SidewallerTire & wheel calculators

245/45R20 vs 255/45R20

255/45R20 is 1.2% taller (+0.35 in) and 0.39 in wider than 245/45R20.

OK
Close match

255/45R20 is 1.2% taller than 245/45R20. That is inside the ±3% most shops treat as a straight swap.

245/45R20255/45R20Change
Diameter28.68″29.04″+0.35″+1.2%
Width9.65″10.04″+0.39″+4.1%
Sidewall4.34″4.52″+0.18″+4.1%
Circumference90.1″91.2″+1.1″+1.2%
Wheel20″20″Same
Revs per mile703695−9
SideTread
245/45R20255/45R20
Speedometer shows 60 mph60.7mph

Real speed on 255/45R20.

Ground clearance+0.18in

Change in height under the axle.

Width per side+0.20in

On the same wheel, split inboard and outboard.

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245/45R20 or 255/45R20?

Can I use 255/45R20 instead of 245/45R20?

255/45R20 is 1.2% taller than 245/45R20. That is inside the ±3% most shops treat as a straight swap. Also match or beat the original load index and speed rating, and check that the wheel width suits the new tire.

Will my speedometer be off?

At an indicated 60 mph on 255/45R20 you are really doing 60.7 mph if the speedometer was set up for 245/45R20. Going the other way, 245/45R20 would make it read 59.3 mph at a real 60.

How much ground clearance does it change?

Half the diameter difference: +0.18 in (+5 mm) under the axle.

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