Facts About Trucks – Everything You Want To Know About Eighteen Wheelers

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    Facts About Trucks – Eighteen Wheelers

    Legal weight for an eighteen wheeler
    The legal weight for an eighteen wheeler is 80,000 lbs. [40 tons].[ 36287 kg Canadian] That is without any oversize or overweight permits.  In comparison,  the average automobile weighs over somewhere around 5,000 lbs.
    legal U.S. weight per axle is:  STEER 12,000 lbs  DRIVES 34,000 lbs  TRAILER 34,000 lbs
    legal Canada weight per axle is:  STEER 5443 kg  DRIVES  15422 kg  TRAILER 15422 kg

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    Length of eighteen wheelers

    The average length of an eighteen wheeler varies greatly depending on the type of cab they are driving.  But the overall average is 70-80 ft. long.  The length of an eighteen wheeler’s cab [by wheelbase] usually averages between 245″ to 265″ wheelbase.  This is measured from the center of the rear wheel to the center of the steer.

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    Length of time needed to stop an eighteen wheeler

    The length of time to stop an eighteen wheeler is 40% greater than that of an automobile.  Depending on the weight of their load,  whether they are bobtailing,  road conditions,  and other factors.  To be sure,  it takes a much greater time to stop than an automobile… period.  Trucks only have 10 brakes NOT eighteen as some have told me they thought.  Trucks made now are required to have anti-lock brakes.

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    What is the turning radius of eighteen wheelers?

    Click HERE for more information on the turning radius of eighteen wheelers.

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    What does an eighteen wheeler cost?

    While there are myriad variables on the costs, the CAB of an eighteen wheeler usually ranges from $130,000 to $180,000 new. New trailers usually range from $30,000 to $80,00. So all in all you could be paying over a quarter-million dollars for a new truck and trailer.

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    What is the “fifth wheel” ?

    The fifth wheel on an 18 wheeler is a round plate above the drive tires that couples  [hooks together] the trailer to the truck.

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    How many gears does an 18 wheeler have?

    The most common amount of gears in an 18 wheeler today is 10 forward and 2 reverse gears.  Although they can range from 9, 10, 13, 15, and 18 gears!

    Eighteen wheeler drivers use a “double-clutch” technique for shifting.  It is much different to drive a truck compared to a car with a standard transmission.  In a car the rpm’s match up and in a truck they do not therefore the clutch is depressed and then depressed again to “match” the gears with the rpm’s.  Most drivers use what they call “floating” which does NOT use the clutch at all except to start and stop.  “Floating” is an acquired skill that takes some practice to get used to.  “Floating” gears saves fuel (when done properly) and saves wear and tear on the equipment.  “Floating” is the preferred method.

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    What is “bobtailing” ?

    Bobtailing is the term used when a truck is driving WITHOUT the trailer attached.

    This is very dangerous especially in wet weather but obviously must be done at times.

    What is the standard height of an eighteen wheeler?

    The standard height of eighteen wheelers is:  13′ 6″

    What Is A Tandem ?

    Tandem sometimes incorrectly refers to a set of TWO tires (Pictured) on a tractor-trailer. However, these are more commonly known as double wheels, dual tires, or ‘dualies.’  They are used for safety (redundancy) so if one tire blows the others will continue to hold up until the tire is repaired.

    The correct definition of Tandem is a set of two axles, with one axle immediately following the other.  By distributing the load over two axles, each axle bears less weight.  Because there are laws limiting the amount of weight that can be carried on each axle, distributing the weight over more axles allows a greater total amount of weight to be carried.

    What Is A Jack-Knife Accident?

    Basically, a jack-knife accident is when the trailer contacts the tractor by the trailer “coming around” on the driver. It is said that once a trailer exceeds a 45 degree angle, compared to the tractor, that a jack-knife is inevitable. This can be caused my many things and happens when the trailer wheels start to skid and actually ends up moving faster than the cab. Usually this happens on icy or wet roads but it can happen on dry roads when the trailer is empty and the driver has to do some very hard braking.

    Eighteen Wheeler Truck Manufacturers

    There are a variety of brand names for eighteen wheelers; among them are: Peterbilt, Freightliner, Kenworth, Volvo, Mack, Western Star, to name a few more popular trucks.

