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Enter your gear ratios, rear tyre diameter and ring and pinion ratio, to find out how many mph you're doing at various rpms. You can also use the results to accurately calibrate your speedo (assuming you have a tacho fitted). If you've fitted non stock tyres, the chances are your speedo is reading incorrectly. Just check which gearbox you have, enter the ratios listed below into the calculator, along with the overall diameter of the rear tyre and you'll have an accurate set of figures to work from.
Here's a list of the ratios for stock 'boxes from 1960 onwards.
Original fitment Ring & Pinion 1st 2nd 3rd 4th 12/1300 4.37 3.78 2.06 1.26 0.89 1500 4.12 1600 3.88 0.92
Commonly used close ratio gear sets for 3rd and 4th are:
3rd - 1.48, 1.56, 1.70. 4th - 1.04, 1.09 1.12, 1.19, 1.21, 1.30. With a Berg 5 speed, you could opt to use a stock 4th ratio (0.89/0.92) for 5th gear (having used closer ratio 3rd & 4th), or a taller 0.82. Tyre diameters are generally between 22 and 26 inches.
Plug in the numbers and see what you come up with.
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