BROMPTON STURMEY 5 SPEED GEAR CALCULATIONS with the FRONT DERAILLEUR OPTION

EXAMPLE & EXPLANATION OF CHART WITH FRONT DERAILLEUR OPTION

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Go to ACTUAL DATA ENTRY CHART

Data
Entry
Area

Rear Sprocket

13	teeth
39	teeth
53	teeth

The number of teeth in the Rear sprocket (You will be allowed to vary this)

SMALL Chain Ring

The number of teeth in the Small Front Chain Ring (You will be allowed to vary this)

LARGE Chain Ring

The number of teeth in the LARGE Front Chain Ring (You will be allowed to vary this)

Small Chain Resulting Sprocket Ratio

3.000 to 1

4.077 to 1

The resulting sprocket ratio with the SMALL chain ring engaged

Large Chain Resulting Sprocket Ratio

The resulting sprocket ratio with the LARGE chain ring engaged

Small Chain Direct Drive Wheel Size

49.1	inches
66.8	inches

The resulting WHEEL SIZE in Direct Drive with the SMALL chain ring engaged

Large Chain Direct Drive Wheel Size

The resulting WHEEL SIZE in Direct Drive with the LARGE chain ring engaged

REAR HUB GEAR SELECTION

Resulting Wheel Size

With Small Chain Ring Engaged …

1st gear

32.5	inches
38.8	inches
49.1	inches
61.8	inches
73.4	inches
44.1	inches
52.8	inches
66.8	inches
84.0	inches
99.7	inches

RESULTING WHEEL
SIZES with SMALLl
Chain Engaged

With Rear Hub 1st gear engaged

2nd gear

With Rear Hub 2nd gear engaged

3rd gear

With Rear Hub 3rd gear engaged (direct drive)

4th gear

With Rear Hub 4th gear engaged

5th gear

With Rear Hub 5th gear engaged

With Large Chain Ring Engaged …