Ski Bum Truck V2.0, F450 Rough Road RV

java

Expedition Leader
Fantastic weekend playing in the snow.

Headed up, just starting to snow
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Getting better
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Parked! Right at the top of the ridge.
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It started dumping!
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Pretty spot.
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A couple wheelers went by in the morning
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Forecast was calling for up to another 12", we decided to bail out to a bit lower elevation. Glad we did, got another few inches, and it was about half the snow where we stopped as up above.

My temp sensor location failed..... Reads way warm!
 

java

Expedition Leader
Thinking about bags vs coils again.... Frustrated by this stupid thing. Worried I am stressing the frame a lot rather than the suspension moving enough.

I was just looking at the bag data again, It shows 5.4" tall at bump stop contact if I am reading correct. If I am only running the bags at 8" tall that is not much movement. (and corresponds to the zip tie test IIRC).

Maybe I'm better trying to find a coil that will allow a bit more movement.... UGH. Not sure I even want to try pink tanks.

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luthj

Engineer In Residence
You will get about 5" or so minimum height, as the internal bumpstop will compress some. You want at least 3" of travel in both directions. More is better but your bags are only good for 12.5 to 5.4", or about 7" of travel. So 3" in compression is reasonable.

I do not know if coils would be any better. Depending on length, spring rate, diameter, you could get some coils that may allow as much as 10" total travel. Obviously compression is limited by your ride height.
 

java

Expedition Leader
You will get about 5" or so minimum height, as the internal bumpstop will compress some. You want at least 3" of travel in both directions. More is better but your bags are only good for 12.5 to 5.4", or about 7" of travel. So 3" in compression is reasonable.

I do not know if coils would be any better. Depending on length, spring rate, diameter, you could get some coils that may allow as much as 10" total travel. Obviously compression is limited by your ride height.

Yes I just don't know either.... That is the hard part. The bags were supposed to be "better" but they feel nearly identical to the stock springs to by butt.

No one publishes spring info that I can easily find for "leveling springs" but I need 1.5" ish lift and ~500lb spring rates from our conversations. Roughly 6" diameter.
 

luthj

Engineer In Residence
Any good performance shop should be able to measure and weight you for coils, and order a custom (or if you are lucky, off the shelf) set of springs.

I can't say they would make any improvement though, not from this side of the internet.
 
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java

Expedition Leader
Any good performance shop should be able to measure and weight you for coils, and order a custom (or if you are lucky, off the shelf) set of springs.

I can't say they would make and improvement though, not from this side of the internet.
Yeah it's an option to explore later still I think.... Ping tanks first

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Chorky

Observer
is it a rough rid, or do you actually think your fully compressing/extending the suspension? Shocks do wonders, can't remember what shocks you are running though. Part of me wants to say that no matter what a heavy truck will always ride somewhat rough. Case in point I have lighter springs in my truck, and more travel than stock. Though not the best shocks, and shocks would make a big difference, it still rides 'rougher' than I would like.
 

java

Expedition Leader
is it a rough rid, or do you actually think your fully compressing/extending the suspension? Shocks do wonders, can't remember what shocks you are running though. Part of me wants to say that no matter what a heavy truck will always ride somewhat rough. Case in point I have lighter springs in my truck, and more travel than stock. Though not the best shocks, and shocks would make a big difference, it still rides 'rougher' than I would like.
I just bought 2.5" external resi adjustable Fox shocks that are supposed to be valved to My axle weights.... Not inexpensive! And.... Feels the same as the 5100's

I feel like it bends right behind the cab, and it's harsh.... Think expansion joints in the freeway are harsh.

@luthj I have thought about that. But still worry about beating the truck to death.

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luthj

Engineer In Residence
The air bags have some damping on they're own, you could try experiment with removing the shocks for a short test.
 

java

Expedition Leader
The air bags have some damping on they're own, you could try experiment with removing the shocks for a short test.
I've thought about it. I'm going to try to quickly rig up the ping tanks first.... I got plugs so I can plug the fittings if needed. Just zip tie tanks to the bumper. Think 1 gal is enough tank size?

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Chorky

Observer
I just bought 2.5" external resi adjustable Fox shocks that are supposed to be valved to My axle weights.... Not inexpensive! And.... Feels the same as the 5100's

I feel like it bends right behind the cab, and it's harsh.... Think expansion joints in the freeway are harsh.

@luthj I have thought about that. But still worry about beating the truck to death.

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Yeah fox isn't cheap. I know when they went on my jeep, it was a stunning difference! I guess my question regarding it would be, or rather argument, might be that having a big heavy truck ride like a cadi is a tall order. Now, granted my truck rides smoother than my dad's brand new 3500.... I have 1500's on my truck and they're ok for long slow suspension travel movements, but not the short quick jolts, like what you are also having trouble with. I would be willing to bet though that the external adjusters, though helpeful, are not fully what is needed? Do you know if the actual valves have been built accordingly or is it just the external res? I think the adjustments on the res is different than the actual valves, or so that's how fox explained it to me with my jeep. I have the 2.0's with external adjustable res.

