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

[luthj]

I don't think 3.0s are necessary with a 1:1 ratio/solid axle, the 2.5s should get all the force you need. The only benefit of the 3.0s would be better cooling in that case.

As far as travel, I would consider limiting the front to ~10". Especially with a softer rate. Too much travel can actually cause handling issues on road, and even rollover danger.

Which is probably why the 250/350 have such stiff springs. They are trying to improve road safety, as these trucks have a significant rollover risk, especially with service bodies or the overloaded campers folks use.

Spring wise, are the ford springs an odd shape? Its been a while, but custom coils are not prohibitively expensive, and you could get exactly the length and rate you need. Thats one of the main benefits of converting the rear to coils, you can tune the spring rate without the expense of new leaf packs, and height can be set with spacers or adjustable buckets.

 

[Metcalf]

I have 2.5s on my much lighter truck. I wouldn't want less on an F-350.

Good data point. What kind of application are we talking about?

 

[luthj]

I am running 2.0 with external resi/adjuster on my rear axle. Axle is semi-float, weighs about 400lbs. Wheel/tire combo is about 70lbs each, total rear weight is about 5,000lb currently. The 2.0s do a good job, and have plenty of reserve damping. Fade is minimal even after 45 minutes on the washboard.

2.5s are necessary on the front of shade's tacoma due to the motion ratio of the IFS. Given you will be 1:1 with the solid axle, you should be well within the normal tuning profile at 350lb per in. You could call up accutune and ask if thats something they would recommend for the 2.5s.

2.5" units have ~60% more piston area than 2.0s, though in practice it may be more effective area due to shaft sizing.

I am currently building an IFS setup for my van, 4,000lb max front weight. Motion ratio of 1.6:1, 8.5" travel, unsprung weight in the 250lb range. I settled on a 700lb/in spring with several inches of preload, and 2.5 shocks.

 

[shade]

Good data point. What kind of application are we talking about?

2012 Tacoma Double Cab, Short Bed
Front - Extended travel Fox 2.5 with remotes, Wheeler's SuperBumps (foam bumpstops)
Rear - Fox 2.0 piggybacks, with OME rear springs (top overload removed), Timbren SES bumpstops
Smallish tyres - 265/75-16 Cooper S/T Maxx

I have an aluminum plate bumper and winch with synthetic line up front, and about 500 lbs of GFC camper & Decked drawers in the bed. Full 1/4" aluminum skids & steel sliders. Adding the GFC introduced more constant load, and the rear could use some help now. I have a rear shock relocation kit I need to install so I can free up the rear, and I'm going to add a leaf to the springs for a little more support. I run the front shocks with about an inch of pre-load. Overall, the truck is only lifted 2 inches over stock, and that's as high as it'll ever be.

I find that the truck does everything I want off-road, without wallowing around on pavement. No rock crawling or hucking at Pismo, but it's handled trips to Canyonlands/Maze, bombed around Death Valley, etc. I also tow a heavy trailer with it around town for construction work. Based on that, I think we have similar use cases, albeit in different weight classes.

With a lighter truck, I think it may be easier to find the right compromise on the rear suspension. The weight range an F-350 can see varies much more than a puny Tacoma.

 

[shade]

I am currently building an IFS setup for my van, 4,000lb max front weight. Motion ratio of 1.6:1, 8.5" travel, unsprung weight in the 250lb range. I settled on a 700lb/in spring with several inches of preload, and 2.5 shocks.

I'd like to watch a dashcam video of the first time you put the new front end to the test. You'll be overjoyed.

 

[Metcalf]

I don't think 3.0s are necessary with a 1:1 ratio/solid axle, the 2.5s should get all the force you need. The only benefit of the 3.0s would be better cooling in that case.

As far as travel, I would consider limiting the front to ~10". Especially with a softer rate. Too much travel can actually cause handling issues on road, and even rollover danger.

Which is probably why the 250/350 have such stiff springs. They are trying to improve road safety, as these trucks have a significant rollover risk, especially with service bodies or the overloaded campers folks use.

