This first event of the time trial season is the Club Medium Gear. A Medium Gear is a maximun of 72″. To check your gear is no more than 72″ the distance travelled for one pedal revolution is 18ft 10.1/4 inches. Single freewheel and gears are allowed, provided the stops are screwed in on your gears to prevent a gear over 72″ being selected.
Mike will be their with his tape measure to verify gearing, so no trying to sneak a couple of extra inches! First rider off at 14:15 hrs so please arrive by 13:45 hrs to allow for measuring and adjustment time.
Notes: If you are using single speed with 700c x 23/25 wheels the following chainring/sprocket sizes are appropriate for the medium gear.
46-17 — 71’7”
48-18 — 70’7”
51-19 — 71’1”
With multi-speed gears the machine must be set to prevent the selection of a ratio higher than specified. The ratio selected can be determined by using the following calculation. Number of teeth on ring divided number of teeth on block multiplied by 26.5 (700c x 25).
Achievable Combinations (dependent on tyre size these are for 21mm clincher):
39 – 15 – 68.6″ (disadvantage straight off the line)
52 – 20 – 68.6″
53 – 20 – 69.9″
54 – 20 – 71.2″
To measure the distance travelled, hold the machine with one crank vertically down, mark the point immediately below the pedal, wheel the machine BACKWARDS in a straight line until the same pedal is at the bottom, mark the second point. The distance between the marks must not exceed 18 ft 10 ins (5.74 metres).
It may be possible to achieve this by adjusting the limit stop on the rear mechanism to prevent the higher ratios being selected and/or adjusting the stop on the front mechanism to prevent the large chainring being selected. Chalk will be available to chalk the ring if locking is not possible.
Unrestricted bikes may be ridden for those just looking for a time.