What are the weight limits on doubles and triples trailers?

I'm interested in becoming an LTL driver at YRC or Old Dominion. Both YRC and Old Dominion use pup trailers that are about 30' long. If a tractor is pulling two pup trailers or three pup trailers, that might change the weight limits.

We all know that for a standard tractor pulling a standard 53' trailer, the weight limits are 12,000 lbs. on the steers, 34,000 lbs. on the drives, and 34,000 lbs. on the tandems.

Is the weight limit still 12,000 lbs. on the steers if one is pulling two or three pup trailers?

Is the weight limit still 34,000 lbs. on the drives of the tractor if one is pulling two or three pup trailers?

If one is hauling two or three pup trailers, what are the weight limits on the tandems of each of the pup trailers?

 

You are wrong on stating steers are 12k. They are the lesser of the three.
1. Axle rating. Anywhere from 12k to 20k.
2. Tire rating. 6,125 is a common one, but by no means the only one.
3. State limits, with the bulk if them being 20k or so.

Also tandems are 34k yes, but single axle is 20k. And dollys have a rating, plus the axles on the pup.

 

I learned in truck driving school that the legal weight limit for the steering axle is 12,000 pounds. Anytime my steers have been overweight at a weigh station, DOT did not give me a ticket if I adjusted the 5th wheel in a way in which the steers were not over 12,000 lbs.

Last I checked, 12,000<34,000

What do you mean by "axle rating"? Do you mean the weight limit of the steering axle?

What do you mean by "tire rating"?

State limits on what?

As I recall, a pup trailer just has one trailer axle, not two. So would the weight limit on the axle of a pup trailer be 20,000 lbs?

 

Basically he's saying your steer axle can be anywhere from 12-20k, as long as the tires are big enough to handle the weight. General road tractors, 12k is a good limit. Tri axles with jumbo tires, 20k is the limit

 

105.000 legal limit for triples in Idaho and Utah

 

On the steer axle. Just because 12k is a "rule of thumb" as 34 (drives) plus 34 (trailer) leaves 12k on an 80k rig doesn't mean that's what is legal.

Axles have a weight rating. Tires have a weight rating, and finally each state has a weight rating. The legal limit is whatever is the lesser of the three.

If that's the case, then the axle or tire rating was 12k in that case.

 

Steer tires are never a concern for me unless I’m running close to gross. They always weigh around 10k on my truck. Drive axle has a 20k limit (or 34k on a twin screw). Pup and dolly have 20k limits. Gross is still limited to 80k for doubles, so you can’t load every axle to the limit. Triples have the same axle limits, but the gross limit depends on the state. It’s 120k in Kansas.

 

CDL schools teach that nonsense for a couple of reasons. Primarily because it's easier and simpler. Also because many of the instructors don't know any better. I know I didn't when I started training, because I was taught 12/34/34. A reason that most drivers don't know that steers can run heavier than 12,000 is until recently no one spec'd a general freight truck with a beefy front axle - there was no need. My 2004 Century, with full tanks and the 5th wheel all the way forward, was only 11,900. Newer trucks are heavier - my 2019 Cascadia weighs almost 1,900 pounds more than my 2004 Century. Truck companies started ordering larger front axles to allow for more cargo weight.

If you open up your atlas you will see a Bridge Law table - that is what will determine legal weights. It's a formula that compares number of axles and their spread. Most single axles are legal up to 20,000. Put two together and max legal weight is 34,000, but put them on a 10 foot spread and they can be 40,000.

A single axle day cab hauling doubles will still have 5 axles spread over at least 50 feet, so gross weight is still 80,000. You can do the math for the various axle groups, but getting over axle weight on doubles doesn't appear to be a common problem, from my perspective at least.

Now getting a CAT Scale to axle you out - that's a headache. It's not that hard, but it's a convoluted process that few truck stop employees understand.

 

A good rule of thumb when I pull doubles is. 40k 20k in the front box 20k in the rear box. I’m talking freight weight. Or a combo like 24k in lead and 16k in rear. Whatever keeps me under 40k in freight weight. My terminal has no scale and I have to hit two weigh stations in the first 2 hours of my trip and I’m never over weight. The max they can load without being over on a drive single axle is 24k in a pup. 28 ft trailer. 24k is iffy can be over on the axle if loaded wrong. I have a gauge for suspension so I know when it’s over weight on my drive axle.