One of the big changes we’ve seen for the 2022 season is the resurfacing of pull rod front suspension, which we haven’t seen in Formula 1 since the early 2010s. This is different from the push rod suspension we’ve seen recently, and so the push rod vs pull rod argument is very much alive again.
Push rod and pull rod suspension systems in F1 both allow the car to remain stable on an uneven track surface or when going over kerbs. Push rod suspension has a rod going from the bottom of the wheel to the top of the nose, while a pull rod goes from the top of the wheel to the bottom of the nose.
With each team having a unique design in their suspension, you’ll probably hear a lot about the pull rod vs the push rod suspension argument throughout the 2022 F1 season. For that reason, we’ve gone through everything you need to know about pull and push rod suspension below.
What Do These Elements Do?
Before we dive into the differences between push rod and pull rod suspension, it’s important to understand where to find these elements on an F1 car, and what their purpose is.
These rods are attached to the wheels of the car, with one on each wheel in between the wheel tethers. The rods then go into the body of the car where they are attached to ‘rockers’ which translate the push/pull motion into a rotary force on the torsion bar.
Torsion Bars & Springs
A torsion bar does the same job as a spring, except it is more compact and better suited to smaller spaces such as inside a Formula 1 car. The torsion bar is connected to the dampers and anti-roll bars, which are components that absorb the impacts and the shocks sent through the wheels, and they keep the entire chassis stable.
These components form the basis for the front suspension of an F1 car, but you’ll also find these components at the rear of the car too. The result of these interconnected rods, torsion bars, dampers and anti-roll bars is that the car will remain stable when going over bumps or kerbs.
The internal components such as the rockers, torsion bars, and the dampers all remain the same, regardless of whether a car uses pull rod or push rod suspension. The only difference between push rod and pull rod is where they are placed within the car, which is either higher up or lower down, as we’ll see in the next few sections.
Push Rod At The Front, Pull Rod At The Back
It should be noted that, in the last decade or so, we have traditionally seen F1 cars running push rod suspension at the front of the car and pull rod suspension at the rear. The reasons for having push rod at the front will be discussed soon, but having pull rod at the back allows for better packaging of aero components, so it really all comes down to fitting everything on the car properly!
We should also note here that, for this entire article, we’re taking a very simplified approach to F1 suspension. There are lots of technical articles, videos and guides out there for those that want to check them out. But for the sake of simplicity, we’ll be considering pull rod and push rod suspension in very basic terms, and therefore we won’t go into too much detail about other components.
What Is Push Rod Suspension In F1?
Push rod suspension can be identified on an F1 car by the strut going from the bottom of the wheels upwards into the car. It is attached at the bottom of the wheel and moves into the top of the nose of the car, where it pushes against the suspension internals to keep the car stable over bumps.
When the front tires are raised up, such as when the cars go over a bump, the rod that is connected to the bottom of the front tires is also raised up. This “pushes” against the suspension rocker inside the nose of the car.
Pushing the rocker rotates it in the suspension system contained within the nose, which in turn pushes the torsion bars, dampers and springs in order to absorb the shock being sent through the suspension of the car.
A push rod suspension setup requires the internal assembly (rockers, torsion bars and dampers) to be built at the top of the chassis, which is where we have seen in the past decade. We’ll discuss the implications of this below, but now let’s take a look at pull rod suspension.
What Is Pull Rod Suspension In F1?
Pull rod suspension does the exact same job as a push rod suspension, keeping the car stable over bumps and kerbs. The only difference is that it has a reversed arrangement, with the strut going from the top of the wheel to the bottom of the nose, resulting in a pulling action on the internals.
With a pull rod setup, when the car goes over bumps or kerbs, causing the tires to be raised up relative to the chassis, the rod that is connected to the top of the front tires is also raised up. This “pulls” against the suspension rocker inside the nose of the car, as instead of being pushed closer towards it as in a push rod setup, it’s raised and pulled away from the rocker.
Pulling the rocker rotates it in the suspension system contained within the nose, which in turn pulls the torsion bars, dampers and springs to absorb the shock that is sent through the suspension of the car.
A pull rod suspension setup requires the internal assembly of rockers, torsion bars and dampers to be built at the bottom of the nose, rather than at the top as with a push rod setup. You can easily identify a pull rod setup with this strut going from the top of the wheel to the bottom of the chassis. In the last decade or so, pull rods have usually been found at the back of the car.
You might be wondering why the difference between these two suspension elements is so important if they do the same job. While they might have the same purpose in reducing the shocks and bumps going through the chassis, they open different avenues for car design, especially in the aerodynamics department.
Advantages & Disadvantages Of Push Rod Suspension
Advantages Of Push Rod Suspension
The advantages of push rod suspension are:
- Easy to access
- May be lighter than pull rod
- Can provide an aerodynamic advantage
Push rod suspension can be identified by the strut going from the bottom of the wheel to the top of the chassis. The internal assembly is therefore at the top of the chassis, and this includes the rockers, torsion bars, dampers and springs.
The advantage of using push rod suspension is that it is easier to work on than pull rod suspension. A mechanic can work on the suspension system from the top of the car, as it’s very easy to access.
Push rod suspension can also be slightly lighter overall, which will save weight on the car, something F1 teams always try to do. We’ll talk about this in more detail in a minute, but essentially, the angles at which push rods meet the chassis mean that the surrounding wishbones (structural components that attach the chassis to the wheels) take less load and can be lighter.
Finally, push rod suspension typically gives an aerodynamic advantage too, allowing the airflow over the front of the car to be channeled in specific ways towards sidepods and diffusers and various other components on the car. However, this advantage may be a disadvantage under certain circumstances, depending on how the car is set up. More on that in the pull rod section.
