Help Please

I don't know what thread to put this in, but I need some help.

I need to find the correct backset for new rims I wanting to buy. This is for open wheel 1931 Ford Model A car. There is no fenders, so were talking side of the car to side of the car on the Ford Model A.

The Body of the car is 56.5 inches wide.
My Ford 9 inch rear end is 65.25 inches or sixty five and a quarter.
8.75 divided by 2 equals 4.375 inches so
4.375 inches of the Ford 9 inch sticking out both sides of the body

The tire I'm running on the rear is 285/70/R15

specks for that tire is...

30.75 Tall
8.6 inch Tread
11.5 Section
R15 inch rim

I don't know crap about figuring this. I wouldn't mind it being an inch and half or 1.5 inches off the body or more if its needed.

Can someone please tell me exactly what my rim's backset is to ask for when I buy my rims, I clueless.

Thanks for any help,
Micah

What width of rim are you wanting? I'm assuming you'll want to run a 10" (I'm running the same size of tire on a 10" rim). You can do it on 8" but they look awfully bulgey. Although that is just me wondering.

Are you factoring in the curve of the body in your body width measurement? Is your rear end measurement from mounting surface to mounting surface?

Here's an equation I made for you:

C=(0.5*D)-(0.5*B)-A

A=Distance from body to inside of wheel (not accounting for tire sidewall bulge outside the edge of the wheel)
B=Body width
C=Wheel backspace
D=Rear end width mounting surface to mounting surface

And you gave us:
A=1.5
B=56.5
D=65.25

Which makes your backspace 2-7/8". That will make your wheel a custom build in most cases, I believe. So you might want to try and find a wheel with 3-3/4" backspace and use a spacer, to make wheel choices easier.

What kind of wheels were you looking at? Aluminum mags, steel?

Mine are steel and were all custom backspacing from Wheel Vintiques because their standard backspace is 4" for an 8" wheel and 5" for a 10" wheel. My 10's are 3-3/4" Backspace.

You might want to add a little more for your tire bulge, half an inch per side, which would reduce your backspace by a half inch. I think you'll be needing spacers.

05snopro440

Yes, that's taking in the curve of the body. I rolled down rear windows and measured directly above the widest part of the body. Yes, that's from mounting surface to mounting surface on the rear end. It will defiantly be steel rims. I haven't chosen a rim width, its all still up in the air. In Summit mag I'm looking at Wheel Vintiques Gennie in Gray Primer to paint my color scheme. From what you guys have said I will start with 10 inch width. I'm hoping to have 500+ horse power and I've heard not to run spacers, but I could be wrong.

And Thanks for all the Help!
Micah

Have a look at the Wheel Vintiques website, and look at page 65 of the catalog. To get the offset you want you can't buy them from summit, you'll need to either order from WV directly or from a dealer that custom orders from them. The reason being that your wheels will need to be custom built to the backspace you need. I know because I went through it.

Page 65 shows the minimum and maximum backspace based on the wheel series and size Those gennies in 10" wide have a minimum backspace of 2-3/8" when they're reversed. You'll probably need to be around that backspace anyways, once you factor in the balloon of the sidewall and body roll.

I don't think the spacers would be a problem, but custom built wheels are my preference. To be clear I'm talking about the billet spacers that torque to your studs and then have their own set of studs.

I bought my wheels bare and had them powder-coated a custom colour.

Figure out the look you want also. I have never liked rims that were wider than the tire tread. I am running M/T 12x15s on 10" wide rims. To me that looks perfect. I have had 10x15 rubber on 12" wide rims, and didn't like the look at all.

Obviously, I am in a minority here, because most used aluminum wheels (including the ones on my newish car) have curb rash.

i'm with skip on a narrower rim. i prefer a 8" rim on that tire. look forward to seeing it no matter which way you do it. wish i could help you on this but it is a hands on thing for me.

Here's a calculator that might help:

http://www.rimsntires.com/specspro.jsp

That's a great calculator!

That is the nicest calculator I've seen. I looked at quite a few of them on the net but most were based on adding the original wheel and tire size on the original car.

I cut to the chase, I called the Vintique and got to talk to the guy that will be making the actual wheels. He laughed and said he could figure it in his sleep.

Looks good on the calculator too!!! Now waiting the 4 to 6 weeks for the custom wheels.

Micah