Inconsistent gear change problem

[Dan Broadberry]

Hi all,

I'm having a problem with my rear derailleur. I have a 7 sprocket casette and when I change from 5th up to 6th the derailluer does not always move the chain onto the correct sprocket. However, strangely when I then change the adjuster from 6th (the chain is actually still on the 5th sprocket because of the problem) up to the 7th (top gear) the derailleur moves the chain through 6th and then correctly onto 7th. Bizarrely, however, the problem doesn't always happen. Sometimes the shift from 5th to 6th occurs just fine.

Originally I thought this may just be a simple misalignment but after servicing my bike and aligning both the front and rear derailleurs correctly the problem persists.

The most frustrating thing about the problem is that when I have the bike up on the stand for a service and I work through the gears in both directions, on all chain rings, the rear derailleur changes to the appropriate sprocket perfectly. I cannot re-create this problem with the bike in the stand as it only occurs while I am actually riding the bike making it very hard for me to work out what is actually wrong! This problem also only occurs from 5th up to 6th, all other shifts in both directions work fine i.e. 7th down to 6th is fine as is 6th down to 5th!

I am truly baffled!!!

Any ideas?!

Thanks in advance for any help.

Dan

 

[jpr95]

Clean/lube all the pivot points on the derailleur, lube your shift cables (or replace them if they're rusty), clean/lube the cable guides beneath the bottom bracket. Then, if the problem still persists, start bumping up the tension on your rear derailleur by giving the adjustment screw a quarter turn counter-clockwise at a time.

 

[CAMPYBOB]

Worn chain and/or freewheel/cassette teeth?

 

[slmaurice]

Sometimes I like to disconnect the cable to the rear derailleur, remove the rear wheel and make sure the derailleur pivots back and forth freely. Then pull on the cable to make sure it slides back and forth with minimal drag. If both these tests seem ok, then it's time to start looking at worn components. Check your chain stretch and inspect the small cog gears on the rear derailleur.

 

[alfeng]

Quote:Originally Posted by Dan Broadberry . The most frustrating thing about the problem is that when I have the bike up on the stand for a service and I work through the gears in both directions, on all chain rings, the rear derailleur changes to the appropriate sprocket perfectly. I cannot re-create this problem with the bike in the stand as it only occurs while I am actually riding the bike making it very hard for me to work out what is actually wrong! This problem also only occurs from 5th up to 6th, all other shifts in both directions work fine i.e. 7th down to 6th is fine as is 6th down to 5th!

I am truly baffled!!!

Any ideas?!



Does your bike happen to have a rear suspenion?

 

[Dan Broadberry]

thank you for all the responses, I had a fiddled around while I was out and about today with the cable and used the adjuster screw to increase the tension which seems to have resolved the problem. However I will have to give this a thorough test tomorrow to make sure it wasn't fluke.