The Golden Wrench

A blog about bicycle repair and maintenance by the mechanics at Freewheel Bike.

Tuesday, March 9, 2010

Bicycle Repair Classes

If there is one thing that I love more than working on bikes it's teaching people how to work on bikes. That's why I love teaching the repair classes at our Midtown Bike Center. My favorite class is wheel building.
There are usually three to four people in a class. On the first day we lace the spokes between the hub and the rim and start getting the spokes tight. The second day is the hardest. We have to true, round and center the rim. Then we stress the wheel to relieve tension on the spokes which allows them to unwind. Then we add a layer of tension and repeat, and repeat, and repeat..... You see, in order to build a good wheel you have to add many small layers of tension and this can become tedious to some. During this process we constantly check spoke tension with the Park Tool TM-1
At some point we determine that we have reached an acceptable average spoke tension, usually around 100-110 kgf. It's at this point in the class that I break out the Park Tool Tension Conversion Calculator and the students kinda groan, roll their eyes and polity excuse themselves from class. You can't imagine how excited I was in the last wheel class when my solo student, Frank, stayed with me the whole way. We even tension balanced his wheel! He said he was some kind of engineer, mechanical engineer maybe, which might explain why he didn't mind graphing out spoke tension then manipulating different spokes to get them all closer to the same tension.
Frank built up a Shimano FH-M756 hub with DT 2.0-1.8 spokes and a Stan's ZTR Arc rim. Here is what the spoke tension looked like in Frank's wheel before we started balancing the tension:

We followed the tension balancing instructions from Calvin's Corner and ended up with spoke tension that looked like this:

After four tries Frank still had one spoke one the non-drive side that was too tight. Luckily he owns a TM-1 and a wheel truing stand so that he can finish this at home (balancing spoke tension takes a lot of time).

A wheel with well balanced spoke tension will stay true longer, spokes will last longer and the rim will be less likely to crack. This is why so many people demand hand built wheels.
At Freewheel Bike we offer a wheel building class about once a month. We have parts for you to use in class so that you don't have to buy the parts or you can bring your own. If you want a wheel built and tension balanced but don't want to do it yourself we offer the Pro-Wheel Build at both locations for $70 a wheel.

Be the first to answer the following trivia questions and win this King hat.

What is the thread pitch of a 2.0mm spoke?
What does "kgf" stand for?
E-mail answers to

3/10/10 11:35am we have a winner. The answers are; 56tpi and "kilogram force". Thanks for playing.