5.5: Ride Heights basics

Static ride height is one of the key setup adjustments, and also one of the easiest to get right. For example, for many cars converting a qualifying setup into a race setup (or vice versa) only means adjusting fuel and the static ride height. In this article we’ll explain what ride height entails, how you can adjust it, and how it affects other setup adjustment.

Static versus dynamic ride heights
Ride height (measured in mm or in) defines how far off the ground the chassis sits. Static ride height is what you configure in the garage. Dynamic ride height is the actual ground clearance at any moment in time as the car goes around the track. The dynamic ride height changes throughout a lap, for instance when a car goes over a curbstone, or when downforce compresses the springs. The dynamic ride heights also changes throughout a stint, for as the fuel burns off and the tank empties, the car becomes lighter and therefore ‘rises’.

Depending on the location of the ride height sensor (e.g. splitter, tire, etc) and its vertical offset, the ride height as measured in the garage (and as reported in telemetry) does not necessarily equate the actual ground clearance. For example, the splitter ride height sensor (on cars that have one) may be positioned a few centimeters above the bottom of the splitter. As a result, you’ll get a non-zero reading even if the splitter bottoms out. And obviously every single car is different, so the first thing you need to find out when you start setting up a new car is what “bottoming out” means in terms of ride height reading.

Purposes of changing the ride height
1: Lower center of gravity means less lateral weight transfer, which means more grip
For cars that are not very aero dependant the ride heights are primarily used to affect the center of gravity. A lower sitting car generally has better handling because a lower center of gravity means less lateral weight transfer. And we’ve discussed in 5.3, lateral weight transfer reduces the total available grip.

2: Balance between downforce and drag
For cars where aero is a defining factor in car setup, the ride height is the key to optimizing aero performance. Each car is different, but in general there’s an ideal ride height range that produces maximum downforce. Similarly, there is an ideal ride height range that minimizes aero drag. These two ranges may or may not overlap. Each car is different and it takes a bunch of experimentation with each new car to find out what works and what doesn’t. By statically and/or dynamically adjusting the ride heights, you can optimize the aero performance of the car.

3: Ground clearance
The final factor, relevant for both downforce and no-downforce cars, is clearance from the ground. You may want to adjust the ride heights to avoid bottoming out on bumps and curbs. Like discussed in the spring rates article, bottoming out can cause handling issues as one or multiple tires may become unloaded or lose contact with the track altogether, and it can also severely lower speed when the car is dragging onto the track.

Example
One of the most common setup scenarios is converting a qualifying setup to a race set. In most cases the additional weight due to the added fuel is bringing the car ‘out of tech’, which means it’s too close to the ground and isn’t legal to race. To pass tech inspection, you need to raise the ride height.

Typically, it’s best to keep a note of the target ride heights as they are in the qualifying setup and try to resemble those as close as possible on the race setup. In order to increase ground clearance, you’ll need to decrease the perch offset on each wheel, or increase the pushrod length (when available). Matching front and rear ride heights may be all you need to convert a qualifying setup to a race setup.

For cars where the gas tank is located far from the center of gravity of the car (e.g. the BMW Z4 GT3 has it’s tank fairly far back in the car), setting the race fuel ride heights could be trickier. As fuel is burnt throughout a stint the front or back of the car will get lighter, increasing the ride height. You may have to take this into consideration when determining the static ride heights with a full tank.

How suspension geometry affects ride height
Different simulators implement this differently, but in iRacing you cannot set the ride heights with one parameter. Instead, on each wheel you can adjust the spring perch offset, or increase the pushrod length (when available). Adjust these properties until your achieve the desired measurement for ride height.

Keep in mind that many suspension elements are connected. Significant changes to spring perch offset, or to pushrod length could also impact camber and toe. Each time you make a change to ride heights you should remember to also take a look at camber and toe. If your camber has changed, change it back to the old (desired) value. This may change your ride height again, so you may have to do a few iterations of ride height adjustment, camber adjustment, until you achieve the desired result. The same applies to each wheel’s toe-in.

When adjusting ride heights
You need to keep ride heights in mind each time you change any of the following:
Spring rates: Stiffer springs raise the car, softer springs bring it closer to the ground. When changing spring rates you want to make sure that you maintain the ride height from before the spring rate adjustment (otherwise you’ll be applying two changes to the car).
Tire pressure: The tire is effectively a spring, and significant changes in tire pressure affect ride heights too.
Camber & toe: As already discussed, camber and toe adjustments may affect the ride height. Modify the suspension geometry so that you achieve the new desired camber (or toe) at that same ride height.
Fuel load: Added fuel (per the example above, for full race distance as opposed to for qualifying) adds more weight to the car, which compresses the springs more, which reduces the ride heights. Each time you add and remove fuel you’d generally want to do so without actually modifying the static ride height (with some exceptions, depending on car or track).

