Second Opinion, and a few questions

[Aron]

Hi! I posted a similar question on another forum (popupportal.com), and it was suggested that I pose the questions on here as well. I'm relatively new to trailer camping (I've rented a travel trailer a few times), and I think that I'm ready to take the plunge into ownership. To that end, I would appreciate a second (or third) set of eyes on my calculations to verify that what I'm looking at is reasonable.

I have a 2015 Ford Expedition 4WD EcoBoost, with the tow package. Per the Owners Manual, GCVWR is 15,100 lb, max tow rating is 9,200 lb, and max tongue rating is 920 lb with a weight distributing hitch. Per the sticker on the door frame, the GVWR of the tow vehicle is 7,500 lb, FAWR is 3,550 lb, RAWR is 4,300 lb, and payload is 1,364 lb. I've weighed the vehicle on a professional scale with a full 28gal tank of gas, and the weight is 6,080 lb.

* Question One: Why would the payload be 1,364 if the actual weight is 6,080, which should make the payload 1,420lb (difference of 56lb)? I've heard that the yellow sticker takes into account a 150lb driver, but the manual doesn't mention anything about this (and the difference isn't that far off). I may have some fluid levels a bit low, but I wouldn't think that they would be 56lb worth...

This difference matters because as far as I can tell payload appears to be the critical factor in my calculations. My family of 4 and I currently weigh a total of 585 lb (though they're still growing), and I plan to hold on to this trailer for a number of years, so I have to plan for their full weight. I estimate that fully grown we'll be at about 700 lb total. So, assuming that we keep minimal extra gear in the tow vehicle while driving, that leaves approximately 664 lb (or is it 720?) of available payload for trailer tongue and weight distributing hitch. The little bit of research that I've done tells me that WDHs weigh 60-110 lb, and since payload is so valuable, I'm assuming that I can find one closer to 60lb, leaving about 600 lb (or 660?) of payload for tongue weight.

I have 3 kids, so I have a fairly limited selection of trailers on the market to choose from. I plan to do some multi-day travel trips with this trailer, so I'm not really interested in a popup or hybrid due to the significant setup/takedown time of the beds. The kids are opposed to sharing beds, and I'm not interested in converting sofas or tables to beds every day, so I really want 3 individual bunks to keep the peace. And my payload limits me from the really big bunkhouses on the market (plus, my fear of towing a 38' monster).

The trailer that I'm currently looking at is the K-Z Spree 240BHS: http://www.kz-rv.com/products/spree-travel-trailers/240BHS.html
GVWR 6500 lb, dry weight 5170, dry hitch weight 570. Assuming 160 lb for propane and battery, 384 lb of water (40 gallons + 6 for heater), and 500 lb of assorted gear (I measured 532lb the last time we rented for a 2 week trip, but there's some stuff we never used), the loaded trailer should weigh approximately 6214 + options. Since I haven't purchased yet, I don't know what the actual weight is, but I'm guessing that 86 lb is a reasonable guess for options, meaning a loaded weight of 6300 lb. Total combined vehicle weight would be 13,140 lb, which is 87% of max combined weight. If we assume worst case scenario of a fully loaded 6500lb trailer, the total combined vehicle weight would be 13,340lb, or 88% of max.

Here's where the real guessing comes into play. Tongue weight is supposed to be 10-15% of trailer weight, which would calculate to 630-945 lb (less if I don't carry water, and limit some of the gear). Obviously, due to the payload capacity, I'm going to have to keep it right around 10%, which seems like it should be feasible because this specific trailer has a cargo area in front and back, so I should be able to adjust distribution of weight within the trailer a bit more than most other models. So, if I can adjust it to keep the tongue weight to 630 lb, the tow vehicle would be carrying 7470, which is only 30 lb under max GVWR.

