of the drivetrain is committed to the Fuji for the rest of this season, so it will likely be the end of this year before we get to the build stage. In the mean time, I'll keep gathering parts, and looking forward to what should prove to be a neat little bike.

All for now,



16incheswestofpeoria said...

Did you ever complete the 650B build of the Schwinn World Sport? If so, what was the final bottom bracket height and how did the fork replacement work out?

John Ellsworth said...

I did, yes! The fork swap worked out fine. It's unorthodox, and it definitely changed the geometry of the frame, but the bike doesn't do anything untoward. Actually, the steering feels better in that sense than the small (46cm) Bertoni I picked up for my daughter as a fast bike. That bike has a distinct "flopping" point in the steering, presumably because of its relatively slack head tube angle. Not great. But anyway the Schwinn is fine. I can measure the BB height and will post back.

John Ellsworth said...

Final BB height: 255 mm, so 10 inches. A little low, yes, but it's not a fixie and the cranks are short, and the Q and pedals are narrow. Tires are relatively low-volume 33's from Rivendell (nifty swiftys).

She's never crashed it, but I will ask her if she's touched a pedal down on this bike.

Unknown said...

Thanks for the update. I'm starting to hear of a lot more interest in 650B these days, mostly within the mountain bike community.