2

I don’t know much about bikes so whenever my chain slips off I always just force it onto the cog I can get it on.

I think this has been messing my gears up because I’m having issues where Cycling in some gears will feel the same, or in one gear the chain kind of jumps around and makes pedalling very jerky, so that gear is unusable.

I thought maybe the gears are not correctly set upon the cogs. I though I could realign my chain so that the chain is on the correct cogs. But I can’t find much info on the web on how to do that so I think I may be searching for the wrong things. Can anyone help?

3
  • 3
    If the chain is slipping off, you probably need to get your derailers adjusted. Take to a shop or visit the Park Tools site Sep 22 '20 at 12:08
  • @DanielRHicks thanks I'll check out the vids on that site, little broke atm so would prefer not to take it to a shop
    – MendelumS
    Sep 22 '20 at 12:13
  • Depending on the state of your bike might just need a screwdriver and an allen key (or other key). Most of the time it comes down to wire tension (it wires lose tension with time and derailler will lose the right position). If it hasn't been done in a long time and if you still experience issue after adjusting your derailer, you could by new derailer wires.
    – Jao
    Sep 22 '20 at 12:33
3

Expanding on the comment by @DanielHicks, given the symptoms described, it sounds like you are talking about the shifting at the rear of the bike. Chances are that your rear derailer needs adjustment.

Hopefully you don't force the chain on the correct cog by hand - that's what the derailer is for! In any case, when you push a shift lever, it pulls or releases a set amount of cable, e.g. 2.7mm. This will move the derailer a set amount in either direction (not by the same amount of distance, but that's a long story). As they age, however, cables can stretch, and the cable housing will accumulate contamination inside. A click may not pull the cable the intended distance. You can follow the link in Daniel's comment to a guide as to how to adjust your derailer. Also, it's possible that the derailer's top and bottom limits will need adjustment - these two settings govern the range the derailer can travel, and the limits should align with the biggest and smallest cogs. You may not need to touch them if the bike was set up correctly. Anyway, wrongly adjusted cable tension will cause the chain to skip or slip as you described, or if you shift at the lever the chain may not actually make it to the correct cog.

If the chain is too badly worn, then even if the derailer is correctly adjusted, the chain will skip on some of the cogs. Unfortunately, this requires a replacement chain, and possibly a replacement cassette or freewheel. On more expensive groupsets, you should regularly check your chain for wear using a chain checker. If you replace the chain regularly when slightly worn, it will keep you from having to replace both chain and cassette. On cheaper groupsets, it can be acceptable to just let the chain and cogs wear out and change both - but this does accelerate wear on the front chainrings also. It will depend on your mileage and on your costs.

Reading the title, I initially thought you were asking to do what if your chain slipped off the front chainrings. This is likely not what you asked, but the advice here may be generally useful. Sometimes, when shifting to the little ring, you drop your chain off the inner chainring. This can be exacerbated by bumpy terrain. If this happens, you can often shift back to the big chainring and keep pedaling. The chain will often re-engage (if the front derailer was set up correctly). If you are on a steep hill and this happens, then next time you should learn to shift to the small ring earlier - this is not intended as snark, it merely is one of the many small skills we have to acquire as cyclists. Also, if the front derailer's travel limit is wrongly adjusted, this may exacerbate chain drops. Last, as you are able, learn to slightly ease off the pedals as you make a front shift. This reduces the risk of dropping a chain.

Occasionally, you may lose the chain off the big ring, to the outside. This probably means your front derailer's travel limits were wrongly adjusted, but in any case, you can sometimes recover if you shift to the inner ring and keep pedaling (i.e. the obverse of the recovery procedure for chain drop on shifting to the inner ring). Many big chainrings have a pin sticking out - that's called a chain drop pin, and it often catches a chain that falls off.

2

Sounds like there are two problems: chain coming off the rear sprockets and bad derailleur adjustment. These two things are very likely connected.

A good reference for this type of repair is the Park Tool Repair Help article and videos on rear derailleur adjustment. The chain coming off may be caused by incorrect high or low limit settings, the chain jumping around is probably caused by incorrect indexing.

You should also check that your derailleur hanger is not bent. You can check visually - pick up the rear of the bike and look down the line of the chain. The derailleur cage should be parallel with the crank chainrings. If the hanger is bent a bike repair shop can realign it with a special tool.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.