CAT scale results

[Jon A]

Now only 25% for Ford!!!???? Lol That is crazy!!!! Just can't keep up with what is the "correct way". Or is it the manufactures haven't decided what is best yet???

 

 

I think everytime they do testing it just reinforces the reality that WDH's just aren't what they've been cracked up to be historically. I'm guesing Ford found their even lighter back end caused the new F-150's to be even more sensitive--transferring much weight at all causes the rig to be less safe. At 25% you're pretty much just using the WDH as a big anti-sway device (if it incorporates that feature) which is worth it for a lot of setups.

[ember1205]

 

And FAR too many people with little understanding of vehicle dynamics spread this mis-information. They’re no more “crutches” than your rear leaf springs are. They are springs. Stiff springs are appropriate for heavy loads, soft springs are best suited to light loads.

 

GM picks a compromised rate to do an adequate job during both loaded and unloaded conditions knowing full well they’re optimum for neither. If tuning the truck specifically for heavy loads, they would use much heavier rear springs—as they do in the HDs and big trucks. It’s not rocket science, just basic suspension design.

 

When you pick a spring rate for a suspension, you do it based upon the sprung mass and desired ride characteristics as your main inputs. When the sprung mass is doubled, the required spring rate needed to maintain a similar ride is also doubled.

 

Airbags add spring rate almost exactly as if you swap your leaf springs for a much heavier duty set when towing or hauling something. They’re just much easier to “swap.” The only way to tune a suspension to be optimum when running max payload is to put in springs that would be about twice as stiff as you’d like when empty. Then the vehicle will then “ride like a truck.” HD buyers expect this and will tolerate it more readily than ½ ton buyers, many of whom will use the truck primarily as a commuter car. So companies generally put the softest springs they can get away with on those trucks.

 

 

 

That’s like saying adding a bunch of money to your bank account only “masks” the fact your bank account is empty. No, it FIXES the underlying problem. The primary problem caused by overloading a suspension is that the suspension no longer has enough spring rate as explained above. That’s what the bags can fix. Not crutch or bandaid, but FIX.

 

 

 

 

That’s pretty rare. In fact an amazingly small percentage of people towing with ½ tons use bags at all, much less misuse them so. Probably because they’re misinformed so often on those same boards that bags are some sort of crutch or last resort while a WDH actually “fixes” something, when the reality is much closer to the opposite. I’ll bet for every person you see doing that I can find 10 cranking on their WDH way too much actually making them less safe in many ways than the guy with just bags.

 

Of course nobody should be advocating using bags instead of a WDH any time using a WDH is appropriate. Using BOTH provides the best ride, handling and largest amount of safety one can possibly get. Neither used alone in such an application can “take the place of” the other because they do different things, both of which make the rig safer (as long as you don’t crank on the WDH too much).

 

And for some uses a WDH is of no help—hauling something heavy in the bed, towing over rough terrain offroad, etc, in which case you’ll be damn glad you have the bags.

 

Sorry to tell you this, but a LOT of people use them incorrectly. They inflate them to a certain level and use them to stop the rear suspension from compressing all the way. Period. I see it on ALL of the forums that I belong to. Just because you've changed the spring rate, you don't get to carry more weight on the axle, yet that's what people think they can now do. I see people using them to prevent "squat" and carry 1500 lbs and up in the bed of the truck while also toting along four people and a bunch of other stuff. It isn't just those that are towing that use them in an unsafe way.

 

I would argue that I see far more people saying they have them in their half ton than in all larger trucks combined. In fact, the lower payload rating on the half ton is exactly why they're using them instead of being able to carry the weight by having a heavier duty axle and more suspension between it and the bed.

 

I agree with you that you should use a WDH when it's appropriate, but I would suggest that the issue with a WDH is less proper setup and more incorrect capability. I see a lot of stuff out there that's fairly "purpose built" (meaning that it's really only good for one or two specific amounts of weight tranfer). The ones that have a lot of variability to how much weight they can transfer are quite a bit more costly and too many people that really need a WDH won't spend the money for a quality one.

[Jon A]

 

Sorry to tell you this, but a LOT of people use them incorrectly.

 

That's what you think because you don't really understand how a suspension works.

