Need To Move Ball Mount Aft - Options?

Dalehelman

I wonder why hitch manufacture specify tongue weight limits, but never specify what the distance between the linchpin and center of the ball should be to meet that limit. I find there is a wide range. A lot depending on the amount of drop. Some having a straight vertical drop. Others with an angled drop. Could it be that a few inches either way is just not that critical? Unless the draw bar specifically refers to a reduction lost capacity.

Horigan

That's a good question.  I've seen caution about reduced tongue load capability on some extenders, but not all.  Maybe there is assumed margin in Class 3 hitch receivers.  

Here are some free body force diagrams of a typical 8" hitch (ball to hitch pin) with 500 lbs applied to the ball.  The other blue arrows are the loads on the hitch from the red receiver.  You can see the increase in loads in the receiver, and chassis, with a 12" hitch.

(As a retired mechanical engineer, I haven't done free body diagrams in a loooooong time.)

Dalehelman

@Horigan
love the diagrams thanks.

Verna

I have emailed trailer for a clarification between extended and not extended, but just longer. 

Denny16

An extended hitch is a lever, the longer the lever, the less weight it takes to move the other end load.  So 8-inches will take 600 lbs to load the rear axle of the TV, a 12-inch hitch will only need 400 lbs to,load the axle, you have lost 1/3 of your tongue weight capacity.

Extending the trailer tongue has the opposite effect, and will reduce the tongue weight being applied to thenTV hitch.  Again, this is a lever with the load (trailer) on the trailer axle end pivot and the trailer tongue is the other end of the lever used to apply force to lift the trailer level.
cheers

Dalehelman

I would definitely avoid using something like this

Sharon_is_SAM

This from etrailer - hitch extender vs longer ball mount:

Why Do Hitch Extenders Reduce Hitch Capacity but Long Ball Mounts Do Not

Question: 

Hi, I have a general question about how these items affect hitch capacity. I have been looking at a lot of your expert answers and am confused on the theory. Pretty much everywhere in your technical help I see that a hitch extension will reduce hitch capacity by 50. The reason stated is because the hitch extender moves the load out farther from your vehicle, applying more leverage to your hitch. I understand that theory even though I imagine the 50 figure is just a safe level for liability. I would think there would be a differnet percentage for each length of extension. The problem I have is that it seem like a longer shank or ball mount would do exactly the same thing but I dont see that mentioned. Each hitch has a maximum hitch weight spec. and a maximum trailer weight spec. At what ball distance from hitch is this specd at? There must be some standard because, like you say, the further the load is moved out from the hitch, the more leverage there is. One last confusing point was this comment, Using an extender in a 2-1/2 inch receiver does not decrease the tongue weight capacity of the hitch like it would with 2 inch hitches. Why should that matter? Shouldnt it still be 50? Thanks for taking the time to explain this.

asked by: Dean

Expert Reply:

This is a great question that there isn't exactly a great answer for. Hitch extenders not only put the weight further away from the hitch which would increase the leverage on the hitch, but they also add movement to the assembly which will increase the impact of the tongue weight since there will be play between the hitch and hitch accessory. Think of how a jack hammer works to help visualize what I mean.

I wish there was an exact figure as to how much the tongue weight gets reduced by based on the distance away from the hitch pin hole, but none of the manufacturers are willing to get that specific. 50 percent is a conservative number that is easy for people to remember and adhere to and won't get them in trouble.

Longer ball mounts typically have lower capacities than standard ball mounts, so that is generally how they reflect the lower capacity from the increased leverage.

2-1/2 inch hitches also follow a similar train of thought. While the rule doesn't necessarily apply to the hitch it does apply to the extension pieces. If you look at extender like part # RP45292 you will see it has a much lower capacity than a 2-1/2 inch hitch and based on the differing length its used at the capacity changes as well.

expert reply by: Jameson C

Sharon_is_SAM

http://www.visualsc.com/hitch_calc.htm

Here is a good explanation.  Just add your measurements to calculate the impact on the tongue weight capacity.  The torque increases proportionally to the additional length.  

WilliamA

Another effect of long hitch extensions not often mentioned is that they increase the trailer's propensity to sway. Moving the hitch point away from the axle increases the swing-radius of the hitch. 
WilliamA

Tampakayaker

What is the length of a typical hitch bar?

