Pedals won't turn while sitting on bike

[grogthecaveman]

This is my first post on these forums. It looks like there is a lot of knowledgeable people here. I hope someone can give me some advice! I did a search and did not see this covered here, so my apologies if this is already covered.

I have a Centurion Le Mans bike that has been working fine for a year or so. Yesterday I was riding and I hit a bump on the road. My rear wheel came out of alignment and started rubbing on the frame pretty bad. I walked the bike to a local independent bike shop and borrowed a wrench. I re-aligned the rear wheel and it does not rub on the frame any more. It appears to be seated correctly in the frame. Now the rear wheel turns fine when I lift up the bike and turn the pedal with my hand - not sitting on the bike. But now, when I sit on the bike, I can not pedal forward. What could be the cause of this problem?

I am going to a local co-op today where there are some expert bike mechanics who can probably tell me how to fix it, but just in case, I figured that I can possibly get some info here too. Thanks for any advice!

[grogthecaveman]

might have figured out my problem... looks like the rear wheel is still not seated right.