Why don't pickup trucks have rear swaybars?

[Jarlaxle]

Originally Posted By: KD0AXS
Originally Posted By: Miller88
Originally Posted By: KD0AXS
My F-350 has one. So did my old F-150.


Strange - our 01 F350 4x4 with the heavy service rear suspension does not have a rear sway bar. Leaf springs are so stiff anyway ...


Mine was the previous generation, a 1993. I think it had some sort of heavy suspension package. Along with the rear sway bar, it also had the dual shock suspension in the front.



The camper package includes a rear bar.

 

[KD0AXS]

Originally Posted By: KD0AXS
Originally Posted By: Miller88
Originally Posted By: KD0AXS
My F-350 has one. So did my old F-150.


Strange - our 01 F350 4x4 with the heavy service rear suspension does not have a rear sway bar. Leaf springs are so stiff anyway ...


Mine was the previous generation, a 1993. I think it had some sort of heavy suspension package. Along with the rear sway bar, it also had the dual shock suspension in the front.


Oops, I guess I read that wrong. I thought you were talking about an 01 F-150, not a F-350. The F-150 I had was a 1993. My current 05 F-350 has both the snow plow and camper packages, and the sway bar is part of the camper package.

 

[hattaresguy]

Mine does.

 

[SwampSurvivor]

Ah! Have the snow plow prep package but not the camper package. I'd like to see about adding a rear swaybar to it (if I can fix the bed) when I buy it so I can do a slide in camper.

 

[Bzab32]

Originally Posted By: Jarlaxle
Originally Posted By: KD0AXS
Originally Posted By: Miller88
Originally Posted By: KD0AXS
My F-350 has one. So did my old F-150.


Strange - our 01 F350 4x4 with the heavy service rear suspension does not have a rear sway bar. Leaf springs are so stiff anyway ...


Mine was the previous generation, a 1993. I think it had some sort of heavy suspension package. Along with the rear sway bar, it also had the dual shock suspension in the front.



The camper package includes a rear bar.


Exactly, mine has the stabilizer package a (i think) $120 option that includes the rear sway bar and heavier springs (or leafs for the older) in the front.

 

[slacktide_bitog]

Yeah, GM is known for cutting corners

 

[HerrStig]

Originally Posted By: Shannow
You have to look at how the suspension is supposed to work in the first instance.

When I started playing with cars in the 80s, they were late 65s, early 70s sedans with IFS, live rear axles, and no bars. Sway bars always made them better...playing bar diameters was an easy way of moving over/understeer.

Could be done with clever springs.

As I moved into late 70s stuff, they came with bars, which left me a choice of increasing spring rates, or increasing bar rates...My preference was softer springs and more bar (one of my Toranas, I kept the stock spring rates, and went from 18mm front to 26mm, 12mm rear to 22...was wicked on corrugated dirt roads, but turned so well)

Bars, as has been mentioned make for poor articulation in trucks...in the last mentioned Torana, I would get crossed up and wheel spinning in friend's driveways when they were that artistic looking steep spiral down to a change of direction, slight up, and onto a flat parking surface...the bar would unload the inside wheel.

Which is why light trucks don't have them...they need articulation, and need both wheels loaded to provide traction.

But, and there's always a but, when you look at a cement truck, they are narrow wheelbase, very very high CoG...and have a massive rear anti roll bar, to stop the lean and sway.

My Nissna has a coathanger front bar, and big leaf springs (rated to a tonne carry), and is very predictable. I don't think I want more bar, nor want to add one to the back.

If I permanently affixed a rooftop tent, and other high loads, I would be tempted to emulate the cement truck and add bar for the highway, but would lose articulation to the camping areas.
Correct. The anti roll force has to come from somewhere, and it comes from the inside wheel.

 

[punisher]

As it was explained by a FoMoCo suspension teacher during an air suspension class and whether it would become an option on trucks:

In a truck you just never know how much weight, or how high the CG will get with a load. Most people drive around in empty trucks with relatively little weight on the rear axle, and consequently a swaybar would have to have very little "rate" to render it effective without having an adverse effect on handling. By adverse I mean losing the back end going into corners (especially with a locking differential). If you had a constantly heavier load on the rear axle, then a swaybar makes sense, like in an Expedition, Suburban, large SUV etc.

A swaybar optimized for a 1000lb payload will make an unloaded truck "skittish" on a good day, and dangerous on a bad day (less than great traction on a rainy day). Likewise, a swaybar optimized for an unloaded bed, will be worthless(almost) on a loaded truck. So, for safety reasons (liability), and cost, many trucks did not have rear swaybar packages. Later they were offered, but they had very low "rates" (thin/more "springy") so as to be a semi effective option to boost the sticker price.

Don't get me started on chassis flex and how newer stiffer truck frames have changed suspension requirements. That's a book.

 

[m37charlie]

Originally Posted By: horse123
You don't want a sway bar when you're trying to get traction off road.


You can add a rear Detroit Locker or ARB air locker, then having 2 rear tires on the ground at all times for traction becomes irrelevant. Likewise, my U500 Unimog camper (= higher CG) has front/rear swaybars but also of course difflocks. The U500 is supposed to be "not as good offroad as the U5000" which has no swaybars, but who cares with difflocks? I'm happy to have the swaybars which give me more stability in crosswinds for example, the locking diffs, low gears and CTIS will get it thru any plausible offroad obstacle.

Charlie

 

[Whimsey]

I have a 2002 F150 4X4 SC 8' bed with a heavy tall fiberglass cap. The addition at 5,000 miles of a Hellwig rear sway bar did wonders for the handling in my case. It has an open rear diff and when the tires wear more it does tend to spin the tire(s) when making a sharp turn uphill from a dead stop. But I can control that with the gas pedal. For me it's been a worthwhile add on. The 4X4 is for snow and muddy construction sites so I don't worry about true off road situations. Besides it's too big to be useful off road

.

