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Open Roads Forum  >  Towing

 > Too much spring bar tension?

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Terryallan

Foothills NC

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Posted: 02/22/12 06:01pm Link  |  Print  |  Notify Moderator

Honestly. You can try taking some weight off the front. BUT. Just 1?
/2 trip with the TV nose high, and you will be pulling it back down. Unloading the TV's front, tends to let it float, and sway. Not too much fun.


Terry & Shay
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ktmrfs

Portland, Oregon

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Posted: 02/22/12 07:18pm Link  |  Print  |  Notify Moderator

I'd take a look at your front suspension. Is there a "bump stop" and if so, does the bump stop have 1/2" clearance or more when unloaded? if so, your setup is likely pretty good. If there is a bumpstop and there is less than 1/2" clearance you may be trying to shift to much weight. It's VERY hard to compress the bumpstops so I'd suggest that you don't shift any more weight to the front end once the front end sags enough to touch the bumpstop.

For my truck, GM recomends bringing the front end back down to it's original height only, no further. I suspect two reasons. first, there is minimal clearance to the bump stops unloaded and dropping the front end means compressing the stops. Second, the front is already pretty heavy with the duramax and if your not careful it is possible to overload the front axle.


2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2004.5 Silverado 4x4 CC/SB Duramax/Allison


jerem0621

Tennessee

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Posted: 02/23/12 11:25am Link  |  Print  |  Notify Moderator

Thanks Ron, with 6 links the steering feels quicker. Is this the under steer your describing. My hitch head has the max number of washers in it now. Do you think I should move the entire hitch head down one more hole on the shank to give the TT a more nose down orientation.

I am not someone who judges something by the "good enough" rule. I want it to be as perfect as possible.

After the dual cam install I will get weights.

Sorry about the measurements last night. I didn't get them because I had to hitch in the rain and kind of wimped out. Lol.

Thanks


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jerem0621

Tennessee

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Posted: 02/22/12 07:31pm Link  |  Print  |  Notify Moderator

Thanks everyone. I picked up the trailer tonight from the shop and tried the wd hitch with 7 links instead of 6. The handling on my truck was not near as good. I think I am going to go with what works for me. Equal squat for this F150.

Thanks!

K3WE

Missouri

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Posted: 02/22/12 08:32pm Link  |  Print  |  Notify Moderator

I suppose "the real" answer would be to weigh axle by axle.

But I'm with those that the back of the truck is too high.

Think about this- the back end of an empty truck sits high becuase it has relatively little weight on it. The truck is designed to be loaded down and squatted down. So, hooking to a pickup truck, I would expect to put a lot of weight on the back- get it squatted and then use the WD just to be sure that the front end is carrying some of the weight, instead of being made lighter (as it would be without WD).

Your truck almost looks like an empty truck- exept I can see your front end shoved down a bit.

Now, where in the heck do we come off estimating your axle loads from pictures, when it should really be weighed.....yeah....bad us (and bad you for trying to use a photo that way).

Ron Gratz

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Posted: 02/23/12 07:31am Link  |  Print  |  Notify Moderator

jerem0621 wrote:

---I picked up the trailer tonight from the shop and tried the wd hitch with 7 links instead of 6. The handling on my truck was not near as good.---
Did you measure the front and rear "squat" when you changed from 6 links to 7? Do you know the actual tongue weight? With 1000# bars, adding or dropping one link can make a large change in load distribution. Perhaps 7 links took you too far in the other direction. Perhaps a different amount of rearward tilt could be desirable.

How did you judge the "handling" of the truck? Does the steering seem more responsive with 6 links than with 7? If so, that's not necessarily a good thing.

Adding load to the TV's front end will increase its tendency toward oversteer. Increased oversteer can make a vehicle "feel" better. However, increased oversteer when towing can get you into serious trouble -- especially when rounding a curve.

After you get the Dual Cam installed and adjusted, I would strongly urge you to load the TV and TT as they would be for camping and then find a scale and measure the TV and TT axle loads for the following conditions:

  • Front axle and rear axle for TV only
  • Front axle, rear axle, and TT axles with no WD applied
  • Front axle, rear axle, and TT axles with WD applied
Then you would have a better basis for knowing if the WDH is properly adjusted.

Ron

K3WE

Missouri

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Posted: 02/25/12 02:17pm Link  |  Print  |  Notify Moderator

jerem0621 wrote:

I am not someone who judges something by the "good enough" rule. I want it to be as perfect as possible.


