Mountain Biking - GT Avalanche or Schwinn Mesa?

Hey everyone. I just got into riding again, so I'm looking for some advice off the bat.

I actually have 2 questions. Last week I bought a GT Avalanche 3.0 (disk breaks). I haven't been biking in about 10 years (even though i am only 28), so I wanted something solid but not too elaborate for a new bike. My g/f and I both liked how mountain bikes ride overall, as she bought a Schwinn Mesa, while I got the GT. The bike seemed to fit fine - I'm 5'11" so they sold me a "large" frame.

On our first 2 rides in the new bikes, a few things happened on my GT. First the left pedal broke in half. The GT does have plastic pedals, so this can be understood to an extent. Although, this was only the first ride, and it was on a paved bike path. I am in decent shape, so i'm able to put a lot of strength into going uphill, although I wasn't coming anywhere near putting the bike through any abuse (especially since this was on paved surface, and this is a mountain bike!). I know metal pedals are better for mountain bikes, but the plastic ones breaking on the first ride, doesn't make sense.

On my next ride, the bicycle handle bar came completely loose, almost throwing me off the bike. This might be a matter of screwing the handle bar back in with an Allen wrench, but again, I just bought it.

Another issue as well, when shifting into 3rd gear, the bicycle chain repeatedly would fall off. This was a different situation though, as I was later told that this was because I was incorrectly switching the gears (changing from gear 2-8 to 3-8 all at once - referred to as crosschaining i believe). This was understandable and was a simple correction of riding procedure.

However, all of these other issues worry me a little. I bought the GT from 'Performance Bicycles.' Since the mechanic calibrated the bike prior to me actually taking it, i would imagine the handle bar isn't supposed to come loose so easily after the first week (especially from VERY light riding). I'm wondering if it's because the GT bike itself is just not up to par, or if the store sold me something which had faulty parts, or possibly the mechanic just did a poor job of calibrating everything.

The bike is a 2005 GT Avalanche 3.0 disk - the bike rides very well, until of course the pedal breaks and the handle bar came loose (all on the first 2 rides).

On a different note, my girlfriend bought the Schwinn Mesa. I have tried this bike out as well, and find it rides exremely well - at least as well as the GT rides. Does anyone know how the bike I bought compares with the Mesa, if any of you have had experience? I'm wondering, if my GT is going to repeatedly have these issues that are indicative of mediocre construction, if I should trade it up. It rides well, but if it is going to keep falling apart like this... especially when I haven't even taken this "mountain bike" mountain-biking yet.

Overall, I'm just wondering which bike is known for better performance - the GT Avalanche 3.0, or the Schwinn Mesa? I want to think it's the former, but the issues I've had seem to say otherwise.

Any advice would be greatly appreciated. Thanks!

i am thinking the latter....schwinn mesa. your gf is a smart woman! schwinn has been around for 111 years!

i suspect your handlebar clamp face plate is one utilizing 2 bolts. no? they have a propensity to loosen especially on brand new pieces. a low grade thread locking agent might be useful.

if it's any consolation, they're owned by the same company. pacific cycles, a division of dorel industries

My wife and I both have the 2005 Mesa GS and love it. It's got some pretty solid componets on it and it seems to stand up to quite the beating

Bikes take time to wear in. The pedal may be covered under warrentee at your LBS.

you got your bike at 'Performance Bicycles' that must be a bike shop. if you get your bikes at a sporting good store (like i did) they normaly dont know alot about them. they just know how to assemble them from the box. so i would think that your bike shop would know what there doing. the new guy must've put your bike together!

as with the mesa, i think it is a pice o crap but my dad loves his. i think it rides dorky and hard to handle.

Thanks for the responses. For the past 2 nights I have closely compared the 2 bikes, at least in how they ride on paved surfaces. They are very close to one another. The main differences I noticed (and forgive me if my terminology is off) - the suspension/shocks on the front of the GT seem to absorb just a tad more pressure than then Mesa.

Also, on first glance, I notice the tires on the Mesa seem to be "harder" than the GT. I filled the GT's with the appropriate air, and they still seem softer (actually squishier is the more appropriate word) than the Mesa's. I think this is where I like the Mesa better, as its tires seem to do better on the road. I plan on doing as much riding on paved trails as I do on off-road. I still did not like the hybrids I saw at all, as they could not handle going up steep hills nearly as well as a mountain bike.

Here are the specs on each of the tires:

Mesa: WTB 26" x 2.1" Velociraptor Front and Rear
specific tread pattern

GT Avalanche 3.0: Tioga Factory XC 26 x 1.95

Do the tires make a major difference in performance, or is it more the other components? Does anyone know the major difference, advantages/disadvantages of the tires listed above?

Thanks again for your advice, I've learned a lot on these boards!