Technical


Medium gear explained.

The Maximum gear allowed in a medium gear event is 72", this figure can be confusing. What does 72" mean ?.

Using inches to measure gear sizes dates back to the days of the penny farthing, if it had a front wheel of 72" diameter it was said to have a gear of 72". On modern bicycles the gear size is calculated by multiplying the wheel diameter (in inches) by the number of teeth on the chainwheel and then dividing this by the number of teeth on the rear sprocket. However, to find the distance the bicycle travels for one pedal revolution, the gear size in inches must be multiplied by pi (3.142).

Years ago when 27x1.1/4" was the standard wheel size a 48x18 would give you a 72" gear, nowadays with the smaller 700c or tubular this would leave you somewhat undergeared. As a general rule a 49x18 is a good choice but with smaller tyres a 52x19 can be used. The only sure way to check your gear is to measure the distance travelled for one pedal revolution, for a medium gear this 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.

Gear Table.

Below is a gear table which should be accurate for most modern wheel sizes, I have used 26.4" as the wheel size because this relates to a 700x21 clincher or a standard tub.
C
h
a
i
n
w
h
e
e
l
S
i
z
e
39
42
44
46
48
49
50
51
52
53
54
55
56
57
S
12
85.8
92.4
96.8
101.2
105.6
107.8
110
112.2
114.4
116.6
118.8
121
123.2
125.4
p
13
79.2
85.2
89.3
93.4
97.4
99.5
101.5
103.5
105.6
107.6
109.6
111.6
113.7
115.7
r
14
73.5
79.2
82.9
86.7
90.5
92.4
94.2
96.1
98.0
99.9
101.8
103.7
105.6
107.4
o
15
68.6
73.9
77.4
80.9
84.4
86.2
88.0
89.7
91.5
93.2
95.0
96.8
98.5
100.3
c
16
64.3
69.3
72.6
75.9
79.2
80.8
82.5
84.1
85.8
87.4
89.1
90.7
92.4
94.0
k
17
60.5
65.2
68.3
71.4
74.5
76.0
77.6
79.2
80.7
82.3
83.8
85.4
86.9
88.5
e
18
57.2
61.6
64.5
67.4
70.4
71.8
73.3
74.8
76.2
77.7
79.2
80.6
82.1
83.3
t
19
54.1
58.3
61.1
63.9
66.6
68.0
69.4
70.8
72.2
73.6
75.0
76.4
77.8
79.2
S
20
51.4
55.4
58.0
60.7
63.3
64.6
66.0
67.3
68.6
69.9
71.2
72.6
73.9
75.2
i
21
49.0
52.8
55.3
57.8
60.3
61.6
62.8
64.1
65.3
66.6
67.8
69.1
70.4
71.6
z
22
46.8
50.4
52.8
55.2
57.6
58.8
60.0
61.2
62.4
63.6
64.8
66.0
67.2
68.4
e
23
44.7
48.2
50.5
52.8
55.0
56.2
57.3
58.5
59.6
60.8
61.9
63.1
64.2
65.4

How Fast ?

Below is a table giving your speed in mph for a given gear size and pedal rpm. I have selected a range of gears and rev's which should cover most peoples needs, but if your chosen gear or rpm is not shown here, work it out for your self.

The formula I have used is RPM times GEAR devided by 336
Example, 117 times 72 devided by 336 = 25.07 MPH, which is the magic sub hour medium gear 25.