Spring wise, are the ford springs an odd shape? Its been a while, but custom coils are not prohibitively expensive, and you could get exactly the length and rate you need. Thats one of the main benefits of converting the rear to coils, you can tune the spring rate without the expense of new leaf packs, and height can be set with spacers or adjustable buckets.

I do think 3.0s would border on overkill.....but......you never know till you try. I'm also really curious about a 3.0 internal bypass. The piston is a 2.5, but you can start to get into truly posiition sensitive valving. When you are trying to make something ride really soft/supple on on the road but still have great bottoming resistance without having to use shaft speed to increase velocity based valving....well, it just makes me wonder. External bypass stuff seems like it has too many downsides ( noise, packaging, tube position, etc )

The 2.5 with the DSC adjuster is probably the best all-around solution.

Packaging over a 9" travel shock doesn't really seem practical at low lift heights. The Carli 3.0 stuff even requires a new front upper mount to do that.

Custom front springs are on the table for sure. The stock coils are fairly normal. The bottom has a reduced ID pigtail that fits in a little bucket device which bolts to the inner knuckle on the axle. I've been looking at the possibility of using an off the shelf 3.75" ID coils in some kind of custom top and bottom cup. Eibach has a decent amount of new coils in that size which seem like they would be pretty close to what I need for rate/length.

The 05+ ford seems really roll resistant in the front end honestly. The radius arms provide some built-in bind for roll resistance. The stock front sway bar is also very small. I think it would be pretty easy to decrease spring rate to increase ride quality and increase the diameter for the sway bar to deal with any increase in roll resistance. The rear end doesn't have a sway bar in my application at all, though I think one was offered in some packages.

 

[nitro_rat]

This F350 is stiff. I posted the spring rate table and measurements a few posts pack. ~400lbs/in seems very excessive to me. The front weight on the scale was 3720. Front axle is about 750lbs. Tire/wheel combo is probably 100lbs each corner. That is roughly 2770lbs sprung weight. 1385 per corner. I think the front suspension has about an 8 inch travel shock with 4" of uptravel. That would be a maximum spring rate of 350lbs/in with zero preload....less with a little bit more preload.

I'd like to try less spring rate and much much more shock diameter. Adding 1-1.5" of front uptravel would also be nice to help level things. Packing a 9" travel front lock with the stock bump-stop position looks possible without a complete rework.

I don't think we are looking for the same thing. This won't be just a 'street' truck at all.....

Good shocks are good shocks. Yes, they are expensive. I'm sorry, but an off the shelf generic ( digressive ) valved Bilstien isn't really in the same ballpark. If they work for you that is great. I know from my past builds, and how I use my vehicles, that a 2.0 resi isn't enough shock for this weight vehicle. I want more. Yes, it will cost more, I am accepting that.

I wrote a long reply but I deleted it, I'll just say this: The direct fit Bilstein RR's have vehicle specific valving.

I'll agree that our needs are probably different.

I will add that I generally don't run sway bars on solid axle trucks. I prefer to get roll resistance from a stiffer spring. A front sway bar induces under steer and a rear sway bar helps combat the increased understeer created by the front bar. If you ditch the bars and keep the spring rate a little higher you will have increased turn in performance with negligible body sway compared to the soft spring/sway bar approach. JMO, YMMV...

 

[mk216v]

Defenders have been going everywhere, and been a staple of overlanding for a while.

They ain't got jack for suspension travel and flex.

Rovers typically have longer coil springs to make up for the lack of articulation. Would like to see the same on G-Wagen's, but hasn't happened.

Mine is 08 V10.

Nobody makes a coil for the gas trucks. You could go to an oem spring for a diesel with a snow plow pkg maybe? Or just go big for the backcountry 3.0 system and have legit coilovers. Paying for custom springs is dumb, there are options out there.

I'm building a winch bumper that will offset some of the weight difference for the front springs; and going from mini leaf packs to full packs with long travel bags. Its choppy, especially with an empty trailer. I'm just going to have to bite the bullet on the rear end stuff.

