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Open Roads Forum  >  Towing

 > Vehicle "rise" while towing.

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BenK

SF BayArea

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Posted: 04/16/22 03:01pm Link  |  Quote  |  Print  |  Notify Moderator

Generally, OEM's setup our pickups and SUVs with understeer with only a front anti-sway bar (anti-lean bar) and NO rear anti-sway bar

Exception are 'performance' (boy racer with lots of GO) where they might have a rear anti-sway bar, but most don't know is that the OEM also increases the front anti-sway bars diameter (higher torsional rigidity)

Why IMO...do not recommend installing a rear anti-sway bar and if insist, then to make sure to also change the OEM front anti-sway bar to a larger dia from the SAME after market suppler of the rear bar being installed

With that in mind, the old 'even drop' kept the above handling characteristics, but with the newer suspensions & the new 'drop' or 'return the front axle' recommendations...that 'even drop' has been put aside

I still adhere to 'even drop' for my setups. Maybe not if I ever get another +8K GVWR TV and know that GM's newer 4x4's has a secondary front axle spring in constant contact with the lower A-Arm and can NOT bring the front back to OEM height easily. Else there would be too much WD'ing weight off of the TV's rear axle

Glad to read John mentioning that 'push' trailers impart onto the TV's rear end. And during a freeway speed curve while braking, the trailer will both nose dive during braking to add weight to the TV's read end and 'push' it trying to go 'straight'.

That is where manhandling the setup comes into play.


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

ktmrfs

Portland, Oregon

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Posted: 04/16/22 05:16pm Link  |  Quote  |  Print  |  Notify Moderator

BenK wrote:

Generally, OEM's setup our pickups and SUVs with understeer with only a front anti-sway bar (anti-lean bar) and NO rear anti-sway bar

Exception are 'performance' (boy racer with lots of GO) where they might have a rear anti-sway bar, but most don't know is that the OEM also increases the front anti-sway bars diameter (higher torsional rigidity)

Why IMO...do not recommend installing a rear anti-sway bar and if insist, then to make sure to also change the OEM front anti-sway bar to a larger dia from the SAME after market suppler of the rear bar being installed

With that in mind, the old 'even drop' kept the above handling characteristics, but with the newer suspensions & the new 'drop' or 'return the front axle' recommendations...that 'even drop' has been put aside

I still adhere to 'even drop' for my setups. Maybe not if I ever get another +8K GVWR TV and know that GM's newer 4x4's has a secondary front axle spring in constant contact with the lower A-Arm and can NOT bring the front back to OEM height easily. Else there would be too much WD'ing weight off of the TV's rear axle

Glad to read John mentioning that 'push' trailers impart onto the TV's rear end. And during a freeway speed curve while braking, the trailer will both nose dive during braking to add weight to the TV's read end and 'push' it trying to go 'straight'.

That is where manhandling the setup comes into play.


at least as late as 2016 GM had a rubber bump stop on the front axle that is about 1/2" below the unloaded front end position. It's been easy for me to get the front back to unloaded height, but if you overdo and hit the bump stop or attempt to do the old " get the front and rear to drop the same amount", yes, almost no amount of spring bar will drop the front below unloaded.


2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!


JBarca

Radnor, Ohio, USA

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Posted: 04/17/22 09:33am Link  |  Quote  |  Print  |  Notify Moderator

ktmrfs wrote:

JBarca:

good info that seems to shed light on the changing recomendations.

I'll also add my experience related to 4 people I've helped set up a WD hitch. This was after they complained to me that they felt the trailer was giving them sway and didn't feel comfortable with the way the combo handled.

In each case looking at front "rise" measurements and rear "Sag" measurments I found that the front was always high compared to unloaded and not bringing the front back to even 1/2 the difference. Once I adjusted the setup to bring the front back to at least half or more of the distance (I was shooting for close to unloaded) the problems went away and they were amazed at the difference in handling.

At the time my thought was that with the front end rising they were getting more camber on the front axle which coupled with a lighter front end, heavy back end was letting the front end be to sensitive to steering correction.

Yes, in the extreme it would probably oversteer rather then understeer.

My conclusion after helping all the folks I did adjustment for was to keep increasing front load (dropping the front) till the wander problem disapeared. it seem to take bringing it back to at least 1/2 the difference to be effective.

Now all this was done on smaller lighter vehicles, <1/2 ton trucks, Suburbans etc.


Hi ktmrsf,

By chance were your friends who you helped, first time TT owners, or their first time using or adjusting a WD hitch?

Yes, I agree, many first time TT owners, never had some one explain to them or did they understand what a WD hitch is supposed to do. The dealer setup the tow rig with an empty trailer, and many times, an empty truck and down the road the new owner goes.

Then the new TT owner, loads the camper and the truck. The TT tongue weight changes, the truck suspension changes, yet the WD settings are left from an empty camper.

Then there is the misunderstanding on how to hitch up when using a WD hitch and how to use the trailer tongue jack to lift the camper way up, then snap up the WD bars.

