Community Forums

jdieter · 08-30-2017, 09:17 AM

Just starting the research to move from a class C + toad to a diesel truck and 5th wheel. We've been to several RV dealers to get a feel for the size we want and also a few car dealers going over trucks. At this point it looks like a 1 Ton Duramax, SW, 4wd, crew cab, long bed will provide an adequate safety margin to pull somewhere around a 34ft 5th wheel that would be appx. 9500lbs loaded. It has a payload of 3927lbs so with a appx. 1800lb pin weight we've got 2000lb of people, cargo and a safety margin. What I don't understand is GM's rear axle 5th wheel rating for this truck at 17200lbs. What actually does that number mean? The other truck numbers are GCWR - 25,300lbs, GVWR - 11,600lbs, curb weight - 7,548lbs. Also what number is the recommend towing safety margin of between 15-25% derived from?

dayle1 · 08-30-2017, 10:17 AM

The 17k number is what it can tow. GCVWR minus dry truck weight. Everything you load into the truck reduces that number. The rear axle itself is rated around 10k lbs by the supplier, but real rear GAWR is limited by tires and wheels to around 7k lbs. If you get loaded truck weight by individual axle, then you will know how much pin weight the rear axle can handle. Dry pin weights run typically under 20%. But most cargo goes pretty forward, so adding 1500 lbs of gear may put 30 to 40% of that on the pin. So the guideline is extremely rough number.

jdieter · 08-30-2017, 02:03 PM

So the 17K number for 5th wheel tow capacity in this case is essentially a sales gimmick, as it doesn't factor in anything for the carrying capacity of the truck or the added trailer pin weight.

Old-Biscuit · 08-30-2017, 03:00 PM

That truck will be within ALL ratings with that 5th wheel trailer

I have a 2007 3500 SRW and tow a 34' 5vr that weighs 13,873# (scaled weight) with a 'wet' pin weight of 3070# (22% pin weight)

You want a 'wet' pin weight between 20% - 25% (Wet pin is percentage of total trailer weight that is 'CARRIED' by truck (all most all of which is on trucks rear axle)

With my vintage of truck I am right at trucks rear axle rating (which is 800# lower then your trucks) and under the trucks rear tire MAX Load Ratings

Are you sure about that 5th wheel only weighing 9500#????

dayle1 · 08-30-2017, 03:34 PM

Quote:

Originally Posted by jdieter

So the 17K number for 5th wheel tow capacity in this case is essentially a sales gimmick, as it doesn't factor in anything for the carrying capacity of the truck or the added trailer pin weight.

It is not a sales gimmick, it is the max additional weight it can pull assuming all other numbers are ok. The truck manufacturer has no control over what percentage pin weight any trailer manufacturer designs their units for or how each owner loads gear into the trailer. A rear kitchen floorplan will in general have a smaller increase in loaded pin weight than a rear living floorplan.

Park235 · 08-30-2017, 08:14 PM

Quote:

Originally Posted by jdieter

Just starting the research to move from a class C + toad to a diesel truck and 5th wheel. We've been to several RV dealers to get a feel for the size we want and also a few car dealers going over trucks. At this point it looks like a 1 Ton Duramax, SW, 4wd, crew cab, long bed will provide an adequate safety margin to pull somewhere around a 34ft 5th wheel that would be appx. 9500lbs loaded. It has a payload of 3927lbs so with a appx. 1800lb pin weight we've got 2000lb of people, cargo and a safety margin. What I don't understand is GM's rear axle 5th wheel rating for this truck at 17200lbs. What actually does that number mean? The other truck numbers are GCWR - 25,300lbs, GVWR - 11,600lbs, curb weight - 7,548lbs. Also what number is the recommend towing safety margin of between 15-25% derived from?

we're moving from a Class C to a 41' 5th wheel. I weighted both a 2017 Silverado 3500 HD short bed High Country with 5th wheel hitch prep (full tank of fuel) and an LTZ long bed (no 5th wheel hitch prep & ~6 gallons of fuel) both with very similar equipment. The real weights were 7980 and 7820 lbs + fuel estimated at 250 = 8070 respectively. So in reality the real payloads are only 3600 lbs. Remember numbers in the literature are maximums not real world.

jdieter · 08-31-2017, 07:33 AM

Ok, now I get what the max 5th wheel weight rating is. How about the safety factor. Everything I've found online recommends anywhere from 15-25%. I'm guessing everything needs to be weighed on a CAT scale fully loaded. From what weight number or numbers is the safety factor derived?

jdieter · 08-31-2017, 07:39 AM

Old-biscuit, the 9500 lb rating was from 34' Keystone Cougar lightweight 5th wheel. The dry weight was around 8400lbs and I added 1000lbs for payload. Not sold on this model but using it for reference. Going to buy the truck this year, use the Class C one more year and by the trailer next year. So we are still researching and wanted to make sure we had plenty of truck, no matter what we pull.

mrgrayaz · 08-31-2017, 07:41 AM

Not sure why you need a saftey factor. Remember the engineers designing the tires, hitch, truck, etc already put that into the design of each components.

Run it at what it's rated.

Old-Biscuit · 08-31-2017, 01:08 PM

Quote:

Originally Posted by mrgrayaz

Not sure why you need a saftey factor. Remember the engineers designing the tires, hitch, truck, etc already put that into the design of each components.

Run it at what it's rated.

Exactly^^^^^^

IF truck and trailer are MATCHED then it will be a safe two combo.
(Matched.....within/at RAWR, Rear Tire MAX Load Ratings and GCVWR)

Drivers abilities NOT included.

CWSWine · 09-06-2017, 01:07 PM

Ratings on trucks and 5er are some muddy waters to say the least but this training video put out by RV Safety makes a lot of sense to the numbers

Matching Trucks to Trailers

JIMNLIN · 09-06-2017, 08:17 PM

The 15-25 % safety factor comes from rv side of trucking and in another era when diesels pickups had 160-180 hp and 454/460 big block gas engines put out a whoppin' 225-250 hp and small block gas put out around 195-210 hp/small brakes/small cooling systems/etc.

As mrgray points out a trucks safety factor is built in. With todays new gen diesel cranking out 400hp & 900 torque and 375-420 hp at 375-460 torque for gassers along with huge brakes/cooling systems and very strong tranny/drive trains their is no need for a safety factor.

Commerce operates the same truck at 100 percent capacities and we can do so for several hundred thousand miles.
Pulling a 10k rv won't even make it sweat.

jdieter · 09-07-2017, 08:38 AM

Quote:

Originally Posted by CWSWine

Ratings on trucks and 5er are some muddy waters to say the least but this training video put out by RV Safety makes a lot of sense to the numbers

Matching Trucks to Trailers

Well worth the 20 minutes or so to watch this video... thanks for the link

Gordon Dewald · 09-07-2017, 09:49 AM

Quote:

Originally Posted by jdieter

So the 17K number for 5th wheel tow capacity in this case is essentially a sales gimmick, as it doesn't factor in anything for the carrying capacity of the truck or the added trailer pin weight.

Certainly misleading marketing. It assumes a basic truck with only tow capacity options added. So if you add 4x4, bucket seats, crew/extended cab, larger tires, etc you will be reducing the 17K.

Now the number of people who will be purchasing a basic truck only beefed up with options that maximize towing capacity are going to be very rare.