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

[Metcalf]

Softer and taller. But OEM's are limited by weak shocks and safety regs. You're better off with 4" coils from BDS, Carli, etc.

Coil swaps are free unless you ding up the coils. But the coils are still cheap. Keep in mind that a 4" spring only nets you 2" more travel. So the travel that a coil over ford setup loses, likely is harmless in the 4" range. I'm sticking to shocks and coils in the OEM spots. I can get good enough there. But many are running 2.5 coil overs, and another 3.0 bypass shock in the OEM location up front. And 3.0 bypass shocks in the rear.

I am only looking for about 1-1.5" of lift in front generally. I don't want to cascade all the geometry for everything too far out of wack. I would like to add an inch or two of shock travel. Getting a 9" travel front shock packaged where I could still have all the factory uptravel ( without having to lower the bumpstops ) would be good. Basically retaining, and even add an inch or so, of uptravel from ride height.

As I mentioned earlier, there are not a lot of coils on the market for gas trucks with low lift and what I would call proper spring rates and preload at droop. That is one of the main issues right now and why I have been looking into custom coils or even using the Eibach 3.75ID coils.

 

[mk216v]

Good stuff, an excellent data point from the opposite side of things. I have a few questions.

-Do you hear your bypass shocks?

-Did you try anything in-between getting to this point? One thing I can't find a decent description of is the various differences ( or even rules of thumb ) for when you need more shock diameter. I'm pretty sure I can rule out a 2.0 shock for what I want to do with this truck off-road, it is just too heavy. Some people say you can do a LOT with a proper valved 2.5 shock in a full size. I definitely remember seeing the first KORE and Carli stuff with 2.5s and being amazed. The tipping point in a few areas seems to be between a 2.5 and 3.0 shock as far as packaging, investment, some areas of ride quality, etc. Then throw in the difference between velocity sensitive shocks and position sensitive shocks.....yikes!

Same question here for 2.5" vs 3" dampers. What's a good vehicle weight rule-of-thumb, also taking into account different driving scenarios (I won't be doo-wooping mine thru Glamis Dunes)?

 

[luthj]

Unsprung weight is also important. A big part of the heat loading of a shock is from damping the movement of the axle. Heavier axle/tires, more heat.

 

[mk216v]

Unsprung weight is also important. A big part of the heat loading of a shock is from damping the movement of the axle. Heavier axle/tires, more heat.

Agreed!
Heavier EVERYTHING!(bumpers, winches, wheels, tires, recovery gear, fuel, water, cabin, etc etc etc)
"Simplify, then add lightness..."

 

[luthj]

I have seen dirt rigs running 5,000lb on an axle with 2.0 external resi units. They had no heat issues with reasonable speeds, and a light axle/tire combo. If you went full floating, 11.5" R&P 37" tires, etc, 2.5" would be required. Damping 900lbs of axle and tire is a tough act for any small shock. Even if they can make the force needed, the heat buildup in heavy use can blow seals.

4" is complete overkill for anything but straight up desert racing in extreme weather.

 

[madakira]

Good stuff, an excellent data point from the opposite side of things. I have a few questions.

-Do you hear your bypass shocks?

-Did you try anything in-between getting to this point? One thing I can't find a decent description of is the various differences ( or even rules of thumb ) for when you need more shock diameter. I'm pretty sure I can rule out a 2.0 shock for what I want to do with this truck off-road, it is just too heavy. Some people say you can do a LOT with a proper valved 2.5 shock in a full size. I definitely remember seeing the first KORE and Carli stuff with 2.5s and being amazed. The tipping point in a few areas seems to be between a 2.5 and 3.0 shock as far as packaging, investment, some areas of ride quality, etc. Then throw in the difference between velocity sensitive shocks and position sensitive shocks.....yikes!

I do not hear my bypass shocks at all.


Prior to this build, I had an 04.5 Cummins and I was running King 2.5's in the front and 2.5 double bypass in the rear. I was able to push that truck close to 100mph in the desert and sand dunes. 2.5's properly valved will let you do almost anything your driving ability is capable of. Unless you are pushing over 600hp and desert running, 2.5's will be more than enough.

With proper valving and tuning, a 4.0 should ride just as smooth as a 2.5 daily driving.

You can also think about getting some hoops built for the front end. You would be able to run coil overs, more travel, and minimum lift.

 

[madakira]

Same question here for 2.5" vs 3" dampers. What's a good vehicle weight rule-of-thumb, also taking into account different driving scenarios (I won't be doo-wooping mine thru Glamis Dunes)?

I feel like if you are not hitting high speed stuff, 2.5's will be more than enough. I ran 2.5's on an 04.5 Cummins, and I was eating up everything. I am working on a full size crawler/overland/desert type build and am probably going to run 3.0 coilovers all around, just in case I want to hit some high speed stuff every now and then.

 

[mk216v]

I feel like if you are not hitting high speed stuff, 2.5's will be more than enough. I ran 2.5's on an 04.5 Cummins, and I was eating up everything. I am working on a full size crawler/overland/desert type build and am probably going to run 3.0 coilovers all around, just in case I want to hit some high speed stuff every now and then.

Thx much, appreciate your experience! My build will be under 10k wet, no high speed desert.

 

[b9ev]

I went from stock to bilstein 5100s to Fox 2.0 IFP to my current Fox 2.5s. There was a very noticeable difference between each shock. I wanted to see what the stock valving was like before having anyone tune them. So far I have been impressed and they have 5 to 10k miles on them. When it is time to rebuild them, I will put the old IFPs on it and send the 2.5s to Accutune.

