Gear Chart (in Inches) for 700C Wheels and Typical Chainwheel Sizes
27
Wheel Size: 27.0000 Effective Wheelsize: 27.0000
  39 42 44 45 46 47 48 49 50 51 52 53
12 87.8 94.5 99.0 101.3 103.5 105.8 108.0 110.3 112.5 114.8 117.0 119.3
13 81.0 87.2 91.4 93.5 95.5 97.6 99.7 101.8 103.8 105.9 108.0 110.1
14 75.2 81.0 84.9 86.8 88.7 90.6 92.6 94.5 96.4 98.4 100.3 102.2
15 70.2 75.6 79.2 81.0 82.8 84.6 86.4 88.2 90.0 91.8 93.6 95.4
16 65.8 70.9 74.3 75.9 77.6 79.3 81.0 82.7 84.4 86.1 87.8 89.4
17 61.9 66.7 69.9 71.5 73.1 74.6 76.2 77.8 79.4 81.0 82.6 84.2
18 58.5 63.0 66.0 67.5 69.0 70.5 72.0 73.5 75.0 76.5 78.0 79.5
19 55.4 59.7 62.5 63.9 65.4 66.8 68.2 69.6 71.1 72.5 73.9 75.3
20 52.7 56.7 59.4 60.8 62.1 63.5 64.8 66.2 67.5 68.9 70.2 71.6
Recommended gears for racing: low 90's for mass start events, mid to high 90's for TT events
1J6. Junior Gears. The maximum chaingear ratio for Junior riders is based on age and discipline. 
Track
Age 17-18: Unrestricted Multiply gear inches in above chart times Pi (3.1416) to get the rollout distance.
15-16: 6.78 meters (22'3")(48x15)
13-14: 6.36 meters (20'10.5")(48x16)
10-12: 6.00 meters (19’8”)(48x17)