I have a drop one from Harbor Freight (no length measurements on line) and I'm able to drop my tailgate without hitting the tongue jack.

Would that be considered an "extended" hitch?

Horigan

Typical hitch bar/ball mount is 8" from hitch pin to ball.  At least that what my Curt standard 2" drop ball mount is.

Sharon_is_SAM 's diagram, I would add 4" for that equation.  (hitch pin to forward end of receiver)

Denny16

Long draw bars or extensions, are both bad ideas when towing RV trailers (or any trailer for that point), loads on the TV receiver sremincreased, the TV max tongue weight is decreased and as William pointed out, the longer the distance from the TV axle to to hitch ball, the more trailer sway is induced, and the more unstable the rig becomes.  Be safe, use the correct length draw bar/ball combo for your TV.  In most cases this is 6 to 10 inches.  Why take chances for the sake of a minor convince.
cheers

Verna

Well, I consider etrailer to be an excellent expert in the towing field and I will continue with my 12 1/2” long ball mount. I have never experienced any sway and I feel safe.  I am well within their towing and tongue allowances with my former T@B 400 and my new T@B 320.   

Thank you, @Sharon-is-SAM. I have not received my answer from etrailer, but your quote from etrailer will suffice. 

WayneW

Interesting discussion. I’ve been wondering the same thing because I’m using a longer stinger so I can lower the tailgate on my F150. My engineering student son got involved. He’s scary smart and a bit anal (probably make a good engineer). He said he just felt like modeling something but mostly I think he’s bored this weekend because his girlfriend can’t come visit.

I was more focused on the effect at the attachment point, as diagrammed by @Sharon_is_SAM. But my son pointed out the tensile strength of a single Grade 8, 1/2” bolt is over 10,000 lbs, so whether your receiver is bolted on with multiple bolts or welded on, we’re not coming close to a failure point at the attachment point with a longer stinger. 

My son focused on the load that is transferred to the rear axle which is probably more appropriate. That’s why the provided link asks about gvw of TV, distance from receiver to rear axle, TV wheelbase, etc. There the effect of a longer stinger is much less pronounced - about 10 more pounds based on the numbers I gave him. (He dumbed down his response so I could understand it)

Perhaps this explains why etrailer isn’t too concerned about a longer stinger reducing tongue weight. But an extender introduces multiple movement points and failure points that a stinger does not. Regardless, like @Verna, I’m also now comfortable with my 12” stinger. 

CrabTab

I have a question about longer ball mounts (option #2 in the OP).

Several times in discussions I have seen negative comments on the forum about the hitch extenders. From what I read (researching e-trailer, etc.) they have the same performance characteristics as a longer draw bar. I get the loss of capacity with the longer lever arm. E-trailer says hitch extenders are safe. Why do folks deride them?

Please understand that I'm trying to learn here, not pick a fight.

Thanks in advance.

Denny16

It is not a chance of the trailer or TV attachment point failing.  It is the towing dynamics involved.  The further back from the axle a receiver hitch ball is extended, the less stable the trailer/TV rig becomes.  Will 12-inch draw bar or a total extended length of 12-inches vs the standard 8-inches used to determine the vehicle towing limits make much of a difference?  It does increase tongue weight a bit (lever effect) but as long as this factor is still less than the max tongue weight, it should not be an issue as long as you keep,your towing speed down.  

The faster you tow a trailer with a bumper/receiver hitch arrangement, the more unstable it can become, and in an extended ball mount pivot point, you add in an additional stability issue factor from what I have read in studies conducted.  If you keep your speed under 60mph, you should not have an issue.  The problems occur with most trailer accidents, is when they are being towed too fast for the conditions or improper trailer loading.  I like to stack the odds in my favor, by keeping my speed around 55 mph (max speed for towing in Calif.) and keeping my draw bar as short as possible.  
cheers

