Twitchy steering with a big travel trailer (rear sway bar help?)

[AuroraGirl]

He never mentioned trailer sway although good point/reminder. Easiest way to correct trailer sway typically from not enough tongue weight (which is not the Ops issue) is applying trailer brakes while accelerating.

For another related path of diagnosis , I was going to see if drag behind him affects his squirm , it would help isolate alignment/body roll/steering components/power steering system depending on what it did

 

[AuroraGirl]

As all is tight and new according to you, you may not have enough caster in the front end. Less caster = twitchy. Too much caster = heavy steering but tracks very straight. (Sort of. Not the full description). Seeing how you redid everything on the front, maybe caster angle is shy of what’s specified.

could also be more than a half degree away from eachother (sides), but id think that would be more a tracks to one side than squirm. large caster will also wear the edges of the tire more in turns but its amazing what a little bit of caster does for a vehicle that doesnt have much

if the suspensions could support it with the wheel in the right place in the wheel well, it would be cool to see 6 degrees of caster

 

[AuroraGirl]

idk if the steering has anything to do with the trailer

im saying to investigate alignment and steering system because he has "all new parts all around"
and his trucks squirming is present without a trailer

Anyone whos had a power steering pump stuck at full assist (or behaving intermittently/inconsistently) and a bit of misalignment or wear or lots of new parts at the same time probably has had an uncomfortably squirmy behavior on the road as well.

Not to say that there couldnt be multiple different systems that are independently contributing to the same behavior.

All factors that should be considered and dont need more than a few pictures , double checking by the OP, and consideration among other facts.

 

[Grit dog]

If the tires are not up to task, and the tail is wagging the dog, wouldn't it cause the "dog" to be squirrely? If the front suspension that was swapped in is not 3/4 ton suspension, that may be a contributing factor, and the different control arms, if not factory replacements, may not be geometrically correct for heavy work. His rig looks great being lowered, but it may not be a 3/4 ton anymore.

Tires with too much flex certainly would allow the tail to wag the dog more. You’re correct. I’m just not seeing it in this scenario. Not that it’s not possible or contributing. But the OP did not complain of the trailer swaying/wiggling. Plus he’s using a wdh with sway control. Should track like a train.
Now diving deeper like you did, if he’s got the equivalent of a ford ranger suspension under the truck (hence the excessive airbag pressure??) I did. It consider that. That said, the front axle is at most getting another 500lbs tops from the wdh compared to driving bobtail. Or at most 500lbs less if he isn’t taking up weight with the wdh. The latter would make steering more squirrelly than the former all else equal.
This is one of those cases of chasing a needle in a haystack unless the OP gives all the facts. My assumption was that he still had a relatively competent suspension for the weight, based on the vehicle he started with and the trailer he’s pulling.
I’ve had the experience of towing most kinds of trailers of about every size behind a wide range of light duty trucks. And TTs are sometimes a challenge due to being designed with light tongue weights (TT mfgs are great at marketing some “Half ton towable” TTs that tow like absolute dogshit to keep the tongue weights down. Although this does again not seem to be the case.
Some of it may just be driver experience in knowing what to expect.
Some may be new front end setup (caster). Some may be rear tires? Some may be a super light duty suspension?
Trying to help root that out and OP and IMO more info is necessary since we are not driving his truck and trailer. But rather speculating.

 

[txaggie]

If the tires are not up to task, and the tail is wagging the dog, wouldn't it cause the "dog" to be squirrely? If the front suspension that was swapped in is not 3/4 ton suspension, that may be a contributing factor, and the different control arms, if not factory replacements, may not be geometrically correct for heavy work. His rig looks great being lowered, but it may not be a 3/4 ton anymore.

The front suspension is all new moog suspension oem replacement upper and lower with all new tie rod ends and ball joints. The coils are western chassis c30 2” drop coils. New shocks all the way around. Factory rear 3/4 original leaf springs with 1.5” shackle
Drops and air lift air ride bags in the rear. Definitely all beefy 3/4 ton suspension. In regards to the air bag psi, I might have just aired that up too much. I’ll check the alignment spec in the upcoming days.

 

[DoubleDingo]

The front suspension is all new moog suspension oem replacement upper and lower with all new tie rod ends and ball joints. The coils are western chassis c30 2” drop coils. New shocks all the way around. Factory rear 3/4 original leaf springs with 1.5” shackle
Drops and air lift air ride bags in the rear. Definitely all beefy 3/4 ton suspension. In regards to the air bag psi, I might have just aired that up too much. I’ll check the alignment spec in the upcoming days.

That makes me lean even more towards the P tires being the problem, and also making sure the alignment is spot on so the front wheels don't wander or follow every crack and crevice in the road. The quicker ratio steering gear doesn't help matters, but a slower turn can be executed.

