Wheel and Tire Size ?
 

I know this has probably already been discussed here, but please help me. I just purchased a 68 GTO convertible and I want to personalize it. I would like to add some new wheels and tires. I am leaning towards polished Torque Thrust II 's. I am thinking about 17 x 8 with
4 1/2 " backspace on the rear with 255 / 45 's on the rear. I think this will work. On the front, I am thinking about 17 x 7 with 4" backspace with 235/45's on the front. I am concerned about the front, I have 15 x 7 with a 3 1/2 " backspace and 235 / 60's on the front and I have a rubbing problem on one side under certain conditions.
Any help and experience would be appreciated.
Thanks,
Bob C.

Where does it rub?

17x7 with 245/45R17 worked on the front my 68 with a 4" backspace. 3.75" backspace needs a slightly smaller tire and rubbed the back of the fender with the 245/45R17.

Jon

The driver side front bottom edge of the fender rubbed, cut the edge of the tire. For some reason, I can measure 3/8 " differance from driver side to passenger side front to back.
Thanks,
Bob C.

I've always heard that a 225/60/15 series tire was about the biggest you could go on a 68-72 A-Body. In Jon's case even though he has 17" tires, the diameter of his tire is still smaller than your 15's. (26.1" vs 25.7")

A 225/60/15 is the same diameter as Jon's 245/45/17.

Here's the tire size calculator that I used.
http://www.miata.net/garage/tirecalcold.html

That size wheel/tire combo size also depends on the suspension components. On my 69 the front tire is very close to the fender, but in all of my horsing around I have never rubbed. I use H-O Racing front & rear springs, Koni shocks front/ KYB's rear, Offset upper arm shaft, F-X tall spindle and poly graphite bushings. I also use a 1 3/8" front & rear stabilizers. Wheels are 15X7 front with comp T/A 245/60 and rear is 15X8 comp T/A 255/60
Looks wise you might be able to get by using a 17" wheel, but anything more than that you run the risk of making your car look like it belongs in a Hot Wheels box. The cars were never designed for those huge wheels, plus they look like they are on steroids and throw the cars symmetry out of balance.
Don

Strongly consider

Rear 285/40x17 on 17x10x5.5
Front 245/45x17 on 17x8x4.5

no rubbing issues at all and they fill up the wheel well nicely

actually 255/45x17 should fit in the front as well.

17's on a 68... sorta tuff to pull off. might have to lower it if you go that route.

Here's mine with the torque thrust ... 16"

.

Yes, 255s will fit on the front for width. A 255/45R17 is a 26 inch tall tire and this could get a little tight.

RFCOLEMAN: a 245/45R17 on a 17x8 with 4.625 bs will fit in the rear, but I agree with marauder. Bigger rears will look better.

That is where mine rubbed with the 17x7 with 3.75 bs front.
Measure the back spacing on your wheels to make sure they are the same and check that you have the same front rotors left to right.

Mine with 245/45R17 front and rear on 17x7 and 17x8
http://i232.photobucket.com/albums/e...CIMG1870_2.jpg


I realize my car is not the norm here: I changed to 255/35R18 on 18x9 on the front and 305/35R18 on 18x11 on the rears. Toyo R888 rubber.

Old and new rears:
http://i232.photobucket.com/albums/e...r/CIMG2027.jpg

With new wheels and tires:
http://i232.photobucket.com/albums/e...O/CIMG3429.jpg

Mine could use a little lowering and in hindsight would of put 18x10x5.5s on the rear....

Freak'n sweet ride dude !!!! Post more picture of that beast !


.

ok - Here's those 16" ,,, :-)


.

what size back spacing would I need to fit 18"x11" rims on the rear of a 68 GTO or 10.5" and 9"x18" on the front.

Chris

I ordered some 18x8 5.25BS fronts and 18x10 6.00BS rears from Driverzinc with 245/40-18 and 285/40-18 respectively. Still waiting on them so I can't give real time advice. however they were spec'd out by them, and considering the awesome reputation from the PT forums and that they'd just built a 67 lemans I trust them. Will update when I get the wheels in. should be another 3-4 weeks.

[QUOTE]I realize my car is not the norm here: I changed to 255/35R18 on 18x9 on the front and 305/35R18 on 18x11 on the rears. Toyo R888 rubber.
/QUOTE] Now thats a set of tires wow!!!

I need to get some rubber!!!!

I'm generally a traditionalist when it comes to wheels and tires..no bigger than 15s.. but man...that car looks good with those 16s.
Ok, so 16s are ok with me now. lol

Great post! I was looking to go with16" or 17" but was thinking like Greg Reid.

Now back to original post:

The driver side front bottom edge of the fender rubbed, cut the edge of the tire. For some reason, I can measure 3/8 " difference from driver side to passenger side front to back.
Thanks,
Bob C.

Mine did the same thing but it was do to rusted core support under the rubber washer mount on the drivers side was letting the drivers side fender slip down causing the tire to rub. It got so bad that after leaving a car show I could only make right hand turns all the way home or my tire would rub.

So you may want to have your front core support checked out and repaired before you go any further. That is a common problem with these models.