Weight question

Converting Cargo Trailers into TTTs

Weight question

Postby Lloyd Christmas » Fri Mar 07, 2008 2:30 pm

Hello All!

I scoured the web on cargo conversions and found almost nothing until I located this wonderful section. Partially due to not understanding how to calculate my towing capabilities and the remainder of not knowing how much an average build would add to my total, I am not sure what I will be able to safely tow.

Although I can understand the weight will have a huge variance baesd on materials and additions, I am just looking for some examples of what people have and use to tow it with. I have 2 different vehicles that will do the primary pulling. Both are SUVs with one being a Yukon and other Grand Cherokee Limited - Yukon has the 5.3 and Jeep the 5.7 Hemi. They are rated at GVWR 6600 and 7600 if I am not mistaken. I'm a little fuzzy on what that means.

Basically, what would be a good size for me to safely convert? I was thinking 6x12.

Thanks.
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Postby G-force » Fri Mar 07, 2008 3:43 pm

You need to find out the rated towing capacity, and maximum weight on the ball...both should be in the owners manual (assuming the manufacturere intended it to be used to tow.) Maks sure your trailer falls within those limits. GVWR is the maximum your vehicle is designed to weight full of fuel, cargo, people, etc. For example if a vehicle weighs 4000 pounds and has a GVWR or 6600 pounds, tham means it is rated to carry 2600 pounds of cargo. Somewhere in your manual should also be a GCWR, Gross combined weight rating, that is the total weight of your vehicle and trailer should weight.

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Postby Lloyd Christmas » Fri Mar 07, 2008 5:03 pm

G-force wrote:You need to find out the rated towing capacity, and maximum weight on the ball...both should be in the owners manual (assuming the manufacturere intended it to be used to tow.) Maks sure your trailer falls within those limits. GVWR is the maximum your vehicle is designed to weight full of fuel, cargo, people, etc. For example if a vehicle weighs 4000 pounds and has a GVWR or 6600 pounds, tham means it is rated to carry 2600 pounds of cargo. Somewhere in your manual should also be a GCWR, Gross combined weight rating, that is the total weight of your vehicle and trailer should weight.

Mike


So I think I hear you saying my rigs can 'pull' alot more than they can 'tow'. By that I mean, the power is probably not relevent and I have more than enough....it's the weight I have to watch. I figured the tongue weight would be more important than the total weight as far as preserving my vehicle but it seems like the distribution should factor in to a degree of total. It's hard to imagine that having the same weight distributed all throughout your vehicle's interior would be the same as pulling that much weight properly distributed in a trailer behind you.

I guess what I was looking for here is an apporximate size of trailer (based on just average setups) I can expect to pull with my vehicles.

Thanks.
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Postby brian_bp » Fri Mar 07, 2008 8:16 pm

G-force has already provided they key information to determine the maximum trailer weight. The GCWR should be in each vehicle's owner's manual... likely with a bunch of other good towing information.

In practice, you would almost need to adopt a lead-and-solid-walnut decor to make a 6x12 trailer into a travel trailer too heavy for those tow vehicles. That's a smaller body than my current travel trailer, which is 17' overall, with a 7.5'x14' body (yes, I know it's not quite a "tiny travel trailer"...), and my trailer weighs about 2400 lb empty and 3000 lb loaded. It is light enough for my minivan, and a Grand Cherokee or a full-size SUV like the Yukon should be able to handle double that much trailer if the tongue weight is kept reasonable.

I find my trailer too wide, for visibility and air drag. I think it makes sense to pick the cargo trailer width just wide enough for a workable floor plan (if you need to sleep across the trailer, and are 6' tall, a 6-by-anything doesn't sound like enough), and just long enough to fit everything in without resorting to tacked-on boxes on the tongue or (shudder) the bumper. I think that it's really nice for towing if the body is no wider than the truck.

One aspect of using cargo trailers which I've noticed is that they are usually constructed assuming (reasonably) that they will be stacked full of stuff. An RV, on the other hand, is mostly filled with air, so a "good" or "premium" trailer will be much stronger - and thus much heavier - than necessary. A "basic" or "economy" model might be more desirable. For instance, a 6x12 or 7x14 cargo trailer typically has two 3500-lb axles and a gross weight rating of the entire 7000 lb (or more)... twice what it needs. Even if you can handle the trailer weight, it will likely ride badly if it has springs chosen for 7000 lb and it only weighs 3000 lb loaded.
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Postby rainjer17 » Fri Mar 07, 2008 9:07 pm

most single axle cargos i looked at have a gvw of 3000 and under to keep away from having to add brakes, w/ brakes whatever the axle is rated at. hope that helps, i do my trailer dragging with an '02' f250 super duty powerstroke diesel and for my 6x10 cargo that is overkill! either of yours should be fine
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Postby Lloyd Christmas » Fri Mar 07, 2008 9:45 pm

I would probably add brakes to be on the safe side anyway but knowing all this, I think my bigger concern is gas mileage. I already don't get much better than 15-17 most of the time anyway. I'm hoping I'm light enough that it won't go down a load. I could take 13-14 but much more would leave me question if I had made the right move. There are so many things I like better about a tear or cargo convert versus a typical smaller RV. At some point, a smaller RV probably doesn't get any worse mileage and offers much more comfort, though.

