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Workshop Guide - Setting up a GT 4 car on your own

Setting up your race car is a challenging task and requires some understanding of not only what your car is doing, but also what racetrack you are doing a setup for. However, it is not rocket science, does not necessarily require special programs, and can be broken down in a step-by-step approach for anyone to follow.

This was the reason for my first live workshop, together with the help of Ian – experienced car designer and engineer thanks to his work together with Amir Hosseini for the eSRO races. We spent over 3 hours together live on YouTube to showcase how to develop your own setup:

Of course, you do not have to watch over 3 hours of video ;) That is why I start this topic as a a summary with detailed explanations. I want to see how this resonates with the community, knowing there is already a massive amount of explanation, guides and tutorials out there - I want to take a bit of a different approach and welcome all the feedback you want to share!

Please be aware, this might look like a different approach and it is - we are going a very practical, maybe experimental route without the use of any data analytic tools (except for a little bit of Motec which is not ultimately required) to show you how far you can get without fancy tools and analytics :)

So why a first workshop around a GT4 car? The reason is, a GT4 car is more forgiving on tyres, it does not have as much of mechanical and aerodynamic grip to mess around with and is very much limited in the setup decisions. This makes a custom setup more straightforward and easier to understand especially if you are a beginner in this matter.

In this one session, we started at a lap time of 1:34,6 and ultimately got it down to a 1:31,2 after different changes in setup and learning more about the track and behavior of the car.

We then sat together and compiled this following structure and summary for you, to not only make it easier and less time consuming but also have all the important information written down for you to follow. I hope you find this helpful, enjoy the lecture and will take some of the input with you on track!

So lets get down to business... wall of text for you!

Chapter 1 - Taking a look at the track

Taking a closer look on the racetrack will already give you some pointers for the direction you should focus on when developing your own setup. Does the track require more aerodynamic downforce (grip) or less downforce because it has more (longer) straights where you reach higher speeds and therefore your car should have less drag? Or does it have higher speed turns where you need more downforce? Or is mechanical grip the focus because it is a more technical / tighter circuit with more turns, less higher speeds? Does the racetrack have more bumps or elevation changes than others? And what about weather / track conditions? Will it be a wet race or a dry race? Hot or cold?

These are all relevant questions you should ask yourself before you even start thinking about a setup.

In our live workshop to prepare for the GT4 Madness at Laguna Seca with “The Sim Grid” we knew from the training server, that the track and weather conditions will be sunny and hot, with at least 40° track temperature.

Laguna Seca is a rather technical racetrack as it offers tighter corner sections – like the T1 Hairpin, then into T2 and T3 – but also higher speed sections -T4, T5 and T6, which require more aero dynamical downforce – to then continue into high altitude changes and bumpy sections with T7 and T8 down the Corkscrew. This section is all about mechanical grip and having a proper balance in your springs and dampers. The track then follows up with T9 downhill into T10, not fast and again more on the side of mechanical grip–into the slow T11 on to the finish straight.

To sum this up: We discovered that we need to focus our car setup on the mechanical grip section, to also keep the drag on a minimum for the higher speed sections. Because of the elevation changes and bumps, and the very tricky corkscrew, we need to have the dampers and springs set up softer to absorb as much as possible and keep the car balanced.

As a small note about setups: Professional teams and drivers usually create two different setups for a weekend – One for qualifying (focused on less fuel, high grip as you neither care for fuel consumption nor tyre wear) and one for the race (where you need to manage tyres over a longer distance and want a well-balanced car). We just took a simpler approach to compile a setup around a well balanced car that is usable for qualifying and be a great base for sprint races!

Chapter 2 - Developing your own custom setup

Before you think about any changes you need a base to work with. And you should be aware of your preferred driving style – Do you like it when a car is understeering or oversteering?

