Offroad trailer Vs Roof tent MPG

[Redline]

Very valid points and argument, and I would like to buy-in to the theory as a fan of trailers . However my sense is that there are many more climbs that are difficult for trucks with trailers than off-camber sections that stop or roll a rig with a roof load. Particularly a mildly build overland rig compared to a very tall 4x4. I have nothing to back this up, just a guess. There are possibly many sidehills that make the driver with a roof load nervous or uncomfortable, but does that inhibit the vehicle's ability. Maybe indirectly through the driver?

Also, aren't there many more off-highway rigs out there with roof loads/racks than towing trailers. Seemingly not a huge problem to add a RTT to the roof, particularly if that's all that's added, even though many wisely caution about the negatives.

You're right. But part of my theory is that a racked vehicle will be limited to climbs that are still safe based on it's higher COG. A trailered vehicle can probably make those same climbs with a light trailer, because a very high COG vehicle isn't traction limited, it's rollover limited.

And it's not just about climbs. A "difficult" trail will also probably include some off-camber driving, which is a place that a trailer has a huge advantage compared to a rack.

 

[JIMBO]

:sombrero: Heh Heh, My jeep will roll, before the trailer ever gets near it's COG jeopardy point !!

:costumed-smiley-007:costumed-smiley-007 JIMBO

 

[XJBANKER]

I would love to not need a trailer. My problem is I have a relatively small vehicle (a jeep cherokee) and I always have two kids and a very large dog. Before I bought my RTT I could pack most of my camping gear in a roof rack and keep the back open for the dog. Once I got my tent I realized that I also lost all my packing space on my roof.

I just realized if you really think about it you have a really expensive DOG, not a really expensive friend.

 

[DrMoab]

In more ways than one man.

 

[teotwaki]

I find it's not worth the effort when I'm not hauling the trailer. It's probably a case-by-base basis. My particular truck has enough power to go up most hills at the speed limit without kicking down a gear or going past 1/2 throttle. If a particular truck is more... lightly powered... it might make more sense to do it when not towing a trailer.

Another point about trailers... and this is just my untested hypothesis at this point... some anti-trailer people state that a trailer will prevent you from running a trail that you otherwise could, if you instead stored your gear on a roof rack. This, because with a trailer, you have all that weight on top of an unpowered axle.

I think that if one were to resist the urge to pack the the kitchen sink into the trailer just because you CAN. If you simply take your roof load, and move it into a very light and smartly built trailer, so you're talking about towing only 5-900 pounds... that the drag from the trailer is so little, you could run the same trails you could with a heavily loaded roof rack. Having several hundred pounds on your roof is it's own limitation.

I really agree with being smart about trailer size and load. I am SO guilty of packing too much even without a trailer.

 

[R_Lefebvre]

I'm very guilty of it too. But gladly guilty. If I wanted to go minimalist camping, I'd ditch the truck and just go hiking. Heck, I can get as much stuff into a canoe as I can in the back of the truck. I got the truck and trailer because I want to get get out WHILE enjoying comforts.

 

[SSRx7]

Hmmmm so if I drive my 4x4 pickup with a self contained camper with a rack on top, and pull my utility trailer behind it I more or less have offended everyone by having a rack, a trailer, and an RV altogither...

Actually, I have been pondering this debate as well. I am building my expo trailer out of a full jeep tub with hard top on it, and I want to put a RTT on top of the 'trailer'. Now, I'm not gonna be going rock climbing with this, but more or less to get to the back country to set up camp, and then go exploring in the jeep.

If it is up in the airstream, it will effect mpg. if it is within the airstream, but has a drag coefficient, it will effect mileage.

I can prove my point how much different it would be: Back in 02 before I got into expo stuff, we had a travel trailer that we pulled behind our Astro van. Now that trailer was a little wider than the van and alot taller. On our trip, we went from Florida, up through the smokey mountaings, all the way up thru NY to Canada, then back down through Niagra and west to Rocky Mountain Ntpk, down thru NM, Az, then back along the bottom to Florida again.

