Gearbox Calculator
Gearbox Calculator
When building or rebuilding a gearbox, updaing your gear ratios, or changing out your speedometer sometimes you need to update some things. Using the Classic Mini DIY Gear Calculator below, you can determine the correct gearing for your for your new engine build and find the right speedo gear to use as well.
Maximum RPM
Speedo Information
Top Speed | Turns | Speedometer | Result |
|---|---|---|---|
100mph | 1440 | Smiths - Generic | Under 11% |
110mph | 1408 | Smiths central ('60s Cooper) | Under 9% |
90mph | 1376 | Smiths central (850) | Under 7% |
90mph | 1312 | Smiths Early tri'clock | Under 2% |
110mph | 1300 | Late Cooper Nippon Seiki | Under 1% |
120mph | 1280 | Cooper S Smiths central | Reads correctly! |
90mph | 1280 | Smiths central Pre '84 | Reads correctly! |
90mph | 1248 | Smiths central | Over 3% |
100mph | 1248 | Smiths (Austin 1300GT) | Over 3% |
120mph | 1248 | Smiths (1275 GT/25/1100 Special) | Over 3% |
90mph | 1242 | Nippon Seike | Over 3% |
90mph | 1216 | Smiths post '84 | Over 5% |
110mph | 1000 | All Metro's and Most modern aftermarket | Over 28% |
Gearing Information
Gear | Ratio | Max Speed (mph) |
|---|---|---|
| 1 | 2.583 | 42mph |
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Please note the above figures are approximate values. Before purchasing parts and building your engine we recommend doublechecking your calculations multiple times using more than one source. The mathematical equations used in this tool can be found here: Equation Source Code
SUPPORT THE SITE
Classic Mini DIY is completely free resource supported by our viewers. If you are interested in helping to keep the channel alive, consider supporting on Patreon.
Membership comes with tons of free perks and benefits!