So the first thing to be done is to head out on track with the base aggressive setup. This is always your starting point. And in this first stint you get a feeling for the car on the track and you start to take note around the different aspects you notice: Does it feel like understeering or oversteering? When does it feel like that, when braking into the corner or when exiting the corner? Does the car have much body roll from one side to the other side? Do I lose the backend when accelerating? Does the car move around when braking?

The First Stint

I still consider myself a beginner and not as much of an experienced, versatile Simracer. It takes time for me to adapt and get a feeling for the car on the track, even though it might not be the first time I drive it. So my
lap time after the outlap was at 1:34,6 but after a bit of practice and 7 consecutive laps I was able to settle at 1:33,1.

After these laps I got back into the pits, while Ian wrote down the observations and impressions after watching me via Discord livestream:

The Mercedes AMG GT4 is understeering with the base aggressive setup, especially when braking into a corner. As soon as I lift brake and gently apply throttle, the car started to oversteer and slide out of several corners. The body roll is too much from one side to the other, that makes the inside of all tires lose grip. The corkscrew is unsettling the car very strongly and makes behavior going down there unpredictable. All in all, the car was behaving unpredictable and challenging to control. We are looking into a more predictable, controlled rotation of the car.

The first thing to change and adapt is tire pressure. The recommendation is to reach a maximum of 27 PSI. The lower tire pressure is in general, the higher the contact patch of the tire with the tarmac is. But this will result in more friction, warming up the tire faster and maybe more than you want it. This will result in higher pressure than intended, blowing up the volume of the tire too much.

After adapting the pressures, the first changes in the setup revolved around the Tyre tab. We looked at adapting Toe, Camber and Caster.

What is Toe? If you look on the car from atop, Toe is the angle of your tires making each pair either look like a V shape or A shape. Positive value means Toe In which is the A shape, negative value is Toe Out which is the V shape.
What is Camber? If you look on the car from rear (or front) view, it is the angle of tires from the road surface. This can also make the tire pair front / rear look like a V shape or A shape.
What is Caster? This is the vertical angle of the suspension and steering in the front.

We changed the Rear Toe from 0.1 to 0.13 - this moves the front of the tires more inwards, creating a bit more Toe In. This can be interpreted as some kind of fixed rear wheel steering, as it will help stabilize the car around corners. But be aware, if you put in too much Rear Toe In (or Toe Out), it will increase tire consumption and fuel consumption. The angle of the tires results in higher friction on straight lines, and this will influence tire pressure because of rising temperatures.

The Second Stint

After the first small adaption I headed out on track again with a fresh set of tyres. We immediately discovered that the feeling for the rotation did improve, especially when accelerating out of corners.

Lap time improved to: 1:32,7 after 5 laps of practice.

After these 5 laps I got back into the pits to make the next adjustments. We noted that the rotation looks fine now, but the body roll is to much – this means the car tilting from left to right or the other way around when turning in. When this happens, the contact patch of the tyres to the tarmac decreases, putting more pressure on the outside tyre when turning in.

Based on this observation we increased the Rear Anti Roll Bar from 1 to 2. In the GT4 Mercedes, the Rear Anti Roll Bar has only 3 options to change the setting: – 0 – 1 – 2

The Anti Roll Bars (Front and Rear) are both set at the bottom where wheels and suspension are mounted. Every Anti Roll Bar has holes for each setting you can do in the game. Some cars can set the Anti Roll Bar from 0 to 10, some can even have more variation, or less. So for example, when it can be set from 0 to 6 it means that the mounting of the Anti Roll Bar has 7 different connection points.

The ARB (in short) is connected to swingarms, and by changing the value in the game, it means you change the connecting points of the swingarm to the bar itself. The higher you set it means, the stiffer it will make the front or rear end of your car!

