Q：Tire size is not listed in the chart

To determine the most accurate calibration number for your application (tire choice, body weight, etc.), or if your tire size is not listed in the chart, determine calibration number by performing a 'tire roll out'.

1. Mark a spot on the floor, and line up the tube's valve stem with it. You'll want to choose the wheel that the computer's sensor is being run on.
2. Running the usual tire pressure and with the rider's weight on the bike, roll the tire out one full revolution. When the valve stem comes back around to the ground, make a second mark on the floor. Measure the distance on the floor from point to point.
3. Record this number in mm if your computer requires a 4 digit calibration # (or multiply inches by 25.4 for mm). Record the number in cm if a 3 digit calibration # is required.
4. Enter this number in your computer for your wheel circumference.

ETRTO

TIRE SIZE

L(mm)

L(cm)

INCH

47-203	12x1.75	935	94
54-203	12x1.95	940	94	12
40-254	14x1.50	1020	102	14
47-254	14x1.75	1055	106
40-305	16x1.50	1185	119
47-305	16x1.75	1195	120	16
54-305	16x2.00	1245	125
28-349	16x1-1/8	1290	129
37-349	16x1-3/8	1300	130
32-369	17x1-1/4 (369)	1340	134
40-355	18x1.50	1340	134
47-355	18x1.75	1350	135	18
32-406	20x1.25	1450	145
35-406	20x1.35	1460	146
40-406	20x1.50	1490	149
47-406	20x1.75	1515	152
50-406	20x1.95	1565	157
28-451	20x1-1/8	1545	155
37-451	20x1-3/8	1615	162	20
37-501	22x1-3/8	1770	177	22
40-501	22x1-1/2	1785	179
47-507	24x1.75	1890	189	24
50-507	24x2.00	1925	193
54-507	24x2.125	1965	197
25-520	24x1(520)	1753	175
24x3/4	Tubular	1785	179
28-540	24x1-1/8	1795	180
32-540	24x1-1/4	1905	191
25-559	26x1(559)	1913	191
32-559	26x1.25	1950	195
37-559	26x1.40	2005	201
40-559	26x1.50	2010	201
47-559	26x1.75	2023	202
50-559	26x1.95	2050	205
54-559	26x2.10	2068	207
57-559	26x2.125	2070	207
58-559	26x2.35	2083	208
75-559	26x3.00	2170	217
28-590	26x1-1/8	1970	197
37-590	26x1-3/8	2068	207
37-584	26x1-1/2	2100	210	26
650C	Tubular 26x7/8	1920	192
20-571	650x20C	1938	194
23-571	650x23C	1944	194
25-571	650x25C 26x1(571)	1952	195
40-590	650x38A	2125	213
40-584	650x38B	2105	211
25-630	27x1(630)	2145	215
28-630	27x1-1/8	2155	216	27
32-630	27x1-1/4	2161	216
37-630	27x1-3/8	2169	217
40-584	27.5x1.50	2079	208
50-584	27.5x1.95	2090	209
54-584	27.5x2.1	2148	215	27.5
57-584	27.5x2.25	2182	218
18-622	700x18C	2070	207
19-622	700x19C	2080	208
20-622	700x20C	2086	209
23-622	700x23C	2096	210
25-622	700x25C	2105	211
28-622	700x28C	2136	214
30-622	700x30C	2146	215
32-622	700x32C	2155	216
	700C Tubular	2130	213	700c
35-622	700x35C	2168	217
38-622	700x38C	2180	218
40-622	700x40C	2200	220
42-622	700x42C	2224	222
44-622	700x44C	2235	224
45-622	700x45C	2242	224
47-622	700x47C	2268	227
54-622	29x2.1	2288	229	29
56-622	29x2.2	2298	230
60-622	29x2.3	2326	233

COMPUTERS