Push rod and pull rod suspension are two different suspension geometries used in F1. We have seen both of them used over the years, but in recent seasons, one arrangement has been favored over the other. But what is the difference between push rod and pull rod suspension?
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, there is often much discussion about pull road vs push rod suspension and which one is best. For that reason, I’ve gone through everything you need to know about pull and push rod suspension below.
Where Push Rods & Pull Rods Are On An F1 Car
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, but it works using torsion rather than compression. This allows it to be 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 (preventing the torsion bars from oscillating excessively).
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.
Key Fact: They also help with ride height control, lateral load transfer and, importantly, keeping the tires in contact with the track surface.
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.
We should note here that, for this entire article, we’re taking a very simplified approach to F1 suspension. 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.
Note: For a more detailed guide on the other components, check out our article all about F1 suspension systems
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 and on the track.
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 and dampers 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 primarily seen them in the past decade (at least at the front of the cars). We’ll discuss the implications of this below, but now let’s take a look at pull rod suspension.
Note: Before we do that, it’s worth reiterating that push and pull rods are used at both the front and the back of the car. The big discussion tends to be around which one is used at the front (as that’s the part we can typically see a bit more easily!).
What Is Pull Rod Suspension In F1?
Pull rod suspension does the exact same job as a push rod suspension, keeping the car stable and touching the track. 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 and dampers to absorb the shock that is sent through the suspension of the car.
Key Fact: The pull rod suspension system was introduced to F1 by Gordon Murray in 1974, appearing on the Brabham BT44 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.
Note: Before going any further, I want to emphasize that the relationship between the suspension geometry and the car’s aerodynamics is a complex one. Currently, which one a team uses is primarily dependent on the overall aero philosophy, whereas in the past the geometry itself greatly impacted the aerodynamics.
This means that, while I mention ‘advantages’ and ‘disadvantages’ below, it’s really just a case of compromises and tradeoffs depending on the design of the rest of the car. In many cases, it’s not that a team chooses one over the other because of a specific advantage or disadvantage – they instead use whichever one is optimal for their car’s overall design.
Finally, note that below we’re primarily discussing push and pull rod suspension arrangements at the front of the car. Obviously either can be used at the back of the car as well, and I’ll consider these details when discussing why we’ve seen pull rod at the front of the McLaren and Red Bull cars since 2022.
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
- Allows for more variation in damper positioning
- Can have higher installation stiffness
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, and dampers.
One advantage of using push rod suspension is therefore 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 moment, 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 therefore be lighter.
Damper Positioning & Installation Stiffness
Offering more damper variation allows for more setup variation as a whole, which can be beneficial on its own. But being able to run a stiffer setup allows for benefits in terms of tire degradation, along with overall grip and handling benefits. It is typically easier to set up, and there is a wider window of optimal setup configurations.
Disadvantages Of Push Rod Suspension
There is really only one ‘disadvantage’ of a push rod suspension arrangement, but it’s really just more of a compromise. That is the higher center of gravity as a result of having the internal components (and therefore some of the car’s mass) higher up within the nose.
However, any negative effects of the higher center of gravity are usually canceled out by the aerodynamic design of the car.
Advantages & Disadvantages Of Pull Rod Suspension
Advantages Of Pull Rod Suspension
The main ‘advantage’ of pull rod suspension setups is the slightly lower center of gravity it can allow for.
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, and dampers is at the bottom of the chassis rather than being built into the top of the nose.
This means the pull rod layout can lead to a lower center of gravity, which can provide the car with better stability and grip in the front end, as more of the weight is lower to the ground. However, as mentioned above with the push rod suspension’s advantages of better grip through a stiffer setup, this advantage isn’t going to be a major one.
Disadvantages Of Pull Rod Suspension
The disadvantages of pull rod suspension are:
- Harder to access
- Often heavier overall
More Difficult To Access
One 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, mechanics 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 as is a running theme here, it’s all about making compromises that depend on the rest of the car’s design.
Why Pull Rod Suspension Made A Comeback In F1
We have seen pull rod suspension in F1 (at the front of the car) multiple times over the years. Recently, we saw it on the McLaren in 2013, and we even saw Ferrari use it from 2012 until 2015. But we hadn’t seen it since, until 2022.
With the 2022 aerodynamic rule changes, we have once again seen some teams (Red Bull and McLaren) running pull rod suspension at the front of the cars. 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.
Making Push Rod Work At The Rear
Until recently, running push rod at the front and pull rod at the rear has been the choice of most teams. With the old high-rake cars, this used to offer the advantage of allowing the rear of the car to compress more (as pull rod is generally a softer setup), which improved downforce production at high speed (and reduced drag).
However, with the reintroduction of ground effect cars, the 2022 rule changes essentially removed the need to use pull rod at the rear for this reason. They actually opened up one possibility where a pull rod layout at the front and push rod at the rear could be the better option.
Running push rod at the back allows teams to package the internals of the rear suspension higher up, away from the Venturi tunnels at the rear of the floor, and of course the diffuser. The Red Bull concept in particular relies heavily on diffuser performance, and running push rod at the back and pull rod at the front complemented this philosophy (in contrast to the Ferrari F1-75, which relied heavily on the rear and beam wing setup for downforce production).
Using push rod suspension at the rear of the car made it possible to emphasize the curvature of the diffuser and benefit massively from the downforce potential of this critical part of the car. You can learn more about that philosophy in our article all about the Red Bull RB19.
Ride Height Rules
Another reason pull rods have become more of a potential setup is that the rules also changed to prevent teams from being able to alter the front ride heights with steering lock, at least to any significant degree. This could be achieved by making the most of a method called ‘pushrod on upright’ and it basically allowed the car to get lower to the ground with steering input.
It was a technically complex implementation that I won’t go into too much here, but it had pretty significant downforce implications. Running the front of the car lower to the ground could lead to higher downforce production, which is obviously beneficial for an F1 car in the corners.
This is something that push rod suspension layouts could take advantage of, and running a pull rod layout at the front would mean teams lost out on this powerful effect. But as the 2022 rule changes basically eliminated this by limiting how much the ride height could change with steering input, pull rod suspensions were no longer unfavorable, for that reason anyway.
Bigger Wheels & Lower Chassis
Another rule change that allowed pull rods to come back as a favorable front suspension layout was the introduction of the new 18-inch Pirelli tires. The larger tires gave the teams more room to work with in terms of implementing pull rod suspension on the front of the cars, although this doesn’t necessarily make it an advantage over push rod systems in itself.
The increase in tire diameter from 660 mm to 720 mm and the rim increase from 13 to 18 inches meant there was a much larger volume to place the hub holder in. Before these rule changes, the front of the chassis was too high to make a pull rod layout work well, as the angle from the upper wishbone to the chassis was nearly horizontal.
So, almost no movement would have occurred, making it structurally inefficient. But the chassis height was reduced from 625 mm in 2021 to 550 mm in 2022. This was an important rule change that made the pull rod suspension system a viable one for 2022 and beyond.
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.
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.
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.
Learn More About F1 Suspension Systems
As an aside, if you want to learn more about the suspension systems of F1 cars and where push/pull rods fit into all of it, Chain Bear’s video on the topic is a great introduction (linked below). If you want to see the discussion of push and pull rods specifically, skip to about the 6-minute mark.
Push rod and pull rod suspension in F1 do the same job, which is to keep the car stable and the tires in contact with 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.
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