A couple of days ago I was riding my bike and when I hit a hill and was shifting down through my gears, the chain slipped off the gears. I hopped off the bike and walked it back home, flipped it upside down, and got the chain back on the gears. I figured maybe I was shifting too quickly through the gears or something.
Yesterday I went out to ride again, and shortly after I started - this time on fairly level ground - the chain slipped off again. I put it back on the gears again and rode a bit farther, but yet again it slipped off.
This time when I took it back home (and yet again got the chain back onto the gears), I tried to carefully troubleshoot what was going wrong. I noticed that my troubles always started when I tried to take the left shifter to 3rd (it's an 18-speed mountain bike) or 1st. When shifting to 3rd, it wouldn't transfer to the gear (stayed on 2nd) and when going to 1st it would come past 1st next to the pedal hub. It might help for me to mention that the right shifter was going through all 6 back gears just fine through all this - so I was getting the idea that my problem had something to do with the left shifter only. After manually applying the chain to the 3rd gear, I slowly turned the pedals and noticed that the chain was rubbing up against and sometimes getting stuck on the part in my photo that I've highlighted with a red circle and for which I unfortunately do not know the name (since I'm a bike noob).
My best guess as to the function of this part is that it supposedly helps guide the chain into the front gear set (at the pedals) - but in my case it seems to be interfering with the chain's movement. My questions are as follows:
- What is this part's name and function?
- Should I remove it or adjust it?
- How can I best go about this?
If I had the money I'd just take it to a bike shop and watch them fix it, but I'm broke so unless they'd do it for free that's unfortunately not an option. As I've already indicated, I'm a total novice at bike ownership so I'll appreciate helpful, constructive replies. I look forward to getting this resolved so I can get back to riding. Thanks for your time.
--------------------- EDIT ---------------------
Operating perhaps prematurely, I tried adjusting the positioning of the derailer to stop it from inhibiting chain movement. I noticed the whole assembly was attached to the post via the screw highlighted in the following picture:
I carefully loosened this screw and then very slowly rotated the derailer away from the chain until it had about a millimeter or so of clearance. I then tightened the screw and tested functionality. Now the pedals ran smoothly with the front gearset in 3rd. I took the right shifter down a couple of gears to verify its continued functionality (all was well), and then I tried taking the left shifter down to 2nd. To my dismay, the chain transferred to 1st gear instead - so I believe my configuration is still amiss.
Here are two better shots (with the bike in upright orientation, post-adjustment) of the derailer: