Under. Over. Under!… Over?….

The JeepMonster’s exhaust manifolds arrived late last week, so I called Robert earlier this week to set up a time to take them out to him. We agreed that yesterday afternoon would be satisfactory, so I arrived at his shop about 3:30 to drop them off. While I was there, we discussed the springs – both the coils for the front axle and the leaves for the back axles.

Up until about a week ago, I had been working on the assumption that the back springs were going to be mounted above the axles, both to increase the clearance underneath them and to give additional space between the axles and the frame for flexibility and axle movement. When I talked to Robert about coming over, he told me he had decided that the spring-over configuration was going to be too high, and he had moved the springs under the axles – and that’s where they were yesterday. We both recognized that stock YJ Wrangler springs (which is what he had on hand and we’ve been using for the mock-ups) wouldn’t work in the spring-under-axle (SUA) configuration, because it left the axle and the frame too close together. So I’ve been (desultorily) looking for some springs with about 2.5 inches of lift. In the meantime, Robert was going to force the frame and axles apart by sticking a piece of steel between them, so that he could work on the front suspension.

Last night, I got a text saying, “Don’t look for springs yet – I want to do some more measuring.” O-kay…

Today Robert called me and said he had gone back to the spring-over-axle (SOA) configuration, and he sent me a couple of pictures.

This first one shows the middle-axle spring mounted on top of the axle and compressed (by the weight of the third axle) to about where he thinks it’ll ride when the whole JeepMonster is built and the full weight of the vehicle is on the springs. (The third axle, although not shown well here, is literally hanging about an inch off the ground. Robert thinks that’s a pretty good proxy for all the other weight, like a spare, a winch, a gas tank full of gas, a couple of batteries, and tools & parts, that’ll be weighing the back of the JeepMonster down when it’s all built.) In this photo the spring looks almost flat, but I think there’s still some positive arch in it.


The next photo shows the front shackle. As you can see, there’s a definite forward cant to it, which is what you want when the spring is at what’s called “ride height” – in other words, when it’s just sitting in a garage, or when it’s going down the highway. Having this forward (or backward, if the shackle is at the back of the spring) slant allows the spring to flex better and gives a better ride than if it’s exactly vertical. And you *definitely* don’t want it angling back toward the spring, because then you have very little flexibility and you run the risk of reversing the shackle and jamming it up against the frame – which could cause bent or broken springs, a broken spring mount, or other severe damage to the suspension.


The net result of going back to the SOA style isn’t really any different from getting some lift springs and mounting them SUA, but if I can use the stock springs we already have, then I don’t have to try to figure out whether to get 2 1/2-inch or 4-inch lift springs, and if I happen to break one, stock springs will be much easier to source than lifted ones.

But now I have to find longer coils for the front than I was originally looking for.

Here’s a photo Robert just sent me, It shows the middle axle flexed:


He tells me the tires have 11 inches of travel between the fully compressed and fully extended spring positions. You can see the passenger-side spring is squershed flat, while the driver-side spring is fully extended. I think that’ll be fine – I’ve never intended this to be a super-flexy rig, anyway. What I can’t conquer with flex, I’ll try with locked axles; what I can’t conquer that way, I’ll either give up or use my winch.

Here’s another shot of the flexy Monster – it’s a *little* clearer to see the springs in this photo. You can see the back axle is still SUA, and if you look closely you can see the shackle on the far left corner is almost directly in line with the spring. It would be very easy at this point for the shackle to reverse itself and then jam up against the frame as weight comes back down on that corner. That would not be good.


As a side note, he told me that the “inner wheelbase” is 98 inches and the “outer wheelbase” is 130 inches (or about 11 feet). The original CJ-5 wheelbase is 81 inches, and a CJ-6 wheelbase of the same vintage is 101. By comparison, my truck’s wheelbase (it’s a 2000 F-150 SuperCab) is 138.5 inches. The big difference will be in the overall length. The truck is 225.9 inches or about 18′ 8″. The JeepMonster will have much less overhang at both the front and the rear, although I don’t know yet what the final length will be. The frame is currently 16 feet, but the final length might be different by a little bit.

So if you’ll excuse me, I’m going to go look for information about coil springs, and maybe buy a pair.

Categories: 6x6, Jeep Frame, JeepMonster, Spring Over, Spring Under, suspension, tandem axle | Tags: , , | 2 Comments

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2 thoughts on “Under. Over. Under!… Over?….

  1. Miles Weigold

    Dave, Haven’t read site from the beginning but just looking over the 2015 postings I can’t tell you how much I admire your taking on this task and sticking with it. I also must question, just between us, why in God’s name you would undertake a project of this magnitude. Possibly “BECAUSE IT’S THERE” comes to mind. I’ll be anxious to see progress when I get back in the Fall. Hope things continue to progress

    • Miles, it’s a story that’s been evolving for about 20 years. The 6×6 part is just the latest mutation. Follow the blog and you’ll know everything everyone else does. 🙂

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