Montana Owners Club - Keystone Montana 5th Wheel Forum - View Single Post - Trying to make sense of towing numbers...

WOXOF · 12-11-2019, 09:30 PM

I'm a newbie and have yet to purchase our 5er or truck. We would have made the leap into the RV world years ago, but my work-related position was such that didn't allow me to take a lot of time off. Being fully retired, I've been in the full "due diligence mode" for several months. We don't want to make a misinformed blunder, as this is a huge financial investment/outlay that we'll be making. We've been to 4 RV shows this year, including Hershey in September, as well as going to other shows in past years to keep abreast how the manufacturers were developing their product lines.

We've compared the Grand Design 310GK (35 ft / 15K GVWR) to the Montana 3120 (comparable specifications). I've scoured forums to specifically learn as much as possible about matching the RV to the TV. I've PM'd folks to get their thoughts about their SRW and DRW setups. Their knowledge base has been very enlightening/helpful. I've spent untold hours watching numerous YouTube videos by Big Truck/Big RV and TFL Truck, etc., as well as following some of the full-timer's that document their travel adventures. This group typically have the larger RVs and DRWs. To me, the videos of the test drives don't dig into the numbers very much and are marginally helpful.

I've arrived at the conclusion that my "pucker factor" boils down to the payload capacity of the TV and what will do the job that will keep us safe and be within the legal capacities of both the RV/TV. Having settled on the Montana 3120, I began to research the TV manufacturer's web sites to cull specifications of the SRW SB, LB and DRW's.

I'm agnostic when it comes to the TV and whether it's an SRW or DRW. From what I found the manufacturer's specs are pretty close to each other. I then used a spreadsheet to calculate a number of scenarios. I used the max RV GVWR of 15K lbs as the "worst case," since I don't yet know how much weight I will really be towing in the real world (I can't to to a scale to weigh something I don't own). For the TV payload, I used 600 lbs for passengers and 400 lbs for cargo - total of 1000 lbs. (again, don't know how much will be in the TV). 25% of 15K lbs fully loaded has a hitch weight of 3750 lbs and the low end of 20% is 3000 lbs. I figure that I'd likely fall somewhere in between these numbers.

For the purposes of illustrating what I've learned, using weight specs from the 2019 RAM towing chart (which I realize will need adjustment from the actual TV sticker), the RAM 350 (6.7 HO Diesel/Aisin tranny) SRW SB (7622 lbs curb wt., GVWR 11800 lbs., payload 4180 lbs.) calculations exceed the payload and GVWR a little after the 3150 lbs pin wt. (21%). For the SRW LB, (7878 lbs curb wt, GCWR 12300 lbs., payload 4420 lbs.) the calculations exceed payload and GVWR a little after the 3375 lbs. pin wt (22.5%). At 23% of the RV GVWR, the available payload is 30 lbs over wt., as well as the GVW being exceeded. Would I get to that number - I don't know? Then there's the DRW (8396 lbs. curb wt., 14000 GVWR, 5600 lbs. payload) and calculations never exceeded pin wt. Available payload was 850 lbs more at the full 25% GCWR of the 3120.

Our anticipated travel will be short distances as well as cross-country ventures. The TV will mainly be a daily driver when we're on the road, which will be about 6 months out of the year (give or take). Taking all of the above into consideration, it's looking like that the DRW may be the TV that checks all of the boxes, since it will capably handle the max 25% calculation of hitch weight and our anticipated payload with room to spare.

On the flipside, I do have a friend that has a 2018 Ram 3500 SRW-SB and he tows his 16K lb. Vilano (uses a slider hitch) - states there's no problems with his setup. My conversation with him really has me thinking about which way to go. If I did decide to go the route of the SRW LB, my pea-brain tells me the pin weight couldn't exceed 3400 lbs. before exceeding the published specifications (if I bought the Ram 3500 LB).

Decisions, decisions and a big "gut check" before plunking down the buckaroos. If anyone wants to chime in - go for it.

