See how a taller or shorter tire changes indicated speed. Get actual speed, percent error, and a 25–75 mph table from stock vs new size — free, private.
Enter values to see results
100% browser-based
Runs locally in this tab
No upload required
Your files never leave this device
Nothing is stored
Close the tab and the input is gone
Instant results
No queue and no server wait
Enter stock size, new size, and an indicated speed (default 60). The calculator applies the diameter ratio so you see true road speed, percent error, and the mph difference. That is the number you want before a 33-inch tire on a truck that left the factory on 31s.
Besides the speed you typed, you get a table at 25, 35, 45, 55, 65, and 75 mph indicated. Use it to sanity-check highway cruising and school-zone indicated speeds without re-entering the stock and new sizes each time you change the question.
A taller tire also stretches distance: the workspace shows how many true miles you cover for 100 miles on the odo at that diameter ratio. Pair with Odometer Correction when you care about trip miles or service intervals more than instantaneous speed.
No VIN, no dealer login, and no upload. Diameter comes from the size codes you type. This is geometry, not a GPS calibration of your actual cluster. Close the tab and the sizes are gone from GetUpTools. Nothing is stored on a server.
Use the size the speedometer was built for — usually the door-placard OE size, not the worn tire currently on the truck.
Metric or flotation. Overall diameter is what drives the error, so the full code matters.
Default is 60. The result shows actual speed, percent error, and the difference in mph.
Each row is indicated versus actual for that cluster reading. Use Odometer Correction if you need trip-distance instead of speed.
Straight answers on privacy, limits, and how the workspace behaves.
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