View Poll Results: your towing speed
55mph 167 13.11%
60mph 480 37.68%
65mph 450 35.32%
70mph 144 11.30%
75 mph or faster 33 2.59%
Voters: 1274. You may not vote on this poll

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Old 06-04-2007, 09:51 PM   #113
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Quote:
Originally Posted by AgZep
Ok, let's try another angle. Assuming you've reached your cruising speed (and are thus no longer accelerating), the overwhelming majority of the gas you're burning is being used to overcome aerodynamic drag. Drag increases exponentially with speed. To go twice as fast, you have to overcome four times as much aerodynamic resistance.

On our last trip, we got about 12 mpg at 55 mph. That's with a 28' trailer and a 3/4 ton big block gasser pickup. Do any of you with similar rigs who tow at 75 mph have reliable mileage data to compare? I'm curious how big the difference might be.
1 MPG with Power Stroke Diesel. 5,000 miles towing.
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Old 06-04-2007, 10:10 PM   #114
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Quote:
Originally Posted by AgZep
Do any of you with similar rigs who tow at 75 mph have reliable mileage data to compare? I'm curious how big the difference might be.
My results are somewhat skewed because if I'm going faster than 65 then I'm in a convoy getting a draft from the trucks ahead of me.

I get about 15 MPG going solo at 65 or drafting at 70-75. My best result ever was 19 MPG following my parent's MoHo at a more or less constant 60 MPH going downhill and downwind into New Jersey in 70 degree weather. My worst was 13 MPG going mostly solo uphill and upwind into Ohio on a cold February day.

Somewhat interestingly (to me at least) I recently tried using higher octane petrol and I've been getting about 2-3 MPG better fuel economy - 27.5ish instead of 25MPG - when I'm not towing. I'm curious to see what the difference will be with my Bambi.
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Old 06-04-2007, 11:04 PM   #115
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Does this make sense?

Hi, according to this discussion my 6,300 GVWR Safari with four wheels and tires, load range D, can go 65 MPH with only 30 lbs air pressure and if I add 10 lbs more air pressure, 40 lbs, I can go 75 MPH?
I divided the 6,300 lbs GVWR by 4 putting an average weight of 1,575 lbs per tire. The chart shows at 1,600 lbs per tire I only need to have 30 lbs of air pressure to drive at 65 MPH. And by some of your statements by adding another 10 lbs air pressure I can now go 75 MPH. Airstream manual says to run 65 lbs air pressure and that is exactly what I do. I like to travel on the freeways between 60 to 65 MPH and may momentarily hit 70 MPH for a very short time and distance. If the tire can actually handle 65 MPH with only 30 lbs air pressure, I have a great safety margin. But I wouldn't count on it.
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Old 06-04-2007, 11:45 PM   #116
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Quote:
Originally Posted by Minnie's Mate
1 MPG with Power Stroke Diesel. 5,000 miles towing.
MM,

1 mpg? Or do you mean 1 mpg different than my figures?

There's no practical way to test precisely, but I'm really curious to see how speed relates to fuel consumption. I'm sure a diesel does better whether towing or not, but I wonder if there's a different sensitivity to speed between diesels and gassers.

I was just looking at a recent Trailer Life test of a Nissan Pathfinder towing an SOB about the same size as our Airstream. The Pathfinder got 8.8 while towing, much lower than we get with an 8.1 gas V8 and a drastically heavier rig. I suspect the Pathfinder engine was working really hard under the load.
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Old 06-05-2007, 12:36 AM   #117
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Quote:
Originally Posted by 53FlyingCloud
If I am not mistaken, there's a published list of state law for "towed trailer" speed limit which, is determined by the weight of the towed trailer. (Among other listed requirements, like brakes) Most states allow speed in the 50 to 55 mph speed range, with a few states allowing the higher speed. I would think that it would be prudent for one to check the list for the states that you plan to drive in and, thru...
Drive with care.
While I haven't heard of a list like that, I will say that CA. has a towed trailer speedlimit. It is a general speed limit, if you are towing , it is 55mph. Oregon does too but it only applies to commercial vehicles. Most towed trailer speed limits apply to commercial vehicles only.
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Old 06-05-2007, 04:50 AM   #118
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Of fifty states, more than half allow trailer towing at 65 mph or more. Seven allow towing at 70 mph, and one allows 75 mph.
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Old 06-05-2007, 07:18 AM   #119
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Quote:
Originally Posted by AgZep
Ok, let's try another angle. Assuming you've reached your cruising speed (and are thus no longer accelerating), the overwhelming majority of the gas you're burning is being used to overcome aerodynamic drag. Drag increases exponentially with speed. To go twice as fast, you have to overcome four times as much aerodynamic resistance.

