More psi gives less rolling resistance and more speed for the same effort. If your tire bulges, it is deforming while rotating which uses up energy and causes you to go slower. Of course you don't want to inflate your tires to more than the manufacturer's recommended maximum, so use that as your guide. Better tires will typically have a maximum of 120psi or even more.
Note: The above applies only to road bikes on smooth roads. For a mountain bike on rough or slippery surfaces, LESS pressure gives better traction and better shock absorption, so you should adjust your pressure according to the surface.




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