17 or 18 inch wheels for my '73 Firebird

[wim firebird]

Hi Guys, cant decide between 17 or 18 inch wheels ...need help :-) thinking about 315x11 or 18x9.5 with 315x35x17 or 285x40x18 for the rears. How will the wheels fit with a lowered rear ( allston-g-bar)? And is there any difference in performance between 17 or 18 wheels?? I know the 18's are 3 taller so it wil fill up my wheelwells nice...

[srh3trinity]

I am going with 18's on my 74. You have more wheel/tire and brake options with 18's and you can still get enough tire on the car and have a little bit of sidewall.

[68Formula]

2nd GEN tires were more than 27" tall. Start going shorter, it doesn't quite look right even if you lower it (too much gap all around). So in the sizes you've chosen, 18s would be better.

[rohrt]

Do they not make 17" tire that has enough sidewall to achieve 27"?

[twoformulas]

Yes, 255/50/17 specs out to a 27.1" diameter. There are not a lot of choices in this size, though.

[Norm Peterson]

Hi Guys, cant decide between 17 or 18 inch wheels ...need help :-) thinking about 315x11 or 18x9.5 with 315x35x17 or 285x40x18 for the rears.

I think you'll find better support for ~27" tall tires in 18, so that would be the practical choice. That most of the 2005 - up Mustangs can use 27" tall tires on 18" rims means that the supply of tires that will work shouldn't be drying up any time soon.

FWIW, it appears that there is wider tire mfr support for the 275/40-18 size than for 285/40-18. I honestly doubt you'd notice the difference between the two that a 3/8" shorter diameter and a 1/4" narrower tire section width makes without being close enough to read the tire information that's molded into the sidewalls.

And is there any difference in performance between 17 or 18 wheels??

Theoretically, there is a little (but you'd need to know a lot more than just the wheel diameter to even say which one would actually provide the better numbers). My take - unless you're so completely serious about performance that appearance (aka "filling up my wheelwells nice") counts for absolutely nothing at all, don't worry about this.


Norm