Why is a longer wheel base truck better?

I am looking for more of a scientific answer. I married a scientist so it helps make my mind up when I see it.

Also, is there an idiots guide to torque ratios, motors and towing capacity? When I go to Chevy or Ford's website I feel like it is all written in German! I just installed a german program on my son's computer and that was fun since I don't know any german!

However I digress. I don't understand all the options and what I would need for a given situation. Someone recently told us that when we go to get a TV we should call an RV dealer just to be sure it would work well together. Great idea, but I don't like relying on other people for something as important as the safety of my children.

Thank you for the help!

ok, I'll take a stab without getting too scientific....
longer wheel base would mean longer truck = higher moment of inertia
also
consider that the instability you're looking to control is from the trailer swaying and such, forcing a yawing moment
yawing around the CG
which is countered by friction at the tires, which will be farther away with a longer wheelbase, resulting in greater leverage
longer wheel base.

A longer wheelbase is inherently more stable than a shorter one. For a fifth wheel, a long bed allows a tighter turn than a short bed, although certain hitches and a rounded nose on the camper can help.

Good move on ignoring the RV dealer.

3 Ladybugs said:

Someone recently told us that when we go to get a TV we should call an RV dealer just to be sure it would work well together. Great idea, but I don't like relying on other people for something as important as the safety of my children.

Thank you for the help!

Click to expand...

Most of the RV sales people I've spoken with know less than I do and I'm still learning.  However, even if they're knowledgeable they're a bit conflicted.  If they want to put bread on their table they need to sell an RV.  So they may not have your best interests at heart.  When I was shopping for 5th wheels, one sales person told me my truck, an F250 diesel long bed could pull any Keystone Montana 5th wheel made.  Her statement was based on what she had heard.  Technically my truck could pull most any heavy 5th wheel RV.  However from a safety and mechanical perspective, it would be a high risk combo.  Most if not all heavy 5th wheel RV's would overload my rear axle and likely my trucks GCWR (gross combined weight rating).  That's the total weight of the loaded truck and trailer.  There are both legal and safety considerations when overloading a tow vehicle or RV. 

There are many members of this forum who are very knowledgeable and qualified to answer any question you may have.  If you find a truck or trailer your interested, post a question and wait for answers.  You will not be sorry. 

Grab a yardstick and lay it on your kitchen table with the 1" end closest to you. Place a knife at the center point of the yardstick at the end where it is closest to you to establish a reference of its position.

Place one finger on the 12" point and imagine that 0" - 12" is the TV and 12" - 36" is the unit being towed.

Move the 0" end to the right the width of the yardstick and place a knife along the outside of the yardstick at the 0" end. Also, place a knife along the outside (opposite side) at the 36" end.

Center the yardstick to the reference point.

Next, with your finger on the 12" point, move the 0" end to the left the width of the yardstick and mark both ends with knives as you did above.

Return the yardstick to the reference point.

Now, place your finger on the 24" point and move the yardstick left and right until it is against the knives at the 0" end.

What does this indicate? A longer TV will cause less side to side movement of the unit being towed than will a shorter TV which results in a safer, more comfortable tow experience for the driver and passengers.

First, Gary B is right about all sales people.
blw2 makes valid points as well.

I am working on an article for the library on your very valid question.  My emphasis will be on tow vehicle capacities and 5th wheels.

Note that for virtually all trucks, the specs are mutually exclusive.  If you are pulling a camper near the towing capacity, then you are EXTREMELY limited with respect to payload or any other load carried in the truck.  If you load the truck (or any Tow Vehicle) anywhere near the GVWR, then there is no room left in the GVWR or GCVWR for a trailer of any usable size.  It is a balancing act. 

Truck 5er towing capacities use a 15% pin weight.  In fact, pin weights from Keystone web site data indicate the average (nearly 150 models) pin weight for their line of 5ers is 19.6% and 23.3% for toy haulers.

My degree is in Chemistry, so I understand your desire for scientific facts.  The above comes from research completed thus far.

It's actually the ratio between the wheelbase and the hitch's distance behind the rear axle that makes a longer wheelbase vehicle tow better than one with the same overhang but a shorter wheelbase.

Trailers transmit side forces to the tow vehicle as you go down the road.  Push right on a rear mounted hitch and the tow vehicle will rotate around the rear axle and yaw left.  The ratio between the wheelbase and the length of the rear overhang determines how much leverage these side forces have to influence the direction of travel.

Short wheelbase vehicles have a smaller wheelbase to rear overhang ratio than those with longer wheelbases, so side forces on the hitch have more leverage to affect the direction of travel of a short wheelbase vehicle than one with a longer wheelbase.

Proof of this leverage is the 5th wheel hitch, which puts the hitch directly over the rear axle and eliminates the lever arm between the hitch and rear axle that allows side forces to affect the direction of travel.

This makes 5th wheel trailers inherently more stable than bumper pulled trailers and the lack of a lever arm largely removes the wheelbase of the tow vehicle from handling considerations.

Commercial trucks are a great example. A short wheelbase tractor can pull a 53 ft. box trailer at highway speeds without issues because it's hitch is directly over the rear axle so there's no lever arm to affect the direction of travel.  A longer wheelbase tractor may be preferred for ride comfort or to provide space for a sleeper compartment but there's no handling reason to use one over the other.

I would love to find a 5th wheel that I like but honestly most seem to be for snowbirds. Few are for families. Those that are don't have the features that I am really liking with TT.

