Expedition EL vs Suburban No chevy or ford bashing please.

[Diamondpilot]

It's more about the frontal area / shape of the trailer, than about how much it weighs. I get 7 or 8 MPG (highway) with my 8.5x20 tall box trailer whether it is empty or loaded. It is about 3600# empty and usually 7000# loaded. When I am doing city driving, the weight is a bigger factor, because of frequent stops at traffic lights and then accelerating to 30 MPH from a dead stop just to get to the next red light. I have seen as bad as 4 MPG towing it in the city!

The thing about this one is, the box is 7'6" tall and 8'6" wide. Imagine trying to hold a piece of plywood up-right against a 30 MPH or 60 MPH wind -- there is no way you could do it! Your truck can push that much air out of its way to tow your trailer, but it uses up a lot of fuel.

Frontal area has a little to do with it but it more the rear area. I have a degree in Aero Space but am no expert but if you look at any airplane it will tell you a lot of the story. Most are very blunt on the front end but very tapered on the rear. The induced drag off that back end versus the parasite drag off the front end is far greater and multiplies at a rate of 4 times with speed increases.

Chris

 

[yelbike]

Chris, I've seen you post that fact before and I've thought about it quite awhile. I'm sure the rear drag has a large impact on the total load, but I can't see how it could be more than the front though. Just defies MY logic.

 

[yelbike]

That big block goes moving and pushes all the air out of the way. When the block passes, you have nothing. Think partial vacuum.

Totally agree with your logic, but you have push the air out of the way before the vacuum happens. The vacuum isn't perfectly sealed therefor inefficient. The push of the air must push all of it and be complete.
I agree that the suction/vacuum from the rear must be strong but I think it can only be a less than equal to the front force.

I don't want to come across as argumentative, its just what I see as logical. My physics knowledge only goes first year university deep.

 

[timswi]

I have a 30' V10 gas Class C Ford motorhome and it gets 6.7mpg on a 300 mile mostly highway trip...Count your blessings, you're doing much better than I am.

 

[jeffsw6]

Frontal area has a little to do with it but it more the rear area.

I'll take your word for it! In the owner's manual of my truck, there is actually a limitation on the frontal area for towing. I am sure this is for simplicity since they do not provide formulas for reducing your max towed weight, etc. as you increase drag; but what you are saying sounds sensible but also too complicated for the average guy like me to really understand when shopping for a travel trailer.

 

[yelbike]

I have a 30' V10 gas Class C Ford motorhome and it gets 6.7mpg on a 300 mile mostly highway trip...Count your blessings, you're doing much better than I am.

Wow, yup, makes me feel a little better.

 

[Diamondpilot]

Totally agree with your logic, but you have push the air out of the way before the vacuum happens. The vacuum isn't perfectly sealed therefor inefficient. The push of the air must push all of it and be complete.
I agree that the suction/vacuum from the rear must be strong but I think it can only be a less than equal to the front force.

I don't want to come across as argumentative, its just what I see as logical. My physics knowledge only goes first year university deep.

Actually, vacuum drag or induced drag is squared as speed increases. So 4 times. Its a big deal.

The front end is a constant and is broken by the vehicles shape which is always present no matter if the trailer is hitched up or not.

Chris

 

[yelbike]

Nice looking truck! How does it tow?

Also curious about how it rides on those thin tires. I don't see how these newer vehicles can ride smoothly with the giant wheels and low-profile tires, my girlfriend's Mustang is a rougher ride than any truck I've ever been in!

So I finally got a ride in my uncles 2007 lincoln LT which has 20 rims and stock tire size. I found it to drive much rough and stiff then our expedition with the 22" rims. So really no complaint about ride quality with the 22" rims.

Bought new tires for it last month. 305/40/22 Nitto 420s for $165 a piece from discounttire, now it corners like its on rails.:laughing::shocked:....not really it still weighs almost 6000#s, it doesn't corner....but the tires look cool.

 

[yelbike]

Just a note about the tires. The Nitto 420s are great in summer like conditions. I can't make them spin out on wet pavement unless I really try and knock off the traction control. By no mean are they any good in snow. They are marked as all season tires.......I would totally disagree. Even though they are like new, they completely suck in snow as well as on ice. Even with 4wd, traction control and the fact this vehicle tips the scale at nearly 6000 lbs, its a brutal winter vehicle with these tires on. I'm in the market for a set of winter rims and snow tires now. Totally dissapointed.

 

[yelbike]

Well, I just got back for a short drive to clear my folks driveway while they were away. Those tires have to go. For the first time in my life I just sailed by a stop sign, narrowly missing the dead end sign right to the bottom of a large and deep drainage ditch about 30' down and about 60' from the road way. No one hurt, trucks ok. I got to meet a new neighbour and his 7000 series JD.