17"/18" wheel fitment, tyre sizes??

[brummiewedge]

Hi All, i have bought 7"x 17" front and 7.5"x 18" rears, Do i go for 215/40 or 215 45 17" fronts. i assume 235/40 18" will be ok. Cheers.

[scoule]

215/40 17's are a closer match to rolling radius on the front ...

Original 205/55 x 15, diameter = 606.5
215/40 17, diameter = 603.8 (- 0.5%)
215/45 17, diameter = 625.3 (+ 3.0%)

Rears? What did you have originally?

245/45 16, diameter = (16*25.4) + (2 * (245 * 0.45)) = 626.9
235/40 18, diameter = (18*25.4) + (2 * (235 * 0.40)) = 645.2 (approx +3%)

How about ...
245/35 18, diameter = (18*25.4) + (2 * (245 * 0.35)) = 628.7 (approx +0.25%)

Sorry, no real world experience of these, just the calcs!

[brummiewedge]

Well i asked for it!!

Cheers.

[jonka]

hi
i have just fitted new wheels tyres to my chim 7.5 x 17 front with 215 40 17s and 8x18s rear with 245x35 18 i was told that there was only 4mm in differance but you would lose that if your tyres were new or old there could be up to 18mm differance. hope thats any help.
Jon...........

[brummiewedge]

gone for 215/40-17 and 235/40-18 ATP two piece with stainless rim, and Pirelli's all round, thats who i work for!!

[tahiti450]

You should be fine with that, - that's the sizes I've been running for the last coupe of years. 245/35/18s are tempting, but they are really stretching it on the 7.5 inch rim, the 235 / 40's are about as wide as can be accomodated without significant sidewall - and therefore tread - distortion.

>> Edited by tahiti450 on Friday 19th May 00:17