Some great points here and I've already made some better choices just by visiting. :thumbsup:
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Postby catrinka » Fri Mar 07, 2008 10:17 pm

If you are looking for a light cargo trailer, you might see if you can find a fiberglass one. Mine, from Trailers Unlimited manufactured in Edmonton was 700 lbs empty. Now that I have it converted, it weighs in about 2000 lbs. fully loaded. I pull it with my Buick Rendezvous and hardly notice that I'm pulling it. My gas mileage does drop a bit, to about the same as my city mileage, but still not as bad as a bigger rv.
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Postby Nitroxjunkie71 » Sat Mar 08, 2008 8:14 am

I have a 2005 F-150 with a manual transmission and found out when I picked up my 6x10 cargo trailer that the manual transmission was ultimately the weak link. I also didn't get the tow package when I bought my truck thinking (trailer hitch) I can do that myself. I was not thinking gears.

My full size F-150 - Manual transmission.
with 3.31 gears (max trailer weight) 2,200 lbs
with 3.55 gears ( " " " ) 3,500 lbs

My full size F-150 - Automatic transmission.
with 3.31 gears (max trailer weight) 5,000 lbs
with 3.73 gears ( " " " ) 5,500 lbs

I never knew that a manual transmission made such a difference. After all;
Image

Without having the numbers in front of me I would guess a SUV with an automatic tranny can probably pull more than I can. DUH! :x

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Postby Lloyd Christmas » Sat Mar 08, 2008 11:05 am

I checked out my owner's manual and remain a little confused but a couple of things made more sense. My GVW rating is 7000 pounds on the window sticker. In the book, it says the max trailer weight is 7,800 pounds. I know that won't ever come into play.

So if I have understood and calculated correctly, I can't exceed 7,000 pounds total weight with my vehicle including the vehicle and the weight the trailer puts on the vehicle (via the tongue). My GMC truck weighs about 4500 pounds so I would assume my Yukon would be in that neighborhood. That would leave me with a trailer that could weigh up to 7,800 if only 2,500 pounds was on the tongue....does that sound right? Although I would never expect to approach near that, I think the bottom line is that I could pull anything I would consider.
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Postby rainjer17 » Sat Mar 08, 2008 11:44 am

check and see if there is a cgvw rating, combined gross vehicle weight. tongue weight would be limited by the reciever or bumper rating, plus there is an ideal percentage of tongue weight vs. trailer weight that i think is mentioned in another thread here.
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Postby brian_bp » Sat Mar 08, 2008 1:41 pm

Nitroxjunkie71 wrote:...I never knew that a manual transmission made such a difference. After all;
Image...

The keys are low gear ratio, and clutch size.

A rig like that has such a low gear that it needs to shift up to second at a walking speed, so lots of torque is applied to the wheels without an unreasonable amount being required of the engine and transmitted by the clutch. Since overall gearing is the product of transmission gear ratio and final drive ratio, lowering either helps the ability to get moving from a standstill... and do it without smoking the clutch.

The clutch in a serious truck is obviously bigger than in an light-duty vehicle such as a pickup or SUV... way bigger in proportion to engine power. The clutch is definitely the weak point for heavy hauling in many light-duty vehicles.
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Postby brian_bp » Sat Mar 08, 2008 2:07 pm

catrinka wrote:If you are looking for a light cargo trailer, you might see if you can find a fiberglass one. Mine, from Trailers Unlimited manufactured in Edmonton was 700 lbs empty. Now that I have it converted, it weighs in about 2000 lbs. fully loaded. I pull it with my Buick Rendezvous and hardly notice that I'm pulling it. My gas mileage does drop a bit, to about the same as my city mileage, but still not as bad as a bigger rv.

To me, the Shuttle from Trailers Unlimited looks very suitable for this purpose. Due to the light load of an RV conversion, the single-axle versions (Shuttle models with "S", not "T" on the end) would be suitable. The Shuttle comes in 4-foot-wide (maybe a minimal teardrop style?), 5-foot-wide (like Cathy's), 6-foot-wide (small travel trailer for Lloyd?), and 8-foot wide (full-sized travel trailer?). If you want to sleep across the width, and 7 feet seems ideal, you're out of luck. Each width is also taller than the next narrower series.

My guess is that a 6x14 Shuttle single-axle would weigh around 1000 lb empty, probably roughly 2500 lb as a fully equipped travel trailer, and still be able to carry 1000 lb of stuff, while being an easy tow for either of Lloyd's tugs. A 5-foot-wide would not have standing headroom for many people, but would be a bit lighter and even easier to pull.

I like the idea of one-piece body construction. Well, Cathy's is two-piece, because it is unusually long (for the width).

