If you read the rest of the sidewall, it'll say something like "42 PSI at 600 Lbs load"
Translation: If some donut slayer and his livestock girlfriend weigh together about 700 lbs, then their weight and the weight of the bike will put 600 pounds on each tire, and you'll need to run 42 PSI so the tires won't pop.
If that doesn't apply to you...
A good basic rule on Bias Ply tires is to pick an inflation pressure (cold) ride the bike for an hour at the speeds and with the load you have in mind (solo, 70 MPH, or whatever), hop off the bike and check the pressure hot.
It should go up about 10%.
SO, if you start with 32 PSI cold front, you'd like to see about 35.5 PSI hot.
Higher hot number means hotter tire means it was under-inflated, so wait til it's cold and add a PSI or two and re-test.
When you get numbers you like, write them down.
You'll prob find that the bike has different numbers it likes solo and two up, cold or hot weather, and moderate or aggressive riding.
I'm sure others have their own ideas of a good time  

I have had Metzler tires (M880 and M888) on many different bikes to include the Savage. I have found that they like being inflated towards the max psi listed on the sidewall for best traction and longevity. I usually run them 2-3 psi below max, so if they (M880) says 40 psi max, I will run them at 38 psi.

I like higher tire pressures. The stock pressure feels too squirmy.