Push rod vs. pull rod front suspension
With the onset of new regulations in 2022, a major change we’ve seen (particularly on the likes of the MCL36) is the resurfacing of pull rod front suspension, something that hasn’t been seen in F1 for the past decade. So, what’s better – push rod or pull rod? And what’s the difference?
Push rod and pull rod suspension do the exact same thing: control the wheels to diminish bumps on the track. The main difference lies in the implementation of design elements that can impact the car’s overall aerodynamics.
What are the basic elements of push rod and pull rod suspension?
I’ve found it’s easiest to understand push rod and pull rod suspension to start with the basic elements: where you can find them on the car itself as well as what their role is in the overall mechanics.
Both rods are attached to the wheels of the car: one rod on each wheel. On the other side, the rods go into the body of the car where they are attached to “rockers.” This is what creates that observable push/pull motion into a circular force on the torsion bar.
Torsion Bars & Springs
A torsion bar is a more compact version of a spring. It is connected to the dampers and anti-roll bars: two components that keep the chassis stable by absorbing impacts from the wheels.
Torsion bars, rods, dampers, and anti-roll bars form the front and rear suspension of the car, which primary goal is to keep the car stable when going over bumps or kerbs.
It is important to note that these components don’t change whether a car uses pull rod or push rod suspension. The only difference is where they are located.
What Is Push Rod Suspension?
As mentioned, we’ve seen F1 cars running push rod front suspension (and pull rod rear suspension) since the early 2010s.
You can tell if a car is using push rod suspension if the strut goes from the bottom of the wheels upwards into the car. It’s attached at the bottom of the wheel and connects to the top of the nose, where it pushes against suspension components to keep the car stable.
When the front tyres lift (like when the car goes over a kerb), the rod that’s connected to the bottom of the front tyre is also lifted. This PUSHES against the suspension rocker inside of the nose.
This pushing movement rotates the rocker, which pushes the torsion bars, dampers, and springs with the goal of absorbing the shock being sent through the suspension of the car.
A push rod set up requires that the internal components (rockers, dampers, and torsion bars) be built at the top of the chassis.
Advantages Of Push Rod Suspension
- Easily accessible: A push rod suspension is easier to work on than pull road suspension because a mechanic can easily access it from the top of the car.
- Can be less heavy: this saves weight on the car (which is extremely important!). The structural components that attach the chassis to the wheel take less load and can be lighter.
- Can provide an aerodynamic advantage: allows air flowing over the front of the car to be directed towards sidepods, diffusers, and other components.
Push rod suspension = strut going from the bottom (wheel) to the top (chassis), meaning the internal components of the rockers, torsion bars, dampers, and springs are located at the top of the chassis.
Disadvantages Of Push Rod Suspension
There is a higher center of gravity, which could create worse handling and overall grip. This isn’t really a dramatic thing to note, however, as the overall aerodynamic design of the car takes this into consideration.
What Is Pull Rod Suspension?
Just like push rod suspension, the job of pull rod suspension is to keep the car stable over bumps. The difference lies in its arrangement: the strut goes from the top of the wheel into the bottom of the nose, where is pulls against suspension components to keep the car stable.
When the front tyres lift (when the car goes over a bump or kerb), the rod that is connected to the top of the front tyre is also lifted. This PULLS away from the suspension rocker inside of the nose.
This pulling movement rotates the rockers, which pulls the torsion bars, dampers and springs with the goal of absorbing the shock being sent through the suspension of the car.
A pull rod setup requires that the internal components (rockers, dampers, and torsion bars) be built at the bottom of the nose.
Advantages Of Pull Rod Suspension
- Lower center of gravity: thus providing better stability and grip on the front end of the car because more weight is lower to the ground
- Can fit into a smoother, lower nose design because the internal components are built at the bottom of the chassis: possible aerodynamic advantage
Pull rod suspension = strut going from the top (wheel) to the bottom (chassis), meaning the internal components of the rockers, torsion bars, dampers, and springs are located at the bottom of the chassis.
Disadvantages Of Pull Rod Suspension
- Not easily accessible: if there needs to be adjustments or repairs, mechanics will need to work in a very limited space or remove the entire floor of the car to work on this specific area since rod connects to the nose at bottom of chassis
- Can be more heavy: this increases weight on the car (which is extremely important!). The structural components that attach the chassis to the wheel take greater load and need to be thicker/heavier to compensate. This “weight gain” isn’t much of a big deal, however, because it is lower to the ground.
- Aerodynamic implications: setup needs to be altered to accommodate to pull rod interfering with airflow over front of car.
Why is Pull Rod Suspension making a comeback in 2022?
Bigger Wheels
In 2022, cars are using 18-inch Pirelli tyres, which provides more space to work with. This gives teams the opportunity to implement a pull rod front suspension, which requires more space than push rod front suspension.
Suspension Rule Changes
A new rule change in 2022 is that suspension mounts need to be inside the wheel, so brackets and mouns are not visible on the outside. This rule was implemented to encourage cleaner airflow across the car.
Nose Changes
Contrary to the flat “step nose” of previous years (where push rod front suspension internal parts are located), the nose of the new era of cars must have a smoother slope.
Which Is Better?
Answer: it depends. The entirety of the car design, regardless of pull rod or push rod front suspension, is what matters. Given the rule changes, teams can experiment with an alternative setup in ways they haven’t before.
