Are these 20s? They look great! If so, hows tire life compared to 21 (which I currently have) & 19? Price of tires cheaper? Durability? Really want to switch to 19s for tire life and more security towards pot holes. But dont, want lose traction on quick take offs. Also think 20s look much better than the 19s. If there is a thread on this subject please share. Thanks!