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.
Revolutions per/Mile
3630
Turns per/Mile
1281
Top Speed
107mph
Tire Width
145mm
Tire Profile
80%
Tire Size
10"
Tire Diameter
486mm
Circumference
1527mm
Turns Per Mile
1054
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Speedo Information
| Top Speed | Turns | Speedometer | Result |
|---|---|---|---|
| Smiths - Generic | 1440 | 100mph | Under 11% |
| Smiths central ('60s Cooper) | 1408 | 110mph | Under 9% |
| Smiths central (850) | 1376 | 90mph | Under 7% |
| Smiths Early tri'clock | 1312 | 90mph | Under 2% |
| Late Cooper Nippon Seiki | 1300 | 110mph | Under 1% |
| Cooper S Smiths central | 1280 | 120mph | Reads correctly! |
| Smiths central Pre '84 | 1280 | 90mph | Reads correctly! |
| Smiths central | 1248 | 90mph | Over 3% |
| Smiths (Austin 1300GT) | 1248 | 100mph | Over 3% |
| Smiths (1275 GT/25/1100 Special) | 1248 | 120mph | Over 3% |
| Nippon Seike | 1242 | 90mph | Over 3% |
| Smiths post '84 | 1216 | 90mph | Over 5% |
| All Metro's and Most modern aftermarket | 1000 | 110mph | Over 28% |
Gearing Information
| Gear | Ratio | Max Speed (mph) |
|---|---|---|
| 1 | 2.583 | 42mph |
| 2 | 1.644 | 65mph |
| 3 | 1.25 | 86mph |
| 4 | 1 | 107mph |
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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!