* Question Two: I would be pretty close to the tow vehicles GVWR, but 2000 lb (13%) or more below the total combined weight rating. I've towed with similar weights in the "mountains" of the east coast, but I've never towed out west. Would this setup work in the higher average elevations out west? My impression is that tow vehicle GVWR is mostly limited by the structural vehicle components (axles, tires, frame, etc), and GCVWR would be limited more by engine/transmission/brakes. I know that engines lose some power as you go up in elevation, so I'm not going to be winning any races over the passes, but I *THINK* I'll be able to actually get over the passes eventually (though I'll be trying to avoid the 11,000' passes all the same). The weight on the structural elements wouldn't change, but I'm hoping that my lower GCW will help with the reduced power from higher elevations. What do you all think?

* Question Three: Do you see any fatal flaws in my calculations or assumptions? Better to learn about them now than after I've made a trailer purchase...

* Question Four, regarding weight distributing hitches: Despite what I've been told by multiple trailer dealers, I know that tongue weight doesn't just "disappear" with a WDH. I know that the weight's still there; all a WDH does is transfer some of the load off of the rear TV axle to the front TV axle. But recently I heard that some of the tongue weight also gets transferred to the trailer axles as well. Is there any truth to this? If so, how much should I expect? As I've stated above, I seem to be limited by payload, so any tongue weight transferred back to the trailer would help me add a bit more comfort buffer on the TV's payload (and maybe give me a few more options for WDHs, which seem to mostly be in the 90-110 lb range, rather than 60 lb). But then, how does this weight redistribution interact with the requirement that at least 10% of the weight remains on the tongue? Should I be planning on redistributing weight within the trailer to keep at least 10% of the trailer weight being put on the front and rear axles of the TV, after the WDH is in place? Or does the 10-15% requirement come into play before adding the WDH?

* Question Five, also regarding WDHs: The ratings on WDHs are a bit confusing to me. I've read that some ratings are maximums, and some ratings are distribution ratings, so what exactly should I be looking for (assuming a 6500lb trailer with tongue weight around 650 lb)? Is a 6000lb/600lb hitch going to work for me? Or should I be looking at the 10000lb/1000lb ones? (There don't seem to be 8000lb/800lb WDHs on the market, for some reason.) I've heard that if your spring bars are too strong, they don't properly distribute the weight, so "just going bigger" doesn't necessarily seem smart to me.

Thanks all for your thoughts on this. I've learned quite a bit lurking on this forum recently...when I first purchased the Expedition, I naively thought that "max tow" was the only thing I had to worry about, because that's what they advertise. I didn't even know that there was a payload rating to pay attention to.

[Aron]

Ron Gratz wrote:

Aron wrote:
So, here's my situation: my tow vehicle has a payload of 1364 lb (per the yellow sticker). Wheelbase of 119", and estimating 60" between the ball and rear axle.

I don't have a trailer yet, but I'm currently considering one with a dry weight of 5160 lb (GVWR of 6500 lb). I don't have good measurements on the distance to the rear axle. The trailer is 28'3" long, with an approximate 24' box, so I'm assuming (based upon photos) that the axles are centered or slightly behind the midpoint of the box, which would give a distance from ball to axle midpoint of approximately 195".

I'm thinking of purchasing a Blue Ox Sway Pro 10,000 GTW, 1,000 TW hitch (shipped weight of 96 lb according to the website). It appears that the spring arms are 29" long.

So, assuming that I can properly tension the spring bars to provide a full 2000 lb of load, that should generate approximately 297 lb of load applied to the trailer axles, correct? If I'm remembering my statics correctly, that means that 297 lb of load from the tongue would not be applied to the payload of the tow vehicle, correct? So even if I load the trailer to full 6500 GVWR, and load the trailer tongue to 780 lb (12%), I should not exceed the payload of the tow vehicle, correct? (1364-96-780+297=785) My family currently weighs 585 lb, so that still leaves me with 200 lb of payload buffer in case I can't tension the WDH fully, or if the trailer axles are further back than I think. And assuming that they grow another 100 lb or so, I would still have a 100 lb buffer. And that looks like a worse-case scenario, because I also wouldn't be fully loading the trailer to capacity.

Does all of that check out? Or is there a flaw in one of my assumptions? Thanks!

