EVERYONE THINKS YOU JUST SLAP SOME BIG WHEELS ON YOUR CAR THEN LOWER IT SOME AND IT HANDLES GREAT, WHERE IN TRUTH IT PROBABLY MAKES IT HANDLE WORSE AND BECOME TWITCHY.
YOU NEED TO READ THIS GUIDE.
For this you have to picture an immaginary line running from the top pivvot point of the front shock and the pivvot point of the bottom ball joint then extend that line to the floor.
The distance between the extended centerline of the steering axis and the centerline of the tire where the tread contacts the road. If the steering centerline is inboard of the tire centerline, the scrub radius is positive. If the steering centerline is outboard of the tire centerline, the scrub radius is negative. Rear-wheel drive cars and trucks generally have a positive scrub radius while FWD cars usually have zero or a negative scrub radius because they have a higher SAI angle. Using wheels with different offset than stock can alter the scrub radius as can lowering the car plus different size tyres can alter it too.
(escort mk5 has 0 caster/ mk6 has positive caster)
To understand caster you need to picture an imaginary line that runs from
through the upper ball joint and extends through the lower ball joint. From the side view the
imaginary line will tilt forward or backward. The tilting of this imaginary line is defined as caster
Caster is measured in degrees by using a caster camber gauge. If the imaginary
line described above tilts towards the back of the car, at the top, then you will
have positive caster. If the imaginary line tilts forward then you would have negative caster
Positive caster provides the directional stability in your
racecar. Too much positive caster will make the steering effort difficult. Power steering will allow
you to run more positive caster. Negative caster requires less steering effort but
can cause the car to wander
This is the degree to which the front wheel lean in (or out) from each other. A camber setting of 0 means that both tyres sit flat on the track.
Negative camber is where the tops of the tyres are closer together than the bottoms and positive is the opposite.
The distance between the center of the wheel and the wheel mounting face.
More offset means the wheels sit in, less offset means that the wheels pertrude the arch.