There are a few threads in the archives about this, including some with my comments. I disagree with OKC on this topic. I repeat my two cents here:
You can find one entire thread here:
www.kzrider.com/forum/viewthread.php?tid=22469
But for ease of reference, my comments are repeated as follows:
Go to the tire manufacturer's website for your tires...
...and they will tell you the correct operating tire pressure range. DO NOT use the original Kawasaki specs, as those were for the old style tires used on the bike when it was new. More modern tires have a softer, and stickier, tread rubber. That means a lot of the "flex" needed in the tire is in the tread rubber, rather than in the casing and sidewalls, as in the old days. Therefore, the newer tires have a higher recommended operating pressure range than the old style tires. The casing is therefore a little stiffer, but the rubber is softer, so it works, better than the old style.
From looking at the Bridgestone website (for my Spitfires), I run 29 psi front, and 33 psi rear. It rides straight and steady.
I think some of you are misreading the MSGroup info...
I looked at that article, and note that they are not clear about the "maximum" tire pressure recomendation. The problem is there are TWO maximums.
First there is the manufacturer's recommended operating range. It generally says something like "operating range 26-34 psi", or there may be a chart which corrolates the recommended operating pressure with hi/low speed riding, and hi/low load on the bike. If you run at highway speeds, and with a significant load, then you should inflate toward the upper end of this range. If you are a skinney 110 lb. teenager who only cruises around town, and never on the highway, then you can operate toward the lower end of that range.
There is also a "maximum inflation pressure". That is NOT the operating pressure, it is instead the maximum pressure that the tire should be inflated to when the installer is trying to seat the tire onto the rim. It can be as low as 40 psi, and I have seen as high as 65 psi, depending upon the specific tire. This is the number generally listed on the side of the tire. It is the pressure you must not exceed in order to avoid damage to the tire casing due to over-inflation while standing still.
ALL of the above tire pressure information applies when the tire is COLD (at the normal ambient air temperature). As the tire warms up the pressure increases, as the air inside attempts to expand (which it cannot do much, because it is inside the tire (duh)). DO NOT LET AIR OUT AFTER THE TIRE HAS BEEN RUNNING -- the tire engineers understand all this too, and have built into the design the additional pressure expected at running temperatures. They say measure it cold, then leave it alone. If you think you may have lost air while on a ride (i.e., due to a slow leak), try to let the tire cool for even a short while before checking the pressure and refilling. The tire manufacturers sometimes say to wait hours, but unless you are doing racing speeds I have found that 15-30 minutes is plenty of time. If you are in a big hurry, run some water over your tire to cool it down fast. That only takes a few minutes.
Bridgestone has a good website that gives you specific information about your particular type and size tire. My guess is that the other major manufacturers do too, or you can get it from calling a tech rep for the company.
Remember, underinflated = BAD because the tire can ride off the rim at high speed, or when cornering, or it can cause too much flexing and resulting heat induced failure of the rubber and fiber sidewall.
Also, overinflated = BAD becuase the tire can be too stiff, and thus not maintain a large enough contact patch at the tire/road interface, resulting in a loss of grip (usually when cornering). If the overinflation is extreme, you can damage the tire casing, resulting in a sudden catastrophic failure
The foregoing is for the street bike operator. All you racing guys know far more than me about special considerations and tips for racing applications.