With a TT which is 28' overall, I would recommend a tongue weight percentage of 13%.
For a TT weighing 6500# the corresponding TW, at TW% = 13%, would be 845#.

Based on your dimensions, a TW of 845# would cause a load of approximately 845*60/119 = 426# to be removed from the TV's front axle with no WD applied.
If you want to follow Ford's WDH-adjustment spec which calls for restoring approximately 50% of the load which is removed from the front axle, you would need to adjust your WDH to restore about 213# to the front axle.

Again, using your numbers, to restore 213# to your front axle would require the WDH to be adjusted to transfer about 213*119/(60+195) = 99# to the TT's axles.
The corresponding load applied by each WD bar would be about 99*195/29/2 = 333#.

If you used 1000# rated WD bars and adjusted them to transfer the previously calculated 297# to the TT's axles, the corresponding load transfer to the TV's front axle would be about 297*(60+195)/119 = 636#.
This is significantly more WDH load transfer to the front axle than is specified by Ford.

Ron

Dangit! And I thought that I might have this puzzle solved, too...

I think that I'm going to have to expand my calculations spreadsheet to work out all of these numbers as well.

This was very helpful, thanks!

[Ron_Gratz]

Aron wrote:
So, here's my situation: my tow vehicle has a payload of 1364 lb (per the yellow sticker). Wheelbase of 119", and estimating 60" between the ball and rear axle.

I don't have a trailer yet, but I'm currently considering one with a dry weight of 5160 lb (GVWR of 6500 lb). I don't have good measurements on the distance to the rear axle. The trailer is 28'3" long, with an approximate 24' box, so I'm assuming (based upon photos) that the axles are centered or slightly behind the midpoint of the box, which would give a distance from ball to axle midpoint of approximately 195".

I'm thinking of purchasing a Blue Ox Sway Pro 10,000 GTW, 1,000 TW hitch (shipped weight of 96 lb according to the website). It appears that the spring arms are 29" long.

So, assuming that I can properly tension the spring bars to provide a full 2000 lb of load, that should generate approximately 297 lb of load applied to the trailer axles, correct? If I'm remembering my statics correctly, that means that 297 lb of load from the tongue would not be applied to the payload of the tow vehicle, correct? So even if I load the trailer to full 6500 GVWR, and load the trailer tongue to 780 lb (12%), I should not exceed the payload of the tow vehicle, correct? (1364-96-780+297=785) My family currently weighs 585 lb, so that still leaves me with 200 lb of payload buffer in case I can't tension the WDH fully, or if the trailer axles are further back than I think. And assuming that they grow another 100 lb or so, I would still have a 100 lb buffer. And that looks like a worse-case scenario, because I also wouldn't be fully loading the trailer to capacity.

Does all of that check out? Or is there a flaw in one of my assumptions? Thanks!

With a TT which is 28' overall, I would recommend a tongue weight percentage of 13%.
For a TT weighing 6500# the corresponding TW, at TW% = 13%, would be 845#.

Based on your dimensions, a TW of 845# would cause a load of approximately 845*60/119 = 426# to be removed from the TV's front axle with no WD applied.
If you want to follow Ford's WDH-adjustment spec which calls for restoring approximately 50% of the load which is removed from the front axle, you would need to adjust your WDH to restore about 213# to the front axle.

Again, using your numbers, to restore 213# to your front axle would require the WDH to be adjusted to transfer about 213*119/(60+195) = 99# to the TT's axles.
The corresponding load applied by each WD bar would be about 99*195/29/2 = 333#.

If you used 1000# rated WD bars and adjusted them to transfer the previously calculated 297# to the TT's axles, the corresponding load transfer to the TV's front axle would be about 297*(60+195)/119 = 636#.
This is significantly more WDH load transfer to the front axle than is specified by Ford.

Ron

[Aron]

Ron Gratz wrote:
A pair of 1000# WD bars (two bars rated at 1000# each) typically would be used with a tongue weight in the neighborhood of 1000#.
The amount of load applied to the bars is determined by how "stiff" the bars are and by how much you make them "bend".

