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Old 10-14-2013, 08:36 PM   #771
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like this? I have to do this with my Express van, as the receiver is recessed forward of the rear edge of the bumper....it works fine, but why cut it off?

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Thanks for posting the picture of your dolly. I've been looking for a portable storage solution for the stinger and rock tamers.

Ken
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Old 10-15-2013, 06:47 AM   #772
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Thanks for posting the picture of your dolly. I've been looking for a portable storage solution for the stinger and rock tamers.

Ken
I shamelessly stole the design from another forum member here.....can't remember who to give the kudos to though. I did make mine big enough for the flaps to store inside for winter storage and my batts to sit on top on either side of the stinger. Should free up some floor space.
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Old 10-29-2013, 09:40 PM   #773
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Ok.. I have replacement PP hitch receiver end installed.

The new one was sent with a slightly longer shank so that I can install the RockTamers. I did not have to modify (saw the end off my receiver adapter).

Interestingly I could not find original instructions. I printed out a fresh set and remade all measurements. The interesting part is not my forgetfulness, rather, the outcome. One of my sons helped install initially and that had us mount with "plates down". My measurements resulted in "plates up"... And about an inch higher result for the stinger.

I also added additional washers to the bumper pin.

"Things that make you say 'hmmmm'.."
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Old 01-24-2014, 05:02 PM   #774
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Ok - probably an odd request. Bear with me - some background first...

I'm considering (haven't decided for sure) swapping out my 1000# bars for 1400# bars on my ProPride. Sean recommended 1400 but I went with 1000 because the AS manual said the tongue was 1000 max. Originally, the idea behind the swap was to improve porpoising. However, since adjusting the hitch head to be even (it was off by 1.5" on one side) the porpoising has basically gone away.

The other reason is that at 6" of lift on the WD jacks, I'm only getting 50% FALR. According to my truck's manual, 50% is all I need and in all honesty, the front fender barely moves when I hook up!

So I'm on the fence.

Would 1400# bars reduce porpoising and move more weight to the front axle? If so - how?

Then if that's the case (and here's the odd request) does anyone have video of that process? There's nothing on YouTube about PP installation (which would show the part about WD bars) and more importantly, I'm looking for video of removing them (from a PP on the a-frame) and then reinstalling (or installing new ones).

I asked in a different thread how difficult this would be (I'm not a mechanic! ) and was told it's very easy. I was told the same about correcting the hitch head and it really was. Sean seems to think it will take 15 minutes! But I'd love some specific instructions and video would be even better.

Anyone have such a thing? I might just stick with the 1000s. It's all been good so far!
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Old 01-24-2014, 05:23 PM   #775
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What is FALR?

The 1400# bars are stiffer therefor it takes less travel of the WD jacks to get the same WD. Although they look pretty stiff both 1000 and 1400 bars will flex under load, the 1000 more so than the 1400.

I feel the best policy in cases like this, is to do what the manufacturer of the equipment (in this case Sean) tells you to. I have ~1000 lb. tongue weight. I use the 1400# bars Sean recommended. I have no problems and the ride is good. Sean has sold a lot of hitches to Airstream owners, so I would assume he knows what he is talking about.

This a trade off. The stiffer the bars, the harder the ride. The softer the bars, the more up and down travel (bucking) you will get. I find that with my 1400# bars, I sometimes have to adjust the WD jacks when we first start out with a given loading. I loosen them to get rid of a harsh ride, and tighten them to get rid of a bouncy ride.



Ken
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Old 01-24-2014, 05:26 PM   #776
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I have 1400 lb bars on my 1991 34' and have to crank them pretty hard to restore front tire weight, it's a HaHa but the geometry should be the same. We have towed all over the place and not seen any issues from the higher rated bars. PP and HaHa bars dont follow the same guidelines as regular hitches because of the extra spacing from the ball. Thats my opinion and its worth exactly what you paid me for it!

In my opinion, proposing is a function of the 2 vehicles and reducing it by using WD is at the risk of extra strain on the tongue. One of these days I'm going to put on strain gauges and see what is really happening on the A frame.
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Old 01-24-2014, 05:39 PM   #777
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Ken - FALR = front axle load restoration. The scales say I take 500# off the front axle when connecting, and at 6" of lift on the WD jacks, restore 280# to the front axle (for 56% FALR).

Manual says 50% is sufficient so I may be good as is, and again, the porpoising stopped after straightening out the hitch head. Still - Sean recommended the 1400s at the time of the sale and I'm tempted to swap them out if easy enough to do on my own.
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Old 01-24-2014, 05:44 PM   #778
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...snip...

In my opinion, proposing is a function of the 2 vehicles and reducing it by using WD is at the risk of extra strain on the tongue. One of these days I'm going to put on strain gauges and see what is really happening on the A frame.
Now that's interesting. Hadn't thought of that.

Because they've worked well, there isn't a need per se to swap them out. But I really do wonder if the 1400s would be more appropriate?

