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max hitch weight via hitch rack

10K views 24 replies 12 participants last post by  redlightning 
#1 ·
Wondering if anyone has transported weight on a hitch rack over the recommended 165lb limit? I have a hitch rack for a motorcycle that combined weighs about 275lbs, leary about throwing it on the metris as it exceeds the recommended limit by 100+lbs. Gross tongue weight for metris is rated 500lbs, cant figure out why they have a hitch rack limited to 1/3 the rated tongue weight? Anyone with insight is appreciated!
 
#3 ·
Thank you for the reply. Consulting the Operators Manual has a table that shows capacity of roof rack and a rear mounted hitch rack. Looks like I was generous by 11lbs. Table shows max at 154lbs... See attached picture.

I dont doubt the hitch is capable. Just not sure if the frame attachments for the hitch are what Mercedes used to calculate the max load. Would hate to see my dirtbike break loose and bounce down the highway in my rear view! and potentially cause an accident, in which case an investigation would show I overloaded the hitch and would be liable for any damage (or injury) caused by my negligence... I think I just talked myself out of using the hitch motorcycle rack!!
 

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#7 ·
Agreed. I've personally installed the MB (westfalia) hitch on my Metris, and its a MASSIVE piece of steel. Sitting on the ground by itself its over 70lbs! Its secured by six gigantic bolts through the rear under-frame rails of the van. You could probably load it until the van was squatting to the ground without it failing.
 
#9 · (Edited)
I took a look underneath and made some measurements. The mounting bolts are about 4.5 inches apart and the receiver pin hole is about 9.5 inches from the rear mounting bolts. My normal drawbar puts the ball another 9 inches back.

With a 500 lb load, resolving moments around the rear mounting bolts, 18.5 x 500 = 4.5xF where F is the total upward load on the front mounting bolts. F= 500 x 18.8 / 4.5 = 2056 lb (an approximation, but not far off). Resolving vertical forces, the downwards force on the rear mounting bolts, R=500 + 2056 = 2556 pounds. These are the stated upper limits for attachment to the van and presumably includes a safety factor for bumpy roads etc. Note, with a load leveling hitch properly adjusted, there would only be a 250 pound downward load on both front and rear bolts (depending on the distance back to the trailer wheels). In all cases, loads would be half on each side for the left and right mountings.

I have a 14 inch receiver extension that I use occasionally with a light trailer so I can open the tailgate. With 500 lb on the ball, using the same calculations, F= 3611lb and B=4111. To keep the forces on the bolts within specifications, I would have to reduce the tongue weight to 56%. The warning on the extension says 50%.

I also have a hitch carrier which I have rarely used. It has a 7 inch drawbar and goes back another 20 inches. If the load is centered, it is 17 inches back from the hitch pin, so 26.5 inches from the rear bolts. A 500 pound load (including the carrier weight) would make F= 2944 and R= 3444, so the load would have to be reduced to 70% = 350 pounds to keep F within spec.

There are other factors to be considered as well. A greater load might perfectly OK as long as the road is smooth. Any load placed farther back than the normal ball position could affect handling.
 

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#16 ·
With a 500 lb load, resolving moments around the rear mounting bolts, 18.5 x 500 = 4.5xF where F is the total upward load on the front mounting bolts. F= 500 x 18.8 / 4.5 = 2056 lb (an approximation, but not far off). Resolving vertical forces, the downwards force on the rear mounting bolts, R=500 + 2056 = 2556 pounds.
that is an incorrect assumption. the load is not supported by the bolts directly but by the friction between the mounting plates and the frame, generated by bolt torque (loaded in tension). that's how bolts and screws are designed and dimensioned for.
otherwise one would apply dowels/pins/dowel bushings.

besides that i'd feel perfectly comfortable to load my KTM 500 exc on a hitch carrier on my Metris. i haven't done so yet as i'm still waiting for my lift kit springs from Adventure Van Co.
 
#11 ·
I agree, 275 lb should not be a problem. There is the liability issue, but you can justify that weight. A 500 pound carrier does not mean for all vehicles however, even if it takes a 500 lb trailer nose weight.
 
#12 ·
Don't be afraid to load up a hitch carrier on the Metris. I have a MotoTote hitch motorcycle carrier. The Metris handles my Ninja 300 or FZ07 motorcycle with no issues with the weight. My only issue is ground clearance. It's very low, and speed bumps or driveways are your enemy. I have toyed with the idea of using a hitch riser. I actually bought one, Apex rated at 500 lbs. tongue weight. Several people I know have used them with no issues. I'm not that trusting just yet.
 
#14 ·
Metris, the ultimate Moto hauler! The big bike rides on the transverse rack and the mini's in the cargo bay. The rack does stick out so I have to approach steep entries/exits on an angle. I did install the Sumo Springs in the rear and I imagine they help from bottoming. They were cheap so worth a try. I saw an air spring kit in the UK for like $1000+ maybe a future mod...
 

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#18 ·
Got the Mototote carrier installed. It is about 9" off the ground without load (van is stock height). It's evident that a riser would be needed if running with the van stock height. One concern is that the metal hand guards on the bike are at the window height without much gap. I'm thinking of stuffing an oven mitt and duct taping it to the bar end just in case lol.

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#23 ·
I don't know why you guys are messing with hitches - 1 bike 2 kids 1 wife and all our camping stuff fits just right.
I dd try the aftermarket hitch but its too low to the ground. I use an "add a bike" carrier - it has a bar that prevents handlebar going through your back window. and its much lighter then moto-tote

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#25 ·
Great info. I'm also concerned about that 165 lb bike/carrier limit, but as @imacd has illustrated, it is really a function of force and distance. I want to add a fourth bike on my 1up rack, but I'm over 200 lb total if I do. However, looks like I'm within that 500 lb trailer tongue limit if I convert everything to moments and compare. Apparently I can't attach an .xlsx, but here's a screenshot. Calcs are just sum(force * arm distance) for each item.
 

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