The magnitude of load which could be transferred to the TT's axles would be determined by 1) the combined chain load applied to the two bars, 2) the effective length of the bars, and 3) the distance from ball to midpoint between TT's axles.

Assuming a load of 1000# applied to each bar, effective bar length of 30", and ball to axles distance of 200#,
the amount of load transferred to the TT's axles would be approximately 2*1000*30/200 = 300#.

Let me know if you have specific questions about how to determine trailer-induced load acting on the tow vehicle.
I'm always happy to crunch some numbers.

Ron

This is very helpful, thanks! It's been more than 20 years since I took a statics class, but I remember enough to be comfortable with the calculations. But I don't have much practical experience towing with a WDH, to know how much tension a hitch sized for 1000lb of tongue weight is supposed to provide. Also, I could use a check on my calculations, please.

So, here's my situation: my tow vehicle has a payload of 1364 lb (per the yellow sticker). Wheelbase of 119", and estimating 60" between the ball and rear axle.

I don't have a trailer yet, but I'm currently considering one with a dry weight of 5160 lb (GVWR of 6500 lb). I don't have good measurements on the distance to the rear axle. The trailer is 28'3" long, with an approximate 24' box, so I'm assuming (based upon photos) that the axles are centered or slightly behind the midpoint of the box, which would give a distance from ball to axle midpoint of approximately 195".

I'm thinking of purchasing a Blue Ox Sway Pro 10,000 GTW, 1,000 TW hitch (shipped weight of 96 lb according to the website). It appears that the spring arms are 29" long.

So, assuming that I can properly tension the spring bars to provide a full 2000 lb of load, that should generate approximately 297 lb of load applied to the trailer axles, correct? If I'm remembering my statics correctly, that means that 297 lb of load from the tongue would not be applied to the payload of the tow vehicle, correct? So even if I load the trailer to full 6500 GVWR, and load the trailer tongue to 780 lb (12%), I should not exceed the payload of the tow vehicle, correct? (1364-96-780+297=785) My family currently weighs 585 lb, so that still leaves me with 200 lb of payload buffer in case I can't tension the WDH fully, or if the trailer axles are further back than I think. And assuming that they grow another 100 lb or so, I would still have a 100 lb buffer. And that looks like a worse-case scenario, because I also wouldn't be fully loading the trailer to capacity.

Does all of that check out? Or is there a flaw in one of my assumptions? Thanks!

[Rustycamperpant]

Aron wrote:

Rustycamperpants wrote:
My TV is a 2009 Expy with a TT just a little bigger than the Spree you have listed. See my signature line. My tow was a little squrirrly at times at first until I got the equalizer dialed in. You will have no problem pulling that TT, plus you have a better motor. Yeah, there are times I would like to have a 3/4 ton TV, but the Expy is a great family vehicle for our family of five. I did get rid of the Scorpion tires that were on it and got truck tires though, I did this back when I still had the PUP. If you are happy with the TT you picked out, go for it. Not everyone needs a one ton truck to pull a camper.

PS. I have pulled my TT for two years and I have not had an issue, I usually set the cruse control at 63 and enjoy the ride.

Thanks! Have you done much towing with it in the mountains?

Only once through the Smokies on a trip to South Carolina, not west toward the Rockies though. The 5.4 likes to spin, needs to be up around 4K rpm to make power ... cant be afraid to let it rev up, like any gasser.

[CWSWine]

Here is a easy to use website that you can play with numbers and see where you are at.

Tow Planner

[Ron_Gratz]

Aron wrote:
There's one piece of Ron Gratz's WDH thread that I'm still not clear on. I understand all of the physics/math involved, but it's just assumed that the two 1000# spring bars generate 2000# of "load". Is this supposed to be representative of a system such as a 10,000 GTW/1000 TW system, or one more like a 20,000 GTW / 2000 TW system?

A pair of 1000# WD bars (two bars rated at 1000# each) typically would be used with a tongue weight in the neighborhood of 1000#.
The amount of load applied to the bars is determined by how "stiff" the bars are and by how much you make them "bend".

