fuzzy

will it make much difference to the speedo accuracy if I change my current set up of 4 X 225 x 40 x 18 to 2 fronts @ 225 x 40 x 18 and 2 rears @ 245 x 35 x 18 all on 18 x 8 alloys ? im clutching at straws to make small changes to try to gain that little bit extra width/grip for drag strip launches on a rwd car ?

nick46

If I've worked it out correctly (chances are I haven't!), then the difference in the circumference of the two different tyres is 13.35mm, so doubt that will make too much difference.

nick46

Just read your post again and realised you are going for different sizes front and rear, but still doubt the difference will be anything to get excited about.

scoooby slayer

iTrader: (4)

Any gear speed calculator on Google will tell you the difference at any given rpm

fuzzy

doing some old school maths I reckon the sidewall on a 225 x 40 is 90mm and on a 245 x 35 its 85.75. id expect a 4.25mm difference will make no real difference to speedo reading?
how wide a tyre could I go on an 8" wide rim? is 255 pushing it ? theres plenty space between the inside edge of the rim and the suspension components and a 255 x 35 would only be less than a millimetre difference in overall diameter.
I don't want to pre order tyres if theyre not going to work !

Caddyshack

fuzzy

even less of a difference if I go 255 x 35 x 18...theres only a 6mm difference in the rolling circumference . thatll do

stevieturbo

https://www.willtheyfit.com/

fuzzy

that's the site I used to use years ago.....couldn't remember its name.... with a 255 x 35 tyre the speedo is out by 0,24 which is nothing to bother about

fuzzy

fitted wider 255 x 35 x18 rainsport3 and spun the rear wheels more than ever but got a decent 14.7 time with a passenger but a 4mph slower terminal speed @ 94.4 today.......my quickest before was a 14.1 with no passenger at 98 mph. so in summary wider tyres doesn't seem to have made any difference...