How good can a full-size solid axle suspension be?

[Superduty]

I am gonna revive this thread from the dead. Maybe it will come back to life.

I recently converted a 99 F350 to coils up front using an 08 axle. I used PMF buckets (wouldn't use those again - another conversation). I installed Carli 4.5 coils. The shock I have for it is a a Fox 980-06-101-1 with specs

Extended	29.370
Compressed	19.500
Travel	9.870

I am about 23..25" between the center of the shock mounting eyes at ride height. As installed it will give me 4 1/8" of compression and 5" of droop. According to Accutune this is not ideal. They suggest

Minimum Up travel suggestions (solid axle)
Rock Crawling = 4” Trail Riding = 5” Desert Racing / Ultra4 Type = 7”
We suggest dedicating 1/3 to 2/3 of shock travel for up travel, depending on application.


I am looking for advice on where to set my shock to get the best performance. The shock specs are 9.87 total travel, however the Fox shock has a rubber bumper on the shaft which is about 5/8" so there is about 9 1/8" total shaft showing when the shock is extended. I can move the bottom shock mount fairly easily and that is my plan.

There are currently no bump stops on the truck, so after figuring out the shock mounting point I would like to figure out the appropriate bump stop.

Hindsight being 20/20 I would have definitely gone with the Carli fabricated bucket to get a longer shock and then gone with a 12" shock. The only drawback I see of the Carli bucket is you have to hack up more of the inner fender liner. But it is probably worth it for the ability to run a longer shock and have extra travel (assuming the carli coils can make use of that extra travel, which I think it can).

@toddz69
@Metcalf

 

[Superduty]

For reference here is a photo of the PMF coil bucket. I even hacked up the shock mount portion to get the top mount about an inch higher. It appears to be still "far away" from where the Carli shock mount is.

 

[DzlToy]

9" of travel isn't much to work with on that truck, especially if you are going to use it off road, carry heavy loads or install larger-than-stock wheels/tires. Assuming you are stuck with what you have and cannot now install a 12" travel shock, I would consider something in the range of 5" - 5.5" of up-travel and 3.5" - 4" of droop. Bottoming your suspension is worse than carrying or lifting a tire, IMO. Get good bumps and straps to save your dampers.

 

[Superduty]

9" of travel isn't much to work with on that truck, especially if you are going to use it off road, carry heavy loads or install larger-than-stock wheels/tires. Assuming you are stuck with what you have and cannot now install a 12" travel shock, I would consider something in the range of 5" - 5.5" of up-travel and 3.5" - 4" of droop. Bottoming your suspension is worse than carrying or lifting a tire, IMO. Get good bumps and straps to save your dampers.

The Carli 4.5 pin top claims an 11" travel.
The Carli Dominator system claims 10.5 travel. (uses fabricated coil buckets)
The Carli Unchained system claims 10.5 travel. (uses fabricated coil buckets)

The shock I have is called a 10" travel shock by Fox. I am not sure if that means you create a suspension system with the actual amount of exposed shaft (9 1/8"). I wonder what length shock Carli uses. When they say 11" of travel is that the actual shock travel length? I am thinking that you can get more shock if you use the stem top mount vs the eye. I am not sure Fox makes a 12" travel stem top shock? (probably why Carli uses King for their "pin top").


At this point I am trying to make the most of what I have. I am not sure I want to invest the extra money and work involved to install the Carli coil buckets and be able to run the longer shock. Like I said, hindsight is 20/20, everyone raves about the PMF products, but I am not impressed with the shock mounting on their coil buckets.

 

[DzlToy]

"Travel" usually refers to the usable travel of the damper or shock, yes. In the rock crawling world, we measure what is called total wheel travel or articulation. Stuff your tire up into your fender as far as it will go and mark that point, top or bottom Then go to the other side of the truck and mark the top or bottom, as appropriate, of the tire there. The difference between the two is total wheel travel at the outside of the tire.

The location of the damper or shock on the axle will affect this number. In the desert racing world, for example, coil-over shocks are mounted "up" the trailing arm a fair distance, not atop the axle. Through leverage, this allows a 20" travel shock to create 25 or 30 or 32" of travel, for example. This is difficult to do on a stock or nearly stock pickup truck.

Carli pin top stuff is really nice. A friend had it on a 2018 F-250 and that truck rode like a cloud of tit*ies.

EDIT: These springs are for the solid (rear) axle of a 4Runner and are part of a long travel kit.

Metal Tech FJ Cruiser/4Runner Rear Long Travel Coil Springs Heavy

Check out Metal Tech 4x4—your home for high end off road parts and accessories, specializing in Toyota. Browse our selection of off road products today.

metaltech4x4.com

This progressive rate spring will give you a total of 27" of articulation when combined with our custom made FJ Cruiser/4Runner Icon 2.0 VS Series Shocks, FJ Cruiser Rear Extended Brake Lines, and Metal Tech 4x4 3" Bump Stop Drops Extensions.

It is important to have components that are designed to work well together, allow you to tune the suspension to ride the way that you want it to ride and to carry the loads required. In the example above, the shock does not have 27" of travel, but the outside edge of the tire does, as it swings in an arc.

