650B Conversion Hits A Wall

In my last post, I wrote that the 650B conversion project rolled forward when I purchased a set of new 650B wheels to go on the 1976 Schwinn Le Tour 10 speed frame. I was really jazzed because I knew all I had to do was slap on the new wheels, fiddle with the brakes and I'd be good to go.

Unfortunately, it didn't quite play out that way. I knew there would be an issue with brake reach, as the calipers would have to reach down a little farther from the old 27 inch wheels to the 650B size, about 23 mm more, or 9/10th of an inch.

650B wheel using stock brake

Knowing brake reach would be in issue, I ordered a set of Tektro 556 long reach brakes. These brakes range from 55mm to 73mm from the center of the mounting bolt to center of rim. This was complicated by the fact that the supplier sent only the rear brake, but they've acknowledged the error and have put the front brake in the mail.

However, I wasn't prepared for the disappointment when I got the brake and found that it's no longer than the stock brake that came on the Schwinn!

650B wheel using Tektro 556 brake

In the next picture you can see that I am pinching the calipers against the rim. You can see how far down the mounting bolt needs to be.

Pinching the calipers against the rim to simulate the desired mounting position

The stock brakes have a long hex bolt with nut that runs through concave shaped nuts that hold the brake in place against the horizontal brake mounting tube. The Tektro brakes use recessed mounting. I've read that I can drill the rear hole in the tube and in the fork crown to allow me to use the recessed nut. I've also seen Sheldon Brown's "drop bolt" solution. Any suggestions?

Stock brake on the left. Tektro 556 on the right. Notice the reach is about the same.

Today I got the Panaracer 650B x 38mm tires in the mail. They were about $20 a tire and have an interesting inverted tread. My LBS is ordering some 650B tubes for me.


So, again at a cross roads, I am not sure what to do. Here come the obligatory lists.

Continue to 650B-ify the Schwinn:

• drop bolts on brakes (ugly, but cheap)
  
• have frame maker move the mount (pretty, but expensive)
  
• find longer reach brakes, if they even exist (probably expensive)
  

Abandon the Schwinn/650B project:

• Convert it to 700C and use the original brakes
• Convert it to 700C and use the Tektro brakes after figuring out to to use the recessed mounting bolts
  
• sell the 650B wheels
• keep the 650B wheels and find another frame
  

As usual, I welcome your comments and suggestions.

650B Conversion Rolls Forward

The next stage in the life of the Schwinn Le Tour II project is an attempt to convert it to a 650B "country bike." I don't know if it's doable, but I've made a real attempt to start it, rather than only talking about it.

Today I took possession of a set of low-end 650B wheels (Deore M530), ordered through the Re-Cycle Bike Shop. Mike, the mechanic and owner, is spreading the frame to better accommodate the extra width of the new wheels, as well as checking the spoke tension on the new wheels.

I was amazed as just how small the wheels looked in the Le Tour II frame when he had it up on the work stand. There's an amazing gap between where the existing center pull brake shoes are and where they need to be. Going from a 27 inch wheel to the 650B is quite a jump. According to Sheldon Brown, the 27 inch is ISO 630mm and the 650B is ISO 584mm, making the distance difference half of 46mm, or 23mm.

I ordered some Tektro 556 extra long reach brakes and some 650B x 38m tires. I'm hoping that with the new brakes and tires, I'll be able to get the 650B on the road for a test ride within a week.

Possible complicating issues might be:

• brake mounting compatibility
• lower drop on the frame might make existing cranks too long
• cabling is different from center pull to side pull brakes
  
• not entirely certain I've got all the clearances I need with 38mm tires
• might need new brake levers if new brakes require more cable to be pulled

As usual, I welcome your comments, hints, advice, and gotchas in this endeavor. I'll try to get some pics up later.