The lift chains also have to be adjusted to keep the heels off the floor with mast at 0* vertical. Check the tires for wear, replace as necessary. Check the chains for wear, again replace as necessary, this is also done with a gauge. Once these two conditions are satisfied, you can then adjust your lift chains, starting with your secondaries if you have a three stage mast. Adjust so the inner channel is just a bit higher than the intermediate channel, and run the mast right to the top and see if the stop blocks are hitting. Adjust them down as necessary. You should be in the ballpark then. Now bring the mast down, set the mast to 0* vertical, and run the primary chains up until the fork heels come off the ground, I like 10MM but some go to 1/2". Either is fine as long as the carriage stop block does not hit the mast channel stop. If you cant find a happy medium where the forks are off the ground and the blocks are not hitting, your tires are likely worn out or youre not quite vertical.