 

[Metcalf]

There are currently no bump stops on the truck, so after figuring out the shock mounting point I would like to figure out the appropriate bump stop.

I would do this the other way. Set the bumpstop for the maximum amount uptravel your tire size and suspension will allow from ride height. Then package the shock around that compressed length. It would be nice to find at least 5" of uptravel from ride height.

On the spring side of things, you want to try and maintain at least some preload on the spring at full droop as far as the extended length of the shock.
Shocks don't make great bumpstops or limit straps. I would plan a touch of margin on compressed length and a limit strap on extension if you can.

That is pretty much the window you want to work in for shock length.

 

[Superduty]

@DzlToy I have never ridden in a Carli pin top system, but I have heard nothing but good things about it. I am using the same coil as the pin top and then the shocks were tuned by Accutune, so I am hoping in the end I get a similar ride / performance to the pin top.

 

[Superduty]

I would do this the other way. Set the bumpstop for the maximum amount uptravel your tire size and suspension will allow from ride height. Then package the shock around that compressed length. It would be nice to find at least 5" of uptravel from ride height.

On the spring side of things, you want to try and maintain at least some preload on the spring at full droop as far as the extended length of the shock.
Shocks don't make great bumpstops or limit straps. I would plan a touch of margin on compressed length and a limit strap on extension if you can.

That is pretty much the window you want to work in for shock length.

I think I am locked in for the moment to this shock. I would probably take too much of a hit if I try and sell them.

What is the recommended method to set the bumpstop for max up travel?

 

[Metcalf]

I think I am locked in for the moment to this shock. I would probably take too much of a hit if I try and sell them.

What is the recommended method to set the bumpstop for max up travel?

I like pulling the spring and shock and completely cycling the suspension both in vertical bump and articulation. After doing that a few times, you get a feel for it. Radius arms can make it a little harder if they are stiff. Sometimes pulling a bolt out of one of the axle mounts is worth it for mockup.

If you are locked in on the shocks, I would be looking at playing with the upper shock mount if needed.

If you can't change anything, than you just need to set the bumpstop to protect the shock from full compression hits.

 

[Superduty]

I asked someone with the Carli 4.5 pin top measure the exposed shaft on their truck. It was 4.95 inches. I guess you can get a longer shock when you do the stem at the top vs the eye, otherwise, I am not sure how they can fit in an 11" travel shock (or does King make a more compact shock compared to Fox).

 

[Superduty]

I like pulling the spring and shock and completely cycling the suspension both in vertical bump and articulation. After doing that a few times, you get a feel for it. Radius arms can make it a little harder if they are stiff. Sometimes pulling a bolt out of one of the axle mounts is worth it for mockup.

If you are locked in on the shocks, I would be looking at playing with the upper shock mount if needed.

If you can't change anything, than you just need to set the bumpstop to protect the shock from full compression hits.

I think it makes sense to move the mount(s) so that I have more compression. I could go to 5" of compression, which would leave me 4 1/8" of droop.

Any recommendations for bump stops to use? My main confusion with bump stops and setting them correctly is that apparently some compress more than others. How much they compress seems to be a critical part of setting them correctly. Finding the exact info of how much they compress seems difficult or impossible to find. Setting the bump stop wrong translates into not taking advantage of the full shock compression or potentially messing up the shock. I suppose these are the challenges of doing custom stuff on a truck.

 

[Metcalf]

I asked someone with the Carli 4.5 pin top measure the exposed shaft on their truck. It was 4.95 inches. I guess you can get a longer shock when you do the stem at the top vs the eye, otherwise, I am not sure how they can fit in an 11" travel shock (or does King make a more compact shock compared to Fox).

A lot of the King shocks for Carli have the welded lower eye. That saves about an inch of compressed length vs travel over the thread on version.

 

[DzlToy]

Call Carli and ask what they recommend. Baring that, call ADS, Fox, King, Reiger, or Radflo. You are in the long travel suspension capitol of the U.S., there in Southern California. Finding someone to help get this set up correctly should be relatively easy compared to other places in the country.

 

[Metcalf]

I think it makes sense to move the mount(s) so that I have more compression. I could go to 5" of compression, which would leave me 4 1/8" of droop.

Any recommendations for bump stops to use? My main confusion with bump stops and setting them correctly is that apparently some compress more than others. How much they compress seems to be a critical part of setting them correctly. Finding the exact info of how much they compress seems difficult or impossible to find. Setting the bump stop wrong translates into not taking advantage of the full shock compression or potentially messing up the shock. I suppose these are the challenges of doing custom stuff on a truck.

In order to protect very expensive things like shocks, I tend to set most suspensions metal to metal for max bump. If a poly, foam, or rubber bumpstop fails, it sucks to have all the force end up on the shock.

Another trick is to build in a shim adjustment into the mount for something like a modern foam bumpstop, either on the bump or pad side. Then you can use the shim to help dial back the compression on the foam stop till you are getting close to 100% shaft compression during hard hits.....but at the risk that a REALLY hard hit might compress the bumpstop even further.

 

[Superduty]

@Metcalf Do you have any particular bump stops that you would recommend? I could try and get an OEM Ford one to work. I have heard that they compress a lot, hard to believe as they seem to be very hard material.