Looking at doing wheel alignment for my A6 myself. Looked on YouTube and dozens of useful videos there covering this subject in-depth, BUT three questions!!!
For toe in and out, whether using string method, or laser etc the theory seems to be the same. The Toe In and Out can be checked by checking the alignment against the rear wheel on the same side. This seems to be VERY common in the videos. But how do you know that the rear wheel will be straight? It is simply because it does not steer and so, in theory, should always be straight??? And if so, does this also apply to four wheel drive cars?
For toe in and out (again) another method is to use two plates against the front wheel and measure the gap between them at the front and rear of the wheel. So this would show toe in/out if the measurements are different, but how on earth would you know which side the in/out is happening on as there is no other point of reference, so you could set it with the toe in on one wheel, and toe out on the other and the measurements would be the same, but both wheels would not be straight!!??!!
My last question relates to Camber. I’ve seen a lot of the spirit level type of tools which have a magnet on the bottom and stick on to the brake rotor (disc) and measure the camber that way. BUT this is done with the wheel removed and car jacked up - but how do you know that when the suspension is drooping (i.e. jacked up) that the rotor angle is the same as when the wheel is on and weight on the suspension?? I would guess that the angle would be very different, or is my logic off?
Any help with these three questions much appreciated!!!