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Tuning Guide
Suspension Tuning – For Fast Road & Track Days

Your tyre’s grip on the road allows you to accelerate, brake and turn. There is a limit to the amount of grip your car will have depending upon a number of factors such as the drive layout (RWD, FWD, 4WD), weight distribution within the car, suspension setup and weight transfer. We could of course increase grip by fitting sticky track day tyres and be done with it (although the high side loads generated by these tyres will quickly ruin your OE dampers or road biased coilover kit very quickly). In this article however, we aim to show you how to increase the available grip regardless of the tyre uses. We will assume you won’t be changing the drive layout or weight distribution in the car and so we will concentrate on the changing the suspension setup to increase grip after we have explained about weight transfer and it’s affect on grip.

Weight Transfer – Affect on Grip

Weight transfers occur as a result of the chassis twisting around the car's roll centre. In simple terms, whilst accelerating, braking or steering, your car’s body “rolls” in the opposite direction. If we move weight away from a pair of tyres, grip will reduce, if we move weight towards a pair of tyre, grip will increase.

It stands to reason then, when you accelerate, the weight of the car is transferred towards the rear of the car, the rear suspension compresses and grip at the rear increases whilst decreasing at the front. In a rear wheel drive car this increase in grip at the rear can help to reduce wheelspin, whilst in a front wheel drive car, as the front wheels loose grip due to the rearward weight transfer, wheelspin becomes more likely. The opposite happens when you brake, the weight of the car is transferred towards the front of the car the front suspension compresses and available grip at the front increases whilst decreasing at the rear.

When you turn a corner, the weight of the car is transferred laterally. If you are turning right, weight is transferred towards the left side of the car, the left side suspension compresses and available grip on the left side of the car increases whilst decreasing on the right hand side (and vice versa). It is worth noting that weight transferred whilst cornering can increase grip and get you through the corner quicker ONLY if the steering is used progressively and weight is transferred smoothly. However, if you turn into the corner too quickly, the sudden transference of weight can unsettle the car and cause the tyres to break traction suddenly often resulting in a spin.

So now we understand what is happening to our tyre’s grip on the road when we accelerate, brake or turn what do we really mean by increasing grip? Simply put, we will look at ways in which you increase grip where you need it by altering the setup of your car to transfer weight in the most useful way and what other changes you can make to maintain the maximum amount of tyre contact to the road during cornering.

We will assume you have reached the limits of your available grip whilst cornering and that one of two things is happening, your car is either understeering or oversteering (and for this article, we will assume that you have not induced underster or oversteer yourself by driving too quickly into or out of a corner).

Understeer

In the understeer condition, your car will be trying to plough on straight ahead rather than driving around a corner. Accelerating makes the condition worse, taking your foot off the accelerator and even light braking sees grip return to the front wheels as weight is transferred to them but this takes time.

Reducing Understeer

To reduce understeer we need to induce greater weight transfer to the front wheels to increase their grip. If we stiffen one end of the car, we allow weight transfer away from that end. The easiest way to stiffen or soften the suspension of a car is by fitting a set of adjustable dampers or coilovers (see our BC Coilovers, Bilstein, Gaz Coilovers sections). This is often the starting point for suspension changes as both will allow damping adjustments over a range from hard to soft. Many manufacturers of coilovers offer springs of varying stiffness rates allowing you to experiment with harder and softer springs. Anti-roll bars (see our Hardrace, Ultra Racing, Whiteline sections) act in a similar way to springs, resisting body roll during cornering, stiffer anti roll bars can be purchased, many of which are adjustable to offer differing degrees of stiffness. Try the following to alter the weight transfer characteristics of your car:

  • Try softening the front damping or stiffening the rear damping to encourage weight transfer to the front wheels.
  • Use softer front springs or harder rear springs.
  • Use a softer front anti-roll bar or a stiffer rear anti-roll bar.

You can also make changes to the physical components and set-up of your cars suspension to maximise the tyre contact with road at the front or rear depending upon where more or less grip is required. Depending on how adjustable you cars original suspension is you may need to purchase front or rear adjustable alignment bars (Hardrace, Whiteline) and camber adjustable top mounts (many coilover kits come with these as standard such as BC Coilovers) in order to alter the physical set-up of your specific car.

