If you and your passenger weighs in at a heafty 500 lbs, by all means check the tire pressure before every ride (42 psi cold as recommended by Suzuki) The tire manufacturer says 42 psi is the proper pressure for max load carrying capibility.
If you want maximum grip, use tire pressure as a thermostat for your tire temperature. As we all know, each tire has it's favorite temperature in order to achieve maximum grip. I use an infrared heat sensor to check tire temp. Tire temp will never be a uniform temp across the tread. I check the center and each shoulder to see how much heat I am generating in each area. Sometimes there will be 15-20 degrees difference between the left and right shoulder of the tread depending on whether you are on a left or right hand track. This is why you see lots of crashes on right hand turns if it's a left hand track.
Most street tires I have be on work best at around 30psi cold. Michelins are very sensitive to tire pressure while Dunlops and Bridgestones are more forgiving over a wider range of pressure. What psi works best for you may not work so well for your buddy. Pressure depends on how hard you push the tire. Meaning, the harder the tire has to work the more heat it will generate at any given psi. You may have to add a pound or two in order to keep the heat under control.
If you are hard on the throttle and brakes, your big heavy weight busa will quickly make both tires beg for mercy.
It's certainly okay to run 42psi. The higher pressure will keep the tires cooler and give longer tire life at the cost of a smaller contact patch and less than maximum grip. For me, I usually run 34 psi for everyday play and maybe as high as 38 if I'm slabbing on a long trip.
Air pressure is like bike color, a matter of choice. If you aren't packing a heavy load, your tires will function just fine from 30 - 42psi. It's up to you to figure out what demands you expect to put on a tire.
That's my story and I'm stickin to it even if it is just a matter of opinion!
This explaination makes the most since to me. The only time my tire pressure has been as low as 30psi was due to neglect(not checking my tires and hadnt ridden in awhile). Bike felt really "squirrely" for a few miles so I stopped at a gass station and they were at around 25psi. Juiced em back up to 38 and felt good again. Of course I'm a bigger guy so I dont think I'd go as low as 30 psi because of that. And me and wifey together are around 430lbs so the 42psi for two up is a pretty good number for us.
