In my Giant bike the tire shows 60 PSI, is that the pressure I should maintain or the high limit? What would work best for road, our paved/stone trails?
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Also, what is the rated tire pressure of the tires? Usually you can find it on the sidewall of the tire. A good starting point is to start somewhat below the max rated tire pressure (like with a max 60psi tire I'd start at about 50psi) and adjust upwards and downwards from there.
For most e-bikers as long as you keep your tire pressure in the safe range specified for the tire you should be fine and needn't worry too much.
Also depends on the tire, and the type of riding you do.
I run approx 30psi on my Continental Ruban tires on an EMTB. I could go lower, but it seems a good balance for the combo of off road/on road I do.
When in doubt, just split the difference between the min and max pressures given on the sidewall. Adjust from there to learn how the bike rides at different pressures.
Many, many discussions on this subject. The forum search function is your friend.
My 2.1" tires are rated at 55 or 60 psi. That is what is use in the back to keep from banging the rim with groceries. On the front I run a little less for better ride. Watch your tires at purchase; the LBS sold me some 40 PSI rated **** 4 years ago. Looked just like real tires.
The rating on the tire is a max and largely meaningless. Most tires can be run above max if you really want to (I suspect the number is derived more by lawyers than actual engineers) but generally most people run tires too hard on pavement anyway.
Actual best pressure takes some experimentation. There is an ideal pressure where, for the system weight (rider+bike+cargo) the tire will roll most efficiently. A tire that is too hard will actually not conform to pavement unevenness, which causes it to take more energy to roll. A tire that is too low will lose efficiency too due to casing deformation. Theres a sweet spot in the middle where the casing deforms enough to conform to pavement unevenness but not so much that its sapping more energy than you gain.
My story here is back when I had my first bike commute, I was riding a cyclocross bike with 28mm road tires. I had settled on 120psi as the optimum pressure. It felt fast over the 11 mile commute. I would air the bike up Monday morning, commute all week, maybe do a big ride over the weekend and repeat. But over many months I noticed that I would consistently set my fastest commute times on Wednesday or Thursdays. Eventually I figured out that 120psi was too high. It felt fast, but as the tire lost pressure over the week it actually helped my efficiency and speed (until it dropped below the actual efficient pressure and started slowing me down again). After experimenting some more I settled on 105-110psi as the actual best pressure.
I would start with the Silca calculator Mr Coffee linked above. I checked a few bikes on it and it was pretty close to where I run mine.
When you're not pushing the envelope on battery range, you can afford to bring other considerations into the tire pressure trade-off and to a point, let the motor deal with the inefficiencies. Lower tire pressure will improve ride comfort and reduce sinkage on soft surfaces, but too low will increase the risk of pinch flats and add too much rolling resistance.
I'd encourage the OP to explore the pressure range given on the sidewall and see if he can find a sweet spot before venturing outside those limits.
Make it easy to maintain or experiment with pressure by getting a cordless inflator with built-in gauge like the Ryobi and keep it by the bike. A cheap no-brainer if you already have the battery for your other power tools.