Geometry

Geometry is the way the suspension angles are set to make sure the tyres are as flat on the road as possible when the car corners.

There are three main types of geometry that affect grip:

Camber Angle And Body Roll

1. 'Camber' is the angle of the wheels, when viewed from the front of the car. If they're tipped in at the top from vertical, as most are, then this is negative camber. The idea is that as the car's body rolls, the wheel stands up and presents the tyre flat to the road for maximum grip. Typically, negative camber will increase as the suspension compresses, as the wheel will be moving in an arc about the inner mounting point of the bottom wishbone/link. However, the whole suspension unit will be standing upright as the car rolls, so the amount of static camber is determined by lengthy testing.

Caster Angle

2. 'Caster' is the angle of the strut when viewed from the side of the car - tipped backwards is 'positive'. Think about pushing a wheel with a stick fixed at the centre. Angling the stick backwards will make it not only easier to push but also to steer, and the same applies to the wheels. positive caster tends to give good straight line stability, makes the turn-in to a corner feel positive and helps the steering to straighten up after a bend.

Toe Angle

3. 'Toe angles' are the angles of the wheels when viewed from above. Pointing slightly inwards is toe-in and outwards, toe-out. Typically, front-wheel-drive wheels will have a little toe-out, since as the car accelerates, the front wheels try to pull in and this gives maximum grip. It also helps when the car is cornering and the inner and outer wheels try to turn in different-sized circles, so the inner wheel gets a little more angle than the outer.

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