I have a couple of questions and was hoping for your opinions. I have an appointment this week to have the problems looked at but hate not having a clue what is wrong when I talk to the mechanic (same with my car :) )

1) My chain has come off the last 3 times I have gone for a ride. The first time was on the front chain ring as I attempted to shift. The next two times were on the back rings, once while shifting and once while just getting on and starting. Honestly I can't ever remember losing a chain as a kid/teenager, which tells me something is up here.

2) I think my back wheel has gone out of true just a bit, which looks to be expected from everything that I have been told/read here. However, when I spin the wheel and watch the wheel at the brake pads I don't notice much, but when I look at the tire it looks like it is wobbling quite a bit. Could I have done something to the structure of the tire itself?

I purchased my bike not long ago and had the shop upgrade the rear wheel to a 36 spoke, which was installed about a week after picking up the bike. Do you think the new wheel installation could be causing any of these problems? The bike shop is backed up and it has been about a week since I have ridden because I am afraid of blowing out the tire or do some other damage. I had gotten up to about 10 miles and was really enjoying riding so I am looking forward to getting back on the bike.

New bike with new gears and chain should be something simple. I'm not sure what you mean by the chain coming off. If your deraileurs are out of adjustment then it is possible to shift outside the number of chainrings/sprockets (front/back respectively) you have. This is pretty easy to fix. There are adjustment screws on the front and rear deraileurs. Also you can adjust the cable with the cable adjusters if the deraileur isn't centered on a gear. For example if hear a lot of clicking from the chain (front or back) as if the chain is attempting to shift, but you aren't shifting. If you are a do-it-yourself kind of person then get the manual from the manufacturers website and make the adjustments yourself. That's what I've done in the past.

Sometimes tires aren't imprinted right. I have a tire where the tread takes a jog to one side in one particular spot. When I first looked at it I got scared that I had bent the rim badly, but as you mention the rim didn't seem to shift much when looking at the brake pad. The only thing I might look at is make sure the tire is on straight. Deflate the tire until its soft and shift it back and forth a bit to make sure its sitting correctly on the rim. It might not do anything but it will give you piece of mind.

Good Luck.

John

1) Some people have that problem on their bikes, however it's more a user error than something wrong with the bike. They probably have a triple crank in the front and a 10-speed cassette in the rear. When they are on the lowest (granny gear) gear in the front and shift to the outermost (smallest) gear on the cassette, the chain jumps off the crank. Instead of shifting to the smallest rear gear they should shift up to the center ring on the crank, that way the chain stays on both front and rear gears just fine.

2) When checking for trueness you should only reference the brake channel on the rim, the tire is always misleading to watch. If the tire "wobbles" a little bit I believe that's normal as no tires are perfectly shaped. However if the tires wobble quite a bit then i'd take it into the LBS to check it out. If something happens to the tires while you're riding you can get seriously hurt, so if you're the least bit doubtful of the safeness of the tires i'd definitely get it inspected by an expert.

You probably just need some basic adjustments. Just describe to the tech what is going on to the best of your ability and let him take a look. It's ok to take your bike out for a spin before you pay the service bill.

You can also ask him about your tire. Maybe the tire's malformed???

If our chain is popping off in the front, the limit screws are not set correctly. They allow the amount of derailleur travel while shifting. If it's allowed too much to the outside, it will throw the chain to the outside. If it's in the inside, same applies.

If it happens in the rear, well , the rear derailleur also has limit screws. Sounds like it needs adjusting. Usually at about 90 days, USE IT! The new cables lose tension as they break in, more than likely needs a tune up (free service).

The tires are rubber and not perfectly formed. I spin my tire and notice ovement side to side as if the wheel is way out of true. I've taken off the wheel for acheck and nope, not the rim, just the rubber. I think it's normal.

If the bike is new, chances are the wheel might be a bit crooked. Ask the shop to check and readjust the tension on the spokes. Don't let them get aways with truing alone. If o do, the spokes will begin to weaken and eventually break prematurely. If the shop is good, they will do it. If they are cheeseheads, they won't, find a better shop!:D

The new wheel shouldn't affect the shifting if the shop mechanic adjusted the rear derailleur when he installed the wheel. While fixing a flat, I am very careful not to bang the equipment so that nothing is misaligned. Even so, once in a long while, stuff will need to be redjusted. Plus, some cables are stubborn. They will need to be readjusted a few times within the first year of use.

As far as blowing the tire. check around the rim and tire intersection. You will notice that the tire bead is setting along the rim edge. If it looks fairly even arond the circumference, then it should be ok. If you notice that it's lifted off the rim or a big bubble or the tube pinched between, then you've got trouble. But tha can be fixed by removing and reinstalling the tire.

You aren't shifting the front and rear at the same time are you? That can give the chain a "crack the whip" effect and make it go places it shouldn't. I can throw the chain quite often if I shift both at once. Probably 50% of the time if I go Big:Big to Small:Small on my 3X8. Otherwise, maybe 1-2 times a year.
If not, you might need to screw in the H & L screws on your derailleurs. Just a TINY bit at a time! If you go too far, no harm. It just won't shift far enough and you can back them out a bit.

http://www.parktool.com/repair/byregion.asp?catid=53

If the rim doesn't wobble, but the tire wobbles a lot, something is wrong. Tires aren't perfect, so a tiny wobble is somewhat normal.
Most tires will have a thin "raised line" next to the rim. Look at that to make sure it's the same distance from the rim all the way around.
Check your spokes. Squeeze adjacent pairs together to see if something feels extra LOOSE.

When I am on the lowest (granny gear) gear in the front and I shift to the outermost (smallest) gear on the cassette, the chain jumps off the crank. That's called "cross chaining" and you're supposed to NEVER do that. Similarly, you should never use the highest (largest) front gear with the largest rear gear.

http://www.activesports.co.zw/train_health_nutrition/mtb_cross_chain.htm

Thanks for all of the information. The tire didn't seem to have the wobble until after I had ridden some on the new wheel which concerns me.

That's called "cross chaining" and you're supposed to NEVER do that. Similarly, you should never use the highest (largest) front gear with the largest rear gear.

http://www.activesports.co.zw/train_health_nutrition/mtb_cross_chain.htm

Most of what I ride tends to be pretty flat so I tend to stay toward the middle of the front and rear rings and just deviate off of that occasionally. By "coming off" I meant that my chain completely falls off one of the ring sets and I have to stop and put it back on. The first time could have been user error as I shifted on the front accidently. The two times on the back rings were once while shifting and the other I was just starting again after walking under a partially fallen tree on the trail.

Well it turns out that I had a defective rear tire which the shop upgraded since they didn't have the same one in stock.