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Car Standard Cars Modified Cars
Sprite Mk 1&2 3 early 4 late 4 n/a 1 2 3
Midget Mk 1 2 early 3 late 3 4 (rb)
Engine 948 1098 1275 1275 1500 A A+
Input
Tyre size(check size available in tyre data)  520x13 145x13 145x13 145x13 145x13 165/70x13 155x13 165/70x13
Back Axle No of Teeth on crown wheel 38 38 38 39 41 38 41 41
pinion 9 9 9 10 11 9 11 11
Speedo Drive 3rd motion shaft 5 5 5 5 6 5 5 5
take off pinion 13 13 13 13 21 13 13 19
Speedo available/fitted 1472 1472 1472 1376 1000 1472 1376 900
O/D ratio (if fitted)  1 1 1 1 1 1 1 0.8
Output: 
Wheel turns per mile 914 934 934 934 934 931 913 931
Axle ratio 4.22 4.22 4.22 3.90 3.73 4.22 3.73 3.73
Speedo ratio 0.38 0.38 0.38 0.38 0.29 0.38 0.38 0.26
Speedo turns per mile 1484 1517 1517 1401 995 1512 1309 913
MPH per 1000rpm 15.5 15.2 15.2 16.5 17.2 15.3 17.6 21.6
RPM @ 70 mph (in top) 4502 4601 4601 4250 4061 4586 3970 3239
% speedo error 
NB -ve means reads slow
1 3 3 2 -1 3 -5 1
Notes 20 and 22 tooth speedo drive take off pinions also available.

© Geri Swann-Price