Got mixed results from towing calculator worksheet - advice?

I'll start with the info first:

• TV:1996 Chevy Blazer 4x4, 118k, new trans, 3.42 axle, factory towing package (class III receiver for WDH), 5,300 GVWR-2700front 2700rear, according to autotraderonline.com, truck weighs 4,032lbs, payload capacity is 1,229lb tow rating is 5,600lbs (two people, no cargo), I plan on hauling 500lbs of (3) people/dog plus luggage
• Proposed RV: 2008 Cub/Kodiak 235 HTT, unloaded weight is 3676, GVWR is 4840, weight as posted in cupboard of trailer is 4240. I plan on traveling light with only 2-20lb LPs for fluids and minimal cargo/food (weekend trips mostly)

OK, so here's the mixed results. I wanted to be conservative in my RV selection, so I tried to heed advice from some of the wise staff here and not have the GVWR of the RV exceed 90% of truck's tow rating. 90% of 5,600=5,040 which is more than the 4840 GVWR of the trailer. With this in mind I thought I'd be OK with this RV for my mostly flatland Michigan jaunts.

When I plug all the info above into the "TowingCapacityWorksheet" Excel spreadsheet that I got from the forum, my total rig weight is 96-97% of my GCVWR (which is evidently inadvisable).

To be cautious and responsible to others on the road, I will be sure that my TV is in top shape (suspension, steering, brakes, cooling, clean fluids and filters) while adding a trans cooler, brake controller, sway control and WDH (brake controller, sway control and WDH, since my owners manual recommends it). I know I will be near my vehicle's safe limits, but I refuse to exceed them with the safety of my family and others on the road in mind. I am OK with this rig being a "slow boat to China", but will this RV exceed my TV's limits and make for an unsafe situation?

Hey Mike, it sounds like you've done your homework, and then done it again.  I can't speak for the spreadsheet, but it looks like you are going to be fine.  Heck, almost to the point of being "overready".  Especially as a "weekender", and on mostly flat roads, I can't see as how your're going to have a problem.  Only thing I would watch out for would be that temptation to go beyond what you originally calculated for, because the first trip went so well...kinda thing!  I say get out there and have fun!

Your "mixed results" from two slightly different calculations are pretty much normal. The Tow Capacity number in the sales brochure is for a stripped down model and rarely equal to the tow vehicle GCWR - Actual Vehicle Weight of any actual production vehicle, which will likely have additional features and options installed.  That's one of the reasons we recommend de-rating the Tow Capacity by 10%.

mike_cox said:

I'll start with the info first:

• TV:1996 Chevy Blazer 4x4, 118k, new trans, 3.42 axle, factory towing package (class III receiver for WDH), 5,300 GVWR-2700front 2700rear, according to autotraderonline.com, truck weighs 4,032lbs, payload capacity is 1,229lb tow rating is 5,600lbs (two people, no cargo), I plan on hauling 500lbs of (3) people/dog plus luggage
• Proposed RV: 2008 Cub/Kodiak 235 HTT, unloaded weight is 3676, GVWR is 4840, weight as posted in cupboard of trailer is 4240. I plan on traveling light with only 2-20lb LPs for fluids and minimal cargo/food (weekend trips mostly)

OK, so here's the mixed results. I wanted to be conservative in my RV selection, so I tried to heed advice from some of the wise staff here and not have the GVWR of the RV exceed 90% of truck's tow rating. 90% of 5,600=5,040 which is more than the 4840 GVWR of the trailer. With this in mind I thought I'd be OK with this RV for my mostly flatland Michigan jaunts.

When I plug all the info above into the "TowingCapacityWorksheet" Excel spreadsheet that I got from the forum, my total rig weight is 96-97% of my GCVWR (which is evidently inadvisable).

To be cautious and responsible to others on the road, I will be sure that my TV is in top shape (suspension, steering, brakes, cooling, clean fluids and filters) while adding a trans cooler, brake controller, sway control and WDH (brake controller, sway control and WDH, since my owners manual recommends it). I know I will be near my vehicle's safe limits, but I refuse to exceed them with the safety of my family and others on the road in mind. I am OK with this rig being a "slow boat to China", but will this RV exceed my TV's limits and make for an unsafe situation?

Click to expand...

