I had a 4 wheel alignment done yesterday and the readings mean nothing to me but I need to know if my tyres are going bye bye in 2 minutes...?
This is the readings
Before
After
They couldn't change the camber apparently cos my car is too low and if I up the suspension the camber will come into line?
OK, front
camber first - whilst it isnt a prob having more camber than specified (more negative camber simply means the top of the wheel leans inwards - this is very good for hard cornering
) - ideally, they should be nigh-on identical side to side. Your fronts have a difference of more than a third of a degree. This will probably affect the straight line stability (car will tend to pull to one side). Ideally, you should look to dial that difference out. If your aftermarket suspension has adjustable ride heights - these will need to be tweaked (though many main stealers are just too thick to understand how to do this - PM wheels-in-motion, or look for one of his acredited agents near you). Too much negative camber will see excessive wear on the inner tyre shoulder (but will NOT 'feather' the tread), and too much positive camber will cause excess wear on the outer tyre shoulder, again without any feathering.
Front
caster - do you have WALK? Anyway, caster (always positive - if its ever negative, suggest you start driving in reverse!) only affects the self-centering of the steering whilst the vehicle is in forward motion. The more caster the better, IMVHO, and minor differences don't really matter. Too much caster really will have zero effect on adverse tyre wear.
Front
toe - probably the easiest to understand. Look at your feet on the floor - are your toes parallel with your heels, are the toes sticking out (toe in), or are you slightly wierd and have toes closer than your heels (toe in). On front wheel drive cars, a small amount of toe OUT is desireable, and toe IN for rear wheel drive cars. It is generally OK to 'tweak' toe to individual driver preferences (again, a main stealer will know nothing about this), and it is possible to comfortably exceed the recommended settings by half a degree (upto a max of one degree - but then you need to be aware of changes in handling traits). Toe which is mildly out will cause a feathering of the tyre tread (but wont actually wear an individual shoulder, and more aggressive deviations will cause more agressive feathering). In terms of handling, excessive toe in or toe out will cause front end instability - particularly in a straight line (twitching from the front end and feedback through the steering wheel - when going over cats eyes, white lines, man-hole covers, overbanding, etc - commonly referred to as 'tram-lining').
SAI - steering axis inclination (also known by the old skool term 'KPI' or king pin inclination). Similar to camber, but rather than being a vertical measurement through the centreline of the wheel (camber), SAI is the vertical measurement of the steering axis - ie, from the centre of the strut top mount to the centre of the lower ball joint. However . . . . SAI actually acts more like caster, rather than camber. SAI basically affects the self centering of the steering - but only due to the downwards force of the weight of the vehicle. Forward or reverse vehicle travel isn't really affect by SAI (well technically, it is, but it is very technical, and is down to the radius of an arc - there, that stumped ya!). Both sides should be equal, though not as critical as camber being equal.
Included angle - I
think this is just an aggregate of camber and SAI (though I could be wrong!)
Turning angle difference - this is just the difference between sides when the steering wheel is turned so that the wheels are turned 20 degrees (I think). Google 'ackermann steering' - basically, when steering, the inner wheel travels on a smaller radius than the outer wheel, therefore the inner wheel needs to turn tighter than the outer wheel.
Steer ahead - basically, is your steering wheel off-centre when driving straight ahead.
Rear wheel measurements generally follow the attributes of the front, only rear toe has a noticeable effect on rear-end stability - it is fairly vital to get the rear toe spot on, and equal between sides.
Finally, the
thrust angle - this is basically weather the rear wheels are directly following the fronts (within the constraints of the designed axle track). Big numbers here will see a car 'crab' as it drives along. This needs be as close to zero as possible.
Phew, time for a kip!
