The 50s on the rear are about a half to three quarters of an inch taller than the 45s on the front. Big/little..........not by much, but noticeable. Same width tires. I considered the 45s all the way around because Sumitomo HtRZs were on sale for $81 each. I tried the 45s on the rear, and they just looked too little to me. I knew I wouldn't be satisfied, so stuck with the same combination I have on my Red T.