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Old 01-08-2007, 06:38 PM   #1
gil
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hi guys -

we have been looking at what is available in the truck conversion market and it seems like the freightliner M2's and Columbia's are a popular base platform to start with.

we will only be towing a car or truck, but no trailer and don't want to be stuck in the right hand lane going up steep grades and be at the upper weight limit with a full fuel and water load as well as everything plus the kitchen sink inside the motorhome.

it seems that a lot of diesel pushers have an engine in the 300 hp range (like the M2) and you will see them struggling at times.

are well comparing apples to apples in those situations?

is an M2 towing a car/truck going to keep up with a columbia hauling a race trailer

how much different will the fuel mileage be? (300 hp vs 450 hp)

thanks in advance to all of your input.

gil
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Old 01-12-2007, 05:47 AM   #2
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Gil
I have a few thoughts on these questions. First, a mid-size truck (M2) should have no trouble in the mountains with a 24' coach pulling along a truck. A lot of M2's are equipped with smaller engines. We had a FLD 112C with a small block Cummins and it pulled our race trailer just fine on hills of all slopes.

In my opinion the M2's don't ride as well as bigger cabs. The Cloumbia Class trucks are Class 8 if I'm not mistaken, just a cheaper model in Freightliner's lineup. The Century Class is a bit fancier. I'm not an FL expert so take my words with a grain of salt here.

My experience with fuel efficiency is that the difference will be small. The big trucks are so underutilized that you don't pay a big price.

If fuel efficiency is big for you look at Volvo engines or Cummins small blocks (M11 for example). We got just under 12 MPG pulling a 25 foot coach and a 6000# race trailer.

One thing left out of your questions: The cool factor. I think that Volvo VN's, Peterbilts, and Kenworth T2000's are way cooler trucks and make better looking conversions. As the drive train is virtually the same between platfoms it comes down to looks, and reliablility. I'm already seeing used truck prices spike from the new fuel regs. Get in early.

Good luck, Tony

ToolSet Motorhomes
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Old 01-12-2007, 10:47 AM   #3
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I have an M2 with a 17'10" box (quite small) and I'll share some of my thoughts...

The rig has the MBE926 engine with 300HP and 860 lb-ft torque. We've towed a Honda CR-V and the rig barely even knows it's back there. From what I've read and been told, the fuel mileage depends more on the total weight than on the engine specs. In other words, it takes X horsepower to move the rig and Y gallons of fuel to produce that horsepower. So, my rig might be working a bit harder to go 65 mph than a rig with a larger engine but roughly the same amount of fuel is consumed. We have 10k miles on the rig and are averaging about 9.8 mpg. I'm hoping to get over 10 as it gets even more broken in.

More info...
As delivered, the M2 did ride somewhat harsh. I attribute this mainly to the underloaded front axle (8k pounds on a 12k axle). Adding Donvel air stabilizers (air springs) made a world of difference! I don't have any experience with other rigs so I can't say whether the M2 is any better or worse.

Regarding 'enough power'... There are very, very few occasions where I wish for a bit more power. Overall, it pulls the hills at about 55-60 mph. Getting a running start helps a lot (it doesn't accelerate uphill well at all). For the most part, we're limited by the curves in the road and not the power to pull the grade. (In other words, we have to slow down for the turns before we run out of power to climb.)

There are several 'engineering' approaches to help you decide. There's an Excel spreadsheet that will tell you the amount of HP required to pull a certain weight up a certain grade. The truck dealers can also run a 'profile' for you that gives you almost a perfect picture of your expected performance. I had the Allison transmission rep run a profile for us. With this information we were able to select an axle ratio to optimize performance for 65 mph and knew that we could pull 25k pounds up a 7% grade at about 50 mph.

Hope this helps.
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Old 01-13-2007, 08:27 AM   #4
gil
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hi tony and alan -

thanks for your responses to my questions/concerns.

a couple of follow-ups -

1. we are looking at a 30' conversion.

2. tony - do you have any specific $ comparisons on the "spike" in truck prices. (i am not committed to an m2 or columbia - it just seems like they are the ones you see most on the haulmark, showhauler, type rigs)

3. alan - i would be interested in the spreadsheet yu were talking about.

thanks again!

gil
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Old 01-13-2007, 09:08 AM   #5
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Gil
I have only anecdotal info about truck prices. It seems a year or two ago i could buy a 5 year old, 600K mile, 350 + HP Autoshift truck (Volvo or FL) for under 20K. Lately they are almost 25K. I wish i could give you more detailed info.

My gut tells me that the new truck market will be a buyer's market.

I too would like to see the spreadsheet.

Tony

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Old 01-13-2007, 11:07 AM   #6
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Tony - I sent the spreadsheet to your 'toolset' email address.

Gil - I posted to the 'private messaging' portion of this forum to request the email address to send you the spreadsheet.
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Old 01-13-2007, 11:15 AM   #7
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Quote:
Originally posted by anthony desnick:
My gut tells me that the new truck market will be a buyer's market.
A big part of the spike may be driven by the new emission standards. From the reading I've done, the new trucks are about $10k more than last years. This would certainly drive up the price on used trucks.
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