Quote: Originally posted by telford_mike on 11 November 2003
Max speed in 3rd on 172 / Cup is 88.89mph on the limiter, as measured by timing beam at York dragway.
And according to the maths...
3rd Gear = 12.4mph per 1000rpm = 89.9mph @ 7250rpm
So the theory & the reality tie up correctly in this case!
For information, here are all the ratios for a mk2 172 or Cup...
1st - 5.3mph/1000rpm = 38.4mph @ 7250rpm
2nd - 8.7mph/1000rpm = 63.1mph @ 7250rpm
3rd - 12.4mph/1000rpm = 89.9mph @ 7250rpm
4th - 15.8mph/1000rpm = 110.6mph @ 7000rpm
5th - 20.4mph/1000rpm = 142.8mph @ 7000rpm
The mk1 has longer gearing though and can go faster in the higher gears!