 
P
E
D
A
L
R
E
V
S
P
E
R
M
I
N
U
T
E
 
90
92
94
96
98
100
102
104
106
108
110
112
114
116
118
120
125
130
135
140
150
160
170
G
120
32.1
32.8
33.5
34.2
35.0
35.7
36.4
37.1
37.8
38.5
39.2
40.0
40.7
41.4
42.1
42.8
44.6
46.4
48.2
50.0
53.5
57.1
60.7
E
115
30.8
31.4
32.1
32.8
33.5
34.2
34.9
35.5
36.2
36.9
37.6
38.3
39.0
39.7
40.3
41.0
42.7
44.5
46.2
47.9
51.3
54.7
58.1
A
110
29.4
30.1
30.7
31.4
32.0
32.7
33.3
34.0
34.7
35.3
36.0
36.6
37.3
37.9
38.6
39.2
40.9
42.5
44.1
45.8
49.1
52.3
55.6
R
105
28.1
28.7
29.3
30.0
30.6
31.2
31.8
32.5
33.1
33.7
34.3
35.0
35.6
36.2
36.8
37.5
39.0
40.6
42.1
43.7
46.8
50.0
53.1
100
26.7
27.3
27.9
28.5
29.1
29.7
30.3
30.9
31.5
32.1
32.7
33.3
33.9
34.5
35.1
35.7
37.2
38.6
40.1
41.6
44.6
47.6
50.5
I
98
26.2
26.8
27.4
28.0
28.5
29.1
29.7
30.3
30.9
31.5
32.0
32.6
33.2
33.8
34.4
35.0
36.4
37.9
39.3
40.8
43.7
46.6
49.5
N
96
25.7
26.2
26.8
27.4
28.0
28.5
29.1
29.7
30.2
30.8
31.4
32.0
32.5
33.1
33.7
34.2
35.7
37.1
38.5
40.0
42.8
45.7
48.5
94
25.1
25.7
26.2
26.8
27.4
27.9
28.5
29.0
29.6
30.2
30.7
31.3
31.8
32.4
33.0
33.5
34.9
36.3
37.7
39.1
41.9
44.7
47.5
I
92
24.6
25.1
25.7
26.2
26.8
27.3
27.9
28.4
29.0
29.5
30.1
30.6
31.2
31.7
32.3
32.8
34.2
35.5
36.9
38.3
41.0
43.8
46.5
N
90
24.1
24.6
25.1
25.7
26.2
26.7
27.3
27.8
28.3
28.9
29.6
30.0
30.5
31.0
31.6
32.1
33.4
34.8
36.1
37.5
40.1
42.8
45.5
C
88
23.5
24.0
24.6
25.1
25.6
26.1
26.7
27.2
27.7
28.2
28.8
29.3
29.8
30.3
30.9
31.4
32.7
34.0
35.3
36.6
39.2
41.9
44.5
H
86
23.0
23.5
24.0
24.5
25.0
25.5
26.1
26.6
27.1
27.6
28.1
28.6
29.1
29.6
30.2
30.7
32.0
33.2
34.5
35.8
38.3
40.9
43.5
E
84
22.5
23.0
23.5
24.0
24.5
25.0
25.5
26.0
26.5
27.0
27.5
28.0
28.5
29.0
29.5
30.0
31.2
32.5
33.7
35.0
37.5
40.0
42.5
S
82
21.9
22.4
22.9
23.4
23.9
24.4
24.8
25.3
25.8
26.3
26.8
27.3
27.8
28.3
28.7
29.2
30.5
31.7
32.9
34.1
36.6
39.0
41.4
80
21.4
21.9
22.3
22.8
23.3
23.8
24.2
24.7
25.2
25.7
26.1
26.6
27.1
27.6
28.0
28.5
29.7
30.9
32.1
33.3
35.7
38.0
40.4
76
20.3
20.8
21.2
21.7
22.1
22.6
23.0
23.5
23.9
24.4
24.8
25.3
25.7
26.2
26.6
27.1
28.2
29.4
30.5
31.6
33.9
36.1
38.4
72
19.2
19.7
20.1
20.5
21.0
21.4
21.8
22.2
22.7
23.1
23.5
24.0
24.4
24.8
25.2
25.7
26.7
27.8
28.9
30.0
32.1
32.4
36.4
65
17.4
17.7
18.1
18.5
18.9
19.3
19.7
20.1
20.5
20.8
21.2
21.6
22.0
22.4
22.8
23.2
24.1
25.1
26.1
27.0
29.0
30.9
32.8

Speed charts.

Below are a set of tables giving your speed in MPH for a given time in standard distance time trials,

10 Miles

Time
18-00
18-15
18-30
18-45
19-00
19-15
19-30
19-45
20-00
20-15
20-30
20-45
21-00
Speed
33.3
32.8
32.4
32.0
31.5
31.1
30.7
30.3
30.0
29.6
29.2
28.9
28.5
Time
21-15
21-30
21-45
22.00
22-15
22-30
22-45
23-00
23-15
23-30
23-45
24-00
24-15
Speed
28.2
27.9
27.5
27.2
26.9
26.6
26.3
26.0
25.8
25.5
25.2
25.0
24.7
Time
24-30
24-45
25-00
25-15
25-30
25-45
26-00
26-15
26-30
26-45
27-00
27-15
27-30
Speed
24.4
24.2
24.0
23.7
23.5
23.3
23.0
22.8
22.6
22.4
22.2
22.0
21.8
Time
27-45
28-00
28-15
28-30
28-45
29-00
29-15
29-30
29-45
30-00
30-15
30-30
30-45
Speed
21.6
21.4
21.2
21.0
20.8
20.6
20.5
20.3
20.1
20.0
19.8
19.6
19.5

15 Miles

Time
30-00
30-30
31-00
31-30
32-00
32-30
33-00
33-30
Speed
30.00
29.5
29.0
28.5
28.1
27.6
27.2
26.8
Time
34-00
34-30
35-00
35-30
36-00
36-30
37-00
37-30
Speed
26.4
26.00
25.7
25.3
25.0
24.6
24.3
24.0
Time
38-00
38-30
39-00
39-30
40-00
40-30
41-00
41-30
Speed
23.6
23.3
23.00
22.7
22.5
22.2
21.9
21.6

