Here is something I did: I took one of my similarly-used tires and cut out a cross-section of the tread. This will give you a good idea of how much tread you have to work with and where it is located with respect to the cord. Of course, different tire brands/ratings may have different tread construction characteristics.
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B) - N124DH flying since March 2014 - 620+ hours (as of Apr 2018)!
through June 2018.