Climbing mountains I could keep the van and trailer at speed limit(little wind resistance climbing mountains). But going across the plains states, we encountered heavy head winds and it was all we could do to maintain 50mph. Fuel mileage went from around 10mpg in the mountains, to about 5-6 in the head winds.

Dragging the trailer up hills took less power and therefore fuel, than did on level roads in a headwind. The wind had that much more effect on it.

It really depends on the owner(s) and the vehicle, and where you will be doing most of your driving. If you are crawling rocks for 8 hours, the trailer will cause you to use more fuel because you are dragging the weight, and you have almost 0 wind resistance. If you are cruising long stretches of highway or high speed dirt roads (is there such a thing?), then the rack/rtt will cause you to use more fuel because of wind resistance.

That's how I see it.

 

[Root Moose]

I would love to not need a trailer. My problem is I have a relatively small vehicle (a jeep cherokee) and I always have two kids and a very large dog. Before I bought my RTT I could pack most of my camping gear in a roof rack and keep the back open for the dog. Once I got my tent I realized that I also lost all my packing space on my roof.

This is one of the big reasons why I have no interest in getting another dog, as much as the boys keep asking. There's other big reasons too. Dogs complicate everything too much. I'm such a big meany. The only animals in my house from now on are in the freezer.

Ryan, get everything (i.e. RTT) inside the slipstream of the Jeep when at highway speeds. The lower the RTT can sit on the trailer the better the aerodynamics and the better the resultant MPG. I'd consider making the supports for the RTT telescope somehow if it meant getting the RTT even lower for highway speeds. I figure it would be a worthwhile investment in time and money.

If you can keep the top of the Jeep flat you'll keep the flow over the Jeep smoother longer which means less drag, etc., etc.

 

[R_Lefebvre]

Hmmmm so if I drive my 4x4 pickup with a self contained camper with a rack on top, and pull my utility trailer behind it I more or less have offended everyone by having a rack, a trailer, and an RV altogither...

You also need to use recovery hooks on your bumpers, use chromed lugnuts on steel wheels, and paint your Jeep Sandglow Yellow (Camel Trophy Land Rover colour). You'll really have everybody up in arms then.

It really depends on the owner(s) and the vehicle, and where you will be doing most of your driving. If you are crawling rocks for 8 hours, the trailer will cause you to use more fuel because you are dragging the weight, and you have almost 0 wind resistance. If you are cruising long stretches of highway or high speed dirt roads (is there such a thing?), then the rack/rtt will cause you to use more fuel because of wind resistance.

Sounds like a reasonable assumption to me.

This is one of the big reasons why I have no interest in getting another dog, as much as the boys keep asking. There's other big reasons too. Dogs complicate everything too much. I'm such a big meany. The only animals in my house from now on are in the freezer.

Yeah... I struggle with this too. I really like dogs. But the world is becoming increasing dog un-friendly. Particularly public parks and campgrounds.

 

[teotwaki]

Hmmmm so if I drive my 4x4 pickup with a self contained camper with a rack on top, and pull my utility trailer behind it I more or less have offended everyone by having a rack, a trailer, and an RV altogither...

Actually, I have been pondering this debate as well. I am building my expo trailer out of a full jeep tub with hard top on it, and I want to put a RTT on top of the 'trailer'. Now, I'm not gonna be going rock climbing with this, but more or less to get to the back country to set up camp, and then go exploring in the jeep.

If it is up in the airstream, it will effect mpg. if it is within the airstream, but has a drag coefficient, it will effect mileage.

I can prove my point how much different it would be: Back in 02 before I got into expo stuff, we had a travel trailer that we pulled behind our Astro van. Now that trailer was a little wider than the van and alot taller. On our trip, we went from Florida, up through the smokey mountaings, all the way up thru NY to Canada, then back down through Niagra and west to Rocky Mountain Ntpk, down thru NM, Az, then back along the bottom to Florida again.

