EXAMPLE & EXPLANATION OF CHART with and without the MOUNTAIN DRIVE OPTION
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BROMPTON SRAM 3 SPEED GEAR CALCULATIONS WITH THE MOUNTAIN DRIVE OPTION ENGAGED AND UNENGAGED
Standard
inches
Notes Sprocket ratios other than the Brompton Standard ratio
Brompton Standard Wheel Size
The "Actual" physical wheel diameter size
Data Entry Area
Rear Sprocket
teeth
The number of teeth in the Rear sprocket (You will be allowed to vary this)
Front Chain Ring
The number of teeth in the Front Chain Ring (You will be allowed to vary this)
Resulting Sprocket Ratio
The resulting sprocket ratio
Resulting Direct Drive Wheel Size
The resulting WHEEL SIZE in Direct Drive
REAR HUB GEAR SELECTION
Resulting Wheel Size
With Mountain Drive Engaged …
RESULTING WHEEL SIZES with Mountain Drive Engaged
With Rear Hub 1st gear engaged
With Rear Hub 2nd gear engaged (direct drive)
With Rear Hub 3rd gear engaged
Without Mountain Drive Engaged ….
RESULTING WHEEL SIZES Mountain Drive Disengaged
NOTE: If you do not own the Mountain Drive Option, these are the ONLY Resulting wheel sizes.