[Tenrocca]

You will always find the top arm short then the lower - this being the case there is no way they can remain parallel through the full range of travel.

They are desgned to pull the top of the wheel in at bump - my understanding is that if you were going round a corner the outside wheel would have more weight on it, compressing the suspension - as the wheel gets pulled in at the top it helps the tyre maintain a flat contact with the ground to counteract the body roll.

Hope that makes sence.

Cheers