Speedo Drive Ratios
Please NOTE that these ratio's are theoretical ONLY and they may not even exist in real life. This
is only meant to give you an idea of the ratio you should be looking for and should NOT be used on the road unless
checked against a calibrated Speedometer.
The first thing you need to do is chose the correct wheel/tyre combination you are going to be using. (or
the closest to it).
165/70/10 (145/10)
145/12
155/12
175/50/13
If the size you need is NOT listed above then try to choose the nearest one. If you could also let me know
the circumferance of the tyre and it's size then I will be able to add it to these pages. Mail any inprovements you wish to
see or corrections of the existing text please to GCRC63@mailbox.sci.rl.ac.uk
165/70/10 (145/10)
look up your Diff ratio up in the column on the left hand side, then move right until the number in the table
corresponds to the actual turns per mile of your speedo. (often printed on the face or on a sticker on the back). Then follow
the table up until you get to the top, this will be the drive gears that you need to use (if available).
| Spedo Drive Ratio -->
------------------------
Diff Ratio--v |
5/18
3.6:1 |
5/17
3.4:1 |
5/16
3.2:1 |
6/18
3:1 |
6/17
2.83:1 |
6/16
2.67:1 |
7/18
2.52:1 |
7/17
2.43:1 |
MPH per 1000 RPM
4 Speed 1:1 Drop gears |
MPH per 1000 RPM
5 Speed Jack Knight |
| 2.95 |
867 |
919.8 |
976 |
1041 |
1104 |
1170 |
1216 |
1286 |
19.21 |
22.52 |
| 3.05 |
897 |
950 |
1009 |
1077 |
1141 |
1210 |
1256 |
1330 |
18.58 |
21.78 |
| 3.105 |
913 |
967 |
1027 |
1096 |
1161 |
1231 |
1280 |
1353 |
18.25 |
21.4 |
| 3.21 |
944 |
999 |
1062 |
1133 |
1201 |
1273 |
1322 |
1399 |
17.65 |
20.69 |
| 3.44 |
1011 |
1071 |
1138 |
1214 |
1287 |
1364 |
1417 |
1499 |
16.47 |
19.31 |
| 3.65 |
1073 |
1136 |
1208 |
1288 |
1365 |
1447 |
1504 |
1590 |
15.52 |
18.19 |
| 3.76 |
1106 |
1171 |
1244 |
1327 |
1407 |
1491 |
1549 |
1639 |
15.07 |
17.67 |
145/12
look up your Diff ratio up in the column on the left hand side, then move right until the number in the table
corresponds to the actual turns per mile of your speedo. (often printed on the face or on a sticker on the back). Then follow
the table up until you get to the top, this will be the drive gears that you need to use (if available).
| Spedo Drive Ratio -->
------------------------
Diff Ratio--v |
5/18
3.6:1 |
5/17
3.4:1 |
5/16
3.2:1 |
6/18
3:1 |
6/17
2.83:1 |
6/16
2.67:1 |
7/18
2.52:1 |
7/17
2.43:1 |
MPH per 1000 RPM
4 Speed 1:1 Drop gears |
MPH per 1000 RPM
5 Speed Jack Knight |
| 2.95 |
850 |
900 |
957 |
1020 |
1081 |
1147 |
1191 |
1260 |
19.6 |
22.98 |
| 3.05 |
897 |
931 |
989 |
1055 |
1118 |
1186 |
1232 |
1303 |
18.95 |
22.22 |
| 3.105 |
895 |
947 |
1007 |
1074 |
1139 |
1207 |
1254 |
1326 |
18.62 |
21.83 |
| 3.21 |
925 |
980 |
1041 |
1110 |
1177 |
1248 |
1296 |
1371 |
18.01 |
21.11 |
| 3.44 |
991 |
1050 |
1115 |
1190 |
1261 |
1337 |
1389 |
1469 |
16.81 |
19.71 |
| 3.65 |
1052 |
1114 |
1183 |
1262 |
1338 |
1418 |
1474 |
1559 |
15.84 |
18.57 |
| 3.76 |
1084 |
1148 |
1219 |
1301 |
1379 |
1461 |
1518 |
1606 |
15.37 |
18.02 |
155/12
look up your Diff ratio up in the column on the left hand side, then move right until the number in the table
corresponds to the actual turns per mile of your speedo. (often printed on the face or on a sticker on the back). Then follow
the table up until you get to the top, this will be the drive gears that you need to use (if available).