Whimsey

 

[Texan4Life]

+1 for hellwig.. I have their pro series load helper springs on the rear or my 1500, I have been tossing around getting their rear sway bar kit.

Their kits are priced right and have free shipping from amazon

 

[turtlevette]

Originally Posted By: punisher
As it was explained by a FoMoCo suspension teacher during an air suspension class and whether it would become an option on trucks:

In a truck you just never know how much weight, or how high the CG will get with a load. Most people drive around in empty trucks with relatively little weight on the rear axle, and consequently a swaybar would have to have very little "rate" to render it effective without having an adverse effect on handling. By adverse I mean losing the back end going into corners (especially with a locking differential). If you had a constantly heavier load on the rear axle, then a swaybar makes sense, like in an Expedition, Suburban, large SUV etc.

A swaybar optimized for a 1000lb payload will make an unloaded truck "skittish" on a good day, and dangerous on a bad day (less than great traction on a rainy day). Likewise, a swaybar optimized for an unloaded bed, will be worthless(almost) on a loaded truck. So, for safety reasons (liability), and cost, many trucks did not have rear swaybar packages. Later they were offered, but they had very low "rates" (thin/more "springy") so as to be a semi effective option to boost the sticker price.




This is the best answer. Pickups are way too light in the back which causes an oversteer condition to begin with. Putting a sway bar on the back makes the situation potentially dangerous.

Most passenger cars and trucks are designed with understeer which is much easier for an unskilled driver to handle. Sports cars are closer to neutral but now have active handling to help unskilled and skilled. I put a huge bar on the back of the vette and it was fun to steer with he throttle but a real handfull.

 

[KD0AXS]

Originally Posted By: horse123
You don't want a sway bar when you're trying to get traction off road.


Most pickups sold these days never leave the pavement anyway. Many never even tow a trailer or haul anything other than groceries.

 

[Jarlaxle]

Originally Posted By: turtlevette
Originally Posted By: punisher
As it was explained by a FoMoCo suspension teacher during an air suspension class and whether it would become an option on trucks:

In a truck you just never know how much weight, or how high the CG will get with a load. Most people drive around in empty trucks with relatively little weight on the rear axle, and consequently a swaybar would have to have very little "rate" to render it effective without having an adverse effect on handling. By adverse I mean losing the back end going into corners (especially with a locking differential). If you had a constantly heavier load on the rear axle, then a swaybar makes sense, like in an Expedition, Suburban, large SUV etc.

A swaybar optimized for a 1000lb payload will make an unloaded truck "skittish" on a good day, and dangerous on a bad day (less than great traction on a rainy day). Likewise, a swaybar optimized for an unloaded bed, will be worthless(almost) on a loaded truck. So, for safety reasons (liability), and cost, many trucks did not have rear swaybar packages. Later they were offered, but they had very low "rates" (thin/more "springy") so as to be a semi effective option to boost the sticker price.



This is the best answer. Pickups are way too light in the back which causes an oversteer condition to begin with. Putting a sway bar on the back makes the situation potentially dangerous.

Most passenger cars and trucks are designed with understeer which is much easier for an unskilled driver to handle. Sports cars are closer to neutral but now have active handling to help unskilled and skilled. I put a huge bar on the back of the vette and it was fun to steer with he throttle but a real handfull.


And yet...trucks have had rear swaybars for 25+ years.

 

[01rangerxl]

My 1994 Ranger 4WD has a rear sway bar. My 2002 Ranger 2WD does not, but multiple aftermarket options are available. The now discontinued Roush rear sway bar was pretty inexpensive when it was available.

It all depends on the suspension setup and what the manufacturer thinks is appropriate/the best compromise.

From what I have seen, Ford did not use rear sway bars on most/all SLA IFS Rangers (1998+), but did use them on most/all TIB/TTB front suspension Rangers (1983-1997). The 1994 handles surprisingly well on twisty back roads for what it is...on dry roads at least, I have driven it in the rain like twice. Seems the front suspension was the determining factor for the rear sway bar being there or not.

 

[ExMachina]

Solution: Sway Bar Disconnects
There when you want it for highway travel, like highway trips with the camper or a load.
Nice if it engaged automatically over 30 mph.

 

[splinter]

Originally Posted By: ExMachina
Solution: Sway Bar Disconnects
There when you want it for highway travel, like highway trips with the camper or a load.
Nice if it engaged automatically over 30 mph.

Pip pins are indeed popular with some 'multiple-use' vehicle enthusiasts.

Enter PDCC = Porsche Dynamic Chassis Control. An electronically operated anti-roll bar system.
Kinda pricey and not yet available for Yank trucks, though.

With ABS, TPMS, stability control(s) etc. mandated by DOT/NHTSA et al for active 'safety' purposes,
similar systems may become more widespread as the technology and its hardware becomes less investment intensive.

http://www.excellence-mag.com/of-note/you-ve-got-options-part-ii-porsche-dynamic-chassis-control

 

[punisher]

Originally Posted By: Jarlaxle

And yet...trucks have had rear swaybars for 25+ years.


Well, that Ford class was in 1995 or 96. Left out spring rate as another big factor. That was the whole reason our discussion got started back then as air bags/springs have very soft spring rates and body roll will always be a concern.

EDIT: Sway bar disconnects- imagine one of the sway bar links that was able to be unlocked, or locked, or any degree in between, on the fly. That was one idea spitballed. Like a variable valved shock/link controlled by the BCM where you could have any amount of swaybar lock you wanted almost instantly.