Still would like to see (in video) what the procedure would look like - might help me decide if I feel comfortable trying it.
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Old 01-24-2014, 05:54 PM   #779
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Originally Posted by SteveSueMac View Post
Ken - FALR = front axle load restoration. The scales say I take 500# off the front axle when connecting, and at 6" of lift on the WD jacks, restore 280# to the front axle (for 56% FALR).

Manual says 50% is sufficient so I may be good as is, and again, the porpoising stopped after straightening out the hitch head. Still - Sean recommended the 1400s at the time of the sale and I'm tempted to swap them out if easy enough to do on my own.
I would have to get the manual out to figure out how much work it would be to swap the bars. However I installed mine on my own so I think I could swap out the bars with less work than that.

I don't agree with whatever manual you are quoting. The load placed on the tow vehicle ideally should be proportionally distributed between the front and rear axles.

For instance, lets say the difference between the rear axle's empty weight and max rated weight is 1000# and the difference on the front axle's is 500#, the load should be distributed in such a way so as to put 2/3 of the load on the rear axles and 1/3 on the front. If you unload the front axle at all, you will negatively affect the steering characteristics of the TV. If you unload it enough, it will be unstable and difficult to control.

With your trailer and 3/4 ton TV, it should be easy to keep from unloading the front axles with WD bars heavy enough. Perhaps you need the 1400# bars.

Ken
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Old 01-24-2014, 06:44 PM   #780
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One other thing I think is worthy of mention:

When a piece of equipment has a weight rating, that is the maximum weight it is certified to handle safely. Therefore, if your tongue weight is 1001 pounds, you are technically exceeding its design limits. These weight distribution bars are the same as any tool. You should choose the weight rating that you know you will not have a need to exceed.

Ken
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Old 01-25-2014, 01:15 PM   #781
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I don't agree with whatever manual you are quoting. The load placed on the tow vehicle ideally should be proportionally distributed between the front and rear axles.

For instance, lets say the difference between the rear axle's empty weight and max rated weight is 1000# and the difference on the front axle's is 500#, the load should be distributed in such a way so as to put 2/3 of the load on the rear axles and 1/3 on the front. If you unload the front axle at all, you will negatively affect the steering characteristics of the TV. If you unload it enough, it will be unstable and difficult to control.
A different opinion on the question of restoring load to the front axle is offered here for consideration:

Using a WDH to transfer too much load to the front axle can lead to undesirable TV oversteer. Some TV and WDH manufacturers, in the past few years, have changed their WDH adjustment recommendations.

I think the reason Ford, Chevrolet, Toyota, Equal-i-zer, and others have changed their weight distribution specifications is pretty well summed up in this Letter to Editor by Richard H Klein, P E printed in TRAILER BODY BUILDERS Magazine. The comment which specifically addresses front axle load is:

QUOTE
2. The statement “too much tongue weight can force the truck down in the back, causing the front wheels to lift to the point where steering response and braking can be severely decreased” is not the real issue with heavy tongue weights. The real problem is that the tow vehicle's yaw stability, as measured by “understeer gradient”, is severely decreased. This increases the propensity of the tow vehicle to jackknife in turning maneuvers. Specifically, recent full scale testing conducted by the SAE Tow Vehicle Trailer Rating Committee (and now published in SAE J2807), determined that the use of weight distributing hitch torque should be minimized. In fact they recommend that the Front Axle Load Restoration (FALR) not exceed 100% (100% means that the front axle weight is brought back, via weight distribution, to a weight equal to its “no trailer” condition).
UNQUOTE

A related explanation from a representative of the company which manufactures the Equal-i-zer hitch says:

QUOTE
In the past we had suggested that you should see a small drop on the front suspension. We are always trying to improve things here at Progress – our motto is “Safe and Happy Customers,” and so we are always reviewing our instructions and installation process. Recently, as part of this constant effort our engineers looked more deeply into this aspect of installation. We had always felt that a small drop was a sign that the trailer’s weight was being transferred to the front axle, and that this was essentially a good thing.

As our engineers reviewed the instructions for the last round of renewal of our instructions, they found research results that contradicted our prior thinking. There has been a substantial amount of testing conducted by experts from SAE and the RV Industry Association to find out what will produce the best stability when towing. This towing suggests that you want your front axle’s compression to be close to, but not lower than your free-standing height.

UNQUOTE (Underline added for emphasis.)

Ford now says the Front Axle Load Restoration should be approximately 50%.

Chevrolet/GMC now says the FALR should be 100%, 50% or 0% depending on TV model and TT weight.

Reese now says, "A new term in the industry is (“FALR” – Front Axle Load Return). 100% FALR Means the front fender is returned to the preload position. That is our recommendation for best performance."

Equal-i-zer says the Front Axle Load Restoration should be between 50% and 100%.

