Leaf Spring Suspension Geometry
Leaf Spring Hanging Tips and Tricks.
We've often touted the benefits of leaf spring suspensions. Sure, they are simple. Sure, its technology that could be almost 300 years old, and sure, leaf springs aren't terribly fancy. But hey, they work, and they work well, especially off-road. Leaf springs were also ubiquitous until the introduction of the 1966 Ford Bronco. The first Jeeps, Toyota 4x4s, IH Scout 4x4s, Land Rover 4x4s, Chevy Blazers and trucks, Ford early 4x4s, and more were purely leaf-sprung until the introduction of the Bronco. We've built all kinds of custom 4x4s, ranging from simple aftermarket lift kit installs to fully custom link suspensions, but it's still easy to head back to what's simple and what works. Leaf springs do just that.
So when we decided to rebuild a rusty, battered, abused, and forgotten 1962 CJ-5 as a kind of a cheater rig—one that works, but doesn't look like much—we knew narrow old-school leaf springs had to be part of the formula. Of course because we are cheating, why we should leave things as they would be from the factory? Here's how we hung some cheater leaf springs on our cheater CJ-5 using some subtle, yet cheater methods. We'll follow this up with some more simple, yet non-factory suspension ideas as the project gets closer to being drivable. Then we'll get to see how well it works—or doesn't.
Stretching the wheel base
We started with new replacement shackle and spring hangers for our 1962 CJ-5. They mimic the factory design and are available from a few different places. Starting in the extreme rear, we used the rear-most rivet hole in the frame to locate the front hole of the new shackle pivot using a bolt. We will fully weld these parts in place and might weld a nut inside the frame before the Jeep is done. For now, we're just using heavy tack-welds in case we need to move something later. Our plans also include tying these shackle mounts into some sort of a rear crossmember or bumper.
For the front spring hanger of the rear spring we did the same, namely locating the bracket using the more rearward rivet hole on the frame and the most forward hole on the bracket. This will push the axle back about 2-3 inches, which is perfect for the sheet metal trimming we have planne—and also pushes the rear springs as far back as possible or maybe a little more.
One of the drawbacks to leaf springs is that they both stick forward and back. That can cause the springs to hit obstacles on the trail first. Ironically, on many early Jeeps the leaf spring hangers aren't at the extreme ends of the frame. The front is a few inches back from the front of the frame, and the rear shackle hanger is also a few inches forward of the back of the frame. We don't like that. We want to push the front springs as far forward as possible and push the rear as far rearward as possible to optimize the approach and departure angles. This also means the wheelbase will be a little bit longer; that should help the rig perform a bit better off-road. All four of the factory spring and shackle hangers on our Jeep had been worn to the point of being damaged, so we started by removing the old parts. The easiest way we found to do this was to drill out the center of the factory rivets, and then used an air hammer with a chisel to knock the heads of the rivets off. With the rivets out of the equation, we cut the welds along all of the hangers and knocked them off.
Starting the Shackle Reversal in the front
Starting with some card stock, we made a template for a front leaf spring hanger. We held it in place on the frame and made sure it would do what we wanted. You want the front hanger to be approximately the length of the shackle, so the axle spring perches on the axle we are using can be used unchanged. We're using a narrow-track Dana 30 from a later Jeep CJ in the front of this Jeep and hope to be able to just use some shims to adjust the pinion angle—if necessary at all. We then cut four plates out of 3/16-inch steel plate and drilled holes.
Here's our template next to the tack-welded brackets we will be using. Again, everything is heavy-tacked so we can change directions more easily if something interferes. We're also planning on adding a power steering box to the Jeep, boxing the frame, and building a winch mount and front bumper for the Jeep.
We also added some 2x2 square plates to the front of the spring hangers, and we might add more gusseting to strengthen the whole shebang, including tying in a combination cross member /front bumper.
An old trick off-roaders have used for years with arched springs is to move the shackle or pivot end of the front suspension to the back of the spring. That helps the axle and tire move rearward as the suspension compresses, softening the otherwise jarring hit the suspension can deliver when you hit a rock, a rut, or a pot hole. We're totally doing that. Also, longer springs are softer, and therefore better. Early CJ-5 front springs are 39 1/2 inches long, while Flatfender rear springs are a bit longer—like 41.5 inches long. That little bit of length, along with the shackle reversal, should make our CJ-5 a touch longer up front and make it ride that much better.
The rear of our front shackle reversal
We used a 1-inch hole saw to cut our Jeep's frame for the 1.125 seamless tubing and a sanding drum on a pneumatic grinder.
We then test-fit the sleeves and adjusted the shape of the inside hole to make sure the two tubes are aimed directly at each other.
Last we used our Miller Electric Multimatic 220 welder
For the rear part of our shackle reversal, we could have used a factory front shackle hanger, but that would have pushed the back of the front leaf spring up pretty high. Our plan for this jeep is to recess the upper shackle pivot into the frame rail. We did that using a hole saw and a couple pieces of 1.125 0.120-Wall tubing.
Installing Leaf Spring Bushings for Early CJ-5s
We got these Energy Suspension leaf spring bushings (PN: 202101r ) from Summit racing (https://www.summitracing.com/parts/ens-2-2101r). The trick to installing them in these sleeves or in the springs is to use the included grease to lube up the spring or sleeve. Then, push she polyurethane bushing. Then, grease up a steel sleeve and use a C-clamp to push it all the way into the bushing.
Springs are in place
Here's what the springs look like installed in our Jeep. It might be time to finish-weld everything up and go, but we think we will box the frame first and also install our Saginaw-style power steering box, too.