- First Name
- Nov 19, 2020
- Reaction score
- Mercedes E320, Cadillac XT5, VW Jetta
19 vs 20 diameter is a difference of just over 5%. It works out to closer to 53 rotations per mile. My math gets me 1061 rotations with 19" vs. 1008 with 20".
Another way to think of it is if the car reports 70mph on the speedometer you would really be doing closer to 74mph.
Mike is correct. (My name is also Mike, so I get a two for one!) It is really the tires you have to compare, not the wheels. 225/55 19 tires have a circumference of 2293.674859 mm (approximately ;-)). 245/45 20 tires have a circumference of 2288.648315 mm. Therefore circumference of the 20" tires is 99.78% of the 19" tires. Driving with the 20" tires: if your speedometer says you are going 100 mph, you will actually only be going 99.78 mph. Approximately. Your results may vary.Please check the tire specs. 723 vs 726 revs per mile.