235/75/15 wold be the standard tire sizefor a 79 Lincoln Town Coupe', Town Car, and Mark V. Tire size broken down? 235 is the width of the tread measured in millimeters. 75 is the percentage of the width (in this case 75% of 235 mm) is the tire profile. OR, the sidewall of the the tire from the road to the edge of the wheel rim. A tire that has a size of 235/40/15 would have a far lower profile, or road to rim measurement, and would be considered and higher performance tire. Lastly, the 15 on the tire you had the size question on indicates the wheel rim diameter in inches....
16.5
On a 1999 Lincoln Navigator : Open the drivers door and on the latch pillar you will see an information sticker that shows the original tire size on the vehicle from the factory
On a 1999 Lincoln Town Car : If you open the drivers door , on the latch pillar will be an information sticker that shows the size of the tire on the vehicle from the factory
165/80 r15
215/50R15
I would suggest calling one of your local tire dealers like Direct or Discount Tire Co. and they will be able to tell you what is recommended for that vehicle. back in 1979 the factory tire size was p235 75/R15
235/50R-17
20
Thought it was 31 1/2
1982 Lincoln Mark VI (2 door coupe) uses this size of tire. 205/75/15
215-70-15
215/70/r15