Positioning a straight axle

Hey all, I'm building a 53 ford mainline gasser and have now gotten to the point of putting the straight axle in. The axle is out of a 49-52 era f-1 truck. I'm wondering if there is a "rule of thumb" or any advice as to figuring positioning of front shackle when mounting the axle. I'm thinking about the weight of motor, trans, fenders, hood, etc, and how much travel i can expect once that weight is on the springs. Any advice or pointers would be hugely appreciated.
-Splatt

 

I would first referance your frame with the stock centerline of the original parts. Than decide if your going with a front or rear fixed mount. Usually if the steering is behind the axle than fixed rear mount and vice versa for front steering.
I figured it moved mine 1/2 to 3/4" . The closest way is to remove all the springs except for the main leaf and compress that to determine how much it will move. I used that same axle under my 55 and used the Speedway gasser springs and mount kit. The factory springs for that axle were way too long to set it up anywhere close to the stock centerline for my frame. Moving it too forward would make it an altered, not a gasser.

 

I gotcha, the front shackles would be going past the front of the frame rails. Im grabbing a fender today to see where my wheel position should be. I have a general idea, but want to double check it. Im planning on the rear shackle being fixed.
I guess my biggest question is if my travel is only going to be 1/2 to 3/4, i can attach the rears, then attach my front mounting perch slightly past the length of the spring? if that makes any sense that is, haha

 

If your going to do it that way, mount the axle rearward some of the centerline so when the spring compresses it will move forward towards the original centerline.

 

We used that same axle on my friend's '59 Rambler gasser. Pretty stout springs, and they wont settle much unless you're going with a really heavy engine. We simply put the shackles straight up pependicular to the frame, then tack welded the base. After that we got 3 average guys to get up on the car and get an idea of how much it would settle and what angle the shackles would be. It didn't change enough to move, so we welded them permanently in place after the test.
Those stock springs don't have enough arc to worry about centerline of the axle/wheelbase. Just center it where you want, as it wont move enough to even notice.

 

awesome, thanks for your help guys, i'll let you know how it goes. im putting a mild 302 and toploader in it so it's not a huge amount of weight. i will try the positioning idea with guys on the front, i have a couple larger than average friends...

 

just my opinion but we always move the axle forward at leas 1 inch from stock wheelbase . they start looking funn y when you go up and dont move it out a litttle bit. every gasser we have done has been done this way. and we have done 30 or so...

 

dragrcr, forward an inch with the solid mounts in the back?

 

If the spring won't compress much, that would work like dragrcr50 said.

Rearching the springs help shorten them up quite a bit also if you need them shorter. I rearched mine 4" and of course it shortened them up about the same amout, but ended up going with new springs instead. The speedway springs are 1 3/4" wide just like the factory springs.

 

cool, thanks everyone! i'll let you know how it goes and post pics.