Length of hitch?

Butch

Perhaps I am using incorrect terminology but I am trying to ask a question about the distance the ball mount is from the rear of the TV. The first Curt hitch looked to be about a foot from the rear of the TV, but it towed nose up - slightly. I bought a new hitch (coupler?) that is lower by about two inches but it is not as long as the first, perhaps extending 6” from the TV. Is there a perfect length? What are the ramifications of being too long or too short? Thank you for your advice. Butch

ras

IMHO, the difference between two inches and six inches is fairly insignificant. There are extenders that add anywhere from 18 to 34 inches, Most folks who add that much are trying to clear a side opening tailgate on an SUV or adding a couple of bike racks. Those longer extensions definitely have an effect on the stability when you're on an undulating surface or exposed to gusting cross winds (they set up an oscillation where your trailer is moving back and forth and left and right)), As long as your tongue weight is within bounds and the line between your tow vehicle and the rv is level or slightly low, I don't think that 4 inches will hurt. Anyone using those longer extensions definitely needs trailer brakes so they can slow the trailer without slowing their vehicle and kill the oscillations.
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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.

LuckyJ

@Sharon_is_SAM said:
This from etrailer - hitch extender vs longer ball mount:

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

...............

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.

Euh, if you read this correctly, you shouod understand tgat tge capacity is also reduced by the lenght of tge ball mount.

The differnce is that a hitch as a load capacity ex 500lbs. If you add an extension, 50% would now be 250 lbs. When you use a longer draw bar, tge bar capacity would only be 250 lbs instead of tge short 9ne that would be 500lbs. Equal to the hitch receiver.

So 250 lbs because of a hitch extension that reduce capacity from the 500lbs or 250lbs capacity longer draw bar on a 500lbs hitch equal tge same overall capacity.

So no matter how you look at it, the further distance from the hitch frame, the lower the load capacity. Plain and simple.

WilliamA

This is perhaps one of the most mis-understood topics in trailering. There is a huge amount of debate about it going on across internet forums pretty much daily. There is an active thread on the T@B forum as we speak. So for those who are truly interested, I'll have a go at an explanation:

First, a few definitions are in order.

1. The "receiver" hitch is the part that bolts to your tow vehicle. Rated by "class", i.e. I, II, III or IV. Let's assume everyone is using either a class III or class IV receiver.

As the OP said, let's call the insert that goes in the receiver the "coupler". It's the part that the ball is bolted to.

Now for the trailer. The trailer reacts to the movement of the tow vehicle in three axis: roll, pitch and yaw. Roll is the movement of the trailer around an imaginary line drawn from the hitch through the trailer to the rear. For example, if your trailer is moving and one wheel goes up on a rock while the other goes in a hole, it's going to pivot on its roll axis. Pitch is how the trailer moves around the axis drawn through the wheels. If the hitch goes up, the trailer is moving on its pitch axis. If the trailer is unhooked in your driveway and you pull the tongue in a circle, it's pivoting on its yaw axis.

Mass...Weight. It's impossible to talk about towing a trailer without understanding what the mass effect is and what it does. For the purpose of this conversation, let's just skip all the mass, velocity, weight physics and recognize that the faster the trailer is going, the heavier it is. That's why you can stop at 5 mph in 3 inches while it takes 120 feet to stop from 55 mph. It's weird, I know. But the fact remains, the faster you are going, the more potential there is in your trailer. The more potential energy, the longer it takes to stop. That's mass-effect. One last thing about mass before I move on. This is important: when you begin to slow down, the trailer will want to slow down in a straight line. If you're hauling your trailer down to a stop while in a curve, it'll want to go straight. I'll get back to that in a minute.

What is a hitch coupler, really? It's a lever. Need to move a heavy stone in the yard? Grab a board and pry it up. The longer the board, the bigger the stone. It's just a lever.

Static vs dynamic:

Now let's hook it all up and go for a ride. Drop the trailer hitch down onto the ball of your coupler and it adds the tongue weight of the trailer to the tow vehicles' suspension. The tow vehicle squats down an inch or two. That's"static" weight. It's not moving. Head down the road and things start to get interesting.

Let's assume you don't have any brakes on the trailer for a moment as we move down the road. You're at 40 mph on a nice, straight road and there's a stop sign. You get on the brakes. What happens? The tow vehicle pivots on its pitch axis. The front end goes down (dives, or squats) and the rear end rises because the tow vehicle is pivoting through its pitch axis while the tires become the pivot point. As that happens, the front suspension bears more weight while the rear axle gets lighter. That's why vehicles have bigger brakes in the front, and also why RWAL (rear wheel anti lock) brakes were invented. For the purpose of this conversation, let's just say your vehicle has a perfect 50/50 weight bias. Half the weight is on each axle. In a hard stop from speed, that bias may be as high as 80/20, with 80% of the vehicles' weight transferred to the front axle. Now hang a trailer off the back and repeat. Now you've got a really interesting physics problem. The rear axle of the tow vehicle has gotten lighter, with less corresponding traction from the tires. The trailer wants to keep going. It's pushing on the tow vehicle, making the rear of the tow vehicle lighter still. The tow vehicles' rear tires come to the point where there is not enough traction. As I said earlier, the trailer wants to go in a straight line. The combination of trailer pushing, curved road and hard braking overcome the traction coefficient of the tow vehicles' rear tires and the trailer pushes the rear of the tow vehicle around into a jack-knife. It happens ALL the time.

