Brakes and Tires
Chevy Silverado
Dodge Ram

Do bigger tires effect the speedometer How do you calculate the difference I had 30 inch tires and now have 33 inch tires?

Top Answer
User Avatar
Wiki User
2011-09-12 22:04:14
2011-09-12 22:04:14


Putting larger diameter tires on any vehicle will affect the speedometer and odometer readings. If you know the revolutions per mile for the original tires and the larger tires, you could calculate the speed difference. If they are already on the vehicle, you can also drive down the highway, set the speed at 60 MPH and measure the time it takes to drive between mile markers. One mile at 60 MPH takes 60 seconds. If it is not 60 seconds between mile markers, the difference is the speedometer error.


Your tires are 10% larger than the car thinks. Therefore, you travel 10% more than your car recognizes. This has two effects:

Your actual speed is 10% MORE than what your speedometer is reflecting. (When your speedometer reads 60, you are actually traveling 66)

10=11, 40=44, 100=110 etc.

Your actual mileage is 10% MORE than what your odometer is reflecting. (When your odometer reads 100 miles, you have actually traveled 110)

So when you see a cop doing a speed trap, remember to slow down accordingly.

When you sell your car, don't forget to disclose that you have larger tires and that the odometer should read more miles than it does.

Related Questions

User Avatar

It will affect the speedometer. For example, bigger rims will make you go faster than what the speedometer is actually reading. If it say's 50mph with regular rims, then with larger rims you will be going faster.

User Avatar

no it will not. Bigger rims (wheels) will make the car faster in a straight line but more difficult to turn. Smaller ones will have the opposite effect. The speed difference is about +- 2% of whatever the speedometer is reading.

User Avatar

if the diameter will be greater or less then the speedometer will be effected

User Avatar

Larger tires will affect the speedometer. There may not be a large difference in your application, but there will be a difference. You may be reading 45mph, and really be going 48mph. the worst problem will be in your odometer after a few thousand miles. your odometer will be WAY off once you have traveled a few K miles. I would suggest going to a local transmission shop to have your speedo re-calibrated for the larger tires. If you go much larger than that, check with your local mechanic on how well your transmission will be able to turn such a large tire. you may need to be re-geared.

Copyright © 2020 Multiply Media, LLC. All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply.