You guys know us, we are all about achieving maximum performance. Maximum suspension performance takes more effort than just throwing a set of coil overs in, sway bars and some poly bushes. Just like dyno tuning engines, your suspension can be tuned to suit the way you drive and where you drive. Obviously a circuit car will have completely different suspension compared to an off road racer. We are not talking about the major parts here we are talking about the adjustments we can perform working with what you have.
Proper set up is crucial to handling and tyre life.
All good coil overs will have adjustable compression and rebound, good suspension arms will allow for adjustment, even sway bars and links can be adjustable. It is these adjustments and what to do with them I want to chat about. Actually we will focus on alignment adjustments. Coil over adjustments will be saved for another day.
Suspension tuning is all about grip. Well balanced is the term we use to describe a set up that maximises the available grip. Upgraded suspension components increase the capacity of the overall system but it is the fine tuning that allows changes to suit driving style and chassis.
Let’s start with the really basic stuff. Caster, camber and toe.
An image is best used to illustrate Caster.
An image is best used to illustrate Caster.
In the image the pivot points (ball joint / strut mount) of the steering are angled. The line drawn through them intersects the road surface slightly ahead of the centre of the tyre. This is positive caster. Positive caster provides self centering — “the wheel casters around in order to trail behind the axis of steering”. A side effect of this is less responsive and heavy steering, the use of power steering gets around those issues. Positive caster as in the picture improves directional stability by reducing any tendency to wander (this is the self centering in action). Caster angles of 7 degrees or more and often used on race cars and even some road going vehicles. Why so much caster? Larger caster angles increases camber gain when corning. More on that later.
Before power steering small castor angles were used only because the effort required to turn the steering wheel was too great. Just try to turn your steering wheel with the car rolling without the engine running. This was especially noticeable at low speeds. With power steering common caster angles of +3 or greater is normal. Cross caster is a little trick manufactures like to use. This is simply a different caster angle from left to right. Manufacturers like cross caster because they think it is safer for a car to drift slightly away from the road centre line when grip on the steering wheel is released.
Set one side caster 0.5 of a degree lower and the car will naturally drift to that side. Even with equal caster most cars will drift due to the road camber. Not a massive drift, but take your hands of the steering wheel and the car will drift to the side of least caster. On an uneven road surface this is normal.
This is the beautiful thing with adjustable arms. We have total control over the settings and the way the vehicle will drive. We can set caster angles however we like. Here is the thing. Adjustable arms are expensive to make. Manufacturers will save costs wherever possible and adjustable arms are not commonplace on your average car.
Caster rarely if ever will impact on tyre wear. So go nuts, in most cases the more caster the better. Caster is simply the amount the tyre is sitting behind the pivot points so no impact tyre wear is completely logical.
Before power steering small castor angles were used only because the effort required to turn the steering wheel was too great. Just try to turn your steering wheel with the car rolling without the engine running. This was especially noticeable at low speeds. With power steering common caster angles of +3 or greater is normal. Cross caster is a little trick manufactures like to use. This is simply a different caster angle from left to right. Manufacturers like cross caster because they think it is safer for a car to drift slightly away from the road centre line when grip on the steering wheel is released.
Set one side caster 0.5 of a degree lower and the car will naturally drift to that side. Even with equal caster most cars will drift due to the road camber. Not a massive drift, but take your hands of the steering wheel and the car will drift to the side of least caster. On an uneven road surface this is normal.
This is the beautiful thing with adjustable arms. We have total control over the settings and the way the vehicle will drive. We can set caster angles however we like. Here is the thing. Adjustable arms are expensive to make. Manufacturers will save costs wherever possible and adjustable arms are not commonplace on your average car.
Caster rarely if ever will impact on tyre wear. So go nuts, in most cases the more caster the better. Caster is simply the amount the tyre is sitting behind the pivot points so no impact tyre wear is completely logical.
Camber
We have all heard that guy that boosts some crazy camber like -7 degrees camber or something similar. What he is talking about is static camber. Negative or neutral static camber is common. As per the picture. Camber is the tilt of the wheel compared top to bottom viewed from behind or in front of the wheel.
