I recently got my two tires replace on my ninja ex 250.the tires say that tire preasure should be 42 psi front and back.But the guy who installed them told me to leave the front one at 32 and the rear tire at 34 psi.Should I leave them how he said or should I leave them at 42 psi like the tire says?They are pirelli tires, sport demonsizesfront 110/70 17rear 130/70 17
28/32 is a good starting point. Higher pressure will make the tire last longer, but may take longer to get up to a good working temperature. Lower pressure will have the opposite effect because the tire will squirm more, heat up quicker but work harder, so it will have a shorter life. Lower pressure can mean the tire will be slightly less effective in the wet, because the channels will be closed a little. Drop your pressure by 1-2 PSI on a cold, dry day, raise it 1-2 PSI on hot days, or in the rain. Be aware that if you change your tire pressure by more than 1-2 PSI, the handling WILL be affected, maybe for the better, maybe not. Be careful.
There is a sticker on the bike which gives you the recommended tire pressures, front and rear. They will be the same as the ones listed in your Owner's Manual. Use those pressures, and ignore what is on the tire.
There are two sets of numbers to go by--one from the motorcycle mfgr, one from the tire mfgr. The motorcycle mfgr knows best because he's tested the tires on that very bike. The tires themselves are marked with pressure ratings, but those are maximums. My guess is that the higher of these is better. If you ride the bike at 32/34 for a while and then boost it up to 42/42 you will notice a difference! Plus the tires will last longer at the higher pressure.
