When using a '40 ford front spring in the rear, (40.5in eye to eye) what is the mounting perch width used? I know it needs to be spread some. Oh, and I searched for over an hour with no result. Thanks in advance. Gary
arent you supposed to put the shackles on and set them in a certain position and measure eye to eye, cant think of it right now. and should you , well I, remove a leaf or two to use a front spring in the rear? im wondering my self cuz i was goin to use my forty ford spring in the rear of my car.
There are a couple of ways of measuring this, so you might get some different opinions, but the way I do it is to measure eye to eye, and add 3". 3" Is the length of both shackles parallel to the spring. The shackles them selves are usually 11/2" eye to eye, times two. So 40.5 + 3" = 43.5". This installs the shackles so at rest they are 90 degrees to the ground, when you put weight on the chassis, the spring will get a bit longer and the shackles will end up at a 45 degree angle to the ground. Perfect. By the way, if you have a Speedway catalog, they explain this in the front suspension section.
Most rear spring run 5-7 leafs. The front spring will be just a touch stiffer because it is a bit shorter, but that is still where I would start.
One last thing - Don't forget that the early Ford front spring that you are both using is only 2" wide versus 21/4" for a regular rear spring. If your using aftermarket rear spring hangers, now is a good time to machine the shackle bosses down to 2", before you weld them on.
Chota5, I just measured my rear spring for you. My perch eyes are 42" apart. This puts my shackles at a 45 deg. angle. If you aren't running a panhard bar, then you may want to space the hangers out another 1/2" (1/4" per side) to get a little shallower angle on the shackles. Without a panhard bar 20-30 degrees will work better. 42.5" is stock perch width on the front of a '40 Ford ('37-41 should all be the same.) You would think that would be the case, but running a front spring on the rear actually has the opposite effect. The front spring is going to be "softer." When I first got my coupe together, I was using a stock '39 front spring on the rear. I felt that it was too soft, it would squat a good bit under hard acceleration, and would occasionally bottom out. So when I put the car back together this last time, I started with a NOS '40 front spring and added leafs from the old spring to stiffen it up some. I now am running 16 leafs, and it seems to work well this way.
Thanks bass! I didn't have a stock '37-'41 type wishbone around here to measure. '35-'36 yes, later no. I'm amazed that you have as many leaves in your spring as you do, Have you driven it yet with that many in the pack? the last couple of cars I have set up using this spring have been relatively light modifieds and buckets, so I should have said that. By the way, love your coupe! That trip through downtown Dallas on one of the mad fabricators videos is one of my favorite car videos of all time!
Can anyone provide pics of their set up? Bass I don't know how yours is so low. Almost flat like. Mine has a much bigger arch.
Stretching a model A rear spring is kind of hit and miss. I have had allot of them that don't require spreading to put in place, and those that the spreader wouldn't move enough. I believe it has to do with how many millions of miles the spring has on it under a car. I wouldn't be surprised if Bass de arched his a bit to get the flatter profile. I don't have any current photos of stuff I have done, just never thought to photograph that I guess. We now know the measurement for a stocker, and I know my technique works well too. Time to pick a path and just do it...
When the springs are installed ina stock 40' they are rather flat. I am puttting a 40' rear spring in my coupe. Its alot smoother than an A spring and it allows me to have more room in the trunk for the rumble seat. btw just in case sombody wanted to know stock 40' rear spring perch eye to eye is 48"
My spring had a lot more arch when it was off of the car. I had to spread it to get the shackles on it with a spring spreader. After it has some weight on it, it settles a bit too, so keep that in mind. Are you sure you have a '40 Ford passenger car spring? I know that '40 Merc has more arch, and pickup springs may have more arch as well.
Spring is 40.5" relaxed. I set the outside shackle hole c/l @ 45". this is with no weight and the shackles should fall to 45* with weight. Use a spring spreader.
That's interesting that you are a couple of inches over what has been said on other hamb threads besides this one. When I asked, and got, the 42.5 spec, I wanted to test it first, so i just tacked the 35/36 bone brackets in place at 42.5 I put a 2x4 (wooden) across the back of the frame, then I had some 5/8 threaded rod that went though the ends of the wood. Those were hanging a few inches above the shackles. Then I bent up two 1/8" thick band steel into an J bend that slide into each shackle to weld to the threaded rod. The J shape hooks under just the spring eyes and you can pull the frame down to your ride height to check the shackle angles. Mine "looks" ok at 42.5 so far, but the car is not fully weighted, nor have I set up the leaf stack for a good ride. I do have an old professional spreader from a shop my Dad ran in the 50s, but I think the Olds rear was in the way...not quite sure, but I think I tried the spreader first.
Roundvalley, thanks for the pics, that's what my setup looks like as well. So wouldn't de-arching require a wider perch width? Thanks everyone for the help.
The Jalopy Journal
