What does 225/45R17 mean?

225 is the tread width in millimeters, 45 is the sidewall height as a percentage of the width, R means radial construction, and 17 is the wheel diameter in inches.

How much bigger tire can I go without problems?

Stay within 3% of your stock overall diameter. Beyond that your speedometer drifts, gearing changes, and rubbing risk climbs — especially on lowered cars.

Will a bigger tire make my speedometer wrong?

Yes. A tire 3% taller than stock makes your speedometer read about 3% slow — when it shows 60 mph you're actually doing about 62. Smaller tires read fast.

Tire Size Calculator

Compare any two tire sizes in seconds. Enter your current size and the new size you're considering — we'll show the diameter difference, speedometer error, and a straight verdict.

Tire size 225/45R17 reads as 225 millimeters of tread width, a 45% sidewall aspect ratio, radial construction, and a 17-inch rim. Overall diameter is (width × aspect ratio ÷ 100 × 2 ÷ 25.4) + rim diameter — about 25 inches here. Stay within 3% of your stock diameter and your speedometer, gearing, and clearances all behave.

How to read the result

Within 3%: Safe zone — speedometer stays accurate, clearances behave like stock.
3–5%: Check clearances carefully and expect a small speedometer error.
Over 5%: Too far — gearing, speedometer, and ABS behavior all shift, and rubbing risk climbs.

The math behind it

Overall diameter = (width × aspect ratio ÷ 100 × 2 ÷ 25.4) + rim diameter. The percentage difference between old and new is what your speedometer feels: a new tire 3% taller means your speedo reads about 3% slow at any speed.