Will Bigger Tires Fit?

Tire size calculator / Speedometer

Speedometer error calculator

Changed your tire size? Enter the old and new sizes to see how fast you are really going, and how far off your odometer is.

mph

You're really going 67.8 mph.

Worked example

Here is what common upgrades from a 265/70R17 tire do to your speedometer and odometer:

New size (from 265/70R17)Height changeReal speed at 65 mphEvery 100 odometer miles
275/70R17+1.7%66.1 mph101.7 real miles
285/70R17+3.5%67.3 mph103.5 real miles
285/75R17+7.0%69.6 mph107.0 real miles
35x12.50R17+10.7%72.0 mph110.7 real miles

Why it happens

Your speedometer counts how fast your wheels turn, not how fast you move. A taller tire covers more ground with each turn, so at the same wheel speed you are going faster than the dial shows. A shorter tire does the opposite.

Compare sizes and check fit

Common questions

How far off will my speedometer be with bigger tires?

By the same percentage your tires grew. Tires that are 3% taller make you go about 3% faster than the speedometer shows: at 65 mph on the dial, you are doing about 67.

Does my odometer change too?

Yes. With taller tires your odometer counts fewer miles than you really drive, by the same percentage as the speedometer. That can matter for warranties, leases and service intervals.

Can I fix my speedometer after changing tire size?

Usually. Many dealers can update the tire size in the vehicle's computer, and handheld programmers are sold for many trucks. Older vehicles may need a different speedometer gear.

Is a speedometer error a safety problem?

It can be. Reading low means you may be speeding without knowing it. Large size changes can also affect anti-lock brakes and stability control, which use wheel speed. Keeping within about 3% avoids most of this.

Know someone who just got new tires? Send them this free calculator.