Running over GVWR. questions.

[rootusrootus]

When a trailer gets a GVWR, how is that determined? I assume it's a combo of factors, but is there a dominant one? Axles? I'm running a little hot on my 261BH. Weigh station says 7200 on the axles when I'm loaded with water. Napkin math (extrapolating from known weight of the truck vs what it weighed on this trip) puts trailer at about 8200, and GVWR is 7695. But I don't need to go that far, the axles are rated at 3500 each. So I'm 200 over on those. Tires are rated at 1850 (dual), so not quite over on those. But they are Westlakes .

It's a 90 minute drive out to our campsite, and no good place to stop on the way for water, so I just fill it at home. I don't have a lot of unnecessary junk in the trailer, so I don't really see any easy way to shed enough weight to go below GVWR.

What's going to break first, most likely? I mean, the Westlakes of course are a good candidate, but I'm going to ditch those at the end of this season anyway and put some Goodyears on. So next up is axles. Can I replace them with bigger ones? Should I? Would it matter? I mean, how tightly spec'd is the trailer frame itself, and is there any way to find out? I know I can't change the *actual* GVWR after the fact, but I want to make sure I'm as safe as possible.

[NB Canada]

Why wouldn’t you think you could change axles??
You can throw money at it all day
Don’t forget your springs

[NB Canada]

Btw my Westlakes are rated for 2150 each on my trailer. They have performed perfectly for 3 seasons and many miles

[Tigger1]

Too bad you can’t find water closer like at a Rest Stop, Travel Center, Cabela’s, etc. From your post it appears water is putting you over. I also seem to remember seeing a water truck at a campground awhile back which I assumed was filling fresh tanks for paying customers. Maybe there’s a service like that in your area.

[Second Chance]

The "Dual" rating on tires is for applications where they are side-by-side as on dual rear wheel trucks. The full load capacity rating is what you would use for an application such as on your trailer.

You are right in suspecting that multiple factors go into calculating the GVWR. Chassis material, design and construction, springs, axles, tires/wheels and brakes all figure in. It would take an automotive engineer to give you odds on what would "break first." It may not be a matter of breaking something, either, if an overload situation contributed to an inability to stop in time to avoid an accident. At 8.35 lbs./gallon, your fresh tank weighs over 500 lbs. when full. I would find a way not to travel with a full fresh tank and not take risks.

Rob

[rootusrootus]

Yeah the Westlakes on my trailer are rated at 2150 but only for single use, says 1870 for dual. I assume that's to account for the load the tire will take if one of the pair blows out.

But I'm planning to ditch the Westlakes anyway, so I'm not too concerned about that. And I'm under the 1870/ea limit anyway.

I know I can put bigger axles on, it's only money, but will the trailer frame just become the next failure point right after that? Or is it likely the frame has more margin engineered into it?

I also don't really know what happens when an axle fails, or how far over you have to go before it becomes a significant risk. I assume there's a bit of tolerance. For certain when you go down the road the axles routinely get forces a lot higher than the resting weight, for short periods.

[rootusrootus]

Too bad you can’t find water closer like at a Rest Stop, Travel Center, Cabela’s, etc. From your post it appears water is putting you over. I also seem to remember seeing a water truck at a campground awhile back which I assumed was filling fresh tanks for paying customers. Maybe there’s a service like that in your area.

Yeah it's a tough situation. We camp on the other side of the mountain, and we already live out on the edge of suburban city to begin with. It quickly goes to no service way before we reach the campground.

The "Dual" rating on tires is for applications where they are side-by-side as on dual rear wheel trucks. The full load capacity rating is what you would use for an application such as on your trailer.

Ah, good to know, thanks. I thought it might be a dually rating, but then I second guessed that because I wasn't sure trailers of this size often enough had such a configuration. Decided it more likely meant dual axle, and was trying to account for the load the remaining tire would experience if the other axle had a blowout.

In the short term I guess I'll just try to cut the water back a bit. It's 515 pounds full, and puts me 200 over the axle rating, so I'll see if I can get by with a half fill. We usually end up dumping a fair amount before we hit the road to return home, so there's some margin. Of course the last time I underfilled it on purpose thinking we had plenty, we ran out ;-). It's an art form.

I think I'll also dick around a bit with the loading. If my math is right, I'm only putting around 1000 on the tongue, so I could easily load that up a bit higher and take some off the axles. Also explains why it gets noticeably more wiggly coming home with empty fresh water and full blank tank (which is at the back).

[Hoopy Frood]

JMO of course, but I don't think your trailer will explode, or start shedding pieces if you're a couple hundred pounds over weight. I think the GVWR, is mostly centered on the tires. I've seen axles derated by a couple hundred pounds so they won't be rated for more weight than the tires. I would run it, and watch it. Watch for cracks around the spring hangers, flattening springs, and other issues, but those things happen even when the GVWR isn't exceeded. I'm not advocating traveling way over GVWR, but my 351 is carrying 14,400 lbs. on two 7,000 lb. axles, and has a GVW of 17,500, and its GVWR is 16,800 lbs. I never carry any more than a few gallons of fresh water for flushing the toilet.

To me it's what you feel comfortable with, and how it tows. If it pulls solidly, and, more importantly, stops well, I'm happy.

[TerryH]

GVWR seems to be a bit arbitrary in some cases. Our 2021 Momentum 31G has a GVWR of 12,000 lbs. Magically the 2022 Momentum 31G has a GVWR of 13,000 with exactly the same frame, axles and springs. Same for most of the travel trailer style Momentum trailers. A bit frustrating for those of us with the older trailers. I monitor our springs, hangers and frame very carefully. Unfortunately, once that GVWR is set by the manufacturer no measure of upgrading will ever change it.

[rootusrootus]

more importantly, stops well

That's my next target. For whatever reason, on this last trip out, when I did my brake check I just wasn't too impressed. The brakes were working, but they didn't try too hard to stop the truck like they usually do. Ramped up the brake controller the last few notches, now it's maxed out at 10.0 (Ford OE controller) and it was ... acceptable, I guess, but not inspiring. Better on the trip home for some reason, but still at full gain. Time to figure out why the brakes on this trailer are weak. Disc brakes sound wonderful, but it's a cheapo trailer to begin with. I bought it entirely for the floorplan, but it's quite a downgrade in quality from my old Jayco (which wasn't a high end trailer or anything itself, but it was put together a *lot* better).