 

[bucket]

To that point, the best rotation is the one that keeps the treadwear even. Which barring alignment issues or correcting uneven tread depth is typically straight front to back. Because front tires feather or cup one direction and rear tires the other direction. X pattern doesn’t correct feathering or tread cupping. JMO. 90% of rotations I do end up being just front to back. Even more important on big at and mt tires

Agreed. I base every rotation on the current situation with tire wear, whether it's front drive, rear drive, heavy vehicle, light vehicle, etc. Sometimes it's a side swap. Sometimes its a front/rear swap. Sometimes its an X swap. Sometimes it's an X swap with a side swap up front. Sometimes it's an X swap with a side swap in the rear. It just depends.

Possibly. Although I’m not seeing 5klbs on the rear axle without the OP explaining why he’s using airbags to that extent or at all.
Nor am I seeing it possible to have anywhere near enough weight in the rear axle especially if the wdh is pulling any weight off. Those bags at 60psi will jack the truck up in back above empty ride height even with no wdh.
More needs to be verified before blaming the tires.

I don't know what the weight bias is with a Suburban, but I'd venture to guess that it's maybe a 60/40 split. Couple that with some tongue weight and luggage in the rear, there's going to be some weight back there. A lighter rated tire might be up to the task, but generally speaking, a higher rated tire (and quality... there's some really crappy E rated tires) will perform much better than a lighter rated tire. A sturdy carcass will reduce tire squirm greatly and squirm is often a large contributing factor to twitchy steering.

 

[bucket]

I forgot to add, I once had a C20 Suburban that drove great. It had some old E rated Michelins on it and two were badly dry rotted, so I replaced them with some cheap Pep Boys tires that had similar load ratings. The sidewalls were floppy and I was very skeptical, but I installed them anyway. With no other changes, the interstate driving became very twitchy, especially with a side wind. And that was with no trailer.

 

[txaggie]

I forgot to add, I once had a C20 Suburban that drove great. It had some old E rated Michelins on it and two were badly dry rotted, so I replaced them with some cheap Pep Boys tires that had similar load ratings. The sidewalls were floppy and I was very skeptical, but I installed them anyway. With no other changes, the interstate driving became very twitchy, especially with a side wind. And that was with no trailer.

Do you think a rear sway bar does any good in my setup in addition to the e rated tires?

 

[Radiohead]

Rear sway bar on the Burb will help but squares didn't have them except for the duallies.

Unless ordered on SRW in the camper special world, perhaps part of Z83 on the glovebox list for 1979. That feature along with the big block is what sold me on it originally.

 

[Grit dog]

Do you think a rear sway bar does any good in my setup in addition to the e rated tires?

I think I’m being convinced that you don’t have experience towing or understand the principles very well. Not a big deal other than it could be as much or more of a factor than your vehicle. I also think answering all the questions asked from those trying to help you with your problem is very important, before coming up with more questions.
And no, based on what you finally posted about your suspension, and given your equipment, a rear sway bar is of zero actual use. Either as a solution to the problem you think you have or for actual improved towing performance.
E tires? Fck, dunno what to say. May as well go buy them and a sway bar and report back. You’ve already been told how to test that. Have you done that?

 

[txaggie]

Possibly. Although I’m not seeing 5klbs on the rear axle without the OP explaining why he’s using airbags to that extent or at all.
Nor am I seeing it possible to have anywhere near enough weight in the rear axle especially if the wdh is pulling any weight off. Those bags at 60psi will jack the truck up in back above empty ride height even with no wdh.
More needs to be verified before blaming the tires.

With the shackle drop on the rear springs, this rear end squats like crazy with the trailer attached. Without the airbags aired up, the tongue weight drops 100 pounds.

Once the bags are aired north of 50 psi and the weight distribution hitch is setup, it’s displaying 3k worth of weight tension post adjustment.

 

[bucket]

With the shackle drop on the rear springs, this rear end squats like crazy with the trailer attached. Without the airbags aired up, the tongue weight drops 100 pounds.

Once the bags are aired north of 50 psi and the weight distribution hitch is setup, it’s displaying 3k worth of weight tension post adjustment.

Burbs always look like they are squating like crazy with some tongue weight. In stock form, they sit more level compared to pickups that tend to ride ass-high.

All I know is, my stone stock '78 C20 Suburban pulls my 30ft tt wonderfully. It's not as heavy as yours, but around 5k dry I think. But I have pulled loads upwards of 15k and still no twitchy steering. You need to be more alert and careful with your steering inputs while driving of course, but that's just the nature of towing.

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[HotWheelsBurban]

Unless ordered on SRW in the camper special world, perhaps part of Z83 on the glovebox list for 1979. That feature along with the big block is what sold me on it originally.

Good to know! I learned something already this morning!

 

[txaggie]

Burbs always look like they are squating like crazy with some tongue weight. In stock form, they sit more level compared to pickups that tend to ride ass-high.

All I know is, my stone stock '78 C20 Suburban pulls my 30ft tt wonderfully. It's not as heavy as yours, but around 5k dry I think. But I have pulled loads upwards of 15k and still no twitchy steering. You need to be more alert and careful with your steering inputs while driving of course, but that's just the nature of towing.

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Thanks. The other i encountered was that 3 out of 4 tows have been in 20-40 mph winds. I know that has a lot to do with it as well.