Hot Rods Suspension designs

Howdy Y'all,
Im getting ready to start designing my 1929 Model A Tudor sedan front suspension, what would yall recommend? Im running a 1958 MEL engine, the car is hopefully staying around 2500 lbs, and im running fender-less. Im also running a 32 ford frame. The main goal is driveability, but my daily is a 1951 ford f1 pickup so "driveability" is a relative term. Just shoot your recommendation and experiences out there, im appreciative of any help.

 

Well 99.99999 % including me on here will say that a Model A has to have the cross leaf and an I beam axle with bones or hairpins. Done right they handle decent an ride reasonably smooth.

 

cool, what is the normal amount of drop to run on an I beam? how much is too much? is there advantage to running a suicide setup?

 

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What kind of budget did you have in mind???

 

I'd like to stay relatively inexpensive, but in the end I would rather the best result. Cost is kind of secondary

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This a Socal 4” drop axle with reversed eye leaf spring. The split bones are later 30’s that had the leaf spring mount castings out in front of the axle. I cut them off since we were not going to use them in this application. Also, the front ends of the bones were adjusted to get more caster into the axle approximately 5-7 degrees. Probably can’t go much lower then this as far as this type of(spring over axle) setup goes. If you go suicide you can get it down a good bit more but you creat other complications for yourself..

 

What kind of complications should I expect from a suicide spring setup?

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I suspect that setting it up with a suicide spring mount you’ll be moving the axle forwards and the axle will probably be nearly parallel with the frame. These two factors will play into how you are going to facilitate steering the front wheels.. The flatter the steering linkage is situated in relation to the ground the less likely you are to creat bump steer. What type of steering gear or box will you be using? Also, pay attention to your Ackerman.. If you’re going to have a radical rake to the chassis then you will have to put more angle into the front radius arm mounts to get you back to 5-7degrees of caster angle.. How are you going to mount your shocks and what type tubular of friction..?

I picked up a book on hotrod chassis design and suspension setups I would suggest that you do your homework on this type of setup so you can get your head thinking about it.. It can be done but you’ll be adding some areas that will test your ingenuity..

 

Do you guys find that putting the steering linkage in front of the wheels makes for a better driving car with less bump steer.

 

On a solid front axle the tie rod and drag link are best if kept behind the axle. That Ackerman is less likely to be effected negatively.. Bump steer is caused when the tie rod and/or drag link are operating on a slope/angle relative to the ground. The flatter they are situated the less likely you are to create excessive bump steer..

 

Yeah I'll definitly have to do my homework. I'm not sure about steering box, any recommendations? I might try and run rack and pinion if it's possible, I'll need to look into it. As far as shocks go, I'm going tubular.

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Ya, do some homework. Rack and pinion with an I beam axle has proven to be problematic at best in most cases. A suicide front suspension can be done safely with the right components and geometry. You just see way too many poorly thought out ones. And when a component fails, well the name says it all!

 

I’m not one to tell some one how to build their car..! What works for me is to get some ideas flowing and some pieces to work with and eyeball the hell out of it.. take measurements and figure out the location of the necessary components.. Figure out where you have congestion and or conflict with parts that want to be in the same space.. I would also think about how you intend to use the subject vehicle here.. Will this be a driver, a show car, or somewhere in between.. A show car can be as radical as you want if it never sees the road it won’t matter how well it steers or drives down the road. A vehicle that sees some road time would need a significantly less extreme build plan for it not to be a handful to drive..

As for the method of steering, I’m not sure a rack and pinion would be workable here. Typically a steering rack is mounted to the chassis and connected the spindles. For it to work it may need to be mounted to the axle. The thing I’m not sure of is whether it will be happy there bouncing and vibrating from the road surfaces.. I’ve seen them done but it’s not a common approach on a hotrod.

 

Thanks for the advice! It's a driver above all else, but I'm no stranger to a handful on the road. My daily is an original 1951 ford pickup, the steering box is shot in that. The main goal is to kind of bridge the gap between wild and drivable.

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Rule #1 on a straight axle
Forged
A Vega box is the easiest to set up in my opinion.
Why run a suicide on a 32 frame. Are you cutting off the front part of the frame?
The steering will feel better with the drag link behind the axle.
The drop depends on your tire size and ride height. There is no formula that we can tell ya with out knowing what you want.
There are a few ways to lower the front and can be used in combination
Flatten out the front x member
Reversed eye/ lowered springs
Dropped axle.

 

Do you mean a forged front axle? And i can cut the frame, right now I'm in the planning phase. I know the lack of parameters can make it a bit hard to answer the question, but I didn't want to limit my options before I knew what I was talking about. I wanted to see what the community used and what worked for them, for instance, what combination of parts provides the best handling? Stuff like that

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Yes forged axle.
Do not cut those frame horns until ya figure out what you want.
You can drop it without removing it’s good looks.
A flattened crossmember with notches for spring clearance, a dropped spring and axle
Post a pic or a pic of what you want and the HAMB doctors can diagnose

 

Are you aware that a 430 MEL weighs 1070# not counting the tranny? That's almost double of a lot of engines that are used in "A's". You are not dealing with a normal load for a beam axle in a model A.
SPark

 

Ford axles have held up many blown hemis

 

I’d never cut up a 32 Ford frame, original or aftermarket. Too beautiful a design to monkey with.

 

Yes sir, it's a pretty heavy engine, though I weighed mine and it's only around 640 lbs, maybe you are thinking of the ford super duty engines? Those are some heavy boat anchors. I have accounted for the extra weight though, I might add a leaf or two if I need it. A flathead weights 570 lbs for comparison

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Sorry, I misspoke, it was 740 lbs

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Maybe the 1070 was with the tranny still on it (also cast iron case). I weighed mine so we could figure springs but then sold it before we used it. Went with an FE and it was lighter.
SPark

 

Yeah it's a pretty heavy unit, the FE is a fantastic engine. I got the MEL on a good price though, and it's got that cool weird factor to it. Plus the torque available is just wild.

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To answer your suicide front end question, the tie rod is the main problem, it’s challenging enough to bend steering arms to get the tie rod over or under wishbones or through hairpins while maintaining full steering motion but when you put the spring back there it just gets worse. I would stick with a Model A crossmember, a forged dropped axle and reversed eye spring. You could use a flat front crossmember (Paul Horton’s is good) if you have to be lower still. Remember not to violate the scrub line rule in the attempt to make your car low.


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Thanks! It's looking like I'm going to do that, In my looking around, I definitely like the cleaner look of the spring over axle

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I found this one looking around, this is about as low as I would want to go

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Yuck!

 

You do realize that chassis has nothing to do with a 32 chassis right? That chassis is clearly stepped up front and though it’s not visible, it’s most likely stepped out back as well. That’s the only way to get it that low.. Also, the body is channeled down over the frame..