Usually 24-28 PSI if I'm racing. If I'm just on an XC ride locally maybe a tad more to lower the risk of flats. I double wrap my tubes (old inner tube wrapped around the newer one) and I run more pressure than most however the added weight has kept me flat free for over 10 years. Use this tip: Log your tire pressure before each ride, then you'll have a ball park as to what works for you. Don't forget to pinch or push on your tires also, that way you can start to develop a feel for what you like - this is handy during practice runs when I start with about 45-50lbs, it usually takes 2-3 runs to get it just right but it's quick and it works.