    How Many Axles Does An Eighteen Wheeler Have?

    An eighteen wheeler has a total of five (5) axles.

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    { 23 comments… read them below or add one }

    Beginner June 27, 2013 at 3:45 am

    Recently I just started a job into the truck driving industry. The company I work for has automatic transmissions and we also have the ability to gear them down when necessary. Was told to use the manual part as well as the jake on deep down grades. But here is where I have a very serious question. When it comes to where a sudden stop is mandatory. To prevent injuries to another motorist, to ourselves, and to the semi. Can I manually gear the truck down, still using the jake to get the semi to stop and this will not cause transmission problems? We all know to look ahead for brake lights but things happens when they appear out of advance warnings. I had used this method before, switching to manual and hitting the lower gears, also having the jake on. I was told this is not a time to use this manually gearing down…My thought are, if it’s good for one way of holding back, why should it not be used this route? Can someone please tell me why I cannot do this? Does this wear on the truck? I need a reason why answers not just because you just shouldnt do so answers or otherwise I am not going to understand how it can hurt….Thank you


    Dan July 3, 2013 at 7:34 pm

    A sudden stop or an emergency would require very fast responses, brake hard and steady and use the anti-lock to steer around your problem, or stab break and stop in a straight line. The engine brake and downshifting require too much time. these methods are designed for controlled breaking down hill, or a planned slow down like an exit ramp.


    Pearson July 23, 2013 at 9:44 pm

    Hi Dan I really find all your information of great interest because I am planning to start training to get my CDL license so I will just go over these until I can get more information, thank you.


    R Burgio August 13, 2013 at 4:38 am

    if i add 4000lb to an 18 wheel trailer 3/4 of the way to the rear of the trailer. what will be the increase to the truck axles( both front and rear axles)


    bob February 20, 2015 at 7:05 pm

    it depends on what pin hole your trailer tandems are in and where your fifth wheel is. you have too many variables, better to just scale every time.


    tiera johnson August 13, 2013 at 10:30 pm

    Hi I’m up to get my CDL license can sum one give me a web site to go on for a lil more studying


    Samuel Barradas August 13, 2013 at 10:37 pm

    If you’re looking for CDL practice tests, we have several here that are highly recommended: http://www.thetruckersreport.com/cdl-practice-tests/


    Bill Leseberg September 10, 2013 at 9:23 am

    Samuel – You made an error in your drawing on what “wheelbase” is, and the distance is wrong also. Wheelbase is not the width of a truck, from outside of tire to outside of tire, that is the “track”. Wheelbase is “always” measured from a front axle/wheel to a rear axle/wheel, not from side-to-side. Wheelbase of a tractor/truck (measured between rotational centers of wheels or axles) is measured from the front axle/wheel of the tractor/truck to the rear axle of the tractor/truck. The overall wheelbase of a tractor-trailer will be measured from the front axle/wheel of the tractor to the rear axle/wheel of the trailer.

    Above you show a wheelbase at 245″ – 265″, that is 20′- 5″ to 22′-1″, only the enormous CAT and EUCLID off-road trucks are that wide.


    war January 6, 2014 at 2:00 pm

    Actually, wheel base is measured from center of front axle to center of rear axle group. if you have tandems at the rear, you would measure to the center of the tandems, if you have three axles at the rear of the tractor, wheel base would be measured to the center axle. if you have only one axle at the rear, wheel base would be measured to the center of that rear axle. if you have a lift axle and two drive axles, the wheel base would change as you raise and lower the lift axle.


    Jeff September 16, 2013 at 1:50 am

    Double check your weight info – it’s up to 20k/axel and 34000 per tandem axel group. In my case I can run up to 19,000 steer 17,000 per axel in drive group and 19,000 per axel in my split axel trailer group (more than 10′ between axels)


    John Horsley September 13, 2014 at 8:39 pm

    Your right on federal highways. States have their own steer tire weight limits


    Paul October 20, 2013 at 1:07 pm

    I just wanted to add some information about the legal weight of a semi truck:

    In the US:

    There are one set of rules that are set by the US Federal government and they say that for highways that are federally funded (interstates and some other bigger roads) the minimum weight that states HAVE TO allow is 80,000 lbs.