 

 

 

They inflate them to a certain level and use them to stop the rear suspension from compressing all the way. Period. I see it on ALL of the forums that I belong to.

 

 

Do you mean statically? You think the suspension should be compressed all the way statically? I can assure you, you do not want that. Or do you mean bottoming out over bumps? Unless a bump is really severe, you don't want that either.

 

When do you think the suspension should be "compressed all the way" and why do you think this is a good thing?

 

 

 

Just because you've changed the spring rate, you don't get to carry more weight on the axle, yet that's what people think they can now do.

 

Better inform GM, because that's exactly what they did with the NHT. Of course if you're talking about changing the number on the sticker, nothing you do after purchase can do that, whether it's aftermarket or replacing parts with genuine GM NHT parts.

 

As far as actual capability and safety in the real world, yes, making the rear suspension able to carry more weight is exactly what you've done--or put in a way that's more correct when staying under the limits, it'll carry it's max capacity more easily while handling better and being safer. I guess those are bad things?

 

 

 

I see people using them to prevent "squat" and carry 1500 lbs and up in the bed of the truck while also toting along four people and a bunch of other stuff. It isn't just those that are towing that use them in an unsafe way.

 

The load you describe may actually be within the GVWR of some NHT's, or at least very close. Please explain why you think it would be safer with the truck "squatted" onto its bumpstops, with very little compression travel left, completely bottoming the suspension over the slightest bumps, bouncing up and down uncontrollably due to a spring rate much too soft for that much mass resulting in amplitudes that exceed available suspension travel.....

 

VS. driving along in a well controlled manor with a higher spring rate suited to controlling the added mass, with the full range of suspension travel still available and soaking up bumps nearly as well as the unloaded truck?

 

The later is safer in every measureable way and very noticeably so if you actually tried both setups.

 

No, simply "leveling" the rear with airbags after loading does not guarantee you will end up with the perfect spring rate for optimum handling for that load. You may end up with a little to much or too little. It depends upon your ride height, how much air was in the bags when empty, etc.... But for most reasonable setups you're going to be "in the ballpark" if that's what you do which is why so many OEMs do exactly that--it's not a bad way to do it.

 

RAM is the only OEM currently doing it for their pickups, but that's basically how they have all three types (1500 air only, 2500 air only, 3500 air supplement) set up to perform--maintain ride height. In fact, their softer-leaf supplemented by bags 3500 suspension looks almost like a carbon copy of mine. Only on a HD scale, of course....

 

For these trucks, with the typical Firestone/AirLift bags used, hitching up a trailer with 800-1000 lbs tongue weight will require 30-50 psi increase in pressure from the bags to maintain the same ride height (again, depending upon what the empty ride height was and how much air the bags had in them to begin with). In my experience, that's about exactly how much you want to add. It provides a solid ride, sure handling, no bounce or porpoising, still allows use of full suspension travel so it soaks up bumps giving a much better ride than bouncing off the bumpstops....

 

In other words, when used the way you describe as "incorrectly," is, in fact, a perfectly good way to use them unless your setup is unreasonable from the start. You only think it's incorrect because you haven't tried it and don't understand how things work well enough to predict results. I recommend you try some. Actual experience will completely change your mind.

[EastCoast HD]

Update...

 

Finally had the opportunity to weigh the TT tongue using a Shurline scale.

 

The TT cargo weight is unchanged from the CAT scale weigh on 9/26.

 

The scale shows a weight of around 925 lbs.

 

 

 

Add 85 lbs. for the WDH, for a total TW of 1010 lbs.

 

There is a 70 lb. discrepancy compared to the previous CAT scale TW of 1080 lbs.

I believe some part of the difference can be attributed to pitch of the trailer when scaled.

 

When scaled using the Shurline, the trailer was perfectly level. Compared to when CAT scaled the TT tongue was lower due to the sag of the TV, resulting in a forward shift of TT weight.

 

So using this new TW of 1010 lbs. and previous CAT scale weights....

 

TV 5820 + TW 1010 = 6830 lbs.

 

GVWR 7200 - 6830 = 370 lbs.

 

370 - 240 (wife, kid, dog) = 130 lbs. available payload.