Ive finally gotten my parts together and plan on putting together my rear suspension in the next few weeks and i have a bunch of questions. Ive done some searching on here for the answers but only found some and may have more questions than i started with. So here goes. I am using a model A frame, stock Model A rear spring, hairpins, Chrysler 8 3/4 rear end, and i am mounting the rear end behind the rear crossmember to add a little to the wheelbase. Most of my questions pertain to where to locate the shackle mounts on the rear end. I have gathered that the shackles should be at a 45 degree angle. Should the the spring be spread before deciding where to weld the brackets for the shackles on the rear and if so how much? I may take out some leaves or switch to another spring if the ride is higher than i want after getting it all together. Will this necessitate moving the shackle mounts? And the shackle mount brackets on the rear, can they be either side up. One way seems to locate the shackles slightly lower but i dont know if this is a no no. And the hairpins, should they be at a 90 degree angle to the axle tube? So many questions i know but i want to do this right. Pics of a proper install would be great, i havent found good pics of the setup i am trying to do yet. Thanks, in advance.
OK, So I can tell this is all new to ya. First, if your going to use a model A stock spring you should get the stock measurements between stock shackle mounts and stay with that number. I can get that for you a little latter if needed. Also you mention a little longer wheel base. Have you considered what that will do to the way the tire fits the fender opening? Adding or removing rear leafs has several effects, not all have to do with ride height. The Wizzard
Yes i do know that taking leaves out affects more than just ride height. I will have to experiment with height and ride later And where the body will sit on the frame isnt set in stone. I am waiting to decide where to mount the body until i see where the tire sits and position it from there for asthetics. Suspension geometry is new to me when starting from scratch. So from your comments i ***ume the eye to eye measurement is reached not while completely unloaded but with the spring under tension?
On this ch***is the center to center on fixed shackle mount is 48". Notice there is only a main leaf to locate the rear end. There is a pair of spacers of 2.5" between axle tube and bottom of frame rail. As I add leafs and weight the shackle will become more vertical. You only mentioned using a Model A frame. What will it have for a body? The Wizzard
Stock Model A rear spring mount dimensions is 49.5" center eye to center eye. Using a stock-style shackle this will give you the stock tension in mounting for the Ford suspension of 28-31. The spring shackles will be straight out from the brackets until weight is placed on the frame. Then they will drop to between 30 and 45 degrees. This tensioned mounting of springs Ford used from 1909-41 is why no Panhard rod is necessary.
49.5 with no weight applied correct? So the correct way to figure out where to mount the brackets on the rear end ***uming i have a stock spring is to weld them 49.5 apart (centered of course) and then spread the spring?
This would be correct. Also being your going open drive line, before you weld on the brackets be sure to set Pinyon angle so you don't end up putting a twist in the shackles. I might add here that pasadenahotrod gave you the correct number for Model-A. The 48" I gave you was off my 36 housing with a Model A mail type main leaf I had made shorter. I had forgotten I had that done. The Wizzard
Ok so i unbolted the spring from the crossmember, and measured it and its only 40.5 inches from eye center to eye center. Not sure what to do since its not a stock Model A rear spring i guess. Its got 12 leaves. How do i know what the spacing should be?
First off.... you're not going to need 12 leaves, but how many you do need will be dependent on several factors. I have 5 leaves in mine. The A main leaf is fitted under tension, so around 40 inches is probably right. These springs pack a serious wallop, so use a couple of 8" G clamps and a length of all thread rod to dismantle and ***emble.... and be very deliberate and careful. The main leaf on its own can be stretched out with a G clamp to fit the shackles mounted in 49 1/2" centres. The hairpins should be mounted so their forward ends mount close in to the driveshaft, and close to the same pivot point as the front universal joint. Dont mount them at 90 degrees to the axle tubes, this is sometimes done, but causes binding and possible breakage down the track.
Thanks i think i get the picture a bit more now. Surprised about not mounting the hairpins at 90 degrees, seems like ive seen most of them done that way. However thinking about how the rear end moves more of in a twisting motion than a straight up and down manner, that makes sense. So i will need to mount them to a crossmember inside the frame rails instead of to brackets on the bottoms of the rails? And the brackets i got to mount the hairpins to the axle, the hole is round, guess id have to oval them out to use them.
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