    States cannot set the limit on interstates lower than 80,000 lbs, but they can set lower limits on state highways. However, there is a catch.. if a state had a higher weight limit in place before this federal law was passed (Surface Transportation Assistance Act of 1982 (STAA)) the state can still allow trucks heavier than the 80,000 lbs limit. The state with the highest weight limits by far is Michigan. The highest grossing truck without a permit in Michigan can top out at 151,400 lbs! With 8 axles on the trailer! Without a permit! Usually these trucks carry loads of raw steel between steel mills and factories.

    In Canada, most of the country allows much higher weights than in the US (but not as high as Michigan). Each province sets their own weight limits independently. A typical combination in Canada is a tandem drive tractor with a tri-axle trailer. This is like the typical 18 wheeler with an extra axle on the trailer (22 tires). Weights vary across the country but they are usually around 110,000 lbs. The second usual combination that is used across Canada is the B-Train. It is a tandem drive tractor pulling a trailer with three axles, and attached to this trailer is a second trailer with two axles. Across Canada, the B-Train weight limit is 139,700 lbs (63,500 kgs).

    Paul at http://www.bigtruckguide.com


    Doran Cooper January 11, 2014 at 9:23 pm

    Do trucks have a legal right to travel on a federally funded highway even if a city or other municipality posts signs prohibiting trucks


    Rudy May 20, 2014 at 1:06 pm

    I see lots of seni trailers with skirting under the trailer, what does the skirting do?


    Samuel Barradas May 25, 2014 at 10:21 pm

    They cut down on wind resistance, improving the aerodynamics and fuel efficiency of the eighteen wheeler. Trailer skirts can increase MPG by a few percentage points, which saves thousands of dollar per year in fuel costs.

    Early versions were rigid and prone to breaking when hit by debris on the highway at 65mph. I’ve heard that some newer versions have flexibility built in and are able to withstand the daily abuse.


    Linda Charlton May 20, 2014 at 5:54 pm

    Can I get the overall length of a typical U.S. Wal-Mart semi tractor trailer? There’s would no indication of any sleeper accommodation to the tractor, so I am guessing this would be closer to 70 than 80 feet.


    Larry December 11, 2014 at 8:41 am

    Linda,,, The overall length of a Wal-Mart trailer, from back door to the nose, is 53ft. and the length of the truck at the point of trailer nose to the front of truck is about 11 to 12 feet and this is a sleeper truck. So the overall length of your average Wal-Mart truck is 64-65 feet long and also the legal width of any truck is 8 to 8.5 feet, anything over that wide requires an oversize permit.


    willard nolan June 5, 2014 at 6:26 pm

    What is the net weight of a tractor trailer truck? How much does a unloaded tractor trailer weigh


    Pat September 5, 2014 at 11:48 am

    My guess is most combinations are 2-4,000 lbs lighter. My tractor is heavier than most, not all. If I remember right my tractor, alone, is around 22,500 with full tanks of fuel.


    carl September 10, 2014 at 9:49 am

    “most” trailers can have a load weight put in the that weighs “about” 43000 lbs, so take 43000 – 80000 gross weight and that give you a truck/trailer combo weights empty “about” 37000 lbs


    John Horsley September 13, 2014 at 8:44 pm

    Trucks weigh 31,000 lbs. +/- with empty 53′ trailer. they max out at 80,000 Lbs., But can carry more with more axles and permits.


    Jeff Winn October 21, 2014 at 2:11 am

    Recently, as I was driving for 3 hours on Interstate 5 in Northern California, I logged the manufacturer of every semi truck I passed.
    Here is the breakdown:
    FreightLiner – 40
    Volvo – 18
    Peterbilt – 17
    Kenworth – 13
    International – 3
    Mack – 2

    Is this an approximately fair representation of market share? Would it be noticeably different, say, on the east coast?
    People sometimes say “built like a Mack truck!” – what happened to that brand?


    dick almblad November 21, 2014 at 7:13 pm

    how many gallons of diesel fuel does an 18 wheeler hold on both sides thanks


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