Your spreadsheet caught us a bit by suprise.  It was posted over two years ago by a member.  You are the first person who has used it since or, at least, the first person to tell us he had.      We use a somewhat difference chain of logic based on the tow rating which a number widely disseminated by Trailer Life in tables on the tech section of its website. 

Using that logic, we would take your 5600 lb tow rating and apply a 10% safety factor to it in the east or 20% in the mountain and Pacific west.  That would give you a discounted tow rating of  5040 lbs in the east, or 4480 lbs in the west. 

We would apply that number against the GVWR of your trailer which you say is 4840 lbs.  Based on that, if you restrict your towing to the east, you are good to go.  However, if you plan any towing in the long steep grades and high altitudes of the mountain west, your rig is sub-marginal.  Why?  Consider something as unadventurous as a visit to the South Rim of the Grand Canyon.  The altitude there is 6000 ft. above sea level.  Your gasser will lose 18% of its rated horsepower -- 3% for every 1000 feet above sea level.  And then there are those 5-10 mile long 6% down grades on the Utah interstates to test your brakes on. 

East ok.  West, think twice.

Thanks for the replies guys! One thing that makes me scratch my head a little is that the RV I was considering (3676dry/4840gvwr) is OK for me by the 10% safety factor rule, BUT (and forgive me that you've probably answered this before) I've seen many other RVs that interest me that have a similar "actual" dry weight but much higher GVWR due to some other factor (axles/frame?) thus putting them out of the range I can tow based on the 10% safety factor rule.

If the "actual" dry weight is the same and I plan on loading these RVs the same, what's the difference? I want to error on the conservative side and like the 10% rule as it applies to GVWR, but I want to compare apples to apples too when selecting an RV.

Or maybe I like the rule only when it says the RV I want is OK!!! 

And don't forget, the most important thing to consider when selecting an RV...it's the one that the DW wants

Thanks again guys, reading all of your posts here has taught me so much!

Ignore the dry weight, it's a fictitious number at best.  Use the GVWR only to compare units.

The different gross weights are a result of the manufacturers rating for how much "extra" stuff you can carry on top of their "dry" weight.  Whether it's from stronger axles, beefier tires, a different calculation used to reach a particular number, who knows for sure.  But each manufacturer will tell you how much you can have above their stated dry weight.  That is the gross weight.  I personally don't feel you should totally disregard the dry weight...it does give you a baseline to work from.  But certainly you should find out the real dry weight and take the other recommendations for the gross weight to heart.

Like Ned mentioned forget the actual dry weight number since it is very likely inaccurate as many things like awnings and other accessories are not included in the dry weight.  Just a fictitious number to confuse people.  Use only the GVWR when comparing units to determine compatability with a tow vehicle.

OK, I wasn't even trying to cause trouble, but I started looking at GVWRs of units I am considering and came across something that doesn't make sense. First, let me say I agree that "dry" weight is an unreliable # (compared to what the unit weighs on a scale) and that I agree with you on that. OK, so I'm looking at a hybrid (trail cruiser tc21rbh) that has a GVWR of 5,508. But the DW doesn't want tent ends now, so I looked at the tc23sb (23' rear hard queen slide). The tc23sb has a GVWR of 5,344. So does this mean that the 23' with the rear hard slide weighs less than the 21' hybrid with a tent end? ??? It would seem that the 21' would weigh less than the 23' to me. This is extra confusing when you look at the dry weights (3164 for the 21' and 3700 for the 23'). Maybe this is just another reason to throw out dry weights?

I hope you can see that I'm only trying to find a way to more accurately find out the true weight of an RV to compare it to another RV, NOT if my TV can or should pull it (that's my cross to bear). I will be working VERY close to 90% of my tow rating. So it is critical to me that I get this right.  500lbs one way or another between RVs in real actual weight is going to make a big difference to me.

And no, taking each unit to a scale is not an option at this point - trust me, I want to! -Mike

The tc23sb has a GVWR of 5,344. So does this mean that the 23' with the rear hard slide weighs less than the 21' hybrid with a tent end?

Click to expand...