In general, the ARB is intended to force each side of the vehicle to lower, or rise, to similar heights, so to reduce the sideways roll of the race car in curves, sharp corners, or large bumps. With the bar removed, a vehicle's wheels can tilt away by much larger distances. The common function is to force the opposite wheel's suspension rod to lower, or rise, to a similar level as the other wheel. In a fast turn, your race car usually tends to drop closer onto the outer wheels, and the sway bar soon forces the opposite wheel to also get closer to the vehicle. As a result, the vehicle tends to "hug" the road closer in a fast turn, where all wheels are closer to the body.

By increasing or decreasing the values of the ARB at front or rear, you can balance the body roll of your race car better and help decrease understeer or oversteer.

In addition to this change of the ARB we also adapted the Wheel Rate in the front for both wheels to the lowest setting, which in this case was just one click. This makes the front softer, to catch more of the bumps of the track, so the car will hopefully not unsettle as much when going through the corkscrew.

An interesting thing to know is that the wheel rate should actually be called spring rate. It has nothing to do with the wheel itself but rather with the spring, as it sets the force (Newtons) that is needed to compress the spring. The yellow line in the graph is showcasing you the resting position / height of the car based on the change to the wheel rate, when car is standing still. What this means is that any change to the wheel rate will also influence the rake / ride height of your car, for example if you make the wheel (spring) rate harder (front or rear), it will raise the car height (front or rear) a little bit.

If you stiffen the suspension at the rear end of the car, you will have more rotation or even tendency to oversteer. If you do stiffen it in the front, the car will tend to understeer.

This is happening because of the centre of gravity, the rolling mass of the car. Just imagine a shelf that has a ball of steel in the middle (your centre of gravity). When you accelerate the car, the shelf moves up in the front and tilts down in the rear, so the ball (your centre of gravity) rolls to the back. You then have more weight on the rear of the car – when you brake it is the other way around. You need to absorb that change in pressure with your wheel (spring) rate, to have the car not bounce to much from front to rear and other way around.

The last change in setup was then regarding the dampers. We increased front left and right bump by 1 click from 10 to 11. We did that because we softened the springs in the front by changing the wheel rate, to compensate for this softer setting the damper should be set a bit harder.

What the dampers do in short is supporting the spring with controlling the bump and rebound. Bump is when compressing the damper, Rebound is when going back into neutral position (not compressed). The values you can set there mean how much of the pressure a damper can take before compressing, or how stiff / soft the Rebound behaves.

The Third Stint

After all these changes I headed out for my third stint. What I immediately noticed was that I had a much harder time going around corners, even though this was fine in the second stint it. This was the result of stiffening the rear anti roll bar. But on the positive side, the Corkscrew felt better, the car was more stable unsettling as much as before.

I was not able to improve the lap time within 5 laps, but we again gained important insight to make more adaptions.

So with the worse rotation of the car in mind, and after changing all the front suspension we started to look at the rear dampers. To compensate the changes of the front, we softened the rear dampers at both wheels by lowering the rear bump from 13 to 11.

And now after having adapted suspension for both front and rear, we looked at the Aero part. Now that we were able to see how the car was set in height, we thought about changing the ride height but opted for testing the adjustment to the rear dampers first. As we changed a lot for the previous stint, we agreed on taking it a bit slower now and just take a small step to not get confused with to many different changes.

The Fourth Stint

I was really struggling with concentration and my typical challenge of not being able to adapt so quickly to changes, so I took a break after a few laps as I was not able to improve at all.

But what Ian noticed when watching me drive was that the car was still understeering, giving me a hard time. He took note that the rear of the car might just be to low when accelerating out of the corner.

We immediately got back to the pits and took a bold step by increasing the rear ride height up to a 110, but at the same time decreased the rear anti roll bar by 1 click back to 1. Without that, the car might have been way to oversteery and nervous to drive. This was an attempt to find a good middle ground in balance.

The Fifth Stint

This was a pretty fun stint as suddenly the car was massively oversteering, feeling very different and much more agile now. We called it “unwanted oversteer” and because of that, I crashed when going hard through the Corkscrew. We kept trying after that, but we noticed that the car is just to twitchy and sensitive to control and bring to the limit.

