Wheel backspacing on a M II

40cpe · November 10, 2008, 09:51:32 PM

I have a Heidts cross member with their stamped lower control arms on my '40 Ford. I read some where that a line drawn from the upper ball joint through the lower ball joint should intersect the road at the center of the tire.

Does any one know what backspacing this would require using a 15 x 6" wheel? I'm asking because I get a "twitch" at the steering wheel when I hit a bump. The car has been professionally aligned with 4 1/2 degree of caster and otherwise drives good. Any other suggestions about what would cause this? Thanks for your advise.
Gene

enjenjo · November 10, 2008, 11:01:29 PM

3" to 4" backspacing will be about right. How much caster did the tech put in it?

40cpe · November 10, 2008, 11:26:57 PM

Quote from: "enjenjo"3" to 4" backspacing will be about right. How much caster did the tech put in it?

4 1/2 degrees. That's all the slot I had. I have 3 1/2 " back spaced wheels on it now. I'm going to buy new tires and thought this would be a good time to rectify any errors with new wheels. It looks like 4 1/8" is the most I can get. Just trying to eyeball that intersection point, it doesn't look like I have enough back space now. And more backspacing will give a little more fender clearance.

enjenjo · November 10, 2008, 11:37:14 PM

Elongate the slots, and go to 6 degrees.

40cpe · November 11, 2008, 08:36:05 PM

Quote from: "enjenjo"Elongate the slots, and go to 6 degrees.

So you don't think more back spacing in the wheels will help?

Can you give me an idea how much more slot it will take to gain the other
1 1/2 degrees?

enjenjo · November 11, 2008, 10:46:14 PM

Quote from: "40cpe"
Quote from: "enjenjo"Elongate the slots, and go to 6 degrees.

So you don't think more back spacing in the wheels will help?

Can you give me an idea how much more slot it will take to gain the other
1 1/2 degrees?

No I don't.

It's never worked for me in the past, but more caster did.

1/4" more slot should be enough. In the rear, slot it in, in the front, slot it out.

40cpe · November 11, 2008, 11:24:11 PM

Quote from: "enjenjo"
Quote from: "40cpe"
Quote from: "enjenjo"Elongate the slots, and go to 6 degrees.

So you don't think more back spacing in the wheels will help?

Can you give me an idea how much more slot it will take to gain the other
1 1/2 degrees?

No I don't. It's never worked for me in the past, but more caster did.

1/4" more slot should be enough. In the rear, slot it in, in the front, slot it out.

I'll do it. Thanks for your experience and advice