Thread: Newbie needs help w/front suspension, Mustang II or Straight Axle

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Im trying to build a Hupmobile Model A, Century six, (4 door, full fendered heavy car) and Im unsure about which direction to go with the front suspension. I have a mustangII that Ive cut out of a car, and after studying it I dont feel great about using it. Seems like alot of parts, and fab work to pull it off, not to mention cost. The straight axle that is original to the car looks good, and Im wondering about changing out the spindles or such to use it again. Ive looked through several mags, and it seems that hairpin/single spring set up is the norm. Why isnt the original springs parallel to the frame rails used? Thanks in advance for any replys. School me on suspension.

Well, for starters, a properly installed and set up independent front suspension will generally ride and handle better than a properly installed and set up straight axle combination. However, as we have seen in some recent posts, even an independent front end can present problems, and on the flip side, there are tons of cars running around merrily on straight axle setups.........mine included.

The reason you usually don't see many cars with the two parallel springs is because; a) most use a Ford front axle setup, and b) on a fenderless car the front of parallel springs stick too far out in front to look good. But the ride quality of parallel springs can be very good, certainly at least as good as the single spring ones.

I think the only fly in the ointment on your setup might be finding spindles or parts to put modern brakes on that axle. Anything is possible with enough talent and work, but I know of no spindles that will bolt on easily to let you adapt modern brakes. Maybe you might want to consider another axle from something like an Econoline where parallel springs were used and with which you have decent brakes and the availability of replacement parts.

One of our other guys may have a solution to your problem too.

Don

Ive been studying the spindles and was unsure about what options I have there. Seems I could have some king pins machined to accomodate something, if thats a good idea. I guess the new spindles will dictate what kind of steering is used? Also will the single spring/hairpin set up work with a heavier car?

Spindles and the ends of the axle can and have been machined to make them work together, but there are other things to consider. One thing is camber angle. The ends of the axle are built with a certain amount of angle inward to them. If you look at your axle you will see the top of the kingpin is leaned inward. Correspondingly, the kingpin is built so that it also has that angle to it, and when the two are mated the end of the spindle holds the wheel in a straight (or almost straight) up and down position, when viewed from the front. As the wheel is turned there is a particular arc to it that facilitates turning properly.

If you machine another cars spindles to fit the angle that the axle leans and the angle that the spindle leans might be different, so the wheel, when viewed from the front, might lean in or out somewhat. That is something that you might have a problem with.

I do remember seeing somewhere years ago where a guy built a Hupmobile and he had updated it with later brakes, etc. But that was probably in the 70's or thereabouts, so I really don't remember the particulars on how and what he used. Like I mentioned, some early Ford, Chevy, and Dodge vans and pickups used a parallel spring front end. If you hit a truck junkyard with a tape measure you might find one that is a close fit, that way you might get away with little or no changes aside from maybe shifting the spring to spring width or shimming the mounts to get more or less caster.

However, don't let this info I am giving you deter you from seeking other ways of doing it. I've never done a Hup so I am only giving you some possibilities, not absolutes. As for if the single spring setup would be strong enough, yeah, especially if you used one from a maybe 40-48 Ford as they were designed to support similar weighing cars. But they would entail some work there too, building a new crossmember to support the spring and mounts to affix the rear of the wishbones too. All doable but still not a drop in.

Don't get discouraged, you will find a good solution in the end, it will just take some research and trial and error. Anytime you play with a car that is not as common as a Ford or Chevy you take on some additional challenges, but having a different car in the end makes it worthwhile IMO.

You are asking good questions and that is the important thing.

Don

I'll offer up a completely different solution. Autoweld will bend up any frame you can draw up from either 2x3 or 2x4 material. They can also furnish IFS systems or you could incorporate the IFS of your choice into your drawings, then source the pieces from a boneyard or donor vehicle.

This is an alternative to fumbling with an OEM frame and adapting it to the Hup or jacking around with the stock straight axle and trying to find a safe solution that will operate well. You can have an IFS, IRS, power rack & pinion steering and 4-wheel power disc brakes in the old girl.

As Don said, you are asking questions at the start and that's a good thing.

I might start off a project like this by sitting the frame on jackstands and mocking up the tires I would use and positioning them where they look best, then measuring the wheelbase and front and rear track to begin my drawings.
Here is a chart of measurements from OEM production cars and trucks that may be of interest to you....
http://www.crankshaftcoalition.com/w...ANGE_TO_FLANGE

Here's Autoweld's site....
http://autoweldchassis.com/index2.ivnu

Opinions between straight axle and IFS will vary predictably, but for my money, it would be IFS and modern components hands-down.

Richard is right. While we all try to save money wherever possible when building a car, we have to remember that we are building a car from the parts bin, and it is going to be expensive no matter how you slice it. Sometimes those complete front end kits like he has mentioned from folks like Autoweld seem ridiculously expensive, in the final analysis they end up being very close to what a home built set up will cost, and are far superior generally in fit and performance.

We had a back half 4 bar kit custom made by Autoweld for my Kids rpu and it made building the rest of the frame so much easier and better. Money well spent.

Don

I agree I probably need to bite the bullet and just buy a kit, but being cheap and stuborn, Im not ready just yet. Even in gather info on what kits to use is a pain in that there can be too much info, and if I read into it too deep, my head starts to spin. Im wondering what it would take to build my own IFS. Something using tubular a-arms, and coil over shocks. Some of the set ups look really clean an straight forward. Im also aware that a true craftsman makes his work look easy.

Originally Posted by Chicken Legs

I agree I probably need to bite the bullet and just buy a kit, but being cheap and stuborn, Im not ready just yet. Even in gather info on what kits to use is a pain in that there can be too much info, and if I read into it too deep, my head starts to spin. Im wondering what it would take to build my own IFS. Something using tubular a-arms, and coil over shocks. Some of the set ups look really clean an straight forward. Im also aware that a true craftsman makes his work look easy.

You can learn to engineer and build your own IFS. I did it and if I can do it, I can assure you that anyone can do it. Get the book "Tune To Win" by Carroll Smith. Read it cover to cover several hundred times. It'll finally just go "poof" right in front of your face and you'll go...."OH YEAH, I SEE HOW TO DO IT" and all will be right with the world. Mr. Smith explains how to construct "paper doll" type suspension setups to scale with stick pins for pivot points. You can play around with caster, camber, scrub, camber gain, instant center, Ackerman and all the other neat stuff using paper and cardboard, then transfer your dimensions to steel. One word about tubing sizes and materials. I used 1 1/8" x 0.188" wall chromoly. Way too tough to bend, grind and weld and too expensive to buy and didn't look that balanced when finished. Use mild steel, 1.000" x 0.120" wall for the bottom arms, 0.750" x 0.120" for the upper arms. There is very little pressure on the upper arms, so you could even use 0.625" x 0.120" and it would look even better to the eye with the 1 inch bottoms and 5/8 inch uppers. Another combo that would look good to the eye is 1 1/4" for the lowers and 3/4" for the uppers.

Once you have read and understood Smith and mocked up some instant centers, you'll see why it is futile to narrow an existing OEM suspension system and still expect it to operate like it did when the instant center was stock.