When I have suggested this type of moulded fiberglass cargo trailer to others, the conclusion seems to be that they are rare... perhaps the Shuttle is unique. They are certainly popular here, in various cargo applications, including rentals (by Trailer Unlimited and other companies, such as Budget).
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Postby brian_bp » Sat Mar 08, 2008 2:23 pm

Lloyd Christmas wrote:...So if I have understood and calculated correctly, I can't exceed 7,000 pounds total weight with my vehicle including the vehicle and the weight the trailer puts on the vehicle (via the tongue). My GMC truck weighs about 4500 pounds so I would assume my Yukon would be in that neighborhood. That would leave me with a trailer that could weigh up to 7,800 if only 2,500 pounds was on the tongue....does that sound right?


Assuming that you mean "if no more than 2,500 pounds was on the tongue", and if you also subract the weight of all passengers and cargo from that 2500 lb, then yes, that's what the Gross Vehicle Weight Rating and empty truck weight imply.

The manufacturers calculate the maximum trailer weight rating from the Gross Combined Weight Rating (GCWR), as G-force and rainjer17 have suggested. It's just like the GVWR, but for the whole combination, instead of just what's carried by the truck's axles. Again, 7,800 lb would only be allowed for the GMC truck if there were no passengers or cargo in the truck. The GCWR should be listed in the owner's manual, and hopefully on the door-jamb sticker which also shows axle ratings and tire pressures.

As rainjer17 mentioned, although you could put up to 2500 lb of tongue weight on the otherwise empty truck without violating the GVWR, the hitch, frame, and rear axle would all be overloaded. There are a bunch of limits, and you need to be within all of them. Almost no one can actually legitimately tow the advertised rated capacity of their truck, and the tongue weight can rarely be a large fraction of the weight of a significant trailer.

Lloyd Christmas wrote:... I think the bottom line is that I could pull anything I would consider.

Despite all of what I said above, I think this is a valid conclusion, given that the trailers being considered will weigh less than two tons, loaded. To be stable, the trailer will need at least a couple hundred pounds of tongue weight, and to avoid the need for a weight-distributing hitch it should be kept to no more than maybe 400 lb. That should be easy to arrange.
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Postby brian_bp » Sat Mar 08, 2008 2:37 pm

Lloyd Christmas wrote:I would probably add brakes to be on the safe side...

Absolutely. GM, like most manufacturers, advises or requires that the trailer have brakes if it exceeds some threshold weight, regardless of the tow vehicle's GCWR. For most cars it is only 1000 lb; the full-size trucks and related SUVs are the only vehicles with a higher limit, and even that is only 2000 lb.

Ford makes it very clear in their literature that the vehicles brakes are intended to handle only the GVWR, not the GCWR, so if the whole rig including trailer weighs any more than the GVWR (which it will, in almost every case), trailer brakes are required.

I use electric brakes with my van and travel trailer, and would not consider going without them, but most people consider that a more obvious requirement. It is interesting to note that my "minivan" has an empty weight almost as high as Lloyd's truck (although my 5120 lb GVWR is lower).
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Postby Lloyd Christmas » Sat Mar 08, 2008 3:45 pm

brian_bp wrote:
catrinka wrote:If you are looking for a light cargo trailer, you might see if you can find a fiberglass one. Mine, from Trailers Unlimited manufactured in Edmonton was 700 lbs empty. Now that I have it converted, it weighs in about 2000 lbs. fully loaded. I pull it with my Buick Rendezvous and hardly notice that I'm pulling it. My gas mileage does drop a bit, to about the same as my city mileage, but still not as bad as a bigger rv.

To me, the Shuttle from Trailers Unlimited looks very suitable for this purpose. Due to the light load of an RV conversion, the single-axle versions (Shuttle models with "S", not "T" on the end) would be suitable. The Shuttle comes in 4-foot-wide (maybe a minimal teardrop style?), 5-foot-wide (like Cathy's), 6-foot-wide (small travel trailer for Lloyd?), and 8-foot wide (full-sized travel trailer?). If you want to sleep across the width, and 7 feet seems ideal, you're out of luck. Each width is also taller than the next narrower series.

My guess is that a 6x14 Shuttle single-axle would weigh around 1000 lb empty, probably roughly 2500 lb as a fully equipped travel trailer, and still be able to carry 1000 lb of stuff, while being an easy tow for either of Lloyd's tugs. A 5-foot-wide would not have standing headroom for many people, but would be a bit lighter and even easier to pull.

I like the idea of one-piece body construction. Well, Cathy's is two-piece, because it is unusually long (for the width).

When I have suggested this type of moulded fiberglass cargo trailer to others, the conclusion seems to be that they are rare... perhaps the Shuttle is unique. They are certainly popular here, in various cargo applications, including rentals (by Trailer Unlimited and other companies, such as Budget).


The 6'6 height is a good feature in a sense. It also would promote some wind drag but appears like possibly less than a more 'boxy' conventional cargo trailer.

Maybe weight savings isn't a big issue for me but added weight sure wouldn't really help anything that I could see.

After reviewing the prices, this probably isn't going to work for me. I originally got interested in tears, cargo conversions, etc. due to the price. A traditional miniature toy hauler would do what I need it to but the prices for something decent are much more than I am willing to pay.....and the even the smaller sizes were a deterrent, too.

I think what I'm looking for is something that is really nice but cheap, really spacious but small, and have all the features included in a heavy camper but yet be light. :) I guess I'll keep looking.
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