have 17x9 factory wheels,i want to go with 18x10 on back and 18x9 on front. other than the fact of no rotation now ,do I need to change anything to keep my speedodometer accurate.

 

tires.....

 

Your speedometer won't change unless you go with tires that are taller than 27" (I'm assuming you're putting these on a 2005+ car).

 

no its a 04

 

Sizes varies slightly by brand.... but roughly a 265/35 on the 18x9 and a 295/35 on the 18x10 will work out for you. It's what I run on mine.

 

not to say your combo doesnt work, but i hated how the 265s looked on my car, next day traded them in for 275 35 on the front, looks much better, and 295 35 on the back no rubbing problems either!

Oh and to answer original question, my little gps unit actually put my car dead on accurate with the speedo with these tires on.

 

17 to 18 would definitely not cause any noticeable changes to your car.

 

like said as long as you get the correct size tires for the rear your speedo should be just fine. I also run 295/35 but you could also run 285/35 or 315/30 and you'll be good to go.