Bicycle Mechanics - Skipping a gear -- what did I foul up?

So today I installed a new (rear) tube on the Giant, and it went about as flawless as one could hope for. It was my first flat repair on this bike.

After I reinstalled the wheel and topped off the tire pressures I took a ride around the block and the shifter (cassette) is requiring a double tap to shift.

The derailleur was not out of adjustment when I parked it with the flat, and I moved the chain all the way down to the smallest cog before removing the wheel.

So what might I have done wrong to cause the shifting issue?

Thanks in advance,
Rick

Specs --
Giant TCR-1
Ultegra components

Make sure the wheel is fully seated in the drop outs. With the bike sitting with both wheels on the ground, open the quick release and apply some of your weight to the bike. Refasten the quick release. Try it again and report back.

Thanks.

Today is slammed with work and I'll not get in from the office until after 7 PM CDT so I'll try it when I get home.

Well, re-seating the axle in the dropouts did not cure the issue. So I must have misaligned something when I removed and reinstalled the wheel.

If I am in the smallest cog on the cassette, when I go to shift I have to push the lever twice.

That pattern repeats itself up through the first three cogs, then only once is necessary.

Suggestions?

Well, re-seating the axle in the dropouts did not cure the issue. So I must have misaligned something when I removed and reinstalled the wheel.

If I am in the smallest cog on the cassette, when I go to shift I have to push the lever twice.

That pattern repeats itself up through the first three cogs, then only once is necessary.

Suggestions?

It *most* likely is a cable tension issue, which may or may not have been conincidental to you messing with the rear wheel during the flat change. If it's not a simple barrel adjuster, solved problem then do this proceudre from top to bottom and report the results.

http://www.parktool.com/repair/readhowto.asp?id=64

Okay, this was the first time I had any issues with this bike. Up to the wheel R & R everything clicked like clockwork.

So, I reseated the axles and it still did not clear up the issues.

My next move was to call the previous owner and ask their take. She said the barrel adjusters up at the shifters would clear it up.

So I suited up and took a ride and tweaked the adjusters and presto, back to normal.

I only had to bump the right side (rear derailleur) about a quarter turn, and the chainring derailleur less than that.

Thanks to all for the information.

Live and learn.