Correctly Determining Rear Shock Mount Placement for Maximizing Shock Utilization

Don't have time to go over everything right now, but a couple things that stuck out.

It's still not an apples to apples comparison to vertical travel. You could raise your bumps an inch and adjust your shocks based on what you're seeing there, but that still doesn't tell you how it will perform with vertical travel.

1. Ask the guy that built them. I had a rough idea how much my super bumps compressed and based my numbers on that. I then made some 1/4" bump spacers to add if necessary after watching how much shock travel I was actually using. You will not be able to compress them all the way while cycling.
2. Wouldn't worry about it. Wouldn't hurt to change the oil.

 

for info and answers. All good shit here.

 

I need to get off the couch and finish my rear setup. I have all of the parts to box in the frame, U-bolt flip kit, Fox shocks and all the hardware to do the job, just missing the motivation...

 

Seems reasonable. Was thinking something similar. Oh, and I asked the guy who built them too. Hoping he knows, but not sure he will...it's been few days waiting on the reply already. Risks of being an early adopter I guess.

Yeah, I totally get that it's not apples to apples; wasn't trying to say it was. Was just trying to give context of the photo since no one on the thread had any.

1. Yep, as mentioned to Zane above, done.
2. Well, that makes me feel a lot better. That was really the only bit I was concerned about with this whole thing. I always love learning the "why" behind things and it's much easier to learn when you do something wrong, learn why it was wrong, and then how to do it right, rather than just get lucky and do it right without knowing.

So, have really enjoyed this whole experience.

 

Great thread here, making me think. Some comments below, but everything I know about suspension comes from full-suspension mountain bikes and watching The Tuesday Tune series on Pinkbike (Vorsprung Suspension). So not an expert on applying that to a truck, but I would think some of the same principles apply.

When setting up your air spring rate for rear mountain bike suspension, you shoot for 30% to 35% sag. Different weight riders need more or less air pressure to reach that amount of sag, which gives you 65% to 70% up travel, and droop equal to the sag. Then you adjust your rebound damping to compensate for the spring rate -- higher spring rates need more damping. There's some additional things you can do that deal with how progressive the spring rate is as well (adding "tokens" in the air chamber decreases the volume, making it more progressive, and vice versa).

Thinking about how this translates to leaf springs, I would think you would want to do something similar. Based on the weight you need to carry and the amount of travel you want, combining spring/shackle length (amount of travel) with spring rate (amount of sag) to get the loaded ride height in your sweet spot would be the first step (then choosing the right leaf thicknesses, number of leaves, and overloads to get the progressive characteristics you want). I'm thinking something in the 40% range for sag would be good, giving you a bit more up travel than droop, but also may depend on the actual application.

The next consideration is the damping, and this is related to how the shocks are valved. They say the Fox shocks on the Pro have "zones" -- which means they are intended to start in a certain position, and as they move either direction, different valves are opened or closed to increase or decrease damping depending on where you are in the travel. This is why you can't really mess with the Pro suspension much, as you'll go around the zone tuning they have done.

So, to figure out your shock positions, you kind of have to know how they are valved. If they are valved to be progressive or digressive as they move to the limits of travel, you need to position them in the middle of that when the truck is at the optimal loaded ride height.

Anyway, that's how I would do it.

 

I read a lot of this, skimmed over some of it. @Blackdawg is on the money, and @Squeaky Penguin is there too.

With a leaf spring utilizing factory mounts, and reasonable shackles, you are going to have limitations no matter what. Even if you do crazy stuff with the shocks, there's only so much travel in the factory geometry available.

My recommendations for cycling and getting the most out of a first gen rear setup with factory location leaf pack is below:

1 - Disassemble the leaf pack, and re-install the main leaf with a spacer to represent the missing leaves, or invert the rest of the pack so the main leaf is isolated.

2 - Put your wheel/tire combo back on the axle.

3 - Jack the axle up until your bump stops engage, or you reach your desired maximum compression location. At this point you will need to account for bump stop compression on impact, and keep that measurement in mind.

4 - Place the upper shock mount and shock, and compress the shock so that you have just enough shock shaft left showing to account for the compression of your bump stop, plus 1/4" to 1/2" as a safety buffer.

5 - Now you have your maximum compression, you can tack in the upper and lower shock mounts, and start to cycle the suspension. Droop it all the way out, subtract 1" for every 12" of strap needed (to compensate for stretch) then spec and install limit straps. From here you can start to jack up one side at a time to account for articulation. This will reveal contact points, issues with either your bumps or limit straps, or spacing issues.

Ride height is irrelevant when you do this. It's important for your use of the truck, and how you want it to look, but for your shocks, it doesn't matter. When cycling the suspension with factory replacement parts, you don't get to be too creative with certain variables, you're kinda locked in. All you're doing is setting up the truck to use the maximum amount of shock travel as possible. Travel and ride height are not dependent on each other.

 

My post is based on two assumptions - you're utilizing shocks outboard of the frame (can also be inboard if re-located correctly) and that they're 10" travel or greater.

