Ok. Firstly ALL of your comments are helpful to trikers out there for them to be aware of what can happen. Love how you guys really get into the topic.
My VW based trike is no different in that planing has been such a dangerous problem as soon as there are puddles ahead of me I slow right down.
My thoughts have been along the lines that the tread doesnt allow the quantity of water to be extracted from the tires quick enough and the light weight is a big factor.
Thanks for bringing the subject up. It has always worried me. I run 295/50R15 on the rear and a 600-16 hot rod tire on the front. In the past the front was a Michelin motorcycle tire with much less tread and more prone to planing than the deeper treaded hotty.
For whats it worth.