No, it means that something in the way it is built (frame, suspension, brakes, etc.) is different and makes its' weight capacity less than the other one. There's no way you can tell what it is; you simply have to accept that it can carry 164 lbs. less stuff.

mike_cox said:

OK, I wasn't even trying to cause trouble, but I started looking at GVWRs of units I am considering and came across something that doesn't make sense. First, let me say I agree that "dry" weight is an unreliable # (compared to what the unit weighs on a scale) and that I agree with you on that. OK, so I'm looking at a hybrid (trail cruiser tc21rbh) that has a GVWR of 5,508. But the DW doesn't want tent ends now, so I looked at the tc23sb (23' rear hard queen slide). The tc23sb has a GVWR of 5,344. So does this mean that the 23' with the rear hard slide weighs less than the 21' hybrid with a tent end? ??? It would seem that the 21' would weigh less than the 23' to me. This is extra confusing when you look at the dry weights (3164 for the 21' and 3700 for the 23'). Maybe this is just another reason to throw out dry weights?

I hope you can see that I'm only trying to find a way to more accurately find out the true weight of an RV to compare it to another RV, NOT if my TV can or should pull it (that's my cross to bear). I will be working VERY close to 90% of my tow rating. So it is critical to me that I get this right.  500lbs one way or another between RVs in real actual weight is going to make a big difference to me.

And no, taking each unit to a scale is not an option at this point - trust me, I want to! -Mike

Click to expand...

Don't worry about trouble.  Advice that cannot justify its assumptions is not worth a damn.

Your last sentence gives the whole story.  We are dealing with determining the towing suitability of a truck and trailer without being able to weigh the trailer or the truck.  We insist on using GVWR because that is the only real, stable and easily determinable number available to a buy on a manufacturer's website or a dealer's lot.  It is a number required by the US Dept. of Transportation (DOT).  It is the maximum that trailer should ever weigh for safety's sake -- trailer, dealer add-ons, your gear, your luggage, water, and propane, everything.

The real number you are trying to approximate is the weight of the trailer with all fluids on board along with your gear and stuff, as loaded and ready for the road.   If you can pull that trailer to a public scale and can go thru the weighing procedure we describe in the Library, you will have a number that trumps the GVWR numbers that we use here.  But then, you will already have bought the trailer, no?  "Gee, Mr Dealer, that trailer weighs more than I should be pulling with all my stuff on board.  Can I have my money back?"  Rotsa ruck.  8)

We have not even considered the truck yet.  That tow rating is based on a certain set of conditions and load.  The load assumption is the driver and full fluids.  However, of you add a spouse two kids and a Labrador retriever you have reduced that tow rating some 550 lbs more or less.  (150# per family member, 100# for the mutt.)  Then there is altitude.  Normally aspirated internal combustion engines lose 3% of rated HP per thousand feet of elevation. A visit to the South Rim of the Grand Canyon at 6000 feet will cost you 18% of rated HP.  If you do that Colorado pass that is the horror story in another topic here in the Forum, you would have lost 30% of your rated HP at 10,000 feet.

OK, what does that leave us.

1. Trailer weight: We have GVWR, a number required from the mfr by the US DOT and stamped on the DOT plate on every trailer sold in recent years.  All other numbers that are not scales weights, are guesses at best and sales devices at worst.

2. Truck capacity:  Tow ratings which are available from the compilations made by Trailer Life Magazine in their web site HERE. 

3.  Safety factors:  To account for variables in truck load, truck condition, and such we like to use 10% (90% of tow rating).  Remember 10% is a feel factor, not a hard and fast number.  Do you have a better number?  Then use it.  However, I will stick to 10% in my recommendations.  I also tend to wear belt and suspenders.  ;D    However, you feel about the 10% tho, believe my 20% in the west.  I live out here and have pulled a small TT with a Bronco all over the 11 western states.  My rig has that 20% leeway and I have never failed to pull a pass or gotten in trouble on one - but I have spent a lot of time in 1st gear doing 30mph over Siskyou, Donner, San Rafael, Black Canyon, Moctezuma and a whole bunches of other steep and high passes.

Insofar as comparisons of trailers is concerned, this type of analysis merely compares trailers only on the basis of their towability by the numbers.  It should allow you to immediately winnow out the things you should never attempt to pull and to concentrate on the features of those you can pull.

First, Carl, Let me thank you for taking the time to craft the exhaustive response above - knowledge AND wisdom combined to create a complete and eloquent (yes, I used sp check) reply. You might want to save it to copy and paste into your future replies to yahoos like me!!!

