Pusher and Tag Axles

Adding Pusher and Tag Axles

Adding Pusher and Tag Axles 1024 294 Sorcha O'Grady

With the latest release to the TruckScience Axle Weight Calculator, now you can add second steer, pusher and tag axles to your truck, and see their effect on axle weight distribution, bridge law, etc.

Read on for more about adding axles, watch a short video about the app on the right of this page, or register for a free trial of our Axle Weight Calculator here.

Why add axles?

Adding an extra axle to a truck allows the truck to carry more load. This modification is common in the construction industry, where dump trucks can quickly reach maximum carrying capacity. If it’s ahead of the tandem, a lift axle is called a “pusher”. If it’s behind, it’s a “tag”.

Tag Axle

In the lowered state, a tag axle results in a longer wheelbase.  In some jurisdictions, a longer effective wheelbase allows you to fit a longer body.  In the raised state, it results in a shorter wheelbase, which in turn results in a smaller Turning Radius.

Pusher Axle

Pusher axles increase load-carrying capacity where a longer body is not required.  A common usage of pusher axles is the addition of 2 axles in front of the tandem bogie of a dump truck.

Let’s see how pusher axles increase Payload

In this example, of a Freightliner Severe Duty vehicle, see how a payload of 30,783lb can be achieved when 2 pusher axles have been added…

Freightliner Severe Duty vehicle Payload

Lifting axles

Freightliner Severe Duty vehicle Lift Axles

A lift axle is an axle which can be raised when the truck is partially loaded or empty. In the down position, the lift axle is used to increase the load-carrying capacity of the truck.  When it is raised,  it helps to extend tire life, as well as improve fuel consumption on empty return trips.

A lift axle is a non-powered axle, generally installed in front of or behind the rear driving axles on a straight truck or tractor.  A lift axle is occasionally also applied to a single-rear-axle straight truck.

Steered or Non-steered

Additional axles can be steered or non-steered.  We have not yet modeled the effect of the steerability of the extra axles on the Turning Radius.  If you would like to see this feature enhanced, please pop open the chat window below to add your vote to this feature.

What else is new this month?

Modify wheelbase by click and drag

Freightliner Severe Duty vehicle Wheelbase

Axles can now be clicked and dragged, to change wheelbase and axle spacing, thereby stretching or reducing the chassis length.

Weights Table

Curb Weight, Fuel & Crew, Dump, Total Unladen, Payload, Less Permissible, Overload

The layout of the Weights table has been tweaked to make it more intuitive.  It is now presented as a sum of Unladen Weights plus Payload, to calculate the Gross Weight of the vehicle, as well as the individual axles.  This figure is then compared to the Permissible for the vehicle or individual axles, to determine whether or not the vehicle is overloaded.  By default, payload is calculated as the maximum achievable without overloading the vehicle. But the Payload figure can be overridden, which may result in the vehicle being overloaded.

Saved Calculations

One of our users suggested that we display ‘Saved Date’ for each calculation in the list of saved calculations, so that the list can be ordered by most recently saved first.  This suggestion was deemed to be of benefit to all our users, and so we were delighted to implement it.  If you have suggestions for improving the app, please share them with us.

Specification Comparison

Our Sales Tool Summary Report now optionally includes a vehicle spec sheet comparison, so one can print a summary of a vehicle specification compared with one or more competitor vehicle specifications.  This is very useful to back up sales arguments, when a customer is comparing your vehicle to one or more competitor trucks.


If you’re enjoying using the Axle Weight Calculator, and would be so kind as to recommend it to a friend, you will each receive one month’s credit as a thank you from us.  You can pass a friend’s contact details to us via the green chat button below, or by using the form in the app.

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