Caster difference on a dropped axle?

Question for you alignment gurus...

On my T roadster build (see signature) my '41 Ford axle (dropped and chromed YEARS ago) caster measures two degrees different. When the chassis and suspension were set up over the past few months my buddy Bob, he set the driver's side axle caster at 7 degrees. After we were done we just "happened" to measure the passenger side. Damn. NINE DEGREES!

I've talked to three different alignment shops here in town that do big trucks. All three told me they could straighten it but didn't recommend it, as they intentionally put 1-2 degrees caster in the axle to corrrect for the crown in the road. That, I get.

What I don't get is that if straight axles needed that much correction, why don't the axle manufactures MAKE them that way? I'm pretty sure they're all zero degrees out of the factory and hot rods I've had and driven didn't seem to have much issue with tracking properly at highway speeds.

So my alignment guru buddies, what do you recommend? Straighten it, or complete the car and see how it drives? How much bearing does the different caster have on such a light car?

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I've always compensated for the crown in the road by having about 1/2 degree more + camber in the driver's side wheel than the passenger side to start with and set the caster on both wheels to match. I do know that some guys do the same thing by offsetting the caster.

Personally I'd put it together and drive it first and then decide. Also how are you checking caster? with a caster gauge or just by setting an angle finder up against the axle? The angle finder thing should be close but won't be nearly as exact as checking it with a gauge after the car is together and drivable.

 

Yes, we're using a digital angle finder.

I'm kind of thinking the same, just finish the car and drive it. Besides, two of the three alignment guys need the axle on the car to bend it. Being that the chassis is tack welded currently that's not really feasible.

Thanks for your input.

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Original Ford axles are exactly flat. They are not different side-for-side. Somewhere in time your axle got bent, but who knows why? I'd also suggest just driving it and seeing what it does. Nobody can agree on what the caster should be on hot rods anyway, so maybe those readings will be perfect for your car.

 

DTPOOI Eric

 

That's what I thought. Thanks for the continued input Alchemy! I think I know what/where/how the bend came about. On the axle someone welded a small piece of plate to attach a panhard bar to. You can see the slight bend in it at that point.

ABSOLUTELY MAN!!! And you know I will too!


Just for argument's sake, here's a pic I posted on the build thread.


I misquoted myself above by saying the caster was 7 and 9 degrees. It's actually 5 and 7. For this discussion it's irrelevant, but thought I'd post the correct info.

Again guys, thank for the info, input and advice!

 

Are you sure there is a difference in the axle itself?
Could it not be the bones being not quite identical and making the change?

 

@ 5 and 7 I wouldn't B worried about it Eric.
That puppy ain't gonna weigh enuf to feel the differance

 

You could always make a jig and tweek it back later to match if you drove it and it bothered you.

 

Yep, definitely the axle, but great thought Don. Always appreciate your wisdom!

That's what we'll do brother. IF there's an alignment issue we'll know where to start!

You flatter me and certainly over estimate my abilities! Bob could build such a jig, but I know my limitations.

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