Disadvantages Of Push Rod Suspension
The disadvantages of push rod suspension are:
- Higher center of gravity
However, the push rod does take some compromise in the sense that it could have a negative impact on the aerodynamics of the car, depending on the rules and car setup. It’s the reason we’ve seen the slight ‘step nose’ design in Formula 1 cars in over the past few years as teams had to compensate for the assembly being built at the top of the chassis.
The push rod being built at the top of the chassis also results in a higher center of gravity, which could lead to slightly worse handling and grip overall. However, there won’t be a dramatic difference between the two, and any effect as a result of the higher center of gravity is usually canceled out by the aerodynamic design of the car.
Advantages & Disadvantages Of Pull Rod Suspension
Advantages Of Pull Rod Suspension
The advantages of pull rod suspension are:
- Lower center of gravity
- Can fit into a smoother, lower nose design
A pull rod suspension setup has the strut going from the top of the wheel to the bottom of the chassis, meaning the assembly of rockers, torsion bars, dampers and springs is at the bottom of the chassis rather than being built into the top of the nose.
This gives the pull rod suspension two clear advantages. The first is a lower center of gravity, which will provide the car with better stability and grip in the front end, as more of the weight is lower to the ground. This could be a big advantage to cars that need some better front end grip and more responsive turn in through corners.
Another advantage with the pull rod suspension lies in aerodynamics. Since the internal assembly is built at the bottom of the chassis, the nose of the car can be built in a smoother, more curved form, which could be beneficial to the car’s overall aerodynamic design.
Disadvantages Of Pull Rod Suspension
The disadvantages of pull rod suspension are:
- Harder to access
- Often heavier overall
- Various aerodynamic implications
The disadvantage of the pull rod suspension is that it can be much more difficult to gain access to if it needs to be adjusted or repaired. Because the rod connects to the nose at the bottom of the chassis, crew members will need to either work in a cramped space, or remove the entire floor from the car to work on this area.
Another disadvantage of pull rod suspension is that it may result in a heavier overall suspension setup. Because of the angles that the rods meet the chassis, they can often be thinner and lighter than push rods, but the greater loads applied to the wishbones mean they often need to be thicker and heavier to compensate for this.
The reality is that the weight gain here is somewhat offset by the fact it’s lower to the ground. Plus, the weight differences aren’t going to be huge, so the real advantage or disadvantage is in terms of the aerodynamics, which is why pull rod suspension setups may make a comeback from 2022 onwards.
While push rod setups generally allow for better control over the airflow over the car to the rear, pull rod setups may interfere with this, and so the aerodynamic setup needs to be altered to accommodate for this. With ground effect having made its return to F1, it’s likely that teams can mitigate the aerodynamic losses typically associated with pull rod suspension.
It’s worth mentioning that the reasons teams can usually use the push rod at the front and pull rod at the rear suspension setup is that the aerodynamic effect at the rear is minimal, but the lower center of gravity and more compact packaging is more important at the back of the car.
Why Are We Suddenly Seeing Pull Rod Suspension Again?
With the 2022 rule changes, we’ve suddenly seen teams using pull rod suspensions for first time in the past decade. This mainly comes down to some important rule changes that have allowed the teams to implement pull rods into their cars this year if they choose to do so. While they weren’t banned before, they may just be more favorable now than they were.
Bigger Wheels
The first rule change that has allowed pull rods to come back is the introduction of the new 18-inch Pirelli tires. The larger tires gives the teams more room to work with in terms of implementing a pull rod suspension on their cars, although this doesn’t necessarily make it an advantage over push rod systems in itself.
Suspension Rule Changes
Another rule change for this year is that all the suspension mounts now need to be inside the wheel. This means that we won’t be seeing all the brackets and mounts coming out of the wheel as this has been banned under the new regulations to promote cleaner airflow over the car.
Nose Changes
Finally, the nose of the car must have a smoother slope rather than the flat trajectory and bulge that we have seen in previous years. These almost ‘step nose’ designs are now gone, which is where the push rod’s internal assembly was located, at the top of the nose.
All of these rule changes have allowed the use of a pull rod suspension to perhaps become more favorable than it was in the past. However, this is not the case for all the teams, and whether or not a team chooses pull rod over push rod largely comes down to their overall car design, and the data they collect in wind tunnel and CFD testing before the season starts.
Push Rod vs Pull Rod Suspension: Which Is Better?
Whether or not push rod or pull rod suspension is better than the other largely comes down to how the rest of the car is designed. If an F1 car can make up aerodynamic gains using one over the other, while mitigating losses, the team will choose whichever one leads to a faster car in their testing.
While there might be some slight differences between the two, the main reason for the change in suspension setup is due to rule changes and the fact that there is now more space for an alternative suspension setup, which is something teams haven’t really had in the past decade or so.
More Room To Experiment
This allows teams to experiment a lot with regard to the suspension in ways they may never have before. Essentially, an F1 team could decide to use pull rod suspension because it gives them an aerodynamic advantage at some other part of the car, or perhaps they can package everything more compactly.
Therefore, it may not be a suspension or aerodynamic related reason that the team opts for push rod or pull rod, and this just reiterates that the design choices F1 teams make are important when taken as a whole. It’s unusual for one design choice alone to dictate how well or how poorly a car performs, but instead it’s how all of these design choices work together that makes the difference.
Final Thoughts
Push rod and pull rod suspension in F1 do the same job, which is to effectively control the wheels and dampen any bumps in the track. However, they allow for different design elements to be implemented, with the option teams choose having an impact on the car’s aerodynamics.