What is my actual max tongue weight?

I want to use a hitch-mounted motorcycle carrier on my '14 DC. I have a Draw-Tite Ultra Frame trailer hitch installed and the sticker on the hitch says max tongue weight is 1,200lb. The motorcycle and carrier together would weigh around 370lb. I know the motorcycle carrier, hitch insert/ball, and carrier will work but how do I know what the max tongue weight the truck frame itself can withstand? I can't find the truck's max tongue weight.

 

You should have a yellow/white label on the driver side door jamb that tells you tire inflation pressures, and states the maximum allowable combined weight of passengers and cargo. Hitch weight, motorcycle carrier, luggage, gear, or anything else loaded on the truck counts as cargo. Subtract those weights you'll be adding to your Tundra, including passengers, and what you have left is the allowable trailer tongue weight. The maximum allowable combined weight of passengers and cargo is also in the Owner's Manual, Sec 9-1, Specifications (2017), but you'll need to know your exact truck model number. The exact model number for your truck should also be on a white label on the driver side door jamb.

 

So the motorcycle carrier isn't a trailer, it's a carrier that slides into the hitch receiver and does not have wheels. See the link below.

https://racknrideusa.com/product/rack-n-ride-mx-carrier/

I'm trying to figure out how to do the math per your formular but I can't decide whether to count the bike as part of the cargo or not. My sticker says 1,340lb max weight. My hitch is 84lb, carrier is 70lb, and bike is 300lb. Really won't be carrying anything else besides myself and maybe a gas can so add another 250lb. That's about 700lb. Subtracted from 1,340 is 636lb. But when you put the bike into the formula then what's the point of running the math?

I've asked the question on some other forums and they all say the max tongue weight is probably around 500lb but that seems awfully low considering folks tow their campers.

 

Doesn't matter what you call it. If the weight is being carried by the hitch receiver and the truck's suspension, then it's cargo. As I said, anything that's loaded on the truck, including passengers, counts against your 1340 pound max weight.

Bingo. Your allowable tongue weight would be 636 pounds, but see below:

It's your question. If the motorcycle carrier is occupying the receiver, then why do you need to know the "max tongue weight"? Once you've done the calculation, and you're under the allowable cargo weight, tongue weight is irrelevant because you can't hitch a trailer with the carrier occupying the receiver. But if you could...say the motorcycle and the carrier are loaded in the truck bed...then you could tow a trailer having tongue weight as much as 636 pounds.

Anyone saying they know an allowable tongue weight for a Tundra without doing the calculation above, doesn't know what they're talking about. As an example, lets say you load 1300 pounds of crushed stone in the bed of your Tundra, and then you want to tow a trailer with another 1300 pounds of crushed stone...what is your allowable tongue weight? Answer: Zero. You will have exceeded your allowable cargo weight (1340) the minute you climb aboard.

 

I think I worded my question wrong. I probably should have worded it as "What is my maximum allowable tongue weight?" since I worry about over-stressing the hitch receiver/truck. What I'm really wondering is if I can safely use the motorcycle carrier linked above with a 300lb motorcycle. Given your reply, I think I can.

 

For that small bike on the carrier, it's not close to being an issue imo. I don't know, but at some point, with more weight on the receiver, you would likely need to take GAWR (gross axle weight rating) for the rear axle into account. Those ratings are also listed in the owner manual for each specific model.

Fwiw, 370 pounds total tongue weight would be light for your Tundra. If tongue weight is typically 10 percent of trailer weight, then owners towing RVs here typically have tongue weights well beyond that level, but they are using weight distributing hitches to move some of the tongue weight to the front axle.

 

Since you have an aftermarket frame hitch on the vehicle, your max tongue weight will be determined by the specs it was designed for. I would contact Draw-Tight for the correct specs.