That's admirable- just so you understand that "perfect" for one condition may not be perfect for another condition. (Hauling fresh water to a dry camp towards the front or not so fresh water from dry camp towards the back, or running the trailer more empty).

JBarca

Dublin, Ohio, USA

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Posted: 02/25/12 09:25am Link  |  Print  |  Notify Moderator

Hi jerem0621

Good for you for having an open mind. This has led you to better understanding the dynamics of your rig.

There are mechanical differences of the DC that dual friction sway controls cannot offer and it is the claim to fame of the DC.

The dual friction sway controls added more stiffness to the connection between the TV and the TT than a single bar. That added friction helps resist the lateral forces of movement agasint the side of the TT. The resistance is fairly equal as the angle between the truck and the TT changes for the lateral forces. The friction sway control system cannot self compensate in force when resisting the lateral force acting on the TT and when TT is returning back to center after the force is gone. And once the static friction lock breaks free and the sway bar starts sliding the holding power goes down.

In order to change the holding power of a friction based anti sway control (The DC is in this league as well) you have 2 variables that affect how strong a hold the system has agasint the lateral (side) forces acting on the TT.

* The coefficient of friction between the 2 sliding parts.
* The force acting on the 2 sliding parts.

It really comes down to those 2 variables and is the difference between the 2 styles of anti sway control.

Lets look at the friction for a moment.

The DC is a high friction anti sway control system. In this case it is steel on steel in place of steel on brake pad material. The coefficient of friction between steel and steel dry is .07 - 0.8. Between brake pad material and cast iron dry is 0.4 and wet is 0.2.

The steel on steel may vary a little pending conditions, may range 0.6 to 0.8 and greased up really good may go down to 0.2.

High end brake pad material used on race cars can get higher then 0.4 and may approach 0.5 to 0.6. The ratings where against cast iron and not steel. Brake pad on steel goes down. What exactly the brake pad materiel is used on $50 friction sway control? Good question but it is safe to say it is at least as good as 0.3 maybe 0.4.

See here for more on this. http://www.engineeringtoolbox.com/friction-coefficients-d_778.html

So at the 1st look, dry steel on steel has a higher coefficient of friction then steel on brake pad material. The next part is the force. If the force on the brake pad material is high enough it can overcome the lack of higher coefficient of friction.

Lets look at the friction sway bar. This system has a lever welded to a 1/2-20 bolt in many cases. And that bolt can create a lot of force. If you tighten it to 100 ft. lb. you could approach thousands of pounds of point pressure. The problem is you cannot use that much in this setup as the connection is so tight the telescoping bar will buckle in a turn. So you have to use something less. Which may only be 5 ft. lb. of torque which may produce approx 600# of force. Maybe more or less but in this league.

Now the DC forces. The tension on the WD bar chains directs the force acting on the WD bar steel on steel of the DC. You really cannot dial in that force like you can on the friction sway bar lever. It comes along for the ride from setting the WD on the truck. How much tension is in the chains comes from the tongue weight, the adjustment of the WD hitch, the distance of the TT axles to the ball, the truck wheel base and the rear overhang. Each TT and TV can be different on chain tension.

The difference between friction sway bar and the DC is the mechanical action of the mechanisms. While you can crank up a friction sway bar to be extremely powerful, you cannot use it as it will bend the bar. The DC gets its holding power from the tension in the WD chains created by the WD bar. In most cases the WD chains force is higher then the lever produced point pressure of the friction sway bar. The DC can use the higher force and not buckle the cam or the WD bar. The DC can take advantage of the higher force where the friction sway bar cannot.

The DC can create a higher holding power device due to the actual higher force generated and not buckle the mechanism and from the higher coefficient of friction advantage.

The next advantage to the DC which sets this hitch apart from the friction sway bar or even the Equal-I-zer hitch comes from the cam. There is the laws of physics fact that once a static friction lock breaks free, sliding friction takes over and the holding power goes down due to sliding friction. This occurs on the friction sway bar, the Equal-I-zer and the DC. The DC has an added benefit to help compensate. As the V grooved WD bar rides up the cam it changes the WD bar tension and increases the WD chain force. This increase in force "helps" compensate for the lost holding power of sliding friction. The other friction hitches do not have this advantage.

