Projects leaf spring perch measurement

I am considering buying a spring from Speedway # 910-43102, its 39" from eye to eye. when I add the 11/2" shackles x 2 = 42". How much more do you add to stretch the spring to get the measurement for the spring hangers to be welded to the axle tub, so I can get the right angle on the shackle. I hope that this makes scents.

Mike

 

I just bought it. Instructions say add at least 1-1/2" to each side. My front spring is spring plus shackles plus 1/2" so I'll add another 1/4" per side for rear. The spring is stiff. I set it up on some cardboard so end would slide and jumped on it and end moved less than an inch.

 

I thought I saw a guide in the Speedway catalog that tells you how to calculate it.

Yep, found it. Page 27 in my catalog which is #243 (2006)

Pete

 

Striper
I have catalog # 259 ( 2008 )
I was woundering if you could post the calculate.
Thanks

 

At work at the moment. Should be able to post something tomorrow.

 

Thank You

 

The tech tip in the catalog is for measuring for a front spring if all you have is a bare axle.

It says to measure the distance from perch bolt hole to perch bolt hole (centre to centre), and subtract 4 1/2". That 4 1/2" obviously takes into account the shackle length and the offset of the perches.

It also says that if you assemble the spring so that the shackles are horizontal when not under load that they will end up 40 to 45 degrees when loaded (perfect). This part is probably the most useful to you as I think you are talking about a rear set up.

So from that I say your spring at 39" + (1 1/2" x 2) = 42" between centres for your axle mounts.

You didn't say what this spring is going in but presumably it's a hot rod which is fairly light in the rear. I wouldn't add much if any to that 42" measurement because the spring probably isn't going to compress a great deal.

Pete