| Spedo Drive Ratio -->
------------------------
Diff Ratio--v |
5/18
3.6:1 |
5/17
3.4:1 |
5/16
3.2:1 |
6/18
3:1 |
6/17
2.83:1 |
6/16
2.67:1 |
7/18
2.52:1 |
7/17
2.43:1 |
MPH per 1000 RPM
4 Speed 1:1 Drop gears |
MPH per 1000 RPM
5 Speed Jack Knight |
| 2.95 |
803 |
850 |
903 |
963 |
1021 |
1082 |
1125 |
1190 |
20.75 |
24.33 |
| 3.05 |
830 |
879 |
934 |
996 |
1056 |
1119 |
1163 |
1230 |
20.07 |
23.53 |
| 3.105 |
845 |
894 |
950 |
1014 |
1075 |
1139 |
1183 |
1252 |
19.72 |
23.12 |
| 3.21 |
873 |
925 |
982 |
1048 |
1111 |
1178 |
1224 |
1294 |
19.08 |
22.37 |
| 3.44 |
936 |
991 |
1053 |
1123 |
1191 |
1262 |
1311 |
1387 |
17.8 |
20.87 |
| 3.65 |
993 |
1052 |
1117 |
1192 |
1264 |
1340 |
1392 |
1472 |
16.77 |
19.66 |
| 3.76 |
1023 |
1084 |
1151 |
1228 |
1302 |
1380 |
1434 |
1516 |
16.28 |
19.09 |
175/50/13
look up your Diff ratio up in the column on the left hand side, then move right until the number in the table
corresponds to the actual turns per mile of your speedo. (often printed on the face or on a sticker on the back). Then follow
the table up until you get to the top, this will be the drive gears that you need to use (if available).
| Spedo Drive Ratio -->
------------------------
Diff Ratio--v |
5/18
3.6:1 |
5/17
3.4:1 |
5/16
3.2:1 |
6/18
3:1 |
6/17
2.83:1 |
6/16
2.67:1 |
7/18
2.52:1 |
7/17
2.43:1 |
MPH per 1000 RPM
4 Speed 1:1 Drop gears |
MPH per 1000 RPM
5 Speed Jack Knight |
| 2.95 |
786 |
833 |
885 |
944 |
1000 |
1060 |
1101 |
1165 |
21.19 |
24.84 |
| 3.05 |
813 |
861 |
915 |
976 |
1034 |
1096 |
1139 |
1205 |
20.49 |
24.02 |
| 3.105 |
827 |
876 |
931 |
993 |
1053 |
1116 |
1159 |
1226 |
20.13 |
23.6 |
| 3.21 |
855 |
906 |
963 |
1027 |
1088 |
1154 |
1199 |
1268 |
19.47 |
22.83 |
| 3.44 |
917 |
971 |
1032 |
1100 |
1166 |
1237 |
1285 |
1359 |
18.17 |
21.3 |
| 3.65 |
973 |
1030 |
1095 |
1168 |
1238 |
1312 |
1363 |
1442 |
17.12 |
20.07 |
| 3.76 |
1002 |
1061 |
1128 |
1203 |
1275 |
1351 |
1404 |
1485 |
16.63 |
19.5 |
If you encounter any problems or just want a chat about anything just mail - gcrc63@mailbox.sci.rl.ac.uk
