The Inside Scoop On Lingo About Trucks

The other day I was talking to someone about DOT stuff and they gave that look. Do you know the look?

The one look that resembles a dog listening to a high pitch squeal?

That look.

I could tell that they were 200% confused about what we were just talking about.

We took about 20 minutes explaining everything that I just flew through in 2 minutes of conversation.

That’s when I knew I needed to write a blog about this.


Here it is

Today we are going to go into the weeds about the lingo around different types of trucks.

Let’s start with the basics.

The steer axle is the front axle of a truck.  The one that steers the truck.

Drive axles are the back axles.  The ones that push the truck forward.

Dually, is 2 tires together on the same side of the axle. 

Super single, is one tire (usually a drive tire) that is FAT and wide.  It takes the place of a dually. 

425 steer.  When you hear people talk about 425s or 385s or whatever, they are referring to the MM their tire is wide.  These are common on heavy haul trucks, dump trucks, and concrete trucks, just to name a few.  

This allows them to have more weight on the steer axle by having wider tires.  (as long as the axle is rated for it)  just to put it in perspective a typical tire is considered 11” wide.  A 425 is closer to 17.5” wide.

A single screw truck is a truck with a drive axle. These are mainly found in local delivery.  A lot of distributors use these as trucks to make deliveries in town.  Sometimes you’ll see them as doubles and triple rigs. These are typically used by someone like UPS moving freight on the freeway from city to city.

A twin-screw, or tandem truck, is a truck with 2 drive axles. This is the majority of semi’s that you see on the highway.  They can haul more weight because they have more axles on the ground. Most twin-screws, or tandem axles, can haul 34,000 lbs on the drive axles.

A twin steer is a truck with 2 steer axles.  These bad boys are found on pump trucks, cranes, and some major heavy haul trucks (mostly in the oilfield).

A Tridem is a group of 3 axles.  These are used to haul even more weight than a tandem.  Most tridem can legally haul 48,000lbs without permits.

A Quad is a group of 4 axles.  These mamma jammas are for when the load gets really heavy. Have you noticed a correlation? 

The more axles the vehicle is set up with, the more weight the vehicle can carry.  

Pusher axle? What the heck is a pusher axle?

 A pusher is an axle that lifts and lowers at the driver’s command.  These are usually found on the drives or trailer axles.  The drive has full control of how much pressure the pusher axle takes off of the other axles and whether it is up or down.  They can be fixed or steerable.

Tag axle.  This axle is one that tags behind the truck or trailer.  You will generally see these on dump trucks and concrete trucks, in regard to common real world application . Again, the driver has full control of the axle. For the most part, these are steerable axles, but I have seen a few fixed.

Steerable axle.  This is an axle that is steerable.  Meaning that the tires turn from side to side.  Most of these are not controlled by the steering wheel, but steer on their own and follow the truck’s natural tendency

Fixed axle. These are axles where the wheels are not steerable.  They always go straight. Just like a drive axle.

Flip axle.  These bad boys are found on the back of lowboys.  They literally flip down and up at the driver’s command. This allows the driver to haul more weight when they are flipped down.

Spreader bar.  These are also found on lowboys.  Remember that flip axle we just talked about.  Well with a spreader bar they can move that axle back and make their trailer longer.  The reason for this is so that they can haul even more weight.

Jeep. No, we are not talking about 4-Wheeling here.  A Jeep is a trailer extension for the front of the trailer.  It hooks directly into the 5th wheel of the truck and has a 5th wheel for the trailer to hook into.  These bad boys usually have anywhere from a tandem to a quad-axle setup. Meaning they have 2-4 axles on them.  They allow the truck to haul even MORE weight.

Dollie. Again we are not talking about your daughter’s toys here.  A Dollie is a means of hooking a trailer to a trailer.  It hooks into a pintle hitch on the back of the first trailer and has a 5th wheel hitch for the other trailer to hook onto.  It also has air and electric lines that run through them to connect the 2 trailers.

Pulling doubles. This is when you pull 2 trailers.  You use a dolly to connect the trailers together. 

Pulling triples. This is when you pull 3 trailers. 

I’m sure that I missed something, but I guess it will have to do into another blog

Hopefully after reading that you might be able to have a conversation with a trucker and know what they are talking about when they say, “boy was it a tough day.  The inside dual of my rear drive piped on me.” 


“Boy that load was so heavy I had to have 2 jeeps and a spreader on my flip just to get it down the road!”

Remember to stay safe and keep the rubber side down! And for more information or questions on your equipment or vehicles, get in touch with us at!

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