25 Miles

Time
47-00
47-30
48-00
48-30
49-00
49-30
50-00
50-30
51-00
51-30
52-00
52-30
Speed
31.9
31.5
31.2
30.9
30.6
30.3
30.0
29.7
29.4
29.1
28.8
28.5
Time
53-00
53-30
54-00
54-30
55-00
55-30
56-00
56-30
57-00
57-30
58-00
58-30
Speed
28.3
28.0
27.7
27.5
27.2
27.0
26.7
26.5
26.3
26.0
25.8
25.6
Time
59-00
59-30
1-0-00
1-0-30
1-1-00
1-1-30
1-2-00
1-2-30
1-3-00
1-3-30
1-4-00
1-4-30
Speed
25.4
25.2
25.0
24.7
24.5
24.3
24.1
24.0
23.8
23.6
23.4
23.2
Time
1-5-00
1-5-30
1-6-00
1-6-30
1-7-00
1-7-30
1-8-00
1-8-30
1-9-00
1-9-30
1-10-00
1-10-30
Speed
23.00
22.9
22.7
22.5
22.3
22.2
22.0
21.8
21.7
21.5
21.4
21.2
Time
1-11-00
1-11-30
1-12-00
1-12-30
1-13-00
1-13-30
1-14-00
1-14-30
1-15-00
1-15-30
1-16-00
1-16-30
Speed
21.1
20.9
20.8
20.6
20.5
20.4
20.2
20.1
20.0
19.9
19.8
19.6

30 Miles

Time
1-00-00
1-01-00
1-02-00
1-03-00
1-04-00
1-05-00
1-06-00
1-07-00
Speed
30.0
29.5
29.0
28.5
28.1
27.6
27.2
26.8
Time
1-08-00
1-09-00
1-10-00
1-11-00
1-12-00
1-13-00
1-14-00
1-15-00
Speed
26.4
26.0
25.7
25.3
25.0
24.6
24.3
24.0
Time
1-16-00
1-17-00
1-18-00
1-19-00
1-20-00
1-21-00
1-22-00
1-23-00
Speed
23.6
23.3
23.0
22.7
22.5
22.2
21.9
21.6

50 Miles

Time
1-36-00
1-37-00
1-38-00
1-39-00
1-40-00
1-41-00
1-42-00
1-43-00
1-44-00
1-45-00
1-46-00
Speed
31.2
30.9
30.6
30.3
30.0
29.7
29.4
29.1
28.8
28.5
28.3
Time
1-47-00
1-48-00
1-49-00
1-50-00
1-51-00
1-52-00
1-53-00
1-54-00
1-55-00
1-56-00
1-57-00
Speed
28.0
27.7
27.5
27.2
27.0
26.7
26.5
26.3
26.0
25.8
25.6
Time
1-58-00
1-59-00
2-00-00
2-01-00
2-02-00
2-03-00
2-04-00
2-05-00
2-06-00
2-07-00
2-08-00
Speed
25.4
25.2
25.0
24.8
24.5
24.3
24.1
24.0
23.8
23.6
23.4
Time
2-09-00
2-10-00
2-11-00
2-12-00
2-13-00
2-14-00
2-15-00
2-16-00
2-17-00
2-18-00
2-19-00
Speed
23.2
23.0
22.9
22.7
22.5
22.3
22.2
22.0
21.8
21.7
21.5
Time
2-20-00
2-21-00
2-22-00
2-23-00
2-24-00
2-25-00
2-26-00
2-27-00
2-28-00
2-29-00
2-30-00
Speed
21.4
21.2
21.1
20.9
20.8
20.6
20.5
20.4
20.2
20.1
20.0

100 Miles

Time
3-20-00
3-25-00
3-30-00
3-35-00
3-40-00
3-45-00
3-50-00
3-55-00
4-00-00
4-05-00
4-10-00
Speed
30.0
29.2
28.5
27.9
27.2
26.6
26.0
25.5
25.0
24.4
24.0
Time
4-15-00
4-20-00
4-25-00
4-30-00
4-35-00
4-40-00
4-45-00
4-50-00
4-55-00
5-00-00
5-05-00
Speed
23.5
23.0
22.6
22.2
21.8
21.4
21.0
20.6
20.3
20.0
19.6
Time
5-10-00
5-15-00
5-20-00
5-25-00
5-30-00
5-35-00
5-40-00
5-45-00
5-50-00
5-55-00
6-00-00
Speed
19.3
19.0
18.7
18.4
18.1
17.9
17.6
17.3
17.1
16.9
16.6

If you cant find your exact time or distance, work it out for yourself, use the formula,
Distance covered times 60 devided by minutes taken.