The magnitude of load which could be transferred to the TT's axles would be determined by 1) the combined chain load applied to the two bars, 2) the effective length of the bars, and 3) the distance from ball to midpoint between TT's axles.

Assuming a load of 1000# applied to each bar, effective bar length of 30", and ball to axles distance of 200#,
the amount of load transferred to the TT's axles would be approximately 2*1000*30/200 = 300#.

Let me know if you have specific questions about how to determine trailer-induced load acting on the tow vehicle.
I'm always happy to crunch some numbers.

Ron

[Aron]

bikendan wrote:

Aron wrote:


But I hadn't considered upgrading shocks. Would that increase the payload?

NO!!!!

That's kind of what I had guessed. So then what would be the purpose of upgrading shocks?

[Aron]

Rustycamperpants wrote:
My TV is a 2009 Expy with a TT just a little bigger than the Spree you have listed. See my signature line. My tow was a little squrirrly at times at first until I got the equalizer dialed in. You will have no problem pulling that TT, plus you have a better motor. Yeah, there are times I would like to have a 3/4 ton TV, but the Expy is a great family vehicle for our family of five. I did get rid of the Scorpion tires that were on it and got truck tires though, I did this back when I still had the PUP. If you are happy with the TT you picked out, go for it. Not everyone needs a one ton truck to pull a camper.

PS. I have pulled my TT for two years and I have not had an issue, I usually set the cruse control at 63 and enjoy the ride.

Thanks! Have you done much towing with it in the mountains?

[Aron]

poppin_fresh wrote:
There are other rigs out there that are similar to the KZ, but might be a better fit if the KZ is too close.

For example, check out the Keystone Passport 2400BH. 4750# dry with 515# hitch weight (according to website).

The kids are really opposed to sharing beds; otherwise, I agree that there would be a number of other options. Still might have to go that way, though. Thanks!

[bikendan]

Aron wrote:


But I hadn't considered upgrading shocks. Would that increase the payload?

NO!!!!

[Rustycamperpant]

My TV is a 2009 Expy with a TT just a little bigger than the Spree you have listed. See my signature line. My tow was a little squrirrly at times at first until I got the equalizer dialed in. You will have no problem pulling that TT, plus you have a better motor. Yeah, there are times I would like to have a 3/4 ton TV, but the Expy is a great family vehicle for our family of five. I did get rid of the Scorpion tires that were on it and got truck tires though, I did this back when I still had the PUP. If you are happy with the TT you picked out, go for it. Not everyone needs a one ton truck to pull a camper.

PS. I have pulled my TT for two years and I have not had an issue, I usually set the cruse control at 63 and enjoy the ride.

[poppin_fresh]

There are other rigs out there that are similar to the KZ, but might be a better fit if the KZ is too close.

For example, check out the Keystone Passport 2400BH. 4750# dry with 515# hitch weight (according to website).

[Aron]

campigloo wrote:
Some good direction given here. I also understand the vehicle dilemma. One thing that can help
on a marginally capable TV is to upgrade the tires. If you have P rated tires consider moving up to a D or E rating. The stiffer sidewall can make it handle much better. Also consider upgrading the shocks. A set of Bilsteins or something comperable can make lots of difference. Good luck and I hope you can find a good match for your situation. It's out there somewhere!

Thanks! I've actually looked into upgrading the tires, but it turns out that my OEM tires are plenty strong (275/55R20 113T, which apparently can carry 2500# each, if I'm reading the ratings correctly).

But I hadn't considered upgrading shocks. Would that increase the payload?

[campigloo]

Some good direction given here. I also understand the vehicle dilemma. One thing that can help
on a marginally capable TV is to upgrade the tires. If you have P rated tires consider moving up to a D or E rating. The stiffer sidewall can make it handle much better. Also consider upgrading the shocks. A set of Bilsteins or something comperable can make lots of difference. Good luck and I hope you can find a good match for your situation. It's out there somewhere!