Hitch for GMC 2500HD + GT30RB

[Profxd]

Originally Posted by BayouBiker

I'm with Larry, I have not seen much in the way of advice from the manufacturer on what is the correct Weight Distribution settings (he did not ask about weight limits). There is the occasional exception from Ford if I recall. My manual and door post labels do not provide guidance, nor does the trailer supplement.

You should check your owners manual it’s there.

[lsbrodsky]

Like I said, is a little picture of measuring the fender before and after then restoring the fender height to 1/2, in the owners' manual really a recommendation of something as precise as 50% FALR? If so, why can't you find anything in writing from the OEM that says 50% FALR?

Larry

[BayouBiker]

The only guidance I find in the provided manual is to consider use of WD and sway control for medium to heavy trailers, to set them up correctly, to refer to the hitch manufacturer and also an illustration that shows the vehicle and trailer perfectly level when set up correctly, Larry and I once again agree, nothing specific on FALR percentage.

[mefly2]

Since there is so much experience posted here, may I ask for an explanation of just how the airsafe hitch works with an equalizer hitch ... does the pre-tensioning of the load bars on the equalizer hitch affect the airsafe function ... al least in one vertical motion?

Thanks - your experience and explanation will help us decide whether to add an airsafe hitch to our TV / AS.

[ROBERT CROSS]

Originally Posted by steelbird312

Bob, I've read dozens of your posts and learned from many of them. I've also belittled the Airsafe UNTIL I talked a buddy into letting me drive his truck pulling the largest Airsteam(his)available. Woah! I never said things like that anymore.
Fact is, I now own an Airsafe wth a Reese, tied to a GMC 3500 SRW, CCLB with an upgraded receiver and pull a 31' Classic. I run my tires at pressures suggested by the tire manufacturers load rate charts, both on the tow vehicle and the trailer. The results: Lovely.
My wonderment is- have you ever taken a setup you thought was perfect and enjoyable- then added an Airsafe hitch into the mix?
If you do, I would bet you a donut, your sentiment would change.

Please keep your opinions ans solutions coming, I respect and utilize many of them!

I never said it didn't work...All I referenced, if you have a proper rig set up correctly it's not needed.

If the TV is suspended too stiffly you need it,👍

STIFF...a downside for the 'big' is better theory.

Bob
🇺🇸

[ROBERT CROSS]

Originally Posted by Profxd

Since 100% FALR is allowed in SAE j2807 testing if it was so much better for stability why don’t the vehicle manufacturers take advantage of it? Wouldn’t it raise the TWR?Why since the adoption of SAE j2807 has no manufacturer recommended 100% FALR?

Because the design of the vehicle can't handle it?

Bob
🇺🇸

[BayouBiker]

The AirSafe technically is a vibration damper at its core, conceptually the same as a spring, kink and shock absorber system. The four tie rods keep the ball mount stable and properly oriented so even with a WD hitch, load and tension is transmitted. They are the links. The Air bag supports and transmits the base loads and provides cushioning to absorb impulses (jarring bumps) and vibrations. It is the spring. Higher loads put more force on the air bag. The shock absorbers provide damping to dissipate the excess energy from the transient loads (impulses and vibrations).

So this is an effective way to isolate the trailer from the vehicle and visa versa. It is a sink for shocks and vibrations so it does not transmit through the vehicle or the trailer.

Since it does not affect base loads and torques it does not change WD and tongue torque at all.

[rp709]

The Propride is worth every penny. Why experience nervous moments in high winds or being pushed around by trucks? This isn’t where I would look to save 3K. You are buying the best trailer towed by the best truck. The Propride completes this elegant combination.

[wulfraat]

Originally Posted by rp709;

the propride is worth every penny. Why experience nervous moments in high winds or being pushed around by trucks? This isn’t where i would look to save 3k. You are buying the best trailer towed by the best truck. The propride completes this elegant combination.

^^^^^^ x2 [emoji4]

[Profxd]

Originally Posted by lsbrodsky

Like I said, is a little picture of measuring the fender before and after then restoring the fender height to 1/2, in the owners' manual really a recommendation of something as precise as 50% FALR? If so, why can't you find anything in writing from the OEM that says 50% FALR?

Larry

Not surprised! The average consumer cannot understand the simple concept of the weight ratings let alone FALR.

[BayouBiker]

In any case the full range of reasonable settings is 0-100%. 100% FALR retains equal weight on the front axle before and after the trailer is added. A fifth wheel and semi-tractor-trailer designs are the most stable and they retain equal weight. The Equalizer manual provides excellent guidance that the target range for most vehicles is between 50% and 100%. Of the target range, 100% provides the most sway control, best steering response, and best suspension geometry. For most vehicles it provides the optimal handling response and stability. The exceptions are performance touring vehicles with suspensions tuned for neutral steering response when not towing. The 50-100% setting effectively are good for vehicles marketed for towing but may not be ideal for vehicles that are not marketed for towing.