If you're using shocks that are less than 10", you'll need to limit your bump or droop travel to compensate and protect the shocks. The pictures below suck, but it shows my up travel at unloaded ride height. The tent and rack are more or less permanent, so i lose height when adding camping gear. I have between 4 and 5" unloaded, with Deaver J59's and about 1.5" of lift. With 3" of lift and 600+ lb ratings, you guys should have at least somewhat equal uptravel numbers. My J59's are not rated for much weight.

 

According to Wheelers, there superbumps compress down to the shoulder. I haven't been able to do this yet but I don't think I've hit anything that would compress everything equally. I'd like to put a gopro back there and watch at some point. Preferably after I have Kings up front.

 

OK, for anyone watching this thread, I wanted to get the full set of steps here at the end of the thread. Happy to incorporate feedback if anything seems wonky:

How-To: Toyota Tacoma Rear Shock Relocation - Determining Leaf Spring Cycle and Mount Positioning

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Sorry, but I have to correct you again based on that picture.

If you set your shocks up properly for vertical travel as I previously described, there's no additional articulation travel to be gained by inboarding the shocks. Leaf springs twist and bind while articulating and will never allow the same amount of travel as they do vertically. I personally run nylocks fairly loose on my shackles to try to help with this, but they still bind. You can look into other options like orbit eyes but those have their own issues as well.

Shocks should be setup as outboard as possible. Outside the frame would be best if there was room.

 

While not the main point of the write-up, so I'll likely remove it from the diagram (edit: I've removed it so these posts don't have their original context, sorry), you absolutely can see more droop with the shocks closer to the center of the truck (at the expense of stability, which is what you gain by moving them outward as I understand). It might not be a ton, but it's definitely there - I can physically see it when I stuff one side and droop the other.

I think what you're saying (and this is why it's probably just better to remove from the diagram) is that it's not really enough to matter when the shocks are vertical. Ya? And, I suppose it's different when you install the shocks like this /\, probably makes the statement less controversial.

 

Not sure you're following. Nothing to do with shock angle.

If you're gaining articulation travel by moving the shocks inboard you either didn't set them up right, or you're limiting vertical travel.

 

Yeah, I'm not following. I really wish we were around a camp fire so you could explain this to me. I have a sneaky suspicion we're actually talking about slightly different things.

 

The measurement between the frame and axle you took while drooping out the entire axle will be greater than the same measurement of the drooped out side during articulation. This is because you're trying to twist the leaf spring down it's entire length which prevents it from reaching the same amount of travel. Therefore, if you set your shocks up correctly based on measurements of vertical travel, there's no travel benefit to inboarding the shocks.

 

Ahh, I see what you're saying now. And I agree with you from a theory point of view - assuming the leafs stay vertical...which I think is what you were saying a couple posts above.

But I don't think they do - at least for me, I get a bit of this... which makes Length(B) < Length(A), and means that a shorter shock at B could yield the same articulation as a longer shock at A.



For me, it's a bit moot anyway - my leafs droop further than the shocks (just a bit) so technically I'm going to need to install some limit straps.

 

I think what he's saying is that while you will certainly find yourself in a situation where one side of the truck is in full compression and the other is fully drooped, as you've shown above, that isn't the metric you want to use to set up your shock placement/length. The absolute maximum your suspension can droop is with both sides fully hanging from the leaf springs, as there is no binding, twist, etc. The absolute maximum your suspension can compress is with both sides fully compressed, for the same reasons, as well as what you showed in your diagram: if you compress the side marked "A", the length "B" gets shorter, thus governing the shock length.

So to properly set up shock placement and measure for length, you will only need to fully compress and droop both sides equally, and testing with one side drooped and one side stuffed should only be for fit testing of tires, bumpstop, etc.

 

He's talking as if the leafs are the limiting factor, not the shock. If you set up the outboard shocks correctly, they will not be your limiting factor, the springs will.

 

You're being dense again, Dan!

Ignore the shocks, yet again.

What I've been referring to as vertical travel is the entire axle moving up and down, not just one side.

Draw that same picture with the axle at full droop on both sides. A and B will now be the same measurement, and, A will be greater than it is in your first drawing.

 

TECHNICALLY, if he's measuring A outside of the leafs, it will be a slightly longer measurement than if both sides are drooped. But that's because now you've turned the leaf spring into the fulcrum, and the axle is the lever. That's why flex LOOKS like it's travelling further, but it's not. It's also why you can get crazy wheel travel out of beamed trucks.

If you set up the shock length correctly, you can get great articulation AND travel out of an outboard setup, but just OK travel and good articulation out of an inboard setup. Same with bump pad placement.

 

I disagree, but it probably depends on which leaf springs you have. 'A' will still be shorter as the leaf spring bind will prevent the axle from even getting to the same point. I.E. measured right at the leaf spring.

My limit straps are tight as could be at full vertical droop, but have over an inch to go at full flex with a tire off the ground.