Figure 19- Measuring rollout for wheel size
To measure rollout for wheel size
Table 1 approximates the circumfer- ence of each tire size. Instead of using an approximation, you can measure the actual circumference of your wheel. You need a helper, your bike, and a smooth floor with enough room to roll the bike about 7 feet (245 cm) in a straight line.
1.With the valve stem of the front wheel directly over the floor Figure 19), sit on the bike.
2.Have your helper mark the floor at the valve stem.
3.While you sit on the bike, have the helper roll the bike forward one revolution of the wheel, so that the valve stem is again directly over the floor.
4.Mark the new location of the valve stem.
5.Measure the distance between the marks, in millimeters.
If you can only measure in inches, convert to millimeters by multiplying by 25.4.
6.Use the result to program your computer, following the instruc- tions on page 22.
24 Setting Custom Wheel Size