Rear suspension on a '37 Ford

[Topsterguy]

On this 37 flatback project I just bought the chassis is pretty much done, and done well, mustang IFS front and 9" rear.  The person that put the 9" in was apparently planning on some sort of coil spring suspension , because there's a triandulated 4 link setup installed with just "blocks" between the axle and the frame for "setup purposes".  Personally I don't like coilovers on fat fendered cars, I think they're too heavy. Looking at the setup I can't see why a guy couldn't use parallel leaves with this. The axle won't roll, just go up and down & keep the pinion angle, and the 4 link would just act as traction bars and sway bar, right?  Waddythink boys!!??

[phat46]

With the four bar setup the rear will move in an arc, probably a small arc but it could still cause binding with leafs. Why not use coil springs with separate shocks? Much heavier cars have used coils than a '37 Ford, think late 50's G.M. Cars.

[Topsterguy]

I thought with the 4 bar having 2 bars below the housing and 2 bars on the top of the housing, actually on the pot, it would cause the housing to move slightly up and down and stay parrallel to the ground, but you might be right. With coilovers I've just never really felt "secure" in the way they're mounted = basically 2 bolts on each side holding up the whole weight of the car. I know that lots of cars used coil springs and I might still look at that , as well as coil overs.......we'll see!  More than one set of eyes and brains are always good!!

[Beck]

I believe somewhere I saw special spring to axle mounts that allow for rotation. (possibly for dirt track cars?)

I thought with the 4 bar having 2 bars below the housing and 2 bars on the top of the housing, actually on the pot, it would cause the housing to move slightly up and down and stay parrallel to the ground, but you might be right. With coilovers I've just never really felt "secure" in the way they're mounted = basically 2 bolts on each side holding up the whole weight of the car. I know that lots of cars used coil springs and I might still look at that , as well as coil overs.......we'll see!  More than one set of eyes and brains are always good!!

[Mac]

Heck, even Chevy 1/2 ton pickups had coils.
Coils are good.

[Topsterguy]

Heck, even Chevy 1/2 ton pickups had coils.
Coils are good.

Yup, you're right, and I'm leaning towards that now, just thought a few ideas would be good.

[GPster]

Is the chassis "X" member intact? With the idea of 4 bars mounts you don't want to be planning on too much mounting on any part of that "X" member if it's cut up and not re-made. The Chevy truck coil idea is good but it will also involve a strong center croosmember. We ( Frank and shareholders) had a four bar figured out for the Crosley and it already needs re-figured. I'd have to remind you about Chassis Engineering's bolt-in leaf spring kits. Years ago they had you looking for Dodge truck's front springs but and Camaro/Nova 10 bolt rear ends but I bet they have revised that kit to things more easilyl obtained. Then your "ride height" can be adjusted by "blocks". Frank said just the other day that he's got two weeks involved in making a four bar and air bag set-up on a truck that they don't make a kit for. On a truck you can take the bed off if you need room to design figure and weld. A '37 Ford body would take a little more to get the body off of. This advise is from someone that can't weld upside-down. If it was a kit and it came with the purchase I'd use it but if you don't have much more than ideas given where the mounts might go maybe you should just keep those bars for trading stock. GPster

[enjenjo]

You can build a bracket to mount a pair conventional coil spring behind the axle, and mount the shocks separately. This gives you a longer spring base, effectively a longer wheelbase, making the ride less choppy. That's the reason Ford moved the springs from on top of the axle like on a model A, to in front of the front axle, and rear of the rear axle on later models. It improved the ride.

[Warpspeed]

I agree,
Using a full linkage suspension with conventional leaf springs will definitely bind and cause some very big problems.

Unless.....you use two spring hangers. The usual one at the back (which is visible), and another one at the front.
That way, the leaf spring can flatten and elongate both ends without binding anything.

The one big advantage of coil springs is that it is much easier to change the spring rate and ride height to get the stance exactly where you want to have it.

[chimp koose]

When you worry about the bolt size on coilover shocks ,think about this for a moment. The front end of a full size vehicle is essentially held up by the threads on two ball joint nuts on the lower control arms.This example may be a little over simplified as those ball joint nuts are in tension and the coilover is in shear,but arent the coilovers on a 5/8 stud?Also any shock loads are dampened by the shock absorber. If your suspension includes travel limiting bump stops, the shock absorbers should really never bottom out where the road shock could be transferred directly through the mounting bolts.When I first started looking at coilover stuff I thought it looked a littly skimpy but it probably isnt as flimsy as one might think.One 5/8 bolt has almost the same cross sectional area as three 3/8 bolts. How much weight have you lifted by two 3/8 exhaust manifold bolts in shear ?

[29abone]

The Jaguar sedan used 4 coil over shocks in the rear ( 4,000 lbs? ).  I would think that you could  use a set of coil overs since you are basically set up for them, just making sure to use adequate mounts and bolts.  I don't know what the shear strength of a grade 8  1/2" bolt is but it has to be close to 100,000 lbs.

[Warpspeed]

The bolt itself isn't going to be a problem, but if you can mount the bolts in double shear at both top and bottom, that will settle it.

If in single shear, the bolt needs to be a very snug fit into a suitably long sturdy crush tube, with a big thick retaining washer on the outboard end of the bolt, just in case the rubber bushing splits or ruptures.

If you are still nervous, you can always mount two coil shocks on each side of the car, the same way Jaguar do it.  
The off road guys with very heavy vehicles do this all the time, and it makes for some much nicer load paths, as well as halving the loads on each coil/shock.

[Topsterguy]

Thanks again, guys!  As always, great points and info here and it's always appreciated!  I'll be going with the coil overs after all seeing as it's set up for that. I figure QA1's - they seem to be popular and they're on my 32 now.   Larry