How to fix one of the most annoying problems with your bike
If you are the kind of cyclist who likes to do more than coast down hills; skips, slips, and grinds while pedaling can be one of the most annoying problems that you may encounter. Listed below are some of the most common symptoms related to a skipping drive train. Each symptom is accompanied with a possible cause (or causes) and solutions that will help you get back on the road and riding smoothly.
My gears don't shift smoothly from one to the other and/or they make a lot of rattling noises.
Cause of the problem:
This is the most common gear related problem that happens to a bike. The cause is usually related to a shift cable that has stretched or needs to be lubricated. Sometimes the cause is a derailleur or derailleur hanger that is mis-aligned.
How do you tell what the specific cause of less than smooth shifting is? A good way to attack this problem is by looking for the more obvious problems first.
For a stretched derailluer cable:
If you have a new bike or you have just replaced your cables and housing, a stretched shift cable could be you problem.
Shift you derailleurs to your smallest cog (on the rear wheel) and your small chain ring (at the pedals). From here with each click of the rear shift lever, your chain should advance exactly one cog larger. The same should be true for the front shifter if your front shift lever has two or three indexed positions. If you are not advancing one gear for each click, you will need to adjust the shift cable tension using the adjusters at the shifters or the derailleurs. Sometimes the cable will need to be loosened at the derailleur, pulled tighter and re-attached. A future "Wrench Connection" will go into derrailleuradjustment in more detail.
For a shift cable that needs to be lubricated:
If your shift cables are not new, you may need to have your shift cables lubricated. Shift your rear derailleur to the largest cog and then without pedaling shift down to the smallest cog. The cable should be slack enough that you can pull it back and forth. If the cable is not sliding smoothly, then remove the cable and lube it with a thin lube. If after re-attaching the cable you still have a lot of friction in the line it may be time to replace the housing and the cable. The housing can get caked with grit and the shift cable can corrode. When this is the case, lubrication may not fix the problem.
For a bent rear derailleur or derailleur hanger:
If you have crashed or you have had a stick in your rear wheel recently, you may have bent the rear derailleur or derailleur hanger.
Start by putting your bike in the middle cog and the small chain ring (for a double crank) or the middle chain ring (for a triple crank). Looking at your bike from behind the rear tire, look down at the chain and the rear derailleur and make sure that rear derailleur is holding the chain parallel to the rear wheel in the up and down direction and the front to back direction.
If this is not the case then you probably have a bent derailleur or a bent derailleur hanger. You can sometimes re bend a derailleur back, but if the mis-alignment is too great then it may be time for a new rear derailleur. Derailleur hangers (where the rear derailleur connects to the frame) can be re bent. For a quick fix you can eyeball the alignment, but there is a special tool that makes it possible to get the alignment perfect. Cycle Path, of course, has this tool.
My chain skips once every so often but not at a constant interval.
Cause of the problem:
This is usually caused by a tight chain link. This kind of skipping is sometimes tolerable but it could be an indication of a safety hazard and should be looked into. Sometimes this is an indication that a chain link is about to break and if this happens unexpectedly you could loose control of your bike.
Holding the bike up, put the chain in a middle cog and pedal backwards. Watch the chain go through the pulleys on the rear derailleur and look for a link that skips. If you find a link that does skip, inspect it closely to see that the side plates are not about to come off of the rivet of the chain.
If the link looks like it is in good shape but it will not bend, then lube the link and try to free it up by bending it with the pivot slightly. If this doesn't work try bending it against the hinge slightly. This will spread the outer plates from the inner plates a little to allow some space for the link to free up. If none of this seems to work you may need to remove the link with a chain tool. A future "Wrench Connection" will go into chain tool use
If you find a link that is coming apart, you will need to get this repaired as soon as possible. If you notice it on a ride, pedal very gingerly using caution and stay seated on your bike. If your chain breaks you don't want to slip off the pedals and put your foot onto the pavement while moving forward.
If your chain does break on a ride, save your chain. Do not throw it away. Chains mesh with cogs and if you don't have your old chain, you may need to buy new cogs and chain rings with a new chain.
If you are on a ride, your chain breaks and you don't have a chain tool you may be able to use some wire (paper clips), string, or small zip ties to patch the chain back together so that you can pedal forward 1/2 pedal stroke and backward 1/2 stroke repeatedly to limp back home. Just make sure that your chain patch job doesn't go through the rear derailleur. It could catch on the pulley cage and wrap the rear derailleur (that would be bad).
Look for these reasons for skip in part two
My chain skips only when I go up a hill or put a lot of pressure on the pedals.
When I put pressure on the pedals my gears slip forward and make a grinding noise.
My gears slip forward and make very little noise at all.