Skipping Gears

badhorsy

HI all,

I've been having some issues with my Shimano 105 gearset. If anyone can give some advice, it would be most appreciated.

Every now and again the rear gears will skip down under pressure. Until tonight this had never happened on the front, but on my way up a hill tonight on the lowest rear cog, the chain jumped from the middle chainring to the lowest on the front.
I've also been having problems shifting upwards on the front. Shifting from the lowest chainring to the middle seems to only work around half the time. If it doesn't work, I have to shift down and then try again.
I've tightened the cable tension, and now everything feels nice and tight, but it hasn't made too much of a difference...

Also, does anyone know why when I'm shifting down the front gears, there is sometimes two clicks, rather than one. Is this the 'trim' function I've read about?

rich_e

The indexing of your gears probably needs looking at, as they can go out alignment, especially on new bikes.

It's not too difficult to do yourself, I'm no mechanic and I managed (using a guide I had in a magazine), took a while, but I had everything running perfectly afterwards.

I'm sure there are some online guides.

Soni

badhorsy wrote:

HI all,

I've been having some issues with my Shimano 105 gearset. If anyone can give some advice, it would be most appreciated.

Every now and again the rear gears will skip down under pressure. Until tonight this had never happened on the front, but on my way up a hill tonight on the lowest rear cog, the chain jumped from the middle chainring to the lowest on the front.
I've also been having problems shifting upwards on the front. Shifting from the lowest chainring to the middle seems to only work around half the time. If it doesn't work, I have to shift down and then try again.
I've tightened the cable tension, and now everything feels nice and tight, but it hasn't made too much of a difference...

Also, does anyone know why when I'm shifting down the front gears, there is sometimes two clicks, rather than one. Is this the 'trim' function I've read about?

Sounds like cable stretch, increase the cable tension on the barrell adjuster, if thats not enough then you need to drop down to the smallest ring to relieve all tension and slacken off the cable clamp on the seat post and pull more cable through.

The two clicks is the trimming function.