[T2] 14" vs 15" wheels

[c.dreike]

Hi,
I'm looking at installing front disk brakes on my 64 with 15" wheels. 
Seems that there is a clearance problem with the 15" wheels but not the 
14". I would have thought that the 15" would have more space for the 
disk equipment than the 14". Is the profile of the wheels that different?

Thanks guys.
Chris
64DD Kamper Kit