Camber, caster and toe are generally the three theories everyone learns in suspension geometry #101, but few people understand how all three concepts work together to make your car nicer to drive. It’s like knowing that ice cream is rad, without understanding… actually, that doesn’t matter. Eat the damn ice cream.
We all want a cool-looking car and sometimes this can negatively affect how your factory suspension works, which is why United Speed Shop Bossguy Ryan spent bulk time working through the black art of geometry to make sure the Magnum IFS units give you a killer looking car that drives beaut, too.
Camber relates to the vertical axis of a wheel, while toe (sometimes called “tracking”) is the horizontal axis of a wheel. If a wheel tucks in at the top and out at the bottom, that car has negative camber, while a set-up with the wheel poking out at the top and in at the bottom has positive camber. On A-arm-equipped vehicles you can alter camber by changing the length of the control arms, using movable ball joints, or shimming the top control arm inwards.
Negative camber tends to put more of the outside tyre’s contact patch to the ground mid-corner and under a vertical (rather than shear) force. Increased caster for the inside wheel will help improve that tyre’s contact patch angle by leaning the wheel into mild positive camber.
Caster is the angle between the vertical axis and the steering axis, running through the pivot point of the wheel. The pivot point is an invisible line running from the centre of the upper ball joint to the centre of the lower ball joint, hitting the road surface just in front of the centre of the tyre’s contact patch (known as “trail”).
This means the wheel casters – or leans – around while turning to trail behind the steering axis. Caster on a road car should be aligned to provide an amount of self-centring behaviour in the steering, improving straight-line stability. However, excessive caster angle will turn the steering heavy and less responsive, and can make the inside wheel lean over too far to return on its own locking the steering in that particular angle.
Toe in (positive toe) has the wheels pointing in towards the centre of the car, while toe out (negative toe) points the inside edge of the front wheels outwards. Toe in is considered more stable at high speeds and having calmer steering response as the wheels turn in to the centre of the chassis, while toe out will generally feel more responsive on turn-in at the expense of sometimes feeling a little more nervous under heavy braking and at high speeds.
As part of tuning your suspension for primo on-road manners taking into account camber angle is important as the tyre will want to roll in a curve as it interacts with the road surface. Having mild toe-out with a wheel alignment running negative camber negates this tendency.
If you’ve been following our series on suspension geometry (check out Bump Steer and Ackermann ) you’re now probably grasping how difficult it is to design a front suspension system to work well on-road, be easily serviceable and package into a variety of different vehicles. Thankfully modern computer design programs like SolidWorks remove time-consuming trial-and-error out of the process of building cool new parts like the Magnum IFS.