Hot Rods Truck Arms/4 Link vs Leaf Springs

I am seriously considering replacing the leaf springs on my 48 DeSoto Hot Rod with truck arms or 4 Link and air bags. School me on the good, bad, and the ugly??
Jack

 

Cannot speak about airbags here without getting a lecture about them not being traditional, or even existing anytime but in recent history, despite being patented about 95-years-ago.

In terms of ride quality those systems rank:

1. 4-link.
2. Truck arms.
3. Leaf springs.

 

On a big fat fender-ed car like a 48 DeSoto I would keep it leaf springs unless you are wanting to go extremely low, or you are looking for a hard launch why reinvent the wheel? Lots of extra work to make the change to either of the others. Just my opinion, others may differ.

 

Each has an installation quirk.

Ease of installation is a factor. You will need to take that into consideration.

 

I am going the truck arm route on my 40 Buick. I spent a LOT of time researching the options- 4 link (both parallel and triangulated), original truck arms, variations of truck arms made by others. I could not go leaf springs because of the way the ch***is is designed.
4 links- a lot of folks make these, and quality is all over the map. Reputable vendors are what I would stay with since they have engineered the product. They do require a lot of measuring, set-up and welding, but offer more room for exhaust routing.
Truck arms-whether you go original or custom, the principle is the same. Custom units usually have a heavy duty Johnny Joint, and can be gotten in custom lengths from some. They are pricey, and require some type of fabricated ch***is bracket, as does the original. Laying out the installation details can take time, but the install is straight forward and less welding on the axle housing.
Not as much room for exhaust, but planning can get around that. If your ch***is has an x-member, it may need modification or shorter arms. I chose original arms, and shortened them 3 inches (see pic). Cost is cheaper going this route, and the arms have some twist built into them for ch***is lean.

 

That's an important note:

Truck arms need to flex. That is how they are intended to work.

That's how GM designed them, and that's how they function in NASCAR.

Truck arms that do not flex are made by those who either don't understand, or don't care.

Reproduction stock-style truck arms are available brand new, should a yard search not produce them

 

**** K.I.S.S. ****

Sounds like you aren't following your own advice.

If engineers spent time and money designing your car to have leaf springs, why would you want to guess-engineer the whole set-up, rather than just purchase springs with the right/desired load rating?
Just asking.

 

My 55 bird had good leafs, shocks, traction masters, and and a rear bar. I replaced it with an Art Morrison tri 4 bar with a rear bar. The coil overs are nice, it works slightly better than the old set up. I learned a lot, mainly that it cost time and money to fix what isn’t broken. I rarely if ever hammer the car enough to feel the difference.

 

The engineering on that car was done over 76-years-ago.

Why not take advantage of nearly eight decades of advances in technology?

 

I agree with your thinking. When I bought the car about 20 years ago, it had Mono leaf, rode great. When one broke, I had made and I installed complete set of leaf replacement. That gives me a very firm ride. Being 77, I appreciate an "easy ride", but don't really want to go back to the Mono set up.
Jack

 

Really wanted to know best for improving ride quality. I built it for driving, and I drive the snot out of it, do not own a trailer, and the car doesn't know the difference between a Wal Mart parking lot vs a show field.

 

Not remembering what the frame crossmembers or X member looks like on a 48 Desoto since it has been close to 60 years since I was under one on a hoist I'd think that staying with leaf springs would probably be the prudent way unless you are planning on bags. That said, a cool thing about a lot of later leaf spring Mopars is that you can slide under one and unbolt the leaf springs brackets and all to use in another vehicle. I've had my head under a mini van I have scoping out the rear springs deciding if I would rather use them or use the truck bars under a pickup box trailer that I figure to junk that is 30 feet away. The truck bars require a sway bar/track bar so leaf springs sound better in that respect.
That said, the guys with Buicks who go truck bar are keeping it simple and without major issues when they replace the torque tube that is already on coil springs. That makes it very simple on a Buick.

 

Because parallel leaf spring technology is over a 100 years old, and still in use because it works so well.
Probably safe to say that the OP isn't planning on racing a big '48 DeSoto, then why go to the time and expense of installing a suspention designed for a pickup truck (or a race car) that MIGHT (?) improve the ride/drivability.

 

cornfield, I do like low, but no hard launching in my future plans. I appreciate your opinion, and my budget probably not going to allow for either. Probably going to trying removing couples of the leafs to see if it softens the ride. Softer ride, my main goal.

 

That would be my exact reasoning for removing it.

 

Stock and custom springs
DeSoto S11C, Custom Springs (1946-1948) - EATON Detroit Spring

 

I really appreciate everyone's input. It's like y'all are in my head with each opinion, which may be a dangerous place to be....

 

^^^^^ Leaf springs can be custom built to the spring rate you want. Add a set of adjustable shocks, and you can get the ride you desire. I am going the truck arm route to go to an open rear and keep the coil spring ride. My Buicks are over in the Southside should you want to come see.

 

With that being said, can I ***ume you prefer EFI over that ****py 100 year old carburation technology? Just kidding

 

Born with nothing, Still have most of it.

 

Truck arms are from the HAMB era.

Leaf springs are from the horse-drawn carriage and buggy era. Parallel leaf spring technology is from 1804!

Between the introduction of the leaf spring, and say the suspension on a 1964 C10, there had been 160-years of technological improvement. Every bit of it without even leaving what is in the era that this board covers.

No electronics or current technology required.

 

The problem with the C-10 suspension is it was designed to do a job, rather than designed to offer a superior ride. It had to handle laden weights 0 lb to 3/4 ton and was not "tuned" to the specific weight of the vehicle

 

Change springs.

 

Have you checked out the shocks? I know you added leaves and agree that is probably the source of the hard ride but it's not all about spring rate. The combination of pulling a leaf or two and changing to a shock tailored to your application may yield a big improvement. Big race teams have a "shock man" and carry multiple sets built for individual tracks. You may not be racing your car but the technology is transferable to the street. Cadillac and the other luxury carmakers using auto-adjusting suspensions turn out some nice riding OT stuff.
You might try a full set of adjustable shocks before you get to the hard stuff. I'd put them on all four corners and play with the adjustment to see if there is any improvement before diving into the spring job. But I'm lazy and always try to take the path of least resistance.

 

Back in the day truck arm, coil spring Chevies were known to have a better ride than the leaf spring Fords. Of course they were "tuned". Any short bed 1/2 ton had way less spring than a long bed 3/4 ton. regardless of make. The springs in any vehicle have to handle loads from 0 lbs. to max load.

 

My plans are to be in Williamsburg this week at the TSA Rod Run.
Right now, not sure. Weather looking iffy, and I'm about 3 1/2 hours away.

 

Except in a Hot Rod.

 

Me too. I have coilovers in front, regular shocks in rear. There are 5 leafs in rear spring.

 

I plan to check out the show on Saturday even with iffy weather as I am within walking distance. You must be on the fringes of the southside if 3-1/2 hours away. I was thinking Hopewell/Petersburg/Colonial Heights area, which is where my Buicks are.

 

One option I haven't seen mentioned yet is what was used under "F" body Camaro's and Firebirds: Two lower suspension links from the rear end to the bottom of the frame, a panhard bar and a torque arm from the rearend pumpkin to the back of the transmission.