phantom shifting

OK, I'm nuts. I had a major tune about 400 miles ago. They changed out the rear cog. It was fine for about 100 miles and now it won't stay in a single gear - and shifting is really sloppy - sometimes I get two gears for the price of one shift. It phantom-shifts when 1. it's under a load or 2. it's a bumpy road.

Does anybody have a fix for this? I'm sure it must be a simple adjustment, but I've fiddled with the shift-barrel thing (on the cable next to the front fork) and it doesn't seem to make a difference. Could the back cog be mis-aligned? Or is there another adjustment I'm missing?

Another question - anybody have a really good book on road bike maintenance they can recommend?

Check the tension spring on the rear derailleur. Sounds like there may not be enough tension on it.

Books - Zen and the Art of Road Bike Maintenance.

V.

Another thought I had - is the rear wheel tight in the dropouts? We had a similar problem with our tandem and that was the cause.

V.

Did you change your chain when you installed the new cassette?

Did your overhaul include new cables? It might be a simple case of cable stretch. Kind of like a new bike that needs the "30-day check-up". A few simple adjustments (barrel adjusters/possible limit screws...should get you going). Call the shop that did the overhaul.

My husband has a book he likes on bike maintenance.
It's "The Bike Book" by Haynes.
Theres a phone no. for up to date information on their titles
The American no. I believe is (805) 498-6703.
They also have an e-mail address
www.haynes.co.uk
Hope this is helpful.
Margaret:D

make sure the rear derailleur hanger isn't bent. Also, new cables will stretch.

~I

Take it back to the shop that did the tune-up. Usually they'll do re-adjustments for free if you've recently paid for a tune-up...

and do purchace Zen and the Art of Bike Maintenance. It's a great reference.