Mine has the carli trackbar and PMF arms. It's more hardcore than I would have done but it was already on the truck when I bought it used.

Sent from my SM-G955U using Tapatalk

FYI, Carli will soon for the '17-20 F-Super Duty, once the '20 7.3L makes it into their shop, they'll begin R&D on both the 6.2L and 7.3L NA V8's.
Pintop King 2.5" setup; https://carlisuspension.com/product...17/ford-leveling-diesel-pintop-2-5-system-17/

I'll be following GooseGear's setup (incl 37s) on my '19 F350 cab-chassis; https://expeditionportal.com/featured-vehicle-goose-gears-overland-f-350/
Really impressed with that articulation.

And custom Deaver full leaf packs vs mini packs!

 

[RAM5500 CAMPERTHING]

I come from a racing background... Lots of internet chatter about shock size, etc... A lot of it bogus hearsay

General rule of thumb to determine if you have proper shock size, or need bigger (any older experienced race shock tuner will agree):

Drive 10 miles or so down a washboard at speed you're comfortable with park, jump out, wrap your hand around the shock...

If you burn yourself, your oil is getting too hot and not doing its job and you need a bigger shock.

It really is that simple

 

[nater]

Im not an expert, but I trust guys who are... for my ram 2500 - I've been told 2.5s. The move to 3 inch shocks would push me into trusing my axle to see the benefit.

 

[shade]

I come from a racing background... Lots of internet chatter about shock size, etc... A lot of it bogus hearsay

General rule of thumb to determine if you have proper shock size, or need bigger (any older experienced race shock tuner will agree):

Drive 10 miles or so down a washboard at speed you're comfortable with park, jump out, wrap your hand around the shock...

If you burn yourself, your oil is getting too hot and not doing its job and you need a bigger shock.

It really is that simple

?

That's pretty much how I ended up with what I've got now. Hole in the Rock Road is not kind to OEM shocks.

Otoh, that rule of thumb may not work so well unless you like collecting inferior shocks with 10 miles or so on them.

 

[RAM5500 CAMPERTHING]

?

That's pretty much how I ended up with what I've got now. Hole in the Rock Road is not kind to OEM shocks.

Otoh, that rule of thumb may not work so well unless you like collecting inferior shocks with 10 miles or so on them.

Well... my comment was somewhat in jest...

All these manufactures selling small inferior shocks for big heavy trucks with big claims. I'm giving a pretty foolproof way to tell that its BS

 

[Metcalf]

I wrote a long reply but I deleted it, I'll just say this: The direct fit Bilstein RR's have vehicle specific valving.

I'll agree that our needs are probably different.

I will add that I generally don't run sway bars on solid axle trucks. I prefer to get roll resistance from a stiffer spring. A front sway bar induces under steer and a rear sway bar helps combat the increased understeer created by the front bar. If you ditch the bars and keep the spring rate a little higher you will have increased turn in performance with negligible body sway compared to the soft spring/sway bar approach. JMO, YMMV...

Yeah, which vehicle do they make those shocks for? Is it the loaded down one, the quad cab, the long bed, the one with the camper, or ??? There are about 6 different OEM spring rates from the front of the 05+ F250/350 with a 150# difference in available spring rate. I don't buy into the off the shelf shock having specific valving. Personally, I don't love the digressive valving in most bilstein shocks. Seems to firm at slow shaft speeds and then you blow through the valving on the upper shaft speeds.

We are probably just going to have to agree to disagree.

 

[RAM5500 CAMPERTHING]

I don't buy into the off the shelf shock having specific valving.

Agree 110%, it’s literally impossible..

All a bunch of marketing BS

 

[rnArmy]

Or you can go low-budget.

Skyjacker 2" taller springs up front, a 2" long-leaf add-a-leaf in the rear, and Bilstein 5100 series shocks all around. Extended bump stops in the front, and Timbren bump-stops in the rear. Figure a couple hundred dollars total for all the suspension stuff, which leaves me more money for other cool stuff.