I would think that having longer travel wouldn't help with the harshness, since thats only a inch or two worht of travel considering the roads your talking about. And yes, those expansion joints suck bad!!!! You need the valves to be super fast to respond at the short end of quick movements, but slow to respond once movement extends past, oh.... 0.75' of travel (well...maybe 1.5' considering how bad I5 and 405 is getting....). I know they can valve them any way you choose within reason. maybe they just valved them for overall weight, and didn't customize them considering use and speed of response?

Also, is your res a single or dual adjuster? They have ones that adjust the high speed, and slow speed movements - or so they used to anyway.

One thing to also note, is that when I did my trucks suspension, I specifically got springs that are lighter weight than the truck itself. So 250 springs for a 350. The fronts are now only 2 leafs instead of 3, and the rears, not exactly sure off the top of my head. anyway, point is that the spring rate is slightly lower than the truck is speced for. So it allows for more, smoother, and quicker movement of the springs, although it also causes the truck to sit lower than it would with the right weight. but, it's the only way I have found around that problem. I personally want to get fox shocks soon as well, with custom weighted springs once final weights are known. But in the end, though it might be better, its still going to be rough to some extent.

I would think that in your case, you will be looking for springs that have a slightly lower compression rate, higher rebound rate, valving with a quick high speed response, and somewhat slower low speed response will do the trick. Now, with bags on, thats a whole different ball game. Also, consider active bump stops. that could help a ton as well, but pricy. Hope that all makes sense as I try to eat dinner haha.
 

java

Expedition Leader
Yeah fox isn't cheap. I know when they went on my jeep, it was a stunning difference! I guess my question regarding it would be, or rather argument, might be that having a big heavy truck ride like a cadi is a tall order. Now, granted my truck rides smoother than my dad's brand new 3500.... I have 1500's on my truck and they're ok for long slow suspension travel movements, but not the short quick jolts, like what you are also having trouble with. I would be willing to bet though that the external adjusters, though helpeful, are not fully what is needed? Do you know if the actual valves have been built accordingly or is it just the external res? I think the adjustments on the res is different than the actual valves, or so that's how fox explained it to me with my jeep. I have the 2.0's with external adjustable res.

I would think that having longer travel wouldn't help with the harshness, since thats only a inch or two worht of travel considering the roads your talking about. And yes, those expansion joints suck bad!!!! You need the valves to be super fast to respond at the short end of quick movements, but slow to respond once movement extends past, oh.... 0.75' of travel (well...maybe 1.5' considering how bad I5 and 405 is getting....). I know they can valve them any way you choose within reason. maybe they just valved them for overall weight, and didn't customize them considering use and speed of response?

Also, is your res a single or dual adjuster? They have ones that adjust the high speed, and slow speed movements - or so they used to anyway.

One thing to also note, is that when I did my trucks suspension, I specifically got springs that are lighter weight than the truck itself. So 250 springs for a 350. The fronts are now only 2 leafs instead of 3, and the rears, not exactly sure off the top of my head. anyway, point is that the spring rate is slightly lower than the truck is speced for. So it allows for more, smoother, and quicker movement of the springs, although it also causes the truck to sit lower than it would with the right weight. but, it's the only way I have found around that problem. I personally want to get fox shocks soon as well, with custom weighted springs once final weights are known. But in the end, though it might be better, its still going to be rough to some extent.

I would think that in your case, you will be looking for springs that have a slightly lower compression rate, higher rebound rate, valving with a quick high speed response, and somewhat slower low speed response will do the trick. Now, with bags on, thats a whole different ball game. Also, consider active bump stops. that could help a ton as well, but pricy. Hope that all makes sense as I try to eat dinner haha.

Hi and low speed adjustment. I gave them my truck specs and axle weights etc, so hopefully they are well valved.

No real room for hydro bumps.

If your in Seattle lmk and you can drive it.

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Chorky

Observer
Also, food for thought, though it may not help or mean anything to you. From my understanding, a bag that is physically larger, meaning it has higher air reserve capacity, will operate smoother than a bag that is smaller with less air capacity, irregardless of its actual weight holding capability. Its like a small bore shock vs a large bore shock. not that you can really change that. I suppose my point being that, depeidning on the weight you are dealing with, the psi needed in the bag to support that weight, you possibly could be better off actually with just high quality coils. I would see about comparing spring rates between bags and springs with equal weight supporting capabilities. but a lower spring rate doesnt necessarily mean a better ride.
 

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