How did the bead area look when you had the tires off? The tire beads?

If they look smooth and undamaged, I would break the beads and apply a good lubricant - (A GOOD parts jobber will have this.) Make sure that you inflate them to the maximum pressure shown on the sidewall, (don't kill yourself trying to go above this pressure!) then correct the pressure to the low side of recommended and go for a 10 mile ride. Adjust pressure to suit.

I had all four leak on our '90 744 TI, the tire shop wire brushed them.

We also had one leak on our '95 855. I had the shop do all four.

Both these cases were tires that had been in place for years without problems.

We had a '90 745 GL that had bead sealer installed by a tire place - it was nice and gummy. The wheels rusted so badly in the bead area (I swear, a 3/8" thick ring of rust on both beads!) that I had to throw the wheels away.

With steel wheels, I wire brush them with an electric drill for power, and spray the bead area with quick-drying paint.