[Philips53]

Yaw inertia is a term I’ve never heard before, and you mention the mass of the TV. Question: I’m considering towing at close my Transit diesel van’s tow capacity rating of 7,500# and the GCWR of 13,500#, but feeling that it will be safe since the weight of the TV would be 62% of the rig. TV is a van which weighs 7,525 loaded + 700# tongue weight = 8,225#. Trailer is 5,700# - 700# tongue weight = 5,000#. Total combined weight = 13,225#. That’s a 62%/38% split. I’m not concerned with the power of the engine, or the transmission. I tow at 69mph on the highway, and am comfortable deciding that to 50mph up or down mountains. Is my logic sound? Flawed? Thanks for any comments.

[BayouBiker]

Yaw inertia is sort of a hacked physics term that is describing the inertial moment of the trailer when spun like a top or pushed sideways from the Yaw point which is the hitch tongue. It is important because large moments of inertia prevents sway since the impulses that would set the trailer oscillating side to side need to be strong enough to overcome the inertia. This is why 15% tongue weight is much more stable in sway than 10% and why 5% is inherently unstable.

On the other hand, this same trailer yaw inertia must be managed by the tow vehicle in cornering. the tow vehicle rear tires must hold the road enough to pull this inertia around the corner. So there is a trade off that depends on vehicle capability to hold the road and resist the trailer inertia.

Hope that make sense....

Anyway to your question. In comparing the weights of a tow vehicle to a trailer it is truly the moments of inertia that matter since it is inertia that the two things are competing with and moments of inertia are dependent only on the mass components. So you compare the full weight of the van and content with the full weight of the trailer. 7,525 to 5,700 or 57% not a big difference but the point where things get exciting is under 50% so you are still in great shape, the van has plenty of heft to resist the trailer.

It is interesting the manufacture has a relatively light combined limit. You say the engine and transmission are fine, and I would agree, what about the brakes and differential? If those are fine and I suspect they are, I would guess they applied the limit to address the high center of gravity and propensity to roll. Not jackknife and roll but just the basic rollover you see with semis on off ramps. So since you are below this limit and assuming you follow the orange truck speed guidance, and assuming you look at brake capability (measure or look up the disk size, 14 inch and larger front and back is golden for that weight, I couldn't find it online too many variations) and differential, you are in good shape at 65-69. This presumes you add WD and sway control of course.

[mefly2]

Originally Posted by BayouBiker

The AirSafe technically is a vibration damper at its core, conceptually the same as a spring, kink and shock absorber system. The four tie rods keep the ball mount stable and properly oriented so even with a WD hitch, load and tension is transmitted. They are the links. The Air bag supports and transmits the base loads and provides cushioning to absorb impulses (jarring bumps) and vibrations. It is the spring. Higher loads put more force on the air bag. The shock absorbers provide damping to dissipate the excess energy from the transient loads (impulses and vibrations).

So this is an effective way to isolate the trailer from the vehicle and visa versa. It is a sink for shocks and vibrations so it does not transmit through the vehicle or the trailer.

Since it does not affect base loads and torques it does not change WD and tongue torque at all.

So how does tensioning the equalizer bars figure in to the functioning of the airsafe ... I can understand absorption of force in one direction by the air bag but not in the other direction due to the bar tension ... ? I have observed tremendous amount of flex in the loaded eq bars when underway on irregular surfaces. Is that correct? How, then, does the airsafe factor in to that function. Without any equalizer hitch, I can see and understand the airsafe functioning; but isn't much of its purpose mitigated by the equalizer load bars? Help, please, to better understand just how the airsafe functions with load equalization.

[BayouBiker]

Like all springs, the AirSafe air bag will only perform through its range of motion. I should have mentioned it is designed to act on vertical motion only(ball rising or falling). The links are rigid to lateral (side to side) and axial (front to back) motions. In the vertical plane, the bag will remain in compression unless a bump is so sever the ball gets completely unloaded and the coupler is pulling on the ball. With weight distribution, this can only happen if the WD tension also becomes completely unloaded as if the ball were lifted high in the air. Absence of this extreme, Airsafe will perform if the ball is either rising or falling.

Weight Distribution tension is also intended to act in the vertical plane. Tension rises as the ball drops and tension falls as the ball rises. The sway control features are intended to act laterally but since AirSafe does not, there is no interaction laterally. Most WD designs unfortunately act radially (in twist). Again AirSafe does not.

So on to your questions.

Your observations are correct, tension and flex both change as the ball rises and falls, and it is tremendous to watch. The AirSafe dampens the impulses and rapid back and forth (vibrations) of both flexes/tension of the WD bars and up and down movements of the ball (they are just slightly out of phase with each other).

AirSafe does not act on the steady state elevation of the ball and does not act on the steady state (static) WD tension and lift on the hitch receiver.

So WD adds stiffness to the system and therefore amplifies the vibrations and impulses the AirSafe is designed to dissipate so in that sense yes, WD makes the AirSafe task more difficult/severe. You could say its purpose is mitigated or you could say the utility of AirSafe is even more important with WD, I don't think either view is incorrect.

Does this help?

