Bridging formula, My math sucks
Discussion in 'Trucking Industry Regulations' started by Rat, Aug 31, 2008.
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The Rand McNally Motor Carrier Atlas has the Bridge table. I don't understand the formula.
W=500 (LN/N1 +12N+36)
W= the Maximum weight in pounds that can be carried on a group of two or more axles to the nearest 500 pounds.
L= Spacing in feet between the outer axles of any group of two or more consecutive axles.
N= number of axles being considered.
Keep in mind that the bridge formula has nothing to do with the maximum distance between the king pin and rear axle group of a 53 foot trailer. 
Don't have tandems moved farther back than 40' in CA. this could cause a guy a whole lot of grief if they're moved farther back than 40'.

w = 500 [ length x number of axles ] divided by [ number of axles minus 1 ] + [ 12 x number of axles ] + 36 take the answer and times 500 .
example ... a 21 ft 4 axle truck . { 21 x 4 = 84 } divided by number of axles  1 { 84 div by 3 = 28 } + 12 x number of axles { 12 x 4 = 48 } + 36.
28 + 48 = 76 + 36 = 112 . weight = 112 x 500 = 56000 lbs .
w = 500 [ ( L x N ) / ( N  1 ) + ( 12 x N ) + 36 . 
any 2 axles spaced less than 8 ft apart cannot exceed 36,000lbs .


Most companies usually use one or two brands of trailers.
When I would start a new company I would slide the tandems all the way back, then take my tape and measure the distance... Then I'd measure the distance between each hole(usually the same) and then just subtract each hole from the original measure(with the tandems slid all the way back) that will give you the length that each hole will put yo at.
All you have to do is write them down, and when ever you need to slide them just look at the bridge formula for the state you are delivering to in the Atlas then look at the numbers you wrote down and wohla you'll know what hole to put it in! Just make sure you do measure each brand of trailler you pull! 
If it's made of wood don't go over it!

okay then. I still can not get it. please in plain english can you tell me how to bridge this truck.
end dump. 3 axles on truck ( front and two drive of coarse ) 2 on trailer one is a drop axle.
where do i measure the axle distance from ? what axle to what axle ?
I have been hauling 85500 , what I am tagged for but my trailer is too short for this, I know that is illegal. I think I can haul 83,000 here in kansas.
thanks
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