what is the factory tire size for a 1985 gmc high sierra?

[Fred B]

i need to know so i can adjust the speedo cable. i've got 36in. mudders on now but will want to go to a different tire soon.

 

[seattlesailor2000]

my 85 k10 still has the door sticker and it shows that the stock tire was a 31/1050 on 8" rims.

you can go to the following site and use their calculators to figure your rpm etc

http://ringpinion.com

btw i'm running 33/1250 with 411 and my speedo is right on (as checked wit a gps.