# My bike changes gears by itself...help!



## LSUDJB13 (Dec 27, 2007)

Alright i've ran into my first problem. My bike hops between gears when i put any kind of load on my pedals. Any reason why its doing this? Thanks for the help


----------



## Linga115 (Mar 23, 2008)

ghost shifting. usually caused by a out of tune derailleur. if this is a new bike, your cables probably stretched and need it re tuned. there are a bunch of tutorials online on how to do it. or if your LBS has a service plan with new bikes take advantage of that.


----------



## sponger (May 14, 2006)

I sorta had this problem a little while ago and it turned out to be a chain in need of lubrication. However, that does not mean that it isn't the problem described above.


----------



## calikid22 (Feb 17, 2008)

I had this problem not long ago too. Go onto youtube and watch some videos on rear derailleur adjustments and see if that helps any. Worked pretty well for me.


----------



## wmodavis (Jun 21, 2007)

automatic transmission


----------



## mike23 (May 11, 2008)

Another thing to check is that the cable is not getting snagged. As I once had this problem and the cable would not move fully in the leader when I changed then I'd put on the power and bingo gear change. But most likely you just need to tune in the gears as the cables have stretched.


----------



## ZoSoSwiM (Dec 2, 2005)

You might have whacked your dérailleur hanger.. it might be out of align and no adjusting will help.. unless you get a straightener. 

I have no luck with them... so I bought the park dérailleur straightener... Great tool!


----------



## Parrotnot (Feb 28, 2008)

The way the gears work is that the levers (or other device) on the handlebar move a cable which runs along the frame to the deraileur (which moves the chain to a different cog). The lever on the handlebar has different settings. Each setting pulls the cable in a particular amount from its loosest setting - and each setting should put the deraileur at the right point for a particular gear selection.

What it sounds like is that the deraileur is no longer sitting exactly at the right point for each gear.

There are several things that take place as a bike gets used which will make this happen.

1) The cable stretches a little bit, so the deraileur is no longer pulled quite enough. There's a simple knob that can be adjusted to compensate for this. This is by far the most likely cause of your problems.

2) The deraileur gets muddy and lubricant is washed off it (so when the cable is pulled or released a bit the deraileur doesn't quite move as far as it is being told to). Cleaning and oiling it might help.

3) The cables get mud and grime on them and no longer run so smoothly. I've heard different advice on whether its a good idea to lubricate these, but on a cheaper bike I'd not hesitate (however you might like to ask other people first).


----------



## Ken in KC (Jan 12, 2004)

*1st Step*

Before you go through a bunch of adjusting, I suggest you change the barrel adjustment on your shifters (and perhaps rear DR, depending on the model).

Move the barrel adjuster one way in quarter turm increments for 2 complete rotations and note whether the shifting improves or gets worse. If the shifting improves, you're on the correct adjustment path. If there is no improvement or shifting gets worse (or you seem to shift correctly but you're cassette is in the wrong gear), reset the barrel adjustment to its original position and adjust the opposite of what you did previously in quarter turn increments.

This will likely fix your ghost shifting issues.


----------



## LSUDJB13 (Dec 27, 2007)

Sweet Thanks for all your help. i'm going to put some of yalls advice to good use tomorrow. I hope to get the problem fixed before this weekend.


----------



## nachomc (Apr 26, 2006)

Did you recently put on a new chain?


----------



## LSUDJB13 (Dec 27, 2007)

Thanks for all the help. I couldn't wait until the morning to fix it so i watched the video and tightened those cables up and it works beautifully. I hope all problems are this easy. thanks again


----------



## Kyle0614 (May 6, 2008)

I wish my bike could do that, but then again I'm just lazy lol


----------



## Xenotime (Jun 1, 2006)

Clean your derailleur, and re-lubricate your cable with oil. Give it a pull before you start adjusting it. So it is stretch to the maximum. 

Re-adjust the derailleur like the other members told you. It could have jumped because the cable is having friction in the cable housing. Lubricating the cable helps. I can't really explain to you how to adjust the derailleur. Is too much writing, go to YouTube and find out about it. If you still have problems, leave me a PM. 

Cheers.


----------

