tire sizes, explain please Options

[Cormudgen]

can someone explain to me what each part of a tire size is?

for example i found a good deal on some 17" rims that have tires included with the size of 215/45/17. i understand that the last number is the rim size they will fit but that is the extent of my knolwedge. one of my fiends just ordered rims for 300zx and the tires included have a really thick(high) sidewall. I don't want my tires to be almost as big as my rims. i understand the more lo profile the tire is the worse ride quality but i am willing to sacrifice that. so can you explain what each number means and recomend a good tire size in both 18" and 17" where my sidewalll wont' be to high.

thanks
cormudgen

[BenMMellor]

you alos need to retain a rolling radius or it will throw the speedo out and you may get done for speeding withour realising..

best size tyre for a 17" rim is 215/40/17

a tyre calculator helps you work out the best size for your rim and keeping the same rolling radius... try this one.

http://www.tyresave.co.uk/tyresize.html