Chain Skipping

[TooManyMatts]

I'm baffled. My MTB gears are changing all on their own. This happens whilst riding under lots of power and when spinning along. It happens over bumps sections too. All that happens is that the chain hops onto the cog below or above on its own accord.

 

 

 

The problem is that when the