If I run 15x8" backspace 4.5" wheels, can I run 235/60 on the front and 295/50 on the rear? Or should I go with 4" backspacing?

 

Play with these numbers and find one that fits. To big of front won't be able to turn with.
www.sizemytires.com/calculators/compare

 

It's just my personal opinion, but l would NOT put 295/50 15s on a car.

I have 15x8s (4.5" of backspacing) all around. 275/60 in back and 255/60 in front. When l had 235s in front l had to use a small spacer (3/16") to keep the tires off the ball joints. The same spacers keep the 255s honest too.

This is on a '66, so I'm not 100% sure how those numbers translate to a '68. The only real way to know is to roll around under the car and take the critical measurements.

 

I think that's what I'm gonna have to do tonight. I'm gonna have to take my measurements and just hope I don't screw them up somehow.

 

I like the 275/60 with a 4 1/2" back spacing. 235/70 in the front for just a little more ground clearance.

 

255/60 should fit in the front with the wheel dimensions mentioned and probably a .25” spacer.
I have 235/70r15 on mine and had 245/50r18 and they fit fine with a .25” wheel spacer. So 4.25” backspacing with an 8” wide wheel.

I think the smaller diameter of a 60 series tire would allow for the 255 width and maybe not need the spacer.

keep in mind with a spacer and aluminum wheel you will need longer studs.

no chance 295s will fit. 275 would fit on rear of mine but I hate staggered tire set ups and I think it would have required none zero offsets. Ricky racer confirmed above 275 will work but I don’t remember if he has a 66 or a 65.

 

Are you still running the .25" spacer with yout 235s on the front? Would 7" wide wheels be better on the front with the 235/70?

 

Another stupid question, when I go from drums to disc brakes, that will alter my backspacing won't it? I assume the new disc setups come with new studs as well??

 

New rotors come with short factory type studs. You didn't (at least I didn't see it) say what rims you're going to use. I've used steel, American Torque Thrust D and Weld drag lites. Draglites require a 3" stud since the mounting is very thick. Rotors shouldn't change the back spacing issue but make sure the center hole in the rim fits them and that the caliber isn't an issue. Factory and aftermarket ain't the same.

 

I don't know the details (drum brake guy here) but certain wheels (14", 15") might not clear certain calipers (esp. the earlier, larger ones). Something to research first.

Pat

 

I had planned to go with an 11" disc setup all around that is designed for 14-15" wheels.

I know it's not everyone's cup of tea but I would like to go with something like the steel Unique brand model 42 or the Vision brand D window model. I wanted to either run 15x8s all around or 15x7 in the front and 15x8s in the rear. I'd rather not play with spacers if I don't have to but we do what we must.

I am gonna do the front brake conversion this weekend so I can at least get my backspacing for the fronts. I'll do the rear with the next check.