We have all heard that guy that boosts some crazy camber like -7 degrees camber or something similar. What he is talking about is static camber. Negative or neutral static camber is common. As per the picture. Camber is the tilt of the wheel compared top to bottom viewed from behind or in front of the wheel.
As it sounds static camber is measured with the vehicle stationary. Various degrees of negative camber is the norm. When set up correctly the tyre tread will be evenly loaded offering the most grip when cornering. Too much negative camber and straight line grip for acceleration and braking will be compromised. Yep too much camber and you will reduce the available grip when travelling in a straight line. Same as castor not all cars will have a way to adjust camber. Camber plates and or camber pins are available for installation are common additions.
Dynamic camber does not get talked about often. It is the amount of camber angle generated when the vehicle accelerates, brakes, and corners. Dynamic camber is the sum of the static camber and the "camber gain."
Camber gain is a result of the suspension geometry. One on the most popular suspension designs, the double A arm allows for tuning camber gain. Using this design the shortening or lengthening the upper arm allows for tuning of the camber gain. Lifted 4WD vehicles will use adjustable upper arms to correct for camber lost when the vehicle ride height is lifted. Now the real trick is measuring dynamic camber. A little trick used is to take tyre temperature across the tread face and dial in camber according temperature spread. A hotter inner edge is too much negative camber, hotter outer edge is no enough negitive camber. Make adjustments, retest and readjust.
Camber thrust is worth a mention. Negative camber will generate what is called camber thrust. Both tyres will push against each other. This is perfectly fine when both tyre have grip on the road. When one tire loses grip, the other tire no longer has an opposing force being applied upon it and as a result the vehicle is thrust towards the wheel with no traction.
When camber is set unevenly the vehicle will drift to the side with the most positive camber. As for tyre wear, yes incorrect camber will cause tyre wear.
Negative camber is popular because of the look. In many cases excessive negative camber is used for a look and not a performance gain.
Camber gain is a result of the suspension geometry. One on the most popular suspension designs, the double A arm allows for tuning camber gain. Using this design the shortening or lengthening the upper arm allows for tuning of the camber gain. Lifted 4WD vehicles will use adjustable upper arms to correct for camber lost when the vehicle ride height is lifted. Now the real trick is measuring dynamic camber. A little trick used is to take tyre temperature across the tread face and dial in camber according temperature spread. A hotter inner edge is too much negative camber, hotter outer edge is no enough negitive camber. Make adjustments, retest and readjust.
Camber thrust is worth a mention. Negative camber will generate what is called camber thrust. Both tyres will push against each other. This is perfectly fine when both tyre have grip on the road. When one tire loses grip, the other tire no longer has an opposing force being applied upon it and as a result the vehicle is thrust towards the wheel with no traction.
When camber is set unevenly the vehicle will drift to the side with the most positive camber. As for tyre wear, yes incorrect camber will cause tyre wear.
Negative camber is popular because of the look. In many cases excessive negative camber is used for a look and not a performance gain.
On camber, drift cars are a little unique. Front end grip is paramount. Static camber may be around 3-4 degrees negative. Camber gain is what needs to be dialled in.
On many suspension set ups camber adjustment is also possible on the rear axle.
On many suspension set ups camber adjustment is also possible on the rear axle.
Toe angle.
Toe in or out is often measured in 0.1 increments of a mm. Now that is a small adjustment. Toe is how far inward or outward the leading edge of the tyre is pointing. Toe in is when the leading edge of the tyres point towards the centre of the vehicle. Setting toe in will push the tyre slightly inwards and this acts to improve straight line stability especially at higher speeds. Toe out is the exact opposite with the leading edge of the tyre set outwards from the centre line. Toe out improves turn in response considerably. Toe out gives a car a twitchy feel. The car will want to track on every little grove in the road.
Toe in or out is often measured in 0.1 increments of a mm. Now that is a small adjustment. Toe is how far inward or outward the leading edge of the tyre is pointing. Toe in is when the leading edge of the tyres point towards the centre of the vehicle. Setting toe in will push the tyre slightly inwards and this acts to improve straight line stability especially at higher speeds. Toe out is the exact opposite with the leading edge of the tyre set outwards from the centre line. Toe out improves turn in response considerably. Toe out gives a car a twitchy feel. The car will want to track on every little grove in the road.
And that is the basics covered.