I have a Racktime TourIt and it measures over 14.5" from the center of the mounting hole to the bottom of the platform. At the rear of the rack, though, there is a cross-member that holds a rear light. Here's a technical drawing that might help you, with tire and fender clearance dimensions:

http://www.racktime.com/images/stori...urit-fr-hp.pdf

It's a nice rack - strong, easy to install, and you can get an optional spring clamp for the top of it, for added flexibility.