 

Maybe just one more comment from me:

Your owner manual defines TWR (Trailer Weight Rating) for your exact truck model. The owner manual also recommends loading the trailer to maintain a conventional 9-11 percent of the trailer weight as tongue weight. As an example, my 2017 DC 2WD has a TWR of 6800 pounds, so Toyota expects a theoretical maximum of around 680 pounds tongue weight for my truck (subject to other cargo limitations).

BUT...The owner manual also recommends using a weight distributing hitch once trailer weight exceeds 5000 pounds. SO...Toyota is recommending that owners use a WDH to shift tongue weight to the front axle once tongue weight exceeds 500 pounds (10% of 5000lb trailer). Maybe that's where that 500 pound number you heard on the other forum came from, but maximum tongue weight is not a single number; it is still subject to the other cargo you're loading onto the truck.

If you're uncomfortable with the load on your receiver, the simple solution is to load the motorcycle and rest of your typical gear, and take the truck to a commercial scale. Have the rear axle weighed, and if that weight is under the rear axle GAWR listed in the owner manual, you are golden.

 

Correct. My payload remaining after mods and passengers is 603 lbs. i pull a moderate travel trailer with a dry hitch of 510 lbs. After LP tanks, batteries, and other trailer load... I'm actually over payload without putting anything in the bed

 

What class hitch is on the truck. They have a maximum tongue and trailer tow rating based on class of hitch.

 

@Sundog signature shows the formula you need. tilt your phone to landscape to reveal the diagram.

 

The above answer from Sundog with the hitch diagram is the most correct.

Having done many calculations for dynamics, strength of materials, and statics in engineering school, what one should consider is TORQUE on the tongue weight. Using cantilever principles, if you are holding a bowling ball close to your chest and then extend your arms fully in front of you, has the weight increased? Really the weight is the same, just the torque on your shoulders has increased due to the length increase between the fulcrum and the forces applied.

Torque = Length x Mass(weight)

1 ft-lb = 1 ft x 1 lbs
5 ft-lb = 5 ft x 1 lbs

An extension of 5 ft vs 1 ft multiplies your force (weight) by 5x. Similarly, placing a 400 lbs motorcycle on the hitch:

400 lbs x (6 inches or 1/2 foot) = 200 ft-lbs of Tq. on the hitch receiver [unrealistic distance for a hitch mounted moto]
400 lbs x (2 ft) = 800 ft-lbs Tq. [more accurate representation, allow for spacing of handlebars]

It's important to know where these limitations come from. Most people do not understand the background details on these restrictions, there are many factors and some would try to think they know better (hello roof rack people: static vs dynamic loads) Realistically, the materials and structure should withstand these weights quite easily, as even a 1/2 inch bolt has a clamping force of thousands of pounds. So why consider torque instead of just weight? It's complicated, and that doesn't translate well into an owner's manual. The real concern (in my opinion) comes from handling qualities and safety factors.

1. Overloading your tongue would primarily affect your font axle, lifting your front end enough that your front tires are more "floating" over the road, therefore reducing steerability. I have personally done this when I was younger and dumber. Small truck, big load.

2. You also affect your suspension, reducing any play and potentially causing damage when there is no "give" over bumps. Other systems than just your struts can be affected. Turning and rollover risks are also increased.

3. In a trailer setup, you change the characteristics of the truck-trailer interface, where a feedback loop forms and the fishtailing can become out of control, and this is also where your weight distributions and center of gravity should be considered. Swerving may become more erratic.

4. Your braking characteristics become affected, although this has more to do with the total mass of the trailer.

5. Other unforeseen consequences when you get into a shitty situation.

Having said all this, it really comes down to the factor of safety (truck can do 100 mph, but lets limit to 80 so end-user doesn't do anything stupid, etc.) and that these GVWR and trailer weights may not apply to a motorcycle hitch trailer. I think you should be totally fine, just don't get too confident and always be mindful of when you approach or exceed those limitations and what that actually means. Complacency kills.

Also keep in mind, much like friction, everything seems like its holding even until that 99%, then you cross that threshold and shit goes sideways real quick.