So you'd like to buy some new skins for your MGB but everyone laughs when you mention the tire size? Well, you are not alone... Until 1974, the recommended standard tire size for MGBs was 155 SR 14, with 165 SR 14 as the "size-up" option. I recently researched the above mentioned problem for my oil spreader and was unsuccessful in locating the correct size, short of Coker Antique Tire with their very modern prices! However, the guys at my local Tire Rack were able to come up with actual dimensions that make this all a lot less painful and much less expensive.
155 SR 14 is 23.7 inches tall.
165 SR 14 is 24.4 inches tall (both acceptable standard sizes).
(Maximum tire width for a 4" wide wheel).
175/70/14 is 23.78 inches tall. (Should have 4-1/2 minimum wheel width).
This is an O.E. size for Mercury Topaz and is in good supply.
185/70R14's is 24.2 inches tall. (Should have 5" minimum wheel width).
195/65R14 is 24.0 inches tall. (Should have 5.5" minimum wheel width).
195/60R15 is 24.2 inches tall.
Note. 195 tires may come close to rubbing on the rear fender arch of a chrome bumber MGB at stock height.