Do lagered beers still need bottle conditioning?

I'm hoping you guys can clear up a question for me.

I made a Brewer's Best Altbier kit and hit my OG and FG fine. I let it ferment all the way out (3 weeks at 60°F), then ramped it down to a 40°F fridge and let it sit there for 6 weeks.

The bottles carbed fine (actually kind of overcarbed) in 3 weeks, but they don't taste very good... they taste thin and kind of sour. More like yogurt than apples, but it's a little hard to tell. Right now I'm just being patient to see what happens to them in time, but I was thinking...

Why would they get better with bottle conditioning if I already lagered them for 6 weeks?

Extra special bonus mystery: I drank 5-6 bottles so far, and while most of them were almost overcarbed, one was hardly carbed at all, and it tasted GREAT. So my carbed bottles taste thin and sour, but the random uncarbed bottle tasted malty and delicious. What's the deal?

I'm going to take a stab at this, although i have not brewed a lager as of yet.
Essentially Yeast produces alcohol from simple sugars. A result of that production is CO2, as well as various other by products and off flavors. Allowing a beer to condition before drinking allows the yeast to clean up (consume) some of these by products.
So regardless of how long you lagered it, you still have to allow the yeast to clean up again after bottle carbonating (because it is essentially another fermentation)
I have had the same thing with a brown ale. Long storage to condition and mellow. 1 week after bottling, I tried one (for science, LOL), and it tasted great but obviously not fully carbed. 3 weeks after bottling i had off flavors. A month after that, i had a fully carbed beer that has no off flavors and tasted awesome!
Hope this helps. Anyone else, perhaps someone with lagering experience, want to weigh in?

I've never experienced what you are talking about, but I HAVE had a lager taste yeasty after 3 weeks of bottle conditioning.

I would agree with kgg that the yeast may need to clean up. Alternatively, you could try giving them a week in the fridge as cold as you can... see if you can knock the yeast out of suspension. Your beer might not be fully dry, but it shouldn't be sour.

Thanks kgg, I hope I have the same results! It's really an ale, but it got lagered, so your experience is probably still applicable.

Was 60 degrees ambient temp? I am not sure about altbier, but 60 is a bit warm going by the recipes that I've seen for lagers. I fermented my oktoberfest at 50 for 3 weeks, then 33 for another 6 weeks. Even then it had some fruitiness that I think was caused by underpitching...

Homercidal said:

Was 60 degrees ambient temp? I am not sure about altbier, but 60 is a bit warm going by the recipes that I've seen for lagers. I fermented my oktoberfest at 50 for 3 weeks, then 33 for another 6 weeks. Even then it had some fruitiness that I think was caused by underpitching...

Click to expand...

60 was fermentation temp (as measured by the fermometer on the outside of my better bottle, I assume it's pretty close to internal temp.)

Altbiers are actually ales, but they're one of those "hybrid" styles, kind of like kolsch. You use an ale yeast and ferment them about as cold as that yeast will tolerate, then lager them just like you would a lager beer.