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Tandem Duals vs Triple Axle goosenecks

Discussion in 'Tow & Trailer' started by BlazerGuy, Feb 16, 2004.

  1. BlazerGuy

    BlazerGuy 3/4 ton status

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    What are the pros and cons of each? /forums/images/graemlins/1zhelp.gifI'm not buying a trailer anytime soon but I just wanted to know the differences. When I get one it'll be long enough to haul 2 K5's and have a dovetail...Thanks /forums/images/graemlins/whistling.gif
     
  2. chevyracing

    chevyracing 1/2 ton status

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    Tri-axle offers more deck support, less flex, 3 7k axles hauls more than 2 10 k axles, 2 less tires to buy on a tri-axle. they pull easier through sand, snow, etc. and they look cool /forums/images/graemlins/peace.gif


    The 10k dually axles have oil hubs instead of grease, that is the only good thing I can think of. Oh, they are a little easier on tires around tight corners.

    John
     
  3. BlazerGuy

    BlazerGuy 3/4 ton status

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    OK, that all makes sense but why do Big Rig trailers use the tandem dual setup??? /forums/images/graemlins/dunno.gif Or is that a whole 'nother can-o-worms??
     
  4. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    OK, that all makes sense but why do Big Rig trailers use the tandem dual setup??? /forums/images/graemlins/dunno.gif Or is that a whole 'nother can-o-worms??

    [/ QUOTE ]

    Tandem axles if you look at them in action have that swivel where all tires will always have contact and a load no mater what the shape of the road is like.
    On a triple axle design you have them independantly suspended so if you hit a bump, each axle will take the bump in turn and get more load on and not share the load.
    I believe the design of the tandem is better for the heavy loads that is why they use them on big rigs even on the tractor not just the trailers.
    The 3 axle is a cheap way to add more capacity whith smaller axles and spreading the support on a bigger prtion of the trailer for an even load which takes the stress off the frame design.
    So you can go with lighter axles, lighter frame and still get the same weight capacity. /forums/images/graemlins/grin.gif
    That by the way is just my observation and analisys, no official input here.
    [​IMG]
     
  5. chevyracing

    chevyracing 1/2 ton status

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    That has to do with totally different laws and designs. One of the laws is called the bridge law. Another is weight....... Totally different animal when you talk about heavy duty trucks versus light or medium duty trucks. (under 26,001 Lbs)

    For instance, most over the road trucks run a dually tandem setup which will allow for 34,000 lbs to be on that pair of axles, 34,000 lbs to be on the tractor dually tandem, and 12,000 lbs to be on the steering axle for a total gross of 80,000 lbs. There are some exceptions to this rule when the tractor and/or trailer run supersingle (one large, wide tire) tires which will have less tread width as a set of dually's in most cases.

    Sometimes you will see a trailer that has dual tandems but they are much further apart than a standard set, that is called a spread axle. The axles are 10'3" from the center of the front axle to the center of the rear axle, this will allow for the trailer to carry a load of 40,000 lbs on that set of axles but the rig still maintains a gross of 80,000 lbs.

    Manuvering and tire wear are another factor. An average truck with a solo driver runs approximately 13,000 miles per month. There are a lot of sharp turns that tears the heck out of a set of tires. The biggest expense over the road trucks have is #1...Fuel, #2....Tires.

    There are some states that have different local laws, take Michigan for example, you will see trailers there that have 13 axles under them that are only 40 feet long, where as most over the road trailers now are 53 feet long with two axles. Obviously 13 axles can carry more gross tonage than 2 axles, but the tare (empty) weight with 13 axles is tremendously higher than 2 axles as well which dips into the amount of payload. That is where the bridge law comes into effect.

    The bridge law dictates how much weight can be carried over a certain span on a given style of highway or road surface. The bridge is actually the distance from the center of the steering axles to the center of the drive axles and then to the center of the trailer axles and then it is configured into a very complicated formula to take those tallies and divide them into the total length of the vehicle with the gross weight and how the weight is distributed in the spans (bridge) of the truck.

    So, a synopsis of what I am trying to say is trucks are goverened as to how long they can be overall and also the bridge, or distance from the center of the front axle to the center of the rear axle and the distance from the rear of the drive axle to the front of the front trailer axle. A longer bridge is beneficial to an average OTR truck because of that bridge distance. A third axle will shorten the bridge distance.

    Montana is a good example of a state that has strict bridge laws. When the ground freezes in the winter they allow more weight on a shorter bridge. (October to March I think)
    When the ground starts to thaw and is soft they govern the amount of weight you can carry by the total amount of tire tread inches that is actually on the ground for about 2 months, then back to normal........????????? Keeps the hiways together supposedly.
     

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