GEARING STANDARDS FOR BROMPTON FOLDING BIKES    

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Wheel Diameter Size

USA

16,375

inches

Sturmey Archer Rear Hub

3 Speed Hub

Pecentage of direct drive

1 st gear

74.19 %

percent

100.00 %

percent

132.26 %

percent

2 nd gear

3 rd gear

5 Speed Hub

1 st gear

66.13 %

percent

79.03 %

percent

100.00 %

percent

125.81 % percent
146.39 % percent

2 nd gear

3 rd gear

4 th gear

5 th gear

Sram Spectro Rear Hub

3 Speed Hub

Pecentage of direct drive

1 st gear

73.00 %

percent

100.00 %

percent

136.00 %

percent

2 nd gear

3 rd gear

Dual Rear Derailleur with 3 Speed Hub

Small rear

1 st gear

73.00 %

percent

100.00 %

percent

136.00 %

percent

73.00 % percent
100.00 % percent
136.00 % percent

sprocket

2 nd gear

(engaged)

3 rd gear

Large rear

1 st gear

sprocket

2 nd gear
(engaged) 3 rd gear
Mountain Drive Gearing  

Pecentage of direct drive

Direct Drive

100.00 %

percent

250.00 %

percent

Low Drive

Herein are the Standard Offerings from Brompton. Other combinations can be requested.

Brompton Standard Gearing

SPROCKET RATIOS

No Gear Reduction

Chain Ring

50 teeth
13 teeth
Standard ratio

3.846 to 1

Rear sprocket

Reduced Gearing Options

Compared to STD

7 % Gear Reduction

Chain Ring

50 teeth
14 teeth
7% Reduced Ratio

3.571 to 1

Rear sprocket

12 % Gear Reduction

Chain Ring

44 teeth
13 teeth
12% Reduced Ratio

3.385 to 1

Rear sprocket

18 % Gear Reduction

Chain Ring

44 teeth
14 teeth
18% Reduced Ratio

3.143 to 1

Rear sprocket

23 % Gear Reduction

Chain Ring

44 teeth
15 teeth
23% Reduced Ratio

2.933 to 1

Rear sprocket

Single Chain Ring Options  

Standard

50

teeth

44

teeth

Reduced Gearing

Single Rear Sprocket Options  

Standard

13

teeth

14

teeth

15

teeth

Reduced Gearing

Further Reduced Gearing

Front Dual Derailleur Offering  

Large sprocket

53

teeth

39

teeth

Small sprocket

Rear Dual Derailleur Offering  

Large sprocket

15

teeth

13

teeth

Small sprocket