Up to you

Once you understand what ride heights are and what interactions ride heights have with suspension geometry, you need to spend a lot of time testing and experimenting with different settings in order to find out what works with each specific car. And in a later article we’ll look more closely how to approach dynamic ride heights.

2.6: Driving basics

untitled-1The optimal lap is easy to describe, but difficult to achieve. It’s a combination of two basic things: utilising the full grip of the tyres through the perfect line. In other words: optimal racing line & optimal speed.

Sounds simple? Mastering this is in fact extremely challenging due to the complex layout of a typical circuit and the behaviour of a racing car at the limit of grip. This is why the following fundamentals are so important to achieving your maximum potential, not only as a beginner but also as a seasoned veteran.

Importance of solid basics, an analogy:
Several months after struggling to learn the guitar, I learned that I’d been holding the pick incorrectly. I stumbled across my mistake randomly whilst browsing internet tutorials, where I discovered the widely accepted, correct grip. Initially the change made my playing worse, however a few weeks later and I’d made massive progress over my previous level.

Racing line
The most fundamental thing a racing driver can learn is the correct line, so we’ll start with the basics for this first. Generally speaking, the optimum line through a single corner is that of the largest radius, as it allows for the highest speed possible for a given amount of grip. Essentially, the goal is to reduce the tightness of a corner as much a possible, which can be achieved by using all of the track.

All of the track
Take for example a 90 degree corner on a circuit roughly five times the width of your car. The line of largest radius is going one which starts from the outside of the corner on entry, sweeps to the inside at the apex, before then tracking out to the outside once again for the exit. This is illustrated in the following image:

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Often the track will either tighten or open on exit. Sequences of corners often require a compromised line, and the length of the straight following a corner will strongly determine if you are better off sacrificing a wide entry for a tight exit, or vice versa.

We strongly recommend referring to the datapacks provided on the VRS app to gain a good understanding for the best line on a particular circuit with a given car. If there’s no datapack, search your car, track and season combination on the iRacing forums or YouTube.

Limit of grip
Generally speaking, the limit of grip is the speed at which a car begins to no longer follow the line on which you intend to stick to. Your goal should be to drive at a speed close to this, but to not exceed it, so that you can follow the best line around a circuit. If you drive too fast, you’ll find the car either runs wide (understeer), or you risk having the rear step out (oversteer).

Common mistakes
The most common errors the average beginner to race driving or sim racing make are the following:

  • They enter slow corners too quickly, and enter fast corners too slowly
  • They brake too late
  • They attempt to brake and turn at the same time
  • They carry too little speed out of corners

A phrase you often hear in racing circles is known as “slow in fast out”. This is a generalisation, but it’s used to reduce the likelihood of the either of the above mistakes from occurring. It’s also much easier to make a correction to your driving when you’re not going fast enough and there’s more grip still available. Focus on carrying more speed out of corners, rather than trying to carry too much speed in. Pay attention also to the type of corner; is it quite shallow or very tight? Adjust your entry speed accordingly.

Brake in a straight line
When braking hard, it’s highly recommended to travel in a straight line. This comes down to something known as the “traction circle”, whereby a tyre only has certain amount of grip in any direction. This means that in order for a tyre to produce any sideways grip required for cornering, it will have less grip available for braking or accelerating.

As such, we recommend to a beginner driver that they deliberately separate braking and turning completely. Combining braking and turning is a more advanced driving technique which definitely has it’s rewards, but it requires more skill and will feature in a future article.

Brake hard enough so you can sense the wheels would lock up if you braked harder, and smoothly release the pedal as the turn in point approaches. You should be turning the car hardest in the middle of the corner (the apex).

Commit to full throttle when you know you don’t need to lift
After driving through the apex, smoothly unwind the steering whilst carefully applying throttle as the exit of the corner approaches. Avoid applying too much throttle too early and then lifting again later, as this will greatly reduce your exit speed and momentum on exit. Exit speed is very important, especially when a long straight follows a corner as you will carry that speed all the way until the next braking zone or lift.

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Up to you:

We recommend that you come back to this article several times in between practice sessions to refresh your understanding as it is a lot of information to process and too much to remember and apply in one session.

As we said: the optimal lap is easy to describe, but difficult to achieve!