I found out the hard way on bike tires. I had a Kawasaki 900 Vulcan. I ran the pressures stated in the owners manual. Tires were shot in 5k. About 3k in I noticed they were looking worn. Found out on some 900 forums that pressures needed to be more. Found out the same thing on the RSV and now on the Victory.
So it appears bike tires are the same as car tires. If you use the pressures on the sill plate, you will get the nice cushy ride the manufacture boasts about. If you want mileage, go with the tire manufactures recommended pressures. Better stability, mileage.