 

[Buliwyf]

I was told that ''mostly the 3.0's are about the same as the 2.5's, but with a thicker stronger shaft for more extreme uses''. Since the shaft is larger, the piston isn't exactly 0.5" more effective. The extra strength is great for coil overs, but regular suspension, on a regular truck, 2.5's are fine. 3.5" is the next huge jump in performance from 2.5's.

Really overthinking this. Toss Accutunes Stage 3 on:

17-19 Superduty Leveling Kit, Stage 3A - Fox - AccuTune Off-Road

This complete kit features everything necessary to level your Superduty up to 2.5" and provides the ultimate on-road and off-road ride. -Front Shocks: Fox 2.5 DSC -Front Coil Springs: 2.5" Lift, Progressive Rate -Front Track Bar: Adjustable, with FK Rod End -Rear Shocks: Fox 2.5 DSC -Front...

accutuneoffroad.com

A set of Deavers, and whatever you want for rear helpers. Bags and cups. Sumo rebel. Maybe the simple Sumo or Timbren bumpstop replacememts.

 

[Metcalf]

I was told that ''mostly the 3.0's are about the same as the 2.5's, but with a thicker stronger shaft for more extreme uses''. Since the shaft is larger, the piston isn't exactly 0.5" more effective. The extra strength is great for coil overs, but regular suspension, on a regular truck, 2.5's are fine. 3.5" is the next huge jump in performance from 2.5's.

Really overthinking this. Toss Accutunes Stage 3 on:

17-19 Superduty Leveling Kit, Stage 3A - Fox - AccuTune Off-Road

This complete kit features everything necessary to level your Superduty up to 2.5" and provides the ultimate on-road and off-road ride. -Front Shocks: Fox 2.5 DSC -Front Coil Springs: 2.5" Lift, Progressive Rate -Front Track Bar: Adjustable, with FK Rod End -Rear Shocks: Fox 2.5 DSC -Front...

accutuneoffroad.com

A set of Deavers, and whatever you want for rear helpers. Bags and cups. Sumo rebel. Maybe the simple Sumo or Timbren bumpstop replacememts.

There is more to shock diameter than just saying .5" bigger since it's area based. The shock shaft takes up a little area, but it is on small side. It is also only on one side of the piston? Just going off OD because I don't want to hunt down piston IDs.....2.0 is 3.14, 2.5 is 4.9 square inches, 3.0 is about 7 square inches, 3.5 is a 9.6ish. I think those are all big jumps.

As I mentioned before, I don't want a 3" front spring, nor do I want one designed for a heavy diesel truck which will give even more lift.
From what I can find, the difference between a gas/diesel for lift is almost 1.5" by itself.

I also mentioned some of the issues with drop out bags earlier. They just don't seem to have a good durability record when used at high speeds. The sumo system are pretty much extra progressive springs. That has consequences on the rebound side of things just like overload springs do.

I like thinking and learning. I don't want an off the shelf universal solution.

 

[Metcalf]

I do not hear my bypass shocks at all.


Prior to this build, I had an 04.5 Cummins and I was running King 2.5's in the front and 2.5 double bypass in the rear. I was able to push that truck close to 100mph in the desert and sand dunes. 2.5's properly valved will let you do almost anything your driving ability is capable of. Unless you are pushing over 600hp and desert running, 2.5's will be more than enough.

With proper valving and tuning, a 4.0 should ride just as smooth as a 2.5 daily driving.

You can also think about getting some hoops built for the front end. You would be able to run coil overs, more travel, and minimum lift.

That is good to hear on the bypasses. I have definitely heard the opposite a few times. Most of the experience I have in bypass cars they where too noisy to hear anything much at all over the engine, tires, etc.

I do think there is a point of diminishing returns for shocks on the daily side of things. The break away friction on larger shocks and shaft sizes seems to go up, this can start to account for a significant amount of low speed valving. Maybe too much at some point?

I'm not really interested in going to a full hoop type replacement system. I think a good middle ground might be the Carli Spring/shock tower that lets you fit a 3.0 on the front end that is a few inches longer. I found a few off the shelf 2.5 Fox eye-eye shocks with the DSC option that look pretty close. Once you get into the 3.0 stuff the choices get pretty slim. I'm pretty curious about finding a 3.0 internal bypass that might work too...only a 2.5 piston, but adding quiet position sensative valving could be a really nice upgrade.

 

[Buliwyf]

You can have them put in a plastic bypass check valve if the ticking bothers you.

Accutune has gas springs, that was just a leveling spring.

 

[Metcalf]

Same question here for 2.5" vs 3" dampers. What's a good vehicle weight rule-of-thumb, also taking into account different driving scenarios (I won't be doo-wooping mine thru Glamis Dunes)?

Depending on the weight of the vehicle and the motion ratio, I have heard that a 2.0 resi shock will be good for about 5-10 minutes of 'spirited' driving where you are going just fast enough not to blow through the compression valving before temps get to the point the oil and seals are an issue. I have a 2.0 fox aluminum body resi on my LX45 project done my Accutune with their 'trail' valving. I have been nothing but impressed. I can push it harder than most on trail and stay out front, but I can drive through the compression valving, there is a limit. I could still add more compression valving, but at a cost for the low end side of things.

 

[Metcalf]

You can have them put in a plastic bypass check valve if the ticking bothers you.

Accutune has gas springs, that was just a leveling spring.

The spring Accutune is offering is the Icon dual rate unit. It is listed as a gas AND diesel spring. All the measurements I can find say it lifts the front over 3" when used in a gas application. I don't want that much lift. I have looked through pretty much all the springs on the market I can find for the 05+ trucks. Same problem. That is why I started looking into custom or other options.