Climbing mountains I could keep the van and trailer at speed limit(little wind resistance climbing mountains). But going across the plains states, we encountered heavy head winds and it was all we could do to maintain 50mph. Fuel mileage went from around 10mpg in the mountains, to about 5-6 in the head winds.

Dragging the trailer up hills took less power and therefore fuel, than did on level roads in a headwind. The wind had that much more effect on it.

It really depends on the owner(s) and the vehicle, and where you will be doing most of your driving. If you are crawling rocks for 8 hours, the trailer will cause you to use more fuel because you are dragging the weight, and you have almost 0 wind resistance. If you are cruising long stretches of highway or high speed dirt roads (is there such a thing?), then the rack/rtt will cause you to use more fuel because of wind resistance.

That's how I see it.

I think it breaks down into two major components: drag due to friction (rolling resistance of tires) and drag due to wind resistance of the trailer. The tires' frictional drag can stay fairly constant with forward speed unless the wind resistance of the larger cross section tires becomes a factor. The wind resistance gets worse with total wind speed (vehicle forward motion and any additional due to headwinds) because of that darned v-squared component but the trailer my present more cross sectional area to the air than the tires.

Of course, roof racks and their payloads are an aerodynamic mess which is why Thule and Yakima cargo coffins do a better job up there.

 

[AlexJet]

That's partially true. It depends a lot on how you go up the hill. If you put the hammer down and charge up the hill with a trailer, you'll never gain the fuel back. The key to good milage is to take it easy going up hills. If you try to hold your speed, and the engine goes into open loop where the fuel/air ratio goes from 14.7:1 to maybe 13:1 or worse, spark timing is retarded, and the transmission kicks down a gear or two, you waste a lot of gas getting up the hill, and you'll never make it up on the backside.

The same is true with an RTT, but I think to a much less effect when talking about hills specifically. Since they weigh so much less than a trailer, they have less effect going up hills.

So, when I'm trying to supermilage with the trailer, I really let it slow down going up hills. I have a Scangauge, so I keep an eye on the open/closed loop status. I will let it slow down within reason, to keep it in closed loop if possible. I will also preferentially kick it down into 3rd gear manually if required. I'd rather be down a gear, than go Wide Open Throttle. Basically, after about 1/2 throttle, you're pouring the coals to it, and Brake Specific Fuel Consumption goes to ****.

If you're in an area with rolling hills, I like to build up a head of steam on the backside, and then "coast" up the next hill. I'll exceed the speed limit within reason, building speed with the throttle less than 1/2 way, so that I can climb the next hill at less than 1/2 throttle, bleeding off speed.

Obviously this all takes some extra effort, but it pays off.

I'm second to that, as I try to use the same method.

 

[AlexJet]

...The downside is that you have to find a place to store your trailer when not in use, and the initial cost of the trailer. Many here have built their own but it still costs 500-1500 from scratch. You wont recover those costs for years. I wouldn't trade my trailer though I use it for utility purposes as well as getting out in the wilderness.

You are way too optimistic....
My build cost me ~$3'000 and it just basic Expedition Trailer.

 

[R_Lefebvre]

Yeah, $1500 to build a trailer raised my eyebrows too. I guess it could be done, but you'd have to be REALLY good with "recycling" things.

 

[AlexJet]

Exactly Rob. My cost which I estimated doesn't include the labour as I've done it myself.

 

[Redline]

I wish I would have done one of my 'mileage tests' after I purchased my KK and before I sold my Chaser with a Eezi-Awn RTT on top.

Since I recently purchased an Eezi-Awn 1600 from Equipt I would have had data from all three set-ups with the same car. Maybe later this year I will get around to testing the two I currently have available in a back-to-back test.