SidewallerTire & wheel calculators

305/35R24 vs 285/65R18

285/65R18 is 0.6% taller (+0.18 in) and 0.79 in narrower than 305/35R24.

OK
Close match

285/65R18 is 0.6% taller than 305/35R24. That is inside the ±3% most shops treat as a straight swap.

305/35R24285/65R18Change
Diameter32.41″32.59″+0.18″+0.6%
Width12.01″11.22″−0.79″−6.6%
Sidewall4.20″7.29″+3.09″+73.5%
Circumference101.8″102.4″+0.6″+0.6%
Wheel24″18″−6″
Revs per mile622619−3
SideTread
305/35R24285/65R18
Speedometer shows 60 mph60.3mph

Real speed on 285/65R18.

Ground clearance+0.09in

Change in height under the axle.

Width per side−0.39in

On the same wheel, split inboard and outboard.

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305/35R24 or 285/65R18?

Can I use 285/65R18 instead of 305/35R24?

285/65R18 is 0.6% taller than 305/35R24. 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 285/65R18 you are really doing 60.3 mph if the speedometer was set up for 305/35R24. Going the other way, 305/35R24 would make it read 59.7 mph at a real 60.

How much ground clearance does it change?

Half the diameter difference: +0.09 in (+2 mm) under the axle.

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