  • Increasing toe-in at the front and/or setting toe-out at the back encourages the rear of the car to break traction more readily than the front which has the effect of increasing grip at the front.
  • Increasing front camber can increase the front tyres contact patch on the road increasing its grip during cornering. Reducing rear camber reduces the rear tyre contact patch at the rear will again encourage the rear to break traction more readily than the front increasing front end grip.
 
Oversteer

In the oversteer condition, your car’s rear end will be trying to get round the corner before the front! Accelerating makes the condition worse, steering into the slide and taking your foot off the accelerator can sort things out unless momentum has taken over at which point a trip backwards into the trackside scenery, tyre wall or crash barrier is very likely. 

Reducing Oversteer

To reduce oversteer we need to induce less weight transfer to the front wheels to maintain grip at the rear. If we soften one end of the car, we resist weight transfer away from that end. The easiest way to soften or stiffen the suspension of a car is by fitting a set of adjustable dampers or coilovers (see our BC Coilovers, Bilstein, Gaz Coilovers sections). This is often the starting point for suspension changes as both will allow damping adjustments over a range from soft to hard. Many manufacturers of coilovers offer springs of varying stiffness rates allowing you to experiment with softer and harder springs. Anti-roll bars (see our Hardrace, Ultra Racing, Whiteline sections) act in a similar way to springs, resisting body roll during cornering, stiffer anti roll bars can be purchased, many of which are adjustable to offer differing degrees of stiffness. Try the following to alter the weight transfer characteristics of your car:

  • Try softening the rear damping or stiffening the front damping to reduce weight transfer to the front wheels.
  • Use softer rear springs or stiffer front springs.
  • Use a stiffer front anti-roll bar or a softer rear anti-roll bar.

You can also make changes to the physical components and set-up of your cars suspension to maximise the tyre contact with road at the front or rear depending upon where more or less grip is required. Depending o n how adjustable you cars original suspension is you may need to purchase front or rear adjustable alignment bars (Hardrace, Whiteline) and camber adjustable top mounts (many coilover kits come with these as standard such as BC Coilovers) in order to alter the physical set-up of your specific car.

  • Reducing toe-in at the front and/or increasing toe-out at the back encourages the rear of the car to break traction less readily than the front which has the effect of increasing grip at the rear.
  • Reducing front camber can reduce the front tyres contact patch on the road reducing front end grip with the effect of increasing rear end grip. Increasing rear camber increases the rear tyres contact patch on the road increasing its grip.
 
Suspension Bushes

Suspension bushes help maintain a cars geometry during cornering (see Hardrace, Powerflex, Whiteline), if they are worn out on your car, it probably isn’t griping as well as it did when it left the factory! Rubber bushes are used by car manufacturers to give a compliant ride as well as suspension location. Uprating your cars suspension bushes to hardened rubber or polyurethane bushes will help reduce geometry changes further to maximise suspension performance. Uprated bushes should be near the top of your list of suspension upgrades, often undertaken whilst fitting adjustable camber bars, right before paying out for a fast road or race 4-wheel alignment set-up.
 
Strut Braces / Chassis Braces

Strut braces and chassis braces (Ultra Racing, Whiteline) will also reduce suspension geometry changes by reducing flex in your cars bodyshell. We are now at the serious end of tuning your cars chassis for ultimate track day performance. You have probably fitted bushes, coilovers, uprated anti roll bars, adjustable camber bars and had a professional race alignment done. You will undoubtedly be going a lot faster and may even be considering a roll cage (Safety Devices Roll Cages) to protect yourself. Well guess what, roll cages will also help stiffen up the bodyshell and reduce unwanted flex in the chassis leading to less geometry change during cornering!
 
One Last Idea
 
Just altering your driving style can improve things! Your tyre will have longitudinal grip (front to back) which allows you to accelerate or brake, and lateral grip (side to side) which allows you to turn. If you are using all the grip longitudinally for braking, you won’t have any grip left for turning. Getting all your braking done in a straight line before you turn will give you maximum grip for turning when you release the brakes and turn in, invaluable advice for those in the early stages of track day driving!
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