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| *Vultures Knob>>>Cycling |
The chain keeps 鈥榡umping鈥?on the smallest two cogs on the free wheel on my bike. What's wrong? |
I鈥檝e tightened the cable and tried re-indexing the gears but no luck. What's my next step? I'm leaning against the idea of a worn chain, though that could still be the case. The reason being is that the skipping usually occurs on the cogs that get the most use. It's not usually the case that the smallest two cogs are the most used. Now, is it the case that the chain is not staying on the gear and skipping to an adjacent cog, or is it that the chain is staying on the gear and skipping over the teeth on _that_ gear? If the chain is jumping from one cog to the next, it's still an indexing problem. If you've retweaked it and it still jumps cogs, it either that you didn't do it right, or you have a worn upper jockey wheel, worn d茅railleur, or worn shifting mechanism, and may even be a bent hanger. Remember too that you cannot mix campagnolo shifters or cassettes with shimano shifters or cassettes unless it's 9 speed. the 7,8, and ten speed drive trains are not compatible between brands. If the chain is skipping over teeth but staying on the correct cog, it may be a worn chain, but it's possible the chain is too long and the upper jockey wheel is contacting the smaller cogs. With the chain removed, look closely at the hanger. If it doesn't look bent, it's probably ok, it would take a visible misalignment in order to create a problem so bad you can't adjust it out. Next, shift the derailleur back and forth between the last two positions. The upper jockey wheel should line up directly under the desired cog in each position. If it doesn't, make sure the stop screw is not set to prevent the derailleur from coming all the way down. Other wise your onto the worn shifter. In any case, your drive train needs work. First things first, replace the chain _and_ cassette. You should never replace one without the other. When installing the new chain, it must be sized properly. With the bike in the small chainring/small cog combination, there should be no chain slack and the upper jockey wheel should be about the width of the chain below the smallest cog. Go to www.sram.com and surf to their technical instruction section. There will be a downloadable video on how to size the chain, as well as set the drop screw on the derailleur, if you have one. If you replace the chain and cassette but it still does it, you probably have a worn shifting mechanism. The cheapest/easiest fix is to replace the upper jockey wheel. After that, you need to look into a new shifter. It's rarely the derailleur unless it was damaged in a crash. Very likely your chain is worn. Replace it. i would lean toward worn chain too, it can also be worn cogs, if you are sure your derailure is set and adjusted right, i would replace the chain next. Take to to a bike shop and get it sorted. Or if it's new still, then take it back to where you bought it ! Nice answer by MadMonkey. I would just add one thing: Put the bike in the offending gear. Lean the bike against a wall (or put it in the repair stand if you have one!), get close to the cassette, pedal backwards with your hand on the pedal, and watch the chain closely as it passes over the top of the gear. If the chain 'jumps' on the top of the cog doing this you may have a stiff or bent link (or links) in the chain. Examine the area of the chain that jumps; you'll immediately see whether this is the case. Stiff links can often be worked out with a bit of lube and by 'flexing' the chain side to side (in it's rigid direction). Bent links can be replaced, or you can replace the chain. Stiff links can sometimes arise if the chain has been cleaned but not well relubed, or if a link is too tight. |
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