I've been plugging away on my A coupe project, using a frame from someone who has a very bad reputation here, that I discovered after I bought it. Anyway, I've been very pretty happy with everything so far and am making good progress and about to address the rear suspension situation, but I can't for the life of me get my head around the optimal rear spring setup. I have an early 60's Chevy rear end that came out of an old dirt track car, with the A spring mounts welded to it (like a banjo) and set up for ladder bars like I am running. It's also the perfect width to run and can handle the SBC that it's getting. I believe this frame is set up to handle a later-style Ford rear end, with the spring behind the axle, and bolted directly to the mounting plate shown in the photo (leading to the rear end being forward of the rear crossmember). I have a few questions: what would the implications of me running the rear end in line with the spring mounting plate (with it directly under the crossmember), other than a couple inches increase in wheelbase? Alternatively, is there some sort of bracket available that bolts to the crossmember, and then extends a few inches for the spring to bolt to? Did the late 30s-40s Fords have something like this? I don't want to have to weld new spring perches to the axle, and don't have the equipment to make that bracket out of the necessary thickness of steel. Much of my confusion stems from the fact that I only know anything about Model As, and this is probably a stupid question. Hopefully the attached photo is helpful since my words probably are not... Edit: here's another photo I found on here of this same frame, with the rear end mounted ahead of the crossmember and the spring bolted right to the plate. I think this is the way it's meant to be done.
Have you established where the center of the wheel needs to be to align it in the body wheel well where you want it? If not, you need to do that first and the rest falls into place. And yes, it looks to me from the photo that the frame was going to use some type of spring behind the axle, perhaps even a '40 front spring which is a popular setup with the style of flat crossmember. So to answer your question, you'll most likely be redoing something.
No, but I understand what you mean - I don't have a body for it yet so I don't know exactly where the centerline of the wheel would fall. Here's another picture I found of what the setup looks like, and it does look like you're right; I guess I'm going to need to weld the correct perches onto that axle. Follow-up question... do I need to be concerned about things like castor for the rear axle when I do that?
That looks like a '40 Ford front spring in the photo. Looks like you'll be running an open drive line, so I like to be able adjust the ladder bars, or links, to get the correct drive line angles. So use an adjustable spring perch so the rear end can pivot without binding the spring.
Are the pictures you are showing random net pics? Looks like a 35-40 rear spring to me , looks like the chassis is designed for a spring behind, if you did it spring on top you would add about 6 “ to wheelbase! “Caster” on rear axle as you say, .... yes on a street car you want the pinion inclination to match the engine and trans inclination, disputes what street rod folks tell you , no you don’t need the swingy adjustable perch thingy
The photo from #3 looks like it was taken from the Hot Rod article “Fabricating A Pavement Hugging Early Ford Chassis”. They used a ‘40 open-drive banjo with 35/36 bones, a ‘40 front spring and the So-Cal crossmember. If you google the article, it explains their setup pretty well. Sent from my iPhone using The H.A.M.B. mobile app
The spring behind the rear axle allows the car to sit lower without losing as much floor space in the trunk/rumble seat/back seat area (depending on which bidy you plan on using). It may be worth consideration to keep the spring behind axle.
All Model A's have the same wheel base and it makes a difference if your going to run fenders and a hood. If you have plans for a non fendered car, you can stretch the frame between the cowl and radiator for a little more clearance. Hoods can be lengthened to compensate for the increase in length. When running fenders and a hood, it's easiest to run a stock wheel base. Caster is not your concern with a rear end, pinion angle is. It's interesting that you refer to your coupe project and don't have a body yet. Pictures of your project would help a lot more than generic pictures from the Internet. There are several Model A threads that show how to build a Model A frame here on the HAMB and it would benefit you to read them several times until you can figure out what your doing. Like wise, there are several kits available that sell all the components to install a rear end with instructions. http://www.wescottsauto.com/WebCatalog/Tech/FrameDiagram1928-31.pdf
You have 2 choices really. The first would be to weld new spring perched to your axle for the spring behind arrangement that the frame is designed for. The spring behind set up is better for floor clearance with a lowered ride height. The second option is to shorten the frame about 7-1/2”. There is not a bolt on solution for your situation. The rotational force the offset spring would have on the crossmember would likely exceed its engineered strength.
I have a Rileys frame as well. I bought my spring from Posie's pretty sure it was a 35-40's spring. I used Pete and Jakes 35-40 for these. https://www.peteandjakes.com/parts/1935-40-rear-spring-mounting-kit-3-inch-housing/ Make sure you measure your rear tubes for the right p/n. If you ran your axle right under the spring and lined up your wheel wells there I think you would be way to "rearward". Is that a word lol. Also, I believe your frame is already stretched 4 inches to allow for firewall clearance.
That frame is set up for a Model A and is stretched. I'm just saying when he does have a body he wants to line up the wheel wells on the axle behind the spring. If the axle was under the spring it wouldn't work on that frame.
Shows the rear perch welded to axle a little clearer. The shock brackets look like something for coilovers. If your not running fenders, it doesn't make any difference if you have to move the body backwards or forward to align the axle with the body.
Thanks to everyone who contributed- I picked up some spring perches to weld for the spring-behind setup, and ordered a Posies spring for it. Hope to get everything welded up with the front wishbone mounts and have the project become a roller next week. Here’s photos of the actual frame and rear with the OG ladder bars that are going to be coming off. Sent from my iPhone using H.A.M.B.
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