changing rims to 18's
 

I am thinking of going to 245/40/18 and 275/35/18. Will my speedometer need to be corrected?

245/50/16 OD- 25.65"
245/35/18 OD-24.75"
275/35/18 OD-25.58"

Only thing that will really be affected will be your front wheel speed

245/50/16 speed @ 100 KPH=62.14 mph
245/35/18 speed @ 100 KPH=59.97 mph
275/35/18 speed @ 100 KPH=61.97 mph

245/35/18 speed variance is -3.61% too slow
275/35/18 speed variance is -0.26% too slow


I always use 1010tires.com for a tire size calculator. I always use stock wheel size 245/50/16 or 275/40/17 because that is what the speedo is calibrated for then you can select up to 4 different tire sizes and compare all aspects of the tires side by side.


oh and the answer to your question is no you won't have to re-calibrate your speedo.

Thanks for you help:)