Bridge Laws - Where to set trailer tandems? How do you figure it out?

I don't run all 48 but have never heard of a distance to front axle. What state is that?

Don't use hole count either. 11 hole in an air-ride Utility much longer than 11 hole in a Wabash.

I have not bought a Rand atlas in many years but the last time I checked it had the wrong info for PA length. My point being don't trust a single source exclusively.

Mikeeee

 

What year was that road atlas ?

 

1) The federal Bridge law is all about weight on axle groups--and bridges, the kind we drive across. Distances between axles are not bridges.
https://en.wikipedia.org/wiki/Federal_Bridge_Gross_Weight_Formula Read the first sentence.

2) The OP is really asking about kingpin-to-rear-axle settings, known as KPRA. KPRAs are never measured to the front axle of a tandem group. They are measured to the center of the rear axle or to the center of the tandem group; it depends on the state. The best-known example of a KPRA is California: the maximum it can be for a 53-foot trailer is 40 feet from the kingpin to the center of the rear axle of the tandem group; the KPRA for a 48 doesn't matter to California. The KPRA for 53s in California doesn't have to be 40 feet; it can be less. It cannot even be three inches more than 40 feet. If you measured 40 feet to the front axle of a tandem group your rear axle would, in California, be a very expensive four or more feet too far back and the fine would be yours to pay. Years ago, Utah's, maximum KPRA, IIRC, was 41 feet to the center of the tandem group (= right between the two axles). They used to measure. I don't know if they still do. Trucker's Atlas, Internet, whatever--the information is out there. Maybe there's even an App.

3) If you're called in at a scale house and they measure your KPRA, they will not measure side panels or holes. They will measure FROM the kingpin TO the center of the rear axle/center of the tandem group and they will not want to hear about panels or holes if you got it wrong.

Years ago the carrier I worked for bought a bunch of new 53s and they told a mechanic to mark the trailers for California. He counted holes, based his measurement on old trailers in the fleet, and marked every new trailer wrong, by six inches, which led to fines at Banning. Your best bet is to invest in a tape measure and, if you have to scale your load and slide tandems, make sure that you don't exceed the maximum KPRA for the shortest state you'll be going through and for the route you'll use. If your axle weights are legal then you're good to go. If you can't legal it by sliding things around AND keeping within the maximum KPRA for the shortest state, the shipper has to reload you. A royal pain, I know.

Finally, cities and states have been "paying attention" to KPRAs and trailer lengths for years. Years. They're not "just starting."

What Mack E-6 said about tail swing. What Otter said too.

 

here is a link to a map, showing lenghts.

http://www.bigtruckguide.com/kingpin-to-rear-axle/

 

It varies from state to state, so consult the chart inside your motor carrier atlas. Some states it is the distance between the kingpin and rear axle group, in which case it is the centerpoint between the 2 axles. Other states it is the distance to the rear axle, in which case, it is the rear axle that is important.

 

That's for sure. That's why I hate California loads, they ride like crap.

 

I think as late as the 2014 hard the wrong info for PA. At least it was different than what was on the PDOT web!

Mikeeee

 

Especially on a spring trailer!

Mikeeee