Trailer coupler rating

furnacebrook · May 14, 2008

Hello, I have a 12' x 8' flat bed trailer with brakes that weighs 1200lbs. It has a 5000lbs rated coupler on it with a 2" ball. The trailer is rated at 7000lbs and I plan on carrying 4000lbs of stove pellets on it a few times a year. This puts it over the coupler rating as well as the reciever drop hitch I have on my truck by 200lbs. The trailer hitch I have on the truck is a class 4 so I'm OK there. The question I have is, why does a trailer manufacturer put lower rated couplers on their trailer when they are rated for much more or, is this Ok to use?

Thanks for any help, Scott

MikeD74T · May 14, 2008

I'm guessing that since you have a rolling load the pull on the hitch will not be 5000 lbs. Likewise since you have brakes the pushing load will not exceed 5000 lbs. Only if you suspend the truck or trailer from the hitch would you exceed the rating of the hitch & I suspect there's a built in safety factor before failure as well.

MikeD74t

chvet73 · May 15, 2008

I don't why they would put an under rated coupler on the trailer. But I do know I would not exceed the rating.

wushaw · May 15, 2008

My BigTex trailer is that way also, 7k trailer 5k coupler and I have a 6k ball. I have had atleast 5k on my trailer many times and it has a 5100lbs of carry capacity.

Trailer manufactures do it all the time...who knows really why.

Skyco · May 15, 2008

Why? Because they are cheap. I bought a 7000lb rated car trailer a few years back and discovered days later the coupler was a 5000 lb rated one. Called the manufacturer who said "Oh it will be fine don't worry" I asked them to put that in writing so if it ever broke and caused an injury or death I'd have proof they said that.
They declined but sent a guy to town who cut off all the couplers at the dealer and mine and welded 7000 lb rated couplers on

wushaw · May 15, 2008

I know I just put in a reply to this but I just remembered something.

I was at Southwestwheel a few months ago getting some trailer parts and they have couplers in big tubs so I pulled a 5k and a 7k Bulldog and layed them on the counter and asked whats the difference....and the only answer was on the 7k coupler there is a 1X2X5/16 or 3/8 flat that is welded at the smallest section of the V just behind the ball retainer.

The rest of the coupler was the same thickness in material so that little piece of flat adds 2k worth of rating????

furnacebrook · May 24, 2008

Thanks for all the input guys,sorry to take so long responding. MikeD74T, I had a feeling you had something with that point. It just did not seem like all these big trailer manufacturers would put these lower rated couplers on if they were going to come apart on the road and I have not heard of any either. So, I got in touch with an old professional welder friend of mine who has made trailers for a living in the past. I asked him the same question posted here. He said the reason is just what you thought. The coupler and the ball and hitch will not have that amount of weight due to the trailer taking most of it. He said just for example, a 7000lbs GVW fully loaded trailer at that same weight would only have about 2000lbs on the coupler and hitch. And its a rolling weight as you mentioned. You would have to suspend the whole tuck and trailer to get the full load to bare on the coupler and hitch. It did still bugged me some though. If I put on a 7000lbs coupler I would need to upgrade to a 2 5/16" ball and a forged drop hitch because mine is only rated for 5000lbs the reciever is rated for 10000lbs as I mentioned so that was Ok. It would cost quite alot more to get it to full rating. I guess I wounder if what Skyco said about them being too cheap to put on heaver rated parts has a factor in there somewhere ? I'm going to keep it the way it is though as I don't usually carry that much weight more than to or three times a year.
Thanks again for the input, Scott

Reg · May 25, 2008

furnacebrook said:
Thanks for all the input guys,sorry to take so long responding. MikeD74T, I had a feeling you had something with that point. It just did not seem like all these big trailer manufacturers would put these lower rated couplers on if they were going to come apart on the road and I have not heard of any either. So, I got in touch with an old professional welder friend of mine who has made trailers for a living in the past. I asked him the same question posted here. He said the reason is just what you thought. The coupler and the ball and hitch will not have that amount of weight due to the trailer taking most of it. He said just for example, a 7000lbs GVW fully loaded trailer at that same weight would only have about 2000lbs on the coupler and hitch. And its a rolling weight as you mentioned. You would have to suspend the whole tuck and trailer to get the full load to bare on the coupler and hitch. It did still bugged me some though. If I put on a 7000lbs coupler I would need to upgrade to a 2 5/16" ball and a forged drop hitch because mine is only rated for 5000lbs the reciever is rated for 10000lbs as I mentioned so that was Ok. It would cost quite alot more to get it to full rating. I guess I wounder if what Skyco said about them being too cheap to put on heaver rated parts has a factor in there somewhere ? I'm going to keep it the way it is though as I don't usually carry that much weight more than to or three times a year.
Thanks again for the input, Scott

The coupler's rating is about the towed load - NOT as you seem to have concluded, about what it can take suspended from or loaded directly onto it.

If you go through the whole trailer you will find similar mismatches in other places, e.g. the tires COULD take more or less load than the axles, typically more. You are limited by the lowest rated component - in it's role, not a fantasy role of hanging the trailer from it.

MikeD74T · May 25, 2008

Reg said:
The coupler's rating is about the towed load - NOT as you seem to have concluded, about what it can take suspended from or loaded directly onto it.

If you go through the whole trailer you will find similar mismatches in other places, e.g. the tires COULD take more or less load than the axles, typically more. You are limited by the lowest rated component - in it's role, not a fantasy role of hanging the trailer from it.

Reg, Yes, that's what we said! BTW I've seen pictures of a tow vehicle hanging off a cliff whth the trailer supporting it, but again, that's not within the components' design criteria. And actually tires may not be rated for 100% of capacity as the hitch carries a significant portion of the load. Have fought with NH DOT, and won, on that one with a 20T trailer. MikeD74t