Tips for repairing bicycles (all bikes, road bikes, mountain bikes, etc).
When a bike doesn't shift (even after adjusting the derailer and cable tension) there are several other areas to check. If the chain is skipping, jumping, rubbing,
etc. then consider the following problems:
Chain links binding.
Go through the chain one link at a time. Each link should move freely without binding. Generally a real tough bind will cause issues with the rear derailer. A bind that is strong will cause the derailer to hop or hick-up every time the chain goes around one revolution. Replace the chain. If it is a fairly new chain, then use a spare link from another chain which is not binding. Buy a quality chain removal tool. Your chain pin removal tool may be bending the links and causing the bind. Also try removing and re-inserting the pin incase this frees it up. Check the linkage flat peices for being bent too much when you take the link apart. Also check the pin and flat peices for damage or protrusions.
Chain pin pushed in too far (sticking out, protruding).
Check the chain pins that hold the chain links together. If there is a pin sticking out, it can knock the chain around.
Chain length too short or too long.
Check chain length by disconnecting the chain (separating it) and pulling it out of the derailer sprockets. Put the chain around the largest (slowest) rear sprocket (gear 1) and put the chain around the largest (fastest) front gear. The chain should be one full chain, plus 2-3 chain links leeway. Although this may not seem to make sense, it is the way you measure the chain length (you'd think it would need to be longer, but it does not).
It is easier to measure the chain for stretching factor if you have a tool that does this (they are a simple metal measuring tool which checks the stretch some links of your chain).
Note: adding more links to chain that is too short, doesn't actually solve shifting problems usually. It just makes sense to have the correct length of chain so that you are not putting strain on the derailer.
Shifter lever (button, gripshift, etc.) precision is off.
It may not be obvious just from looking or pressing the shifter button. Sometimes, a 7 speed shifter can turn into a 6 speed shifter if the spring is gone and/or it is off by one notch. This may not be noticeable, since you are so used to shifting the bike and you do not realize there is one shift increment missing.
Shifter can be bad (off by one notch, broken partially, bad spring, etc.).
Stretched shift cable, binding shift cable, binding cable to sleeves, kink in sleeves, kink in cable, sleeves too long, cable distance from shift lever to to derailer too long.
This "distance" issue happens often with speed bars on road bikes. When a person upgrades their road bike to have aero bars (the ones you rest your arms on to be more aerodynamic), the length of the cable increases from the derailer to the shift lever. This can cause issues, and not much can be done (other than repositioning the bars and the shifters so the cable distance is lesser, if possible).
The other issues, such as a streched or kinked cable/sheeth are easier to fix: replace them.
Teeth worn out on gears and sprockets.
The sprockets can wear down and become pointy sharp and small. Check all the sprockets on the derailer, the rear gears, and the front gears.
A combination of the above problems.
There is usually a combination of problems with a bike, rather than one alone. This is because bikes tend to get neglected, and people just live with the bike's problems for even several months or years.
Front derailer noise:
Noise from the front derailer is not neccessarily coming from the front derailer! The chain may actually be rubbing on the actual chain gear (sprocket) and causing you to beleive the noise is coming from the derailer. Do not always assume that the noise you here is coming from the chain rubbing the metal guide which changes the front gears by pushing the chain. It may be that the chain is actually rubbing the gear along the sides of the chain.
TODO: write book on bicycle repair. The above tips are not even mentioned in many bicycle repair books. Shame on them. These are some of the most important tips to get a bike back into shape. There's no magic tension that all cables have to be and no magic derailer positions - each bike varies slightly. Bicycle books focus too much on consistent and magical methods of tuning bikes, such as exact cable tensions and exact derailer positions on the lowest and highest gear.
Almost anyone can get a new bike tuned who has general bike maintenance knowledge from the books. Set the cable tension up, put the derailer in the correct positions, replace cable. That's common sense. But that is usually never the problem in real life, when a bike no longer shifts properly. It's almost as if the folks who write bike books demo and study new bikes only, and have never touched a bike that has had dirt and stones hit the chain, or been ridden thousands of miles.
New bikes are easy to tune - because there are no kinks in the chain, no modifications to the bike, and no obscure problems. But in fact the above problems are not obscure: they should be listed in all bike maintenance and repair books. They are common problems on all used bicycles with some mileage on them. Ever wonder why old cars have several problems that pop up after they have been driven for 10-15 years? Bikes are the same, but problems occur earlier than 10-15 years. Bikes are also much simpler than cars and much easier to master.
Subject: bicycle maintenance, bike maintenance, bike repair, road bike repair, mtn bike repair, mountain bike repair, bicycle repair guide, bike repair guide, bike repair guides.