[mefly2]

Thanks, BB ... not sure that the airsafe provides as much "cush" with the WD bars tensioned. It would be nice if there was a unit so equipped around here in W MT to at least look at or ride along but have not seen any. Nor, have I been able to get in touch with anyone in Fargo ... only east coast distributor.

[johnrobison]

At my work we operate 2 late modern GM 2500HD trucks and 1 3500HD. They are similar to your Denali and more than enough to pull your Airstream. We have a 23FB that we tow on weekends, but our work trucks haul commercial car trailers weighing 7-15,000lbs. We have towed hundreds of thousands of miles with standard Reese weight distributing hitches on the closed trailers and the standard hitch on the Aluma open trailer, which runs 6-10k loaded. We have never had a significant sway issue with any of them.

I will say I've had moments when it feels a little dicey coming down a long grade, and you're tired already, and the 15,000lb 10 foot tall car trailer start to squirm. A Propride would prevent that.

We have a Propride hitch on the Airstream, and have never had a sway issue with it. The Propride absolutely works. You can feel the difference in stability between that and the commercial trailers. But you almost never see Propride or Hensley hitches on commercial trailers, presumably because the people who tow all the time feel they are not needed.

I used to drive these trucks all the time. Now I am older, and I don't. If I drove car trailers 4 days a week for work, I think I'd just tow the Airstream on a WD hitch, or on the stock hitch on the 3500 truck. Airstreams tow a lot easier than big boxy trailers.

But I don't drive that much now, and I am not as quick as I was 40 years ago. And I may have the wife driving, not me, and she has not driven trucks and trailers for 40 years like I have . . . and so I will keep the Propride on the Airstream.

I hope this perspective is useful.

[EarlM]

Originally Posted by dlfphoto

We are jumping in to Airstreaming with our first trailer setup. Currently awaiting delivery of a 2021 Globetrotter 30RB in a week or so. We've decided on a tow vehicle, the GMC Denali 2500HD with 6.6L Duramax. Now, moving on to a hitch.

The GT30RB has a GTWR of 8800# and a tongue weight of 1050#.

I know that there is a huge following for the ProPride P3 hitch. I get it. The PP seems to be universally adored. But.... on top of everything else, I'm hesitant to drop another $3K on a hitch. And one that seems to take some finesse to master. For our first go around, we'd like to start off with a standard friction ball hitch < $1K. To that end, we're looking for recommendations. So far, I've heard decent things about Blue Ox and Equal-i-zer.

I had a 30 foot classic and I originally had a Hensley hitch. It was a pain to hitch and time consuming. I sold it and took a bath and bought an Equalizer the best decision I could have made IMHO. I know have a 33foot classic and just bought a new 2020 a GMC DENALI 3500 SRW.

enjoy your new Airstream

Earl

[Profxd]

Originally Posted by BayouBiker

Yaw inertia is sort of a hacked physics term that is describing the inertial moment of the trailer when spun like a top or pushed sideways from the Yaw point which is the hitch tongue. It is important because large moments of inertia prevents sway since the impulses that would set the trailer oscillating side to side need to be strong enough to overcome the inertia. This is why 15% tongue weight is much more stable in sway than 10% and why 5% is inherently unstable.

On the other hand, this same trailer yaw inertia must be managed by the tow vehicle in cornering. the tow vehicle rear tires must hold the road enough to pull this inertia around the corner. So there is a trade off that depends on vehicle capability to hold the road and resist the trailer inertia.

Hope that make sense....

Anyway to your question. In comparing the weights of a tow vehicle to a trailer it is truly the moments of inertia that matter since it is inertia that the two things are competing with and moments of inertia are dependent only on the mass components. So you compare the full weight of the van and content with the full weight of the trailer. 7,525 to 5,700 or 57% not a big difference but the point where things get exciting is under 50% so you are still in great shape, the van has plenty of heft to resist the trailer.

It is interesting the manufacture has a relatively light combined limit. You say the engine and transmission are fine, and I would agree, what about the brakes and differential? If those are fine and I suspect they are, I would guess they applied the limit to address the high center of gravity and propensity to roll. Not jackknife and roll but just the basic rollover you see with semis on off ramps. So since you are below this limit and assuming you follow the orange truck speed guidance, and assuming you look at brake capability (measure or look up the disk size, 14 inch and larger front and back is golden for that weight, I couldn't find it online too many variations) and differential, you are in good shape at 65-69. This presumes you add WD and sway control of course.

Brian your explanation and the way you used “large moments of inertia” may be a bit misleading for some. A trailer that has high yaw inertia has a higher tendency to sway. Just because a trailer has 15% tongue weight doesn’t necessarily mean it has high yaw inertia.

[BayouBiker]

Greater trailer inertia moments resist trailer sway because it requires more force to initiate sway and to rapidly reverse direction back and forth. This is why trailers with low tongue weights inherently sway and why the propensity for initiating sway from the trailer decreases as one approaches and exceeds 15% tongue weight. However greater trailer inertia moments taxes the tow vehicle while cornering which could result in over steer. There is a trade off between trailer stability (sway) and tow vehicle stability (over steer and jackknife). Hope this makes it more clear.