wheel radii

logistix · Post by **logistix** » Wed Jun 09, 2004 8:23 pm

hello everyone,
when you look at different sizes of wheels, the corresponding tyre sizes are such that the total radii increases as you increase the wheel size. my 14" wheels have 60 profile whereas 17" wheels have 40 profile. there's a difference of approx. 55mm in total radius, which will affect the tachometer and the counter. how do we deal with this, get the dealer to update the software?
thanks!

Joy · Post by **Joy** » Wed Jun 09, 2004 10:05 pm

Halfway this page you can fill in tire size calculator including difference of rolling radius.

http://www.chris-longhurst.com/carbible ... bible.html

logistix · Post by **logistix** » Thu Jun 10, 2004 12:47 pm

wow thanks, this site has everything about tyres! like i thought, there will be a difference of 5.7 cm in circumference if i upgrade to 17" wheels. is that a big problem for the speedo or shouldn't i worry about it?

carmadaaron · Post by **carmadaaron** » Thu Jun 10, 2004 1:10 pm

im planning 18s with 215/35/18 tyres and i dont think u should b worrying! ceedubya had 225/40/18 on his 1.2 9n and he had no probs