wheel rotation

[DVS-8OR]

i just got 18" rims om my R33 and was wonder if the size of the tire will effect my speedo

on the back 265/35 18

on the front 225/40 18

[51jay]

If you have 9.5inch rims at the back the rolling diameter will be the same as standard and your speedo reading won't be changed.

If they are narrower your speedo will read slower , and faster if they are wider. How much error depends on how much wider or narrower they are

[KamikazeR33]

hope ya dont mind me askin this but did the 18's fit easily?

[DVS-8OR]

with the mags i got the back fitted fine but the front need a 10mm spacers to clear the brakes. This is without lowering the car too so now it sits pretty high

[Duncan]

Hey 51jay, I'm confused, isn't it wheel diameter that affects the speedo, not rim width?

[51jay]

Duncan: That's right but there is an optimal tyre size for any given rim width even though you can fit a range of sizes. Going over or under the optimal size effects to some extent the diameter, but not as much as changing the aspect ratio.

If your 265 35 18's are on a 9.5inch rim they should be the same diameter as factory 205 50 16 on the factory 6.5inch rim . If they are on an 8.5 or 9inch rim they will be slightly bigger. If you have 265 40 on the 9.5inch rim they will also be bigger diam and you speedo will show slower than your actual speed

[Xeron]

Crank out a measuring tape/ruler.

If the new wheel/tyre combo dosn't have the same diamater as the stockos, ur speedo is no longer accurate.