Once the lateral side force on the TT resides, the DC allows the TT to return to center easier by riding down the cam then the constant hold of the friction sway bar. The sway bar actually resists in both directions.

OK with all that said.... I tried to explain the differences between the 2 anti sway controls. You may or may not find a global shift in stability going to the DC. OK what is he talking about now.... LOL

The WD hitch and anti sway controls are only "part" of what makes a TT and TV stable. It is a very important part but there are other factors.

You talked about semi's passing and you feeling the effects. Was the effect enough that you were making steering corrections when this occurred to compensate?

The truck itself plays a large role in a stable towing rig. The suspension, the rear overhang, the wheel base and how loaded the suspension is and the tires. The tires may be the biggest variable and all tires are not created equal.

Sidewall flex in the tire can make or break a stable towing rig. The friction based anti sway controls rely on the truck being planted stable to the road. If the front or rear of the truck wiggles in the side flex of the tire the anti sway control cannot compensate for that. Even the DC will unlock if the lateral force agasint the TT is high enough if the tire side wall flexes enough and you will feel it in the truck.

A simple test for side wall flex is, go to the back of your truck unhitched but loaded to go camping. Lean up against the back tail gate area and look at the tire side wall to the rim. Rock the truck. Feel that wiggle. The tire is not moving on the ground, it is the truck suspension and the side wall flexing. Remember that feeling and then some day go to a buddy in a CG that has LT tires on a stiffer suspension. There is a difference. These new PU's, the F150 for example that has the really thin profile tires, those tires are stiff to side wall flex. I felt one last summer on a camping buddy who has the new Eco boost F150 and those thinner profile tires are stiff. Even my new Fusion car is stiffer in side flex then DW's 2003 Trailblazer due to the thinner profile tire. Air pressure in the tire is another big variable. 5 to 10 psi can be a big difference in some cases.

Point: Mechanically the DC has better advantages to an anti sway damping device over dual friction sway bars. It will depend if you can find the difference which is based on other factors. Not changing any other factor, if the DC preforms better, then you have optimized the WD hitch part as good as you can. If you want higher performance, need to start looking at the other factors in the truck also including TT weight and balance.

Hope this helps and good luck

John

* This post was last edited 02/25/12 10:09am by JBarca *   View edit history


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


jerem0621

Tennessee

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Posted: 02/24/12 10:13pm Link  |  Print  |  Notify Moderator

I think I have this WD hitch dialed in now with friction sway control.

I must recant the earlier experience. I was towing in the rain for the first time on back roads and I left the friction sway control off. The reason is because I thought I was supposed to take them off in wet conditions. Well, I should have left them on and just loosened them some.

On to today experience.

I changed from six links to seven links and measured the front fenders and discovered that my half inch equal squat was gone and I was about 1/4 of an inch within unloaded height on the front fenders.

I double checked my air pressure in my tv tires and made sure that was right. .

I hitched up and turned on my dual friction sway control. Took the rig on the interstate since I added the second sway bar and found the rig to be amazingly stable, once I got over the fact that my equal squat theory could actually be wrong, I settled down behind the weel and enjoyed the drive to the campground.

The dual friction sway control really surprised me for stability. The push - pull effect from passing vehicles was very minimal. I had a big rig do the slow pass maneuver where it seems like it takes forever for the vehicle to pass. There were no I'll effects, no Uncontrollable sway. The rig felt very stable.

The quick dash "oversteer" was gone and the truck handled like it normally does. The ride was more smooth with less harshness over bumps and expansion joints.

I am not sure how dual cam can be better but I am sure going to try!

Anyway, here is a picture from tonight arriving at the campground. Does this look better? The ride is much better. I am a convert to the get your front fenders back to stock height believer now.



Ron Gratz

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Posted: 02/23/12 02:44pm Link  |  Print  |  Notify Moderator

jerem0621 wrote:

Thanks Ron, with 6 links the steering feels quicker. Is this the under steer your describing.---
I was talking about oversteer. And, yes, a "quicker" steering could be an indication of oversteer.

Quote:

---My hitch head has the max number of washers in it now. Do you think I should move the entire hitch head down one more hole on the shank to give the TT a more nose down orientation.
I would wait until you have the Dual Cams installed and then go through the WD adjustment process again. If you are transferring too much load from rear axle to front axle, that can cause the rear of the TV (and front of the TT) to be too high.

Ron

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