Slipping gears

Schoie81

Hi. Got problems with the gears 'slipping' on my bike. Started a week or two ago so last week I adjusted the limit screws and cable tension on front and rear deraileurs. Took it for a little test ride (up and down the road a few times) and all seemed fine. This Monday - 25mile ride and everything is running perfectly, no noise from the drive train and gears changing quickly and smoothly without exception. Problem solved. Or so I thought.... Went out last night, 3miles into the ride and it starts doing it again. It seems to be that its trying to change up into a higher (by which I mean smaller cog on the cassette) gear randomly and not quite moving onto it before dropping back down again. I've tried adjusting the cable tension slightly 'on the fly' but doesn't seem to make any difference.

The only thing I'm wondering now is if the cable is sticking in the cable outers and not moving smoothly. Could that be it? Or anyone suggest anything else? If it is a problem with the cable outers - can they be cleaned somehow, or should I look at replacing them?

Thank you!

dgunthor

sounds like the rear gears need adjusting, some good guides online - park tool, youtube etc or take to LBS

arlowood

Schoie81 wrote:

Hi. Got problems with the gears 'slipping' on my bike. Started a week or two ago so last week I adjusted the limit screws and cable tension on front and rear deraileurs. Took it for a little test ride (up and down the road a few times) and all seemed fine. This Monday - 25mile ride and everything is running perfectly, no noise from the drive train and gears changing quickly and smoothly without exception. Problem solved. Or so I thought.... Went out last night, 3miles into the ride and it starts doing it again. It seems to be that its trying to change up into a higher (by which I mean smaller cog on the cassette) gear randomly and not quite moving onto it before dropping back down again. I've tried adjusting the cable tension slightly 'on the fly' but doesn't seem to make any difference.

The only thing I'm wondering now is if the cable is sticking in the cable outers and not moving smoothly. Could that be it? Or anyone suggest anything else? If it is a problem with the cable outers - can they be cleaned somehow, or should I look at replacing them?

Thank you!

Sounds like you have diagnosed the potential problem.

Basically in any gear apart from the highest (smallest cog) the cable is pulled by your shifter against the tension of the derailleur spring to move the derailleur cage over the line of each cog as you move up the block from smallest to biggest cog.

If your chain is slipping back randomly from a bigger to a smaller cog then it suggests that the cable hasn't moved the cage quite far enough to keep the chain in position. In most cases a tweak on the barrel adjuster to add more tension (turn anti-clockwise) should sort things out. However if the cable is sticking somewhere along its length or in the shifter housing, fiddling with the tension will probably not cure the problem.

I'd go back to square one and disconnect the cable and if you can get at the shifter end of the cable, pull it out of the shifter housing maybe 20cms or so and spray as much of the bare cable you can see with some teflon lubricant spray or similar. Then pull the cable back and forth through the outer housing to spread the lubricant along as much of its length as possible. Also examine the cable for any broken/ frayed strands. If you find any then bin the inner and get a new one.

Re-connect and do your derailleur set up again from scratch. if you need some help then this video is one of the better ones IMHO

https://www.youtube.com/watch?v=SkzvfCaIbyQ

Schoie81

Thanks arlowood - I'll give that a whirl and let you know if it works!!

dee4life2005

I'd also check that your rear derailleur isn't needing a good clean. I've experienced slipping gears before caused by the pivot spring at the top of the jockey wheel cage being a little sticky and needing a good clean. If this is gunked up then the derailleur wont be able to take up the chain tension properly and you'll get intermittent slippage while putting some power down, most usually when accelerating.

Similarly for the pivot bolt (b-axle) where the rear derailleur attaches to the mech hanger.

Its worth giving this a quick check by moving it by hand and checking it springs back properly just to rule it out.

Also, you haven't fitted a new chain or cassette recently?

Schoie81

Cable checked, cleaned and oiled and all adjusted back up. 29miles last night and all running smoothly so it looks like that was the problem. :-)

Dee4life - about due a good clean, so will check out the rear derailleur, but as above - seems to be sorted now. Have had a new chain recently, but problem didn't start when I put that on, so assumed it wasn't connected to that....

Thanks for the suggestions guys...