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I have the new Tommaso (was Timmaso) Imola bike with Tommaso Corsa TC20 wheels. The tire sidewall says "max pressure 90 psi"
The tire is the kenda 700x25c.
I am 5'9" 220 used to be a power-lifter so pretty heavy. Question is can I inflate them to closer to 120 psi due to my weight?
This handy chart shows the recommended pressure for different rider weights. Sadly it doesn't help you or me, both our weights are off the chart.
My road bike has 700x25 tyres, so I picked 100 PSI and aim for just over that when inflating. The tyres are rated to 120 but that feels harsh and I get a lot more flats at those pressures.
Added: Since your tyres say maximum pressure of 90 PSI, you shouldn't go much over that. Kenda's specs say 90 psi is the maximum for the "kenda street black mocha" so while they will survive more, the question is how much more. Instead, consider replacing them with tyres that are suitable for higher pressures.
Note: This chart is purely referencing road tyre pressures. If you have a MTB the pressures drop off really quickly.
Answer: I wouldn't go much over 90 PSI, but others have routinely put 100 PSI in Kenda tyres without issue. Your weight suggests that a higher max-pressure tyre would be the best solution, aim for 120 PSI capable tyres in 28 width.
The people that built the tire put a max pressure on it. You kind of have to trust they put some thought behind it.
More pressure will protect from pinch flats but there is max pressure the tire and rim will take.
The number one risk of too much pressure is blow the tire off the rim. The pressure is force on the tire bead and the tire is simply forced off the rim. Will one pound over force it off the rim - typically no. A tight rim you can go past and I have had some loose (small) rims that I could not even take a tire to the max.
The force on the bead is volume x pressure. That is why bigger tires will have a smaller pressure.
The other risk is blowing out the rim. Not as common but it can happen - typically only on a compromised rim.
As a big boy you should be on bigger tire like a 30mm - 35mm. A bigger tire takes a load better. In the 25mm tires they are for the most part targeting racers and racers rarely weight more than 180 lbs.
In an adult smaller road tire the max is typically targeted for 180 lbs and the min targeted for 110 lbs but that is not an industry standard. In between you can use linear interpolation.
You can find some 25mm tires that go 120 psi but according to the label this tire does not. You can test your tire at 120 but if it blows off the rim you cannot just get a new tube and 90 is good as you have stretched the bead - testing is destructive.
Some people think a higher pressure has more puncture (glass) flats and some think less and I am not going there. The answer is a quality puncture resistant tire.
I'd just use the max. Start overfilling your tires and they'll probably be compromised and you'll bust em.