This adds up to, the new owner thinking, wow these WD bars are really tight, they for sure do not need any more adjustment. And they end up with the front end of the truck being very light and the rear axle, very heavy. The truck handling is bad, and having a lighter truck can make it all that much worse as the the lighter truck really needs the benefit of a WD hitch adjusted correctly.

Close to the same thing above happened to me on my first TT. While I had towed many trailers, open deck, sail boat, enclosed cargo trailers, I never towed a TT needing a WD hitch. So I asked the shop PDI person, what do I need to understand or do to adjust this WD hitch? He stated, just take up a link if you want to move more weight. They wanted to explain more on how to work the appliances inside the camper then a WD hitch or trailer running gear. I was green enough then to not ask further when, why and how do you know what to adjust on a WD hitch? Then the learning started. My one year old 2002 1/2 ton Tahoe was out of cargo capacity the day I filled the camper with cargo. And the 800# WD bars the dealer gave me on an 800# dry tongue weight camper were also, very wrong even after I stated, are you sure I do not need the 1,200# bars? He said no, I would not send you down the road with a miss matched setup.

When I got home and started loading the camper, I realized my mistake as tow ratings are very misunderstood if the truck can't handle the loaded tongue weight of a TT. Before I got myself into an bad situation, I fixed the weight issue changing the truck to a 2003 K2500 Suburban and then even more learning started.. GM torsion bar front ends will not drop once the yellow jounce bumpers hit. I have always said, you learn a lot more when things go wrong...

It too have since helped many, many fellow camping friends understand the same error of my ways and adjusted them back into a very stable towing setup. Some though had to change the truck too.

Point: It is common to have handling issues from the WD hitch being very out of adjustment. And the WD hitch is only one of many factors in a stable towing rig. But it starts with proper TW on the camper, then proper WD adjustment, then comes all the other factors, tire pressures, trailer towing stance, is the truck overloaded and the list goes on.

Experience is something that is learned, over time, you are not born with it. [emoticon]


John & Cindy

2005 Ford F350 Super Duty, 4x4; 6.8L V10 with 4.10
CC, SB, Lariat & FX4 package
21,000 GCWR, 11,000 GVWR
Ford Tow Command
1,700# Reese HP hitch & HP Dual Cam
2 1/2" Towbeast Receiver

2004 Sunline Solaris T310SR
(I wish we were camping!)


ktmrfs

Portland, Oregon

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Posted: 04/17/22 08:27pm Link  |  Quote  |  Print  |  Notify Moderator

yup, hit the nail on the head. I think few sales guys understand WD hitches and the installers if the do aren't the ones that interface with the customer unfortunetly.

John all the folks I helped had very little knowledge of how a WD system works and the dealer did a WD setup with an empty trailer. Unlike them, I had some knowledge of WD setup and redid mine once I loaded up. And I happened to hit this forum with info from you and others on setting up WD properly.

And like you mention GM front bump stops only have 1/2" of clearance or less, so don't try to drop below unloaded height.

And for hookup I've had a few people who tried to hook up with the TV trailer combo in a "V", when in a sloped driveway to the street and they don't realize that the "V" adds a great deal of load to those bars, can be dangerous unhooking if not careful or very hard to hook up even by using the jack to lift the tongue. Once I gave them a physics lesson they had an "ah ha" moment and they realized they just need to pull the trailer out of the driveway and get flat in the street then hook up the bars.

* This post was edited 04/22/22 09:18am by an administrator/moderator *

Boomerweps

Hills of PA

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Posted: 04/18/22 10:11am Link  |  Quote  |  Print  |  Notify Moderator

I want to thank those who discussed the oversteer/understeer aspects.
It now makes more sense to me that the F150s with tow packages come with a heavier, solid front anti-roll bar vice the standard same diameter hollow bar and the effects that has. And that there is no factory rear bar.
It has also helped me make up my mind on NOT getting the Hellwig rear bar. While that would improve daily empty driving, I now think that it would not help towing at best and possibly be an actual oversteer concern while towing. Throw in the recent increased cost of the bar & its now a no go for me.


2019 Wolf Pup 16 BHS Limited, axle flipped
2019 F150 4x4 SCrew SB STX 5.0 3.55 factory tow package, 7000#GVWR, 1990 CC Tow mirrors, TBC


Turtle n Peeps

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Posted: 04/20/22 08:47am Link  |  Quote  |  Print  |  Notify Moderator

Towing; as with most things in life are a compromise. The manufactures are also saddled compromises.

Some say to bring the front end height 100% back to non towing status. Some say 50%. Some say even less.

I say those numbers are useless....or next to useless and here is why.

Essentially, you want all four tires to have the same weight on them whether towing or not. When all four tires have the same weight on them handling and braking is optimized. Ever wonder why trucks now days have the engine jammed up under the dash? Some mechanics think its to make them mad but the real reason is to get the weight bias as close to 50/50 as possible. Now you know.

That being said the proper way to do a towing setup is to weigh the vehicle and try to make all 4 tires the same weight on your tow rig with your trailer attached.