So we set the rear ride height from 110 down to 107 and also took the opportunity to look at the Tyre tab and check the I M O of the tires (Inside, Middle and Outside). These are the indicators for temperatures on the different sections of the tire, and what we noticed is that the difference in temperature was way too high. This means that the tire is struggling for grip – the rule of thumb here is that the difference in temperatures from I to M to O should not be higher than 2°C.

Because of this we adapted the negative Camber from -4° to -3.6° in the front, and the rear from -3° to -2.8°

The Sixth Stint

Took me a few laps to get a feeling for the change, the car was feeling more stable, more forgiving and the temperatures as well as pressures of the tires were improving. I was able to set a lap time of 1:31,7 now.

Ian felt it was now a good time to get a bit more theoretical and start up MOTEC to look at the telemetry of what my suspension was doing. Keep in mind this is just an additional bonus we did for the stream and as this is a whole new, huge and detailed topic I will not go into details here and just provide the short summary of what we saw and changed.

The suspension histogram showed as unbalanced graphs, and as the goal is to make this as balanced and symmetrical as possible we adapted the front left rebound from 10 to 8 and the front right bump from 11 to 9. We also changed left and right rear bump from 10 to 12.

Important information about the Rebound in ACC at this point. Usually, the higher a Rebound is set, it will slow down the rebound of the damper more... and the lower rebound setting means it will have less resistance, increasing the rate at which the rebound happens.

But in ACC it is the other way around as the setup menu handles this different for you. As you increase the rebound value in the setup menu, you also increase the rate of the rebound of the damper, and if you decrease the rebound value it also decreases the rate of the rebound... that is the tricky part of the ACC setup menu, it is not 100% like reality but more straightforward for the user.

The Seventh Stint

With all these changes in mind, I headed out on track to put in my best lap time so far of 1:31,245! With the car feeling very good and stable, we were on the right track to have a really well balanced setup for shorter sprint races!

WORK IN PROGRESS - Last update 12th September 2020 - Fixed Toe Info and Suspension Mistake.
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This is an excellent guide thank you. Question, if I'm already doing high 1.31s using the aggressive setups, how much time would I realistically gain following this process do you think? Surely I'm not going to gain 3 seconds, however, how much of your time gain was track knowledge, driving style and how much was setup gain do you think?
This is an excellent guide thank you. Question, if I'm already doing high 1.31s using the aggressive setups, how much time would I realistically gain following this process do you think? Surely I'm not going to gain 3 seconds, however, how much of your time gain was track knowledge, driving style and how much was setup gain do you think?

Hi Nuld, thanks so much for the feedback :) For me it is a maybe special case haha... I take a long time to adapt to a car, and if I do not feel good with a car I am unable to push it and improve. So here it was part track knowledge, feeling for car and then setup... We even continued testing this evening but after over 3 hours of driving I was just done and tired, not able to focus, I was on track to push below 1:31s at Laguna Seca with the GT4 but whenever I was ahead in time I made a mistake. So in my case I would say that probably around a second worth from the setup, maybe even more.
Hi Nuld, thanks so much for the feedback :) For me it is a maybe special case haha... I take a long time to adapt to a car, and if I do not feel good with a car I am unable to push it and improve. So here it was part track knowledge, feeling for car and then setup... We even continued testing this evening but after over 3 hours of driving I was just done and tired, not able to focus, I was on track to push below 1:31s at Laguna Seca with the GT4 but whenever I was ahead in time I made a mistake. So in my case I would say that probably around a second worth from the setup, maybe even more.
Indeed, this is understandable..my times drop off after 30 mins haha!! It's a shame after you set your best time after your last setup, you didn't go back out on the stock Aggressive setup and see what times you would do as a direct comparison. Maybe next time ;)
Keep up the good work, as I have no idea how to setup a car. :)