Back wheel skidding out On my cycle to work this morning I noticed my back wheel was skidding out as I was going up a fairly steep hill. It did it enough that I thought I'd probably gotten a flat, however upon inspection it seemed fine.

I'm a bit of newbie (perhaps done 25 rides on my new-ish road bike) - am I right in thinking my back tire maybe just needs a bit more air in it? It seemed pretty pressurised although some of the bumps I went over today seemed a bit more more shocking than normal.

Are there some other things I should look for? I wasn't turning very hard at all when it lost traction.

Cheers,
John.

Update - details here:
http://www.sportstracklive.com/track/detail/johnhunt/Cycling/159913

Update2:
Yes, I do wear cycling shoes that clip into the pedals, and it did happen at a particularly steep point on the hill. I guess I ought to try and stay seated a bit more - just after the previous two hills it's a lot easier to attack up the last one.
Check the tyre pressure anyway. You should be within the limits printed on the tyre. I would be a little surprised if low pressure caused sliding, normally it's high pressure on a rough surface that causes your wheel to skip across the top of the bumps and move sideways when it's airbourne between bumps. In that case lifting your bodyweight slightly with your legs can help soak up the bumps and increase traction.

But if you were unweighting the rear wheel by standing and pedalling hard that's not too unusual. Try to avoid it by pedalling more smoothly, ideally from the saddle.

edit: at that speed I think it's just basic bike handling skills. As you ride more that will be both less likely to happen and bother you less when it does. It might help to play on gravel a bit (possibly on a MTB or old bike). If you really want to push that along either mountain biking or bike polo are good ways to improve your bike handling.