Tire diameter vs speedometer reading

Scoob · 05-24-2002, 12:31 PM

If you increase your wheel/tire diameter, which way does that affect the speedometer?

For example, assume a 1.5% diameter increase. At a true speed of 65 mph what does my speedometer show? 66mph or 64mph?

USAZR1 · 05-24-2002, 04:20 PM

A taller diameter tire has a larger rolling circumference and will increase the final drive ratio.(taller tires=taller gearing). So,your speedo will read slower.

carter200 · 05-24-2002, 07:13 PM

See your other post for the answer. USAZR1 is correct :yesnod:

BCinPhx · 05-29-2002, 03:25 AM

Try this ...could help.
:) http://www.miata.net/garage/tirecalc.html
Courtesy of pkmoose

[Modified by BCinPhx, 11:26 PM 5/28/2002]

[Modified by BCinPhx, 11:29 PM 5/28/2002]