On my bicycle tire, it says 60-30 PSI. To what air pressure level do I fill it--- 60, 30, or in between?

You didn't post what type of tire. But here are a few guide lines.

On pavement run the higher pressure. (45+)

On a mtn bike the tire is critical a part of your suspension, so.

On dirt run towards the middle or lower (45~30).

On dirt run the pressure lower if the surface is real soft or muddy.

On dirt if you are a heavy rider run slightly higher pressures.

If you run on real rough trails use only enough air pressure to stop pinch flats.(a pinch flat is a flat caused by hitting an object hard enough to bottom out the tire and put a small hole in the tube, normally it happens in pairs and looks like a snake bite.)

Doogie

Good question! On the roads and streets use the higher pressure. If you ride mtn trails, then you will probably want to back of but not to the 30 pound range.... maybe 45 to 50 pound range. I feel that the lower air pressure on mtn rides gives me a little more stability and better handling than the higher pressure tires. But, on the road the higher pressure is much more efficient for riding.

Soccerref

What kind of bike is it? These are the pressures that my bikes use:

40-60 PSI mountain bike

50-75 PSI hybrid/commuter bike

100 PSI road and recumbent bikes

I think that 30 PSI would be to low for any bike. Try on the upper range 50-60 PSI. You shouldn't be able to squish the tire with your fingers. Check the link to find out everything about tires.

I always go for the max pressure when I ride because I ride mostly roads and I weigh 193 pounds, Having less air pressure increases friction between the tire and the road making it harder to pedal. Also too low, pressure causes flats when the tube gets caught between the tire and rim, The only time you would use less pressure would be if you were off road on sand or loose gravel and wanted the extra traction. Otherwise go for 60.

What type of cycling do you do?

60 is a lot of air and the ride will be stiff. You will get good pedal efficiency on the road, but a rough ride.

30 is low and you will get a bouncy soft feel. On the road, you will have poor efficiency but a softer ride.

If you're mountain biking, there is a lot of more to this - a lot more then people consider.

Bottom lines, you need to find "your pressure" for your style of riding.

Fill it to 60 and then drop it a few pounds at a time to where the ride is comfortable. It will vary with riders weight.

personally i would go in between and keep in mind how much you weigh and what is comfortable for you if you are a heavy person you wouldnt put it on 30 as it might look flat ;)