Yesterday I was playing around with the Ford website looking at trucks based on things said in this thread. We are on the fence whether we will purchase new or used. We are also on the fence over who's truck it will be.  ;D My husband drives to work everyday (about 30 minutes), I stay at home and homeschool. So there are days where I don't drive. There are weeks in the winter where I don't drive all week. I would like to get diesel because I like the fuel economy. But I know nothing about diesel.

Anyway, if you were to build a diesel truck new, what features are important? Do I need a heavy duty alternator? I figure I would if it was powering the TT but I thought I should ask. Do I need 4X4 or is 4X2 okay? We do own a house but we don't haul anything at the moment. We currently have a Camry and an Odyssey. I assume I want the longest wheel base right? Rear axel ratio, the smaller the number the better right?

My in-laws would likely disown us (wait... that would be bad right?? ) if we went to Chevy and my hubby will not go for Dodge.

3 Ladybugs said:

Anyway, if you were to build a diesel truck new, what features are important? Do I need a heavy duty alternator? I figure I would if it was powering the TT but I thought I should ask. Do I need 4X4 or is 4X2 okay? We do own a house but we don't haul anything at the moment. We currently have a Camry and an Odyssey. I assume I want the longest wheel base right? Rear axel ratio, the smaller the number the better right?

My in-laws would likely disown us (wait... that would be bad right?? ) if we went to Chevy and my hubby will not go for Dodge.

Click to expand...

Alternator = yes
4x4 vs 4x2 = 2ok, 4 better - I'd go with 4
Long wheel base =yes and diesel 3/4 ton minimum -do the numbers carefully
Low ratio # = No - higher number = more reduction & better power to tow

Brand of truck is not particularly significant so long as it is suited to the load.

Ernie

Long bed?  Excellent replies above but life beyond the numbers shouldn't be overlooked.  You have a family so I'm guessing a "crew cab" will also be on that truck.  "Crew cab" plus Long Bed equals a negative ease-to-park value.  I usually have to find 3 empty side by side parking spots in order to slide my LB in at an angle.  My mpg with the diesel (2015 F350) when towing and using cetane booster is ~15 mpg, but around town doing errands (not towing) is only about 10 mpg.  A short bed truck might be better in both categories.

Don't get carried away with options... Take a peek here at what I tow with.
http://articles.mopar1973man.com/members-rides/17-mopar1973man/25-2002-dodge-ram-2500

As for the alternator most all newer vehicle are plenty big enough I've got 140A alternator stock.
4WD is better I've seen times on wet grass or pine needle being stuck trying to pull the RV.
Lone wheel base is much better over short. I've got both versus of truck and the loner wheel base is much more stable.
3.55 gears is excellent for towing even in the mountain. If you wanted just a wee bit more power I would opt for 3.73 but don't go to 4.10 gears that is too low for most highway travel.
As for power plant I highly suggest diesel over gasoline. Better power and better lifespan. Exhaust brakes are included with most diesel now.

As for my modified beast. I'm at 253k miles putting out 400 horsepower and about 900 foot pounds of torque. I can tow and keep up with even the 2015 truck with no problems. Still getting 11-14 MPG towing the trailer and 23-25 MPG empty truck.

Hi Ernie,

Ernie n Tara said:

Alternator = yes

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Care to elaborate on that? Not trying to be argumentative, but we're also planning a TV purchase and trying to learn as much as possible, and a (presumably beefed up) alternator never struck us as important.

Thanks,
--
  Vall

Hi TravlinOn,

TravlinOn said:

My mpg with the diesel (2015 F350) when towing and using cetane booster is ~15 mpg, but around town doing errands (not towing) is only about 10 mpg.  A short bed truck might be better in both categories.

Click to expand...

Interesting, never heard of "cetane boosters" before. Doing some googling now on the subject and trying to learn...

Can you please tell us which brand/type are you using?

Thanks,
--
  Vall.

VallAndMo said:

Hi Ernie,

Care to elaborate on that? Not trying to be argumentative, but we're also planning a TV purchase and trying to learn as much as possible, and a (presumably beefed up) alternator never struck us as important.

Thanks,
--
  Vall

Click to expand...

With a camper in tow you have a whole other electrical system tapped into you tow vehicle. all the taillights, marker lights, electric brakes and house battery charging. Example: Cold wet weather while towing, windshield wipers, heater/defroster, headlights and all the lights on the trailer, devices plugged into power port, stereo and amp, refrigerator in RV,  batteries being charged, All these things are putting a demand on the alternator. You probably want more than a 70 to 90 amp alternator for that scenario.

Bill

Hi Bill,

driftless shifter said:

With a camper in tow you have a whole other electrical system tapped into you tow vehicle. all the taillights, marker lights, electric brakes and house battery charging. Example: Cold wet weather while towing, windshield wipers, heater/defroster, headlights and all the lights on the trailer, devices plugged into power port, stereo and amp, refrigerator in RV,  batteries being charged, All these things are putting a demand on the alternator. You probably want more than a 70 to 90 amp alternator for that scenario.

Click to expand...

Makes sense. Will be sure to get an upgraded alternator on ours, then.

Thanks,
--
  Vall.

Bill covered it wel!

Ernie

VallAndMo said:

Hi TravlinOn,

Interesting, never heard of "cetane boosters" before. Doing some googling now on the subject and trying to learn...

Can you please tell us which brand/type are you using?

Thanks,
--
  Vall.

Click to expand...

Vall, I just saw your question.  Sorry to be so late.  Anyway, since this is a different topic from the original posting, I am making a new post topic (at least for me):  "Using a cetane booster in my Ford diesel".  Please check after a few minutes.  TravlinOn

Thanks TravlinOn for the great post!