Tire/Rim purchasing - questions

for the 255, an 8 inch rim would work. the 275 would only require a 9 inch rim. you can put the 275s on a 10 inch rim, but it may look like the tire is a little too small for the rim.
 
I agree. I might go for an 8.5" rim for a 255 but 8 is fine. I agree with bigcat about the rear tires. I had 275's on 9" rims on my Z28 and they were fine. I've tried to get 275's on 10.5" rims this time and it's definitely a stretch (the current drifting look...LOL) so I'll be increasing it to a 285 or 295 next time. See, even I get it wrong.
 
Sounds good guys. I've decided to go with the Carroll Shelby CS67 rim - it's 20x9. However, they are planning to make it in a 18x8.5 and 18x9.5 and by the time I need it, they'll have it out.

With the extra 0.5'' on the width of the wheel for a 255, using knowledge from DML tire calculator and Car Bibles, an 18x8.5 wheel will fit fine on a 255/45/18 tire. However, on a 275/40/18 tire, an 18x9.5 wheel may be a lil too big. When doing the math 275mm = 10.83 inches. On a 275/40 tire, 85% of 10.83 inches is 9.21 inches which rounded to the nearest half inch, is 9 inches. Would the difference between be much using a 18x9.5 on a 275/45 as opposed to an 18x9 on a 275/40?

The reasoning behind using a side wall of 40 and 45 on 275 and 255 tires respectively, is to minimize speedometer/odeometer readings - correct? Does it have anything to do with the stance, or is the the wheel (rim) offset? Likewise a 20x9 would take a 255/35/20, 275/35/20 - according to me using and understanding the calculator?

This should be the last barrage of questions I have on this subject, thanks to you guys for having patience with me and directly me to websites to educate myself. :SNSign:
 
As I've said, the 9" rim is just about perfect for the 275 but a 9.5" wouldn't be too wide.

Keeping the rolling radius is the target irrespective of what sizes you use although I prefer the consistency of the same profile front and rear and prefer the 35 for tire control (the 55 profile on the stock Mustang is hopeless) but again, pros and cons. the only thing is that whatever you do, the bigger rolling radius should be on the back to maintain the stance. The stock Mustang suspension is a bit like a speed boat anyway, up and down and they look daft with the nose in the air.

Looks like you got a handle on the concept now though and I like the wheel choice.
 
check out this months car craft, as they have the secrets to wheels fitment.

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Just when you thought this was over, lol. Upon trying to find Nitto NT-555 in 255/35/20Z for the front tires, I noticed there were none on the list (steeda.com). I then tried to find BF Goodrich 255/35/20, and while I could, I couldn't order them, nor see their specs.

I find it hard to believe Nitto does not have 255/35/20ZR tires, anyone wanna chime in on this (PM me a possible site to purchase from)?

I did find BFGoodrich g-Force T/A KDW at 255/35/20YR, however I was leaning towards Nitto over Goodrich - for no aparent reason other than Nitto sounds cool :D , if someone wants to chime in on the two brands lol.

Appreciate the help guys and girls.