What tire pressures should I use?
Finding that magic number
Sorry, but we're not going to give you a number. We're giving you two.
There are so many variables when it comes to tire pressure that the only person who can determine your correct pressure is you. There are some general guidelines, though.
In general, there's a lower limit of about 26-28 psi, below which you shouldn't go (it invites the tire to pop off the rim) and the upper limit of whatever the tire says is its max pressure. Somewhere between those two is your best tire pressure.
Get a pump
Do yourself a favor and buy a bicycle pump. It takes very few strokes of a floor pump to get air into a motorcycle tire, and then you can check and inflate your tires any time you want. A floor pump is best, but it doesn't have to be a fancy one like this. You don't really need a gauge on it. Use an actual automotive pressure gauge. They're more accurate.
A little theory
Generally speaking, more pressure gives you less grip, and less pressure gives you better grip. But you can go too low, and then the tires overheat and get greasy and slick. Also, the more weight you have on the bike, the higher your air pressure should be. Underinflated tires with lots of bike weight will become hot and dangerous quickly.
Commuters and tourers will mostly run higher pressures, while people who are sport riding will opt for some extra traction by running slightly lower pressures.
It's recommended that you start high and work your way down. With higher pressures, you may lose traction, but it's progressive and easy to back off. Go too low and they can/will get greasy quickly, and it's hard to hold a corner when they're like that.
Your goal will be to have about a 10% difference between hot and cold pressure. More change than that and you'll need to add some air. This is a trial-and-error scenario - just keep adjusting until you're happy.
Most people say you want lower pressure on the front than on the back, due to the fact that there is more weight in the rear. How much is a matter of debate. Most people in the club run about 3-5 psi higher in the rear.
Tires heat up as the tread rolls onto and off the ground because of flex. Heat (gradually) kills tires, so you want to make sure the air pressure is high enough to keep them from getting terribly warm. You can check that by putting your hand on the tire tread right as you park after a ride. If the treads are hot, particularly at the edges, you need more pressure. If they're warm, you're doing it about right. If they're cold (about the temperature of the air) you could safely use less pressure.
Some people find that running higher than the 28/32 recommended by Kawasaki helps avoid problems with cheese-grater bridges, pavement snakes, and other road surface abnormalities.
So, just give me a number, OK?
Here goes: The lowest pressure you should use is what's recommended by Kawasaki for the EX250. That is 28 front and 32 rear. The highest you should ever use is the maximum that is stamped on the sidewall of your tire. If you're fully loaded, or riding with two people, see the section below.
In order to satisfy their lawyers, most tire companies will only tell you to consult your bike owner's manual. And while we're on the legal end of things, remember that the number on the tire is the maximum that you can put in, and not the recommended amount.
For a standard rider and gear, you will probably want to start a couple psi below the max value. If you want more traction, lower your pressure a couple psi and go riding again. Keep in mind the heat/temperature guidelines already discussed. Ride with different pressures and see which ones make you more comfortable.
These recommendations are not tire-specific. Keep in mind that some tires work differently at different pressures. If you are trying a new kind of tire, you may want to experiment a little and see what works best for them.
The best recommendation we can give is to find the pressures that work for you and then check them several times a week. Once a month doesn't cut it.
Tire pressures for touring or loaded riding
From the Dunlop website: For touring motorcycle loading, follow these general guidelines:
Light loads: single rider with some luggage (up to 200 lb. total) - minimum tire pressure of 32 psi front and 36 psi rear must be maintained.
Heavier loads: dual riding and/or luggage (from 200 lb. total up to maximum motorcycle capacity stated in the owner's manual) - pressure of 36 psi front and 40 psi rear must be maintained.
Please Note: For any dual riding or fully loaded use, 40 psi must be maintained in all Dunlop rear tires fitted to touring motorcycles.