Cyclocross - Tire pressure?

The tire pressure that I've been running is ~42lbs. on grass, dirt, sand & short asphalt sections. Sometimes it feels like it's bottoming out :eek: on roots etc. if I stay in the saddle. Another thing is that when I'm cornering relatively fast :rolleyes: it feels as though the rear tire steps out then snaps back. I haven't flatted, rolled the tire (clinchers) or lost control. Is this normal or is the pressure still a bit low? Thanks in advance for any responses.

Thats really low.
Try the max listed on the side of your tire.

Um....that's not actually that low. I run 40psi in clinchers in cross races, as do most people racing. If he's racing cross, that's a reasonable psi to be using. The rim will bottom out from time to time, but the bike will roll much faster off-road with 40psi than if you were running full pressure (70-80).

So...if you're actually riding 'cross-type terrain, not 'gnarly rocky trails', keep running 40ish - you'll be glad you did. If you're riding bumpier, rockier stuff, add pressure to keep from pinching. If you're riding smoother, pavement-only, add pressure to reduce rolling resistance.

As far as the rear tire stepping out - that's what low psi feels like. C'est la vie.

I run 40 - 45 PSI on my size 34 tubulars. If it's muddy I may go down to 35 and have gone as low as 30. I'd be concerned about bottoming out on clinchers though. With tubulars I like to pre ride the course and at least feel it bottom out once or twice then the pressure it right. The step out and snap back in is the deformation of the side wall and again on tubulars this is desired as it actually shocks the impact and keeps your tread on the ground for better traction.