12-11-2019, 09:30 PM	#45
WOXOF New Member Join Date: Mar 2019 Location: Corvallis Posts: 6 M.O.C. #23616	I'm a newbie and have yet to purchase our 5er or truck. We would have made the leap into the RV world years ago, but my work-related position was such that didn't allow me to take a lot of time off. Being fully retired, I've been in the full "due diligence mode" for several months. We don't want to make a misinformed blunder, as this is a huge financial investment/outlay that we'll be making. We've been to 4 RV shows this year, including Hershey in September, as well as going to other shows in past years to keep abreast how the manufacturers were developing their product lines. We've compared the Grand Design 310GK (35 ft / 15K GVWR) to the Montana 3120 (comparable specifications). I've scoured forums to specifically learn as much as possible about matching the RV to the TV. I've PM'd folks to get their thoughts about their SRW and DRW setups. Their knowledge base has been very enlightening/helpful. I've spent untold hours watching numerous YouTube videos by Big Truck/Big RV and TFL Truck, etc., as well as following some of the full-timer's that document their travel adventures. This group typically have the larger RVs and DRWs. To me, the videos of the test drives don't dig into the numbers very much and are marginally helpful. I've arrived at the conclusion that my "pucker factor" boils down to the payload capacity of the TV and what will do the job that will keep us safe and be within the legal capacities of both the RV/TV. Having settled on the Montana 3120, I began to research the TV manufacturer's web sites to cull specifications of the SRW SB, LB and DRW's. I'm agnostic when it comes to the TV and whether it's an SRW or DRW. From what I found the manufacturer's specs are pretty close to each other. I then used a spreadsheet to calculate a number of scenarios. I used the max RV GVWR of 15K lbs as the "worst case," since I don't yet know how much weight I will really be towing in the real world (I can't to to a scale to weigh something I don't own). For the TV payload, I used 600 lbs for passengers and 400 lbs for cargo - total of 1000 lbs. (again, don't know how much will be in the TV). 25% of 15K lbs fully loaded has a hitch weight of 3750 lbs and the low end of 20% is 3000 lbs. I figure that I'd likely fall somewhere in between these numbers. For the purposes of illustrating what I've learned, using weight specs from the 2019 RAM towing chart (which I realize will need adjustment from the actual TV sticker), the RAM 350 (6.7 HO Diesel/Aisin tranny) SRW SB (7622 lbs curb wt., GVWR 11800 lbs., payload 4180 lbs.) calculations exceed the payload and GVWR a little after the 3150 lbs pin wt. (21%). For the SRW LB, (7878 lbs curb wt, GCWR 12300 lbs., payload 4420 lbs.) the calculations exceed payload and GVWR a little after the 3375 lbs. pin wt (22.5%). At 23% of the RV GVWR, the available payload is 30 lbs over wt., as well as the GVW being exceeded. Would I get to that number - I don't know? Then there's the DRW (8396 lbs. curb wt., 14000 GVWR, 5600 lbs. payload) and calculations never exceeded pin wt. Available payload was 850 lbs more at the full 25% GCWR of the 3120. Our anticipated travel will be short distances as well as cross-country ventures. The TV will mainly be a daily driver when we're on the road, which will be about 6 months out of the year (give or take). Taking all of the above into consideration, it's looking like that the DRW may be the TV that checks all of the boxes, since it will capably handle the max 25% calculation of hitch weight and our anticipated payload with room to spare. On the flipside, I do have a friend that has a 2018 Ram 3500 SRW-SB and he tows his 16K lb. Vilano (uses a slider hitch) - states there's no problems with his setup. My conversation with him really has me thinking about which way to go. If I did decide to go the route of the SRW LB, my pea-brain tells me the pin weight couldn't exceed 3400 lbs. before exceeding the published specifications (if I bought the Ram 3500 LB). Decisions, decisions and a big "gut check" before plunking down the buckaroos. If anyone wants to chime in - go for it.