SUSPENSION SECRETS FEATURE – THE BASICS OF CAR SETUP


Matt Cowley of Suspensions Secrets has produced an excellent feature article taking you through the basics of race car setup to consider when preparing for a race weekend on test days, so prepare to take notes and see if you can squeeze that little bit of extra speed out of your race car the next time you’re on track!

Introduction

When a race weekend is approaching one of the most important things on the to-do list is to complete some successful test days where you are able to fine tune the setup of your car for a particular circuit. This is achieved by getting the car to be as balanced as possible and by having the tyre working to its full potential. A great set up should be predictable, provide enough driver feedback and generate as much grip as possible for the conditions, track and tyres.

Most of you will have seen tens of engineers, analysing banks of screens, data logging information and driver feedback to achieve the perfect set up on a race weekend. However, for those competing at club level, focusing on a few key areas of suspension is a great way of achieving a very capable set up with some of your own equipment.

Optimum Components

The vast majority of you will be racing in championships with a control tyre so this section won’t apply to you directly. However, if your tyre choice is open then you should focus on getting a tyre that performs perfectly for your needs. Your tyre choice is very important because all of your suspension geometry tuning efforts, engine upgrades, big brake kits and aero packages are all put into contact with the track by your tyres. The perfect tyre for you will depend upon your budget. If you have a large budget then a soft tyre compound will be best, generating a lot of grip but degrading quickly. Therefore, you will need to buy much more of them for a race weekend than a slightly harder, road legal track day tyre such as an R888R. You will also want to consider your options for intermediate and wet weather driving as a very soft tyre with minimal to no tread will be tricky to handle even in intermediate conditions. Therefore, if you don’t intend to change your tyres too often you might want to go down the road legal track tyre route which has some tread, has a medium compound stiffness and can handle some wet weather too. If you can afford it then the best route is to choose a few different tyres and go testing with all of them. Then you can tell which tyre you will prefer to race on moving forward.

With your tyres chosen, another major suspension upgrade that controls how your car will handle on circuit is a good set of coilovers. There is a lot of options around coilovers, from 1-4 way adjustment, spring base height adjustment, body height adjustment, external reservoirs and adjustable top mounts to name a few. However, if you are new to suspension tuning then the answer is quite simple. For sprint racing, a 2 way adjustable damper without an external reservoir but preferably with camber adjustment for Macpherson strut cars is desirable. For endurance racing, the same aspects but with an external reservoir is your best option.

Having more adjustable options does technically mean that you are able to fine tune your set up further, however, if it is an area that you do not have lots of experience in already then you can actually go slower as you make adjustments to too many areas without realising the impact of those adjustments; making your set up worse. Therefore, a good 2 way coilover is the perfect starting point; allowing you to independently adjust bump and rebound. Having an external reservoir is a more expensive option but for endurance races it will prevent the damper oil from overheating, maintaining damper consistency and control.

The Basics of Setup

The basics of set up that you should be aware of and focus on setting correctly on your test days are:

  • Camber
  • Toe
  • Damper Adjustment/Ride Height

When installing coilovers it is important to ensure that the ride heights are set evenly side to side. This will place your roll centres along the centre line of the car helping the car to handle evenly in left and right directions. If you have access to corner weights then it is highly advisable to corner weight your car once the coilovers are installed. If you don’t have access to corner weights and don’t have time to get the car set up then the best route is to make sure that the ride heights are set evenly side to side.

If you have coilovers installed with bump or rebound adjustment, they should also start the day with the same settings side to side in terms of number of clicks. A good starting point if you are installing coilovers is to have the dampers set to the centre of adjustment as this gives you room to play with either way once you have put a few laps in.

The next area is an area of geometry and has huge effects upon handling. Camber is the angle of the wheel from a front view from vertical. If the top of the wheel leans in towards the centre of the car, that is called negative camber. If the top of the wheel leans out towards the outside of the car then that is positive camber. Most track cars use negative camber, so that when cornering, the car can roll outward and lean onto the contact patch of the tyre to generate maximum cornering grip. Usually, the driven wheels will have less negative camber than the non-driven wheels due to them needing straight line grip to put the power down as well.

The final basic area to be aware of when setting your car up and driving on circuit is toe angle. Toe angle is the angle of the wheel from horizontal from a top view of the car. If the front of the wheel points out to the outside of the car it has “toe out” and if the front of the wheel points in towards the centre of the car it has “toe in”. Toe angle should be set even side to side otherwise the car will handle very differently in different directions.

Adjusting Geometry Track Side

For fine tuning your camber and toe settings there are four pieces of key equipment that any keen racer should have with them on every test day and race weekend. There are:

  • Tyre pressure gauge
  • Tyre Pyrometer
  • Camber Gauge
  • String and Line Kit or Toe Plates

Tyre pressures are a very basic area that we still see being set incorrectly on a frequent basis. Even if your pressures are set evenly side to side, they will more than likely heat up unevenly due to the circuit having corners in different directions and at different speeds; heating up the tyres differently and therefore setting your hot pressures at uneven values. This is why it is very important to check your tyre pressures as soon as the car comes into the pits off track after doing a few hot laps. With the tyres hot, you can then set your pressures to the desired values to continue testing/racing on.

With your pressures set correctly, one of the best pieces of equipment you can own to optimise your set up is a tyre pyrometer. This small device can measure your tyre temperatures below the surface of the tread to provide vital feedback. When measured across the width of each tyre (inside, centre and outside) you are aiming to achieve a 10-15 degrees centigrade difference across the range with the inside edge being the hottest and the outside edge being the coolest.

These temperature values are critical for fine tuning your camber settings which is where the next piece of equipment comes in, the camber gauge. A digital camber gauge is best for use trackside as it allows you to calibrate it for the ground that the car is sat on if you are unable to find somewhere perfectly flat. If the tyre temperatures need to be hotter on the inside edge, then you can increase negative camber, if they need to be cooler at the inside edge then you can reduce negative camber.

Finally, being able to adjust your toe settings is fundamental to adjusting the handling characteristics of your car for different circuits. If you already know your settings and that they are symmetrical then a set of toe plates are a very cost effective way of making toe changes at track. Alternatively you can use the slightly more complex, but more accurate, string and line kit. This will allow you to measure your toe accurately so that you are able to make adjustments to improve the handling characteristics of your car.

For more information on any of the above areas including the use of a tyre pyrometer, adjusting and tuning camber and toe and much more visit our vast range of articles available for free at www.suspensionsecrets.co.uk