[hobbygto65]

I've gathered by most of the post that a 5" back space is needed for max tire size for rear. So what would it be for the fronts?

[hobbygto65]

I've gathered by most of the post that a 5" back space is needed for max tire size for rear. So what would it be for the fronts?

[SimplexFish]

4.5

[b-man]

Without knowing the rim width who could say.

The diameter of the wheel matters too.

[hobbygto65]

I plan on using either 15x7's or 16x7's, I'm not sure about tire size.

[Droptop64]

See my reply in this post.
http://forums.performanceyears.com/g...1/m/9641087021
I went with 16x8's all around, and 4.5 BS. Plenty of room on the front with regards to tierod ends, control arms, ball joints, sway bar ends. The 4.5 BS also placed the rear wheel centered in the well. I'm only running a 235/60 in the rear, but it fills the fender nicely without being tight. Fronts are 215/55.

[b-man]

I run a set of 17X8s on my '64 Tempest, all 4 wheels have 4-1/2" of backspace (zero offset). If I could do it again I would go for more backspacing, 4-3/4" or even 5" would center the wheels better in the wells and allow a wider tire. I run 235/45-17s all around.

With a 15X7 or 16X7 up front 4-1/2" of backspacing would be pretty much ideal.

[elefantrider]

nice ride b-man,
Do you think one could run a 17x9 inch wheel on the rear with 5 inch backspacing?

Approximately, how many inches of clearance do you have on the outside/inside of your rear wheels?

What about on the front with full lock, between the tire and frame? Do you have the stops machined on your quick ratio box?
Thank you in advance for your comments..they're much appreciated here.

[b-man]

To run a 9" wide wheel on the rear of my car all of the extra width would have to be run on the inside, I had my 8" wheels made to sit towards the outside. This makes the backspacing for a 9" wheel 5-1/2" at a minimum, possibly even a 5-3/4" backspacing would be required.

A 275/40-17 tire would be a close fit. Tight urethane (I use them) or del-alum rear bushings are be a must to keep the rear from moving from side to side during cornering.

Up front my steering box has standard stops, the 12.7 quick box came from Lee Power Steering in Sun Valley CA. One must be careful to keep clearance between the inner rim/tire and the outer tie rod ends/steering arms when deciding on front backspacing. Also the tire comes close to rubbing on the front sway bar on full-lock, not really a big concern here though.

The type of front spindle used (stock A-body or taller B-body like I use with Hotchkis upper A-arms) makes a difference too. Once you decide on what you're using suspension-wise along with what rim diameter then you can figure out your plan for the front rims.

Right now my '64 is tucked in the garage with no engine so really I can't give you any useful front clearance measurements.

[elefantrider]

I forgot you had manual steering on this car. What is the standard manual box ratio, something like 20.1? A 12.7 manual with big tires must be a bear to turn when parking.

Lee Power Steering is an interesting company. I used them for my PS box on my '65. I didn't know they did manual boxes too. If i remember correctly, they do mostly power steering boxes for stock cars (NASCAR type).

With 5-1/2 or 5-3/4" backspace, do you think the 17 x 9's would fit in the front as well?

I'll be using a F-body or G-body tall spindle... probably the lighter F-body one (anyone know the weight difference between the two, spindle only) since i understand Bear can put up to 13" PBR big brakes on the F-body spindle.

[b-man]

I forgot you had manual steering on this car. What is the standard manual box ratio, something like 20.1?

Nope, mine has a power box, you can see the pump in this pic. Standard manual ratio 24:1, quick-manual 20:1, power was 17.5:1.



With 5-1/2 or 5-3/4" backspace, do you think the 17 x 9's would fit in the front as well?

Highly doubt it. Again, interference between the outer tie rod end and upper ball joint is a problem as well as the tire hitting the sway bar.

Put 2 bare 15X7 Rally IIs on the front of the car, they have 4-1/2" of backspace. Measure outward by 1" (tells you where a 17" rim will be) and inward by 1" to 1-1/4" (tells you where 5-1/2" to 5-3/4" of backspace will be).

Turn the wheels to full lock (wood blocks under the rims, full weight on the suspension) and check your clearances both inside and out. You'll probably find out that a 9" wheel is too big, but maybe not.

If a 9" wide wheel does fit you'll have to run a 255/40-17 on at most it so the tire sidewall is no wider than the rim itself. I'm betting an 8-1/2" wide wheel with 5" to 5-1/4" of backspace will be the max and very tight with a 245/45 or 245/40 tire.

[b-man]

Keep in mind that the same measurements that work on my car might not exactly work on yours.

The bodies on these cars can commonly sit off to one side on the frame, making clearances from one side to the other a bit different. In this case you must go with the side with the tighter clearance.

You can also loosen all of the body/core support bolts (remove the front and rear bumpers) and carefully jack up the body using two floor jacks. Put one jack under each rocker with a full-length wood 4X4 under the rocker for load distribution.

Get the weight of the body off the frame using the two jacks (don't jack it too high) and carefull pry the body over to center it. Pry between the inner rocker and the frame using a 1/2" thick by 1-1/2 to 2" wide X 3 ft long piece of bar stock or whatever works for you. Don't try this on a car with rusty rockers, not a problem here in So Cal.

I did this on my '64 GTO while I was replacing the rubber body mounts with urethane. The front fender was over by more than 1" before I fixed it.