On our last trip, we got about 12 mpg at 55 mph. That's with a 28' trailer and a 3/4 ton big block gasser pickup. Do any of you with similar rigs who tow at 75 mph have reliable mileage data to compare? I'm curious how big the difference might be.
At 68-70 mph I get (thru about the last 10,000 miles) 10.6-10.8 towing my 31'.
I do use cruise control about 2/3 of the time
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Old 06-05-2007, 07:26 AM   #120
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Quote:
Originally Posted by ROBERTSUNRUS
Hi, according to this discussion my 6,300 GVWR Safari with four wheels and tires, load range D, can go 65 MPH with only 30 lbs air pressure and if I add 10 lbs more air pressure, 40 lbs, I can go 75 MPH?
I divided the 6,300 lbs GVWR by 4 putting an average weight of 1,575 lbs per tire. The chart shows at 1,600 lbs per tire I only need to have 30 lbs of air pressure to drive at 65 MPH. And by some of your statements by adding another 10 lbs air pressure I can now go 75 MPH. Airstream manual says to run 65 lbs air pressure and that is exactly what I do. I like to travel on the freeways between 60 to 65 MPH and may momentarily hit 70 MPH for a very short time and distance. If the tire can actually handle 65 MPH with only 30 lbs air pressure, I have a great safety margin. But I wouldn't count on it.
You are reading it right, that is the safety margin you have!

Can you count on it? yes as much as anything else.

I wouldn't follow AS on this tire pressure issue, follow the tire makers, they do the R&D.

IN your case I would run 40lbs it may be too soft for sway. I would run 50-55. THe reason I would use 65 if I don't need to is a little more safety margin sure.

But when you pump up to 65 look at the surface area of the tire on the ground, now do that with 55 you'll see it has more contact with the road.

Also you will get worn out in the center of the tire along with cupping if overinflated.
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Old 06-05-2007, 11:01 AM   #121
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Quote:
Originally Posted by AgZep
MM,

1 mpg? Or do you mean 1 mpg different than my figures?

There's no practical way to test precisely, but I'm really curious to see how speed relates to fuel consumption. I'm sure a diesel does better whether towing or not, but I wonder if there's a different sensitivity to speed between diesels and gassers.

I was just looking at a recent Trailer Life test of a Nissan Pathfinder towing an SOB about the same size as our Airstream. The Pathfinder got 8.8 while towing, much lower than we get with an 8.1 gas V8 and a drastically heavier rig. I suspect the Pathfinder engine was working really hard under the load.
My F-250 has a trip computer that calculates fuel consumption. If I tow at 75 MPH on the interstate I get 11.6 MPG's. If I tow at 70 MPH, I get 12.2 MPG's. If I tow at 65 MPH, I get 12.4 MPG's. My truck shifts into its final gear at approximately 63 MPH so I don't tow under about 65 MPH on the interstate. My RPM's are the same at 75 MPH as they are at 55 MPH. I have calculated the mileage manually and come up with virtually the same mileage as the trip computer. I keep a close watch on my transmission and water temp gages when I'm towing in the mountains. When I tow on two lane roads and undivided four lane highways, I always tow at the posted speed limit no matter what that speed is.

BTW, the table referenced above is a little askew. In Georgia, the speed limit for trailers is as posted. The Max Tow Speed is 55, but that is for tractor trailers and I have never seen it enforced.
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Old 06-11-2007, 05:34 PM   #122
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We are towing a 1990, 34' Airstream limited and our speed is 55 mph. Seen to many RV's and tow vehicles in pieces off the road because of high speeds and improper hitches/sway bars. My 3/4 ton diesel Ford, 6 speed standard just loves it. Please drive carefully. Happy travelling, Ken
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Old 06-12-2007, 08:18 AM   #123
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Welcome to the forums Ken. Glad you found us and hope to see many post from you in the future.
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Old 01-27-2008, 02:06 AM   #124
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I tow at 65 I get under 12 If I tow at 55 I get almost 15 mpg on gas and its just a more pleasent drive. 55 is the speed limit in CA. If I'm going to have a good time just crusin' it's the right speed. Empty (no tow) to Las Vages and back at high speed (70-75) I get 19.5.
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Old 01-27-2008, 04:06 AM   #125
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I voted 60 - but it's really more like 62 or 63. My Dodge Cummins feels 'in the groove' towing at those speeds. It certainly could go faster, but things feel right.

Not towing, the groove is 68 mph.
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Old 01-27-2008, 11:21 PM   #126
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25 Mph

Hi, I tow at 25 MPH, in school zones, when children are present.
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