One could have two trucks with drastically different weight biases. Case in point is a 2500 Ram with a Cummins in it. The Cummins engine is very heavy and the Hemi is light. That being so, I would put more weight on the rear of the Cummins truck and less on the Hemi truck to make all four tires do the same work even though both are 2500 series truck.

Now, if you set up your truck while towing with a 50/50 weight bias you will have optimized handling but braking won't be optimized. (there is that compromise again) Under panic braking with a 50/50 weight bias vehicle a lot of weight goes to the front of the vehicle and the rear tires do very little.

For "me" I put somewhere around 48/52 front to rear weight bias in my truck/trailer towing combo. This seems to make the best "compromise" for "me" for handling and panic braking.


~ Too many freaks & not enough circuses ~


"Life is not tried ~ it is merely survived ~ if you're standing
outside the fire"

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Grit dog

Black Diamond, WA

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Posted: 04/20/22 09:26am Link  |  Quote  |  Print  |  Notify Moderator

^How do u “put” your weight to 50/50 or 48/52 or whatever?
Of course you can adjust the weight bias a bit with a wdh IF you use one, or IF you are towing a trailer that is even possible to use one on.
But it’s only by coincidence or maybe very careful planning and a specific trailer tongue weight and the placement or removal of additional weight on the truck (or trailer I suppose) that you could even get to your ideal 50/50 bias.
I agree with you on the weight bias concept, if your post is 1000% mis leading to anyone who would actually find this discussion beneficial, because you can’t just “do” what you’re saying without everything I said above magically falling in place or some ridiculous gyrations with adding or subtracting dead load somewhere.


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ktmrfs

Portland, Oregon

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Posted: 04/20/22 12:57pm Link  |  Quote  |  Print  |  Notify Moderator

Turtle n Peeps wrote:

Towing; as with most things in life are a compromise. The manufactures are also saddled compromises.

Some say to bring the front end height 100% back to non towing status. Some say 50%. Some say even less.

I say those numbers are useless....or next to useless and here is why.

Essentially, you want all four tires to have the same weight on them whether towing or not. When all four tires have the same weight on them handling and braking is optimized. Ever wonder why trucks now days have the engine jammed up under the dash? Some mechanics think its to make them mad but the real reason is to get the weight bias as close to 50/50 as possible. Now you know.

That being said the proper way to do a towing setup is to weigh the vehicle and try to make all 4 tires the same weight on your tow rig with your trailer attached.

One could have two trucks with drastically different weight biases. Case in point is a 2500 Ram with a Cummins in it. The Cummins engine is very heavy and the Hemi is light. That being so, I would put more weight on the rear of the Cummins truck and less on the Hemi truck to make all four tires do the same work even though both are 2500 series truck.

Now, if you set up your truck while towing with a 50/50 weight bias you will have optimized handling but braking won't be optimized. (there is that compromise again) Under panic braking with a 50/50 weight bias vehicle a lot of weight goes to the front of the vehicle and the rear tires do very little.

For "me" I put somewhere around 48/52 front to rear weight bias in my truck/trailer towing combo. This seems to make the best "compromise" for "me" for handling and panic braking.


equal weight NO NO NO, optimum weight is to stay near the factory weight distribution % front to rear. for many vehicles today trucks and cars, that's in the 55/45 to 60/40, range there are only a few vehicles anywhere near 50/50 distribution And few if any trucks.

Goal from manufacturer for almost all vehicles today is for the vehicle to understeer under most conditions.

Turtle n Peeps

California

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Posted: 04/20/22 11:27pm Link  |  Quote  |  Print  |  Notify Moderator

ktmrfs wrote:

Goal from manufacturer for almost all vehicles today is for the vehicle to understeer under most conditions.

Hence the reason they plow like a John Deere in the back 40 field.

There is a reason trucks handle bad from the factory and you hit on the reason. They tried to mitigate the problem by jamming the engine up under the dash but as you said, they still can't get 50/50. (nor do they want too) In the old days people used to put a steel plate in the back of their truck. Or bags of sand. The reasons were the same.....to get the truck to handle better in all conditions.

Like I said above, the goal of a well handling road vehicle is to get all 4 tires working the same. I set my towing truck up where the weight bias is around 52/48 when the trailer is connected. Like I said above, this is a compromise, but a compromise that works well.

If you like your truck to plow like a pig in a turn so be it, but I want a well handling truck when I tow.

Wade44

Ohio Farm Country

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Posted: 04/21/22 03:12am Link  |  Quote  |  Print  |  Notify Moderator

marpel wrote:



I have never owned a 2500, so wonder if this is HD specific or if this is now the recommended method for towing with all GMC trucks (don't know about the other makes)?

Marv


Having towed just about everything imaginable from trailers full of hay, to livestock, to you name it my entire life on the farm, with everything from 3/4 ton Fords and GM's to F450's, and at weights which were totally overloaded in a lot of cases, I find it hard to believe you're going to be able to measure any front end rise on a HD truck when loaded down towing conventionally or otherwise.


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