Steve D
The foot print of each tire is about 7" x 7" so any of the three sizes would do. I have this setup myself. I used 2" x 8" and drilled holes through the set of three so I could insert spikes and hold the three pieces together. The idea was to be able to use one, two or three boards depending upon the lift needed. In practice I just drive up the 45� slope on all three boards until my gauge shows level, apply the brakes and block the wheels.
Remember: sharp side down for the spikes - LOL
Larry

>I need some help on dimensions on the leveling blocks/ramps, I plan to build
>this weekend..

>I have seen these in the past , so I understand the concept , just not sure
>how long each section needs to be, and do I use 2x6's,  2x8's or 2x10's...

>Any tips would be great, I plan on cutting 45 degree cuts on the leading
>edges to aid in the tires rolling up these ramps..  I also need to keep as
>small as possible to save space..