Carl L said:

The real number you are trying to approximate is the weight of the trailer with all fluids on board along with your gear and stuff, as loaded and ready for the road.   If you can pull that trailer to a public scale and can go thru the weighing procedure we describe in the Library, you will have a number that trumps the GVWR numbers that we use here. 

Click to expand...

So here you are saying that if I could accomplish the above ^^^^^^, then I could use that number (loaded trailer weighed by itself) instead of the GVWR of the trailer as it would apply to the 10% rule to determine TV suitability?

Carl L said:

We have not even considered the truck yet.  That tow rating is based on a certain set of conditions and load.  The load assumption is the driver and full fluids.   However, of you add a spouse two kids and a Labrador retriever you have reduced that tow rating some 550 lbs more or less.  (150# per family member, 100# for the mutt.) 

Click to expand...

I think that was what that Excel spreadsheet was trying to accomplish - figure out the dry weights of the TV and RV, add all the people, stuff and fluids while making sure tow capacity (or a percentage of the tow capacity) of the TV and GVWR of the TV and RV are not exceeded. If you could pull all that off and still figure in a safety margin of X%, then the worksheet would give your rig the "green light". I would be interested if you have seen this spreadsheet and what you think of it. Thanks again so much- Mike

So here you are saying that if I could accomplish the above ^^^^^^, then I could use that number (loaded trailer weighed by itself) instead of the GVWR of the trailer as it would apply to the 10% rule to determine TV suitability?

Click to expand...

Yes.  If you have a weight of the trailer fully loaded for travel.  The trick is to leave yourself no room to kid yourself -- which is entirely too easy to do. ("Gee, if I will just travel with an empty water tank and don't carry so much junk, things will be ok...."). 

think that was what that Excel spreadsheet was trying to accomplish - figure out the dry weights of the TV and RV, add all the people, stuff and fluids while making sure tow capacity (or a percentage of the tow capacity) of the TV and GVWR of the TV and RV are not exceeded. If you could pull all that off and still figure in a safety margin of X%, then the worksheet would give your rig the "green light". I would be interested if you have seen this spreadsheet and what you think of it.

Click to expand...

I have seen the spreadsheet, and tho I am an old spreadsheet commando myself, that is not the way I would do it.  For one thing it uses Gross Combined Weight Rating (GCWR) of the truck rather than Tow Rating.  GCWR is an equally valid number in terms of source, but is not nearly as widely available as Tow Rating.  The latter is available for a wide range of trucks over about an 8 year span in the TL tables.  Anyway, I am not here to critique the spreadsheet, I audited too damn many when I was paid to do it.  ;D

Carl L said:

I have seen the spreadsheet, and tho I am an old spreadsheet commando myself, that is not the way I would do it.  For one thing it uses Gross Combined Weight Rating (GCWR) of the truck rather than Tow Rating.  GCWR is an equally valid number in terms of source, but is not nearly as widely available as Tow Rating. 

Click to expand...

At the top of the worksheet it asks for the "Tow Vehicle GCVWR" is this the GVWR of the TV + the Tow Capacity of the TV?

If that is the case, and I plug all the numbers in, I'm good to go for a number of RV options near 100% trailer GVWR to tow capacity (provided I travel very light - I know I'm probably kidding myself like you said though)! In the spreadsheet, the limiting factor seems to be the payload capacity of my TV - ie, it can pull it, it just doesn't want to carry the weight of the hitch, people and stuff inside the TV.

Case in point, a certain RV weighing 4250 dry with a 5500 GVWR (when fully loaded) could overload my TV with a 500lb hitch weight, but not with a 400lb hitch weight.

At the top of the worksheet it asks for the "Tow Vehicle GCVWR" is this the GVWR of the TV + the Tow Capacity of the TV?

Click to expand...

You would think it would be wouldn't you.  However, in another thread, damned if I can remember where, that was discussed and it appeared that there were some slippage in the numbers -- well within the 10% factor tho.

(provided I travel very light - I know I'm probably kidding myself like you said though)!

Click to expand...

Well, that is the first sign that you are getting ready to do so, yes.

Case in point, a certain RV weighing 4250 dry with a 5500 GVWR (when fully loaded) could overload my TV with a 500lb hitch weight, but not with a 400lb hitch weight.

Click to expand...

On the other hand, that trailer with a 400 lbs hitch weight would likely be unstable.  Hitch weights on a TT should range between 10% and 15% of the total trailer weight with the lower limit being critical.