Now let's talk about that hitch length. Coupler length isn't the whole story here. What we're actually measuring is the distance from the rear axle to the ball. That's the actual hitch (lever) length. Let's say you've got a stubby two door Jeep Wrangler. It's got a lift kit because, well, it's a jeep. The springs are very soft and the vehicle is tall and heavy. But Jeep Wranglers have a really short hitch length because they don't have much rear overhang. Let's say now you've got a Suburban. It's a very long wheelbase, has a long hitch length and it's heavy. The CG is also much lower than the stubby lifted jeep. The Suburban will have much less weight transfer than the Jeep. But true as well, the hitch (lever) is much longer, so there's a multiplier.

That long diatribe is just one effect of hitch length. There are lots of others.

The primary topic on hitch length is usually coupler length vs coupler "extension" length. Simply put, a coupler has one less joint than a hitch extender. Put an extender on, add the coupler to that and you have two joints.

Disclaimer: I'm not an engineer or rocket scientist. I don't work for Etrailer and am not an "expert". Take what I say as interesting brain food, not advice. If you want advice, get that from facebook, Dr Phil or, lacking other options, Scotty Kilmer.

My small brain and instincts tell me that the difference between an 8" coupler and a 12" coupler is negligible. Add another foot or more and things will start to get weirder.

What does that mean? Trailer sway. The bane of travelers.

One of the most important things to get your head around is this: a tow vehicle and trailer contact the road at three points: steering (front) axle, drive (rear) axle and the trailer axle. If you turn the front wheels into a tight turn, the rear wheels follow in a smaller radius through the turn. The length of the hitch will move the hitch point out past the radius of the rear axle as it turns. The longer the hitch, the larger the radius. This is the trailers' yaw axis. As the rear axle follows the front, a longer hitch adds swing and momentum to the trailer tongue. For es induced by yaw take time to dissipate, so some over-correction is necessary. Different problem, same physics.

Last but not least. I haven't talked about strength of the hitch welds and a load of other stuff. To me, hitch receiver strength is secondary to the physics of the lever effects at play. If you're within the tongue weight and your coupler is 8" long or even 12" inches long, it's a safe bet you won't break the receiver welds.

Trailer brakes:

90% of the tendency for the trailer to jack-knife can be avoided by using trailer brakes. Trailer brakes, when applied, actually force MORE weight onto the tow vehicle rear axle as they force the weight around the pivot of the trailer wheels, pushing down on the tongue. This counteracts the forces trying to lift the rear axle. Think about it.

There are lots of trailer accidents each year and I'd be willing to bet that most are the result of loss of control caused by the trailer "pushing" (through that danged "lever") the tow vehicle beyond the ability of the tow vehicles' rear tires to hold it in line. I'd be surprised to find that hitch welds are snapping off all over the place causing accidents.

So there ya go. A long hitch is a bad idea simply because, like a shovel handle, it's a force multiplier. The longer the handle, the more force.

I'm gonna go and make some popcorn and get comfortable.....

WilliamA

zgfiredude

Well done, Sir.

Butch

Wonderful! Thanks to all of you for the great information. I was concerned that the shorter coupler would greatly restrict my ability to back my trailer into my garage - perhaps causing the trailer to strike my truck while backing in a curve. Not enough room in front of my driveway to back straight in. Have to “swoop!

LuckyJ

@WilliamA said:

......> There are lots of trailer accidents each year and I'd be willing to bet that most are the result of loss of control caused by the trailer "pushing" (through that danged "lever") the tow vehicle beyond the ability of the tow vehicles' rear tires to hold it in line. I'd be surprised to find that hitch welds are snapping off all over the place causing accidents.

So there ya go. A long hitch is a bad idea simply because, like a shovel handle, it's a force multiplier. The longer the handle, the more force.
I'm gonna go and make some popcorn and get comfortable.....
WilliamA

Ok, wow, it is not often that I will come back on one of your explenation, but this time, I do think that I need to. First, I think that you over complicate some of your explenation and at the same time, you are missing very good point.

Braking welds, you could be surpised at how many hitch might not have broken, but are a disaster waiting to happen. I did see a few, none on my vehicules. ( and if I have seen a few, I sure more are outthere)

Cause you are right about leverage. All the weight added to tge end of a lever ( and 'm not talking of 2 in more here cause I do not consider this an extension),

if it generate enough weight to affect vehicule stability (this can come from overloaded tongue weight or to large of a trailer for a TV or a double decker extension) can also affect mecanical or structural integrity. Tge itch extension or double hitch that some people are looking at for the momment are more toward 18 and 24". I'm not tgat good at physic, but I know that a breaker bar is a least twice as efficient from 8 to 16".

But we agree that the longer the extension, the probability of problems increase. 😊