Dalehelman

IMHO if you are driving 55 mph on southern Calif. highways you are a serious traffic hazard. Unless everyone is driving 55. Most of the times while traveling in southern California in various RV over the years. The traffic flow can exceed 75 to 80 mph. Trucks routinely travel at 65 mph. I know because I was one for years. The safest speed IMHO is whatever the traffic flow is, and your equipment needs to be able to safely keep up with the flow. Slow moving vehicles cause others to make necessary lane changes to keep with the flow of the majority. I am not saying this is good or bad. Only that it “is what it is”. 

gulfarea

@Dalehelman I could not agree with you more! On the Utube with Traveling Robert is a video of some car trying to pass a slow moving class A RV on a 2 lane and almost was a head on to the car in the on coming lane. Robert was doing 65 as he should. Even though I like to take the scenic 2 lane roads I take the 4 lane roads just so I don't cause a crash as they can pass with no problem as I am in the right lane doing at least the speed limit. I have had my CDL license for years and have seen plenty of close calls. Art

Denny16

Fine, if you want to pull a trailer at 70-80mph, then you should keep your draw bar at it stock (8-10 inch).  Good luck and stay safe.

I lived most of my youth in SoCal, and the only time you could drive 80mph was at 2-6 in the morning, after 6am, commute traffic slowed the traffic flow to 55-65 mph with 70mph on occasion, on a good day prior to the 90s.  The last time I went through LA it was more like 45-50 mph and mostly stop and go driving on I-5, part of time.  Only after I-5 was opened and on some other new freeways could you do 70-80mph in the late 60s and 70s.  Not so much now.  

In NorCal, highway speeds are slower, with 70mph being the max average traffic flow in some rural areas outside the BayArea.  Every year, we have some visitor kill themselves driving too fast on our non-freeway country two lane highways, by joining the birds and going over a embankment or cliff.  On Hwy 101, which is 4 lanes in most areas now, driving 55-60 in the right hand lane is safe, faster traffic can easily pass in the left lane without slowing traffic, which is not that busy, unlike SoCal.  

Cheers

GatorEgg

All these opinions and debate are interesting.  So.... if I have a long bed truck with a standard ball mount it’s good.  But if I have a short bed truck with an extended ball mount which puts the ball the same distance from rear axle as a long bed, it’s bad?  Hmmmm......

Dalehelman

There are plenty of times when traffic is backed up in So Cal, but when it’s not they more than make up for it.

Denny16

I think we need to go back to a National fixed max speed limit, like 60mph.  Your bank account will thank you, and more importantly the environment will thank you.  Driving slower will increase the MPG of your vehicle (burning less gas) and reduce emissions. 
cheers

Lil_Lucy

Speed limit signs are like most all other signs. Only law abiding citizens adhere to them. All the crazies out there view them as only suggestions.

Denny16

I was hitching up my TaB400 today, and noticed the Warning Sticker on the side of tongue, which had several Warnings one of which was not to use a WDH that exceeded 750 lbs rating.  The last one was, Not to tow with an extended hitch meaning to extend the hitch ball back more from the TV than the stock drawbar.   So using a hitch extension or extended draw bar could void your TaB 400 warranty, or insurance if you had an accident with the trailer.  These warning labels are on the trailer for a reason, we need to read them...

cheers

GatorEgg

Denny16 said:

I think we need to go back to a National fixed max speed limit, like 60mph.  Your bank account will thank you, and more importantly the environment will thank you.  Driving slower will increase the MPG of your vehicle (burning less gas) and reduce emissions. 
cheers

Naw, no national limit needed.  Different areas require different limits.  Just drive properly at what you’re comfortable with.

Dalehelman

IMHO The safest speed limit is what ever the traffic flow is. Interstate 84 through Idaho.

Denny16

That 70 mph is for commercial fifth wheel rigs.  Drive as fast  as you like, it’s your rig.  Idaho is not known for its highway safety, and not all Idaho highways have that fast a speed limit.  Personally, I do not drive that fast, sports cars yes, I did go fast, but pulling a good size trailer, no way.  
cheers

Dalehelman

Not only tractor trailer rigs, but triple trailer rigs as well.

Denny16

Yes, they are crazy in both Utah and Idaho.  

But their main Highway multi lane system is flat and straight.  Going into the mountains, the speed limits drop quickly.
cheers

rcarlson1957

I use jack e up and remove jack when on road - no worries plus easy to step across trailer tongue too.