Equal-i-zer's revised instructions specifically state:
Good adjustment:
You have most likely achieved good weight distribution adjustment if your measurements show the following with the trailer coupled and the weight distribution engaged:
1. From the coupled without weight distribution measurement, the front wheel well measurement is at least halfway back to the original uncoupled measurement. See line C on Front Wheel Well Measure Chart.
2. The rear wheel well measurement is somewhere between the uncoupled height, and the coupled with no weight distribution height. It should NEVER be higher than the uncoupled height. See line C on Rear Wheel Well Measure Chart. See Figure 19.


Ron
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Old 01-25-2014, 01:43 PM   #782
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Wow,

I'm not going to argue with SAE or equalizer, but I am going to have to do a bit of thinking before that makes sense to me.

Do they carry the same logic over to loading the bed of a truck? In other words are they saying to load the truck so that the rear axle carries all or nearly all of the load or even unloads the front axle to some degree?

I would really like to read something that explains all of this in more detail.

Ken
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Old 01-25-2014, 06:05 PM   #783
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Do they carry the same logic over to loading the bed of a truck? In other words are they saying to load the truck so that the rear axle carries all or nearly all of the load or even unloads the front axle to some degree?
Ken, the concern expressed by Richard Klein and the statement by the Equal-i-zer representative pertain to proper adjustment of a WDH when towing a trailer.
Carrying a load in a truck when not towing does not present the same problems.

The concern stated by Mr. Klein is that adding too much load to the TV's front axle via the WDH can severely decrease the "understeer gradient". In simpler words -- too much load transfer can increase the tendency toward "oversteer".

Oversteer can result if the TV's front tires are generating too much lateral force and/or the rear tires are generating too little lateral force. Lateral force depends, in part, on the load on a tire -- increasing load generates more lateral force and decreasing load generates less.

How the TV responds to lateral load depends on distance from a tire to the TV's center of gravity. Lateral load tends to make the TV rotate about its CG.

When a vehicle rounds a corner, lateral load on the front tires multiplied by the distance from front axle to CG tends to rotate the front toward the inside of the curve. Lateral load on the rear tires multiplied by the distance from rear axle to CG tends to rotate the rear toward the inside of the curve. The objective is to keep the front-induced torque equal to the rear-induced torque so there is no tendency for the TV to rotate about its CG.

For the case of a TV with no trailer attached -- if the CG of the TV plus its load is moved rearward (e.g. by adding load at the rear of the box), the load on the front axle is decreased and the load on the rear is increased. For a given tire slip angle, lateral force on the front is decreased and lateral force on the rear is increased. However, distance from front axle to CG is increased and distance from rear axle to CG is decreased. Therefore, the difference in product of lateral force times distance to CG for front and rear is relatively unchanged and there is relatively little tendency for oversteer or understeer -- as long as the load change on front and rear axles is not too great.

If we attach a trailer to the TV, we have, in effect, added a weight equal to the trailer's tongue weight onto the ball. Without WD applied, the effect is similar to adding load to the rear of the TV. The major difference is in the relative magnitude of load removed from the front and load added to the rear. For a 1000# TW, we might have 400# removed from the front and 1400# added to the rear.

Lateral force generated by a tire is not a linear function of load on the tire. If it were, the decreased lateral force at the front would be exactly compensated by the increased front-CG moment arm, and similarly for the rear.

In actuality, the rate of lateral force generation decreases as tire load increases. This means that when more load is added to the rear axle than is removed from the front axle, the lateral force generated by the rear axle is not sufficient to keep the front and rear torques in balance. The TV tends to oversteer (rear end wants to go the the outside of the curve), which might be hard to believe since load has been removed from the front axle.

When WD is applied, things get even worse. Application of WD causes load to be added to the TV's front axle without changing the location of the TV's CG. And, load is removed from the rear axle without changing the location of the CG. The lateral force generated by the front axle will increase and the lateral force generated by the rear will decrease.

Since there is no compensating effect due to changing location of the CG, the increased lateral force on the front will tend to make the front of the TV turn toward the inside of the curve.
The decreased lateral force on the rear will tend to make the rear of the TV swing toward the outside of the curve.
This can lead to a serious oversteer situation which could result in loss of directional control.
This all means that, from a yaw stability point of view, it is best to minimize the amount of weight distribution.
Of course this concern must be balanced by the concern for axle load distribution.
It appears that the RV trailer towing industry is moving toward a 50% FALR as being a good compromise.

Quote:
I would really like to read something that explains all of this in more detail.
So would I. Then I wouldn't have to wonder if what I'm saying is really correct.

The Richard H. Klein Bibliography has some papers which might be of interest. Start with #5 under DOT Reports and B under SAE Papers

Ron
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Old 01-25-2014, 07:02 PM   #784
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Ron,

Thanks for taking the time to compose all of that. After reading through it, it is obvious that it will take some slow and cautious rereads along with drawing some pictures for myself as I go. Maybe this a good excuse to buy a toy truck and trailer. My brother inherited all my toys when we were growing up.

If I run into something I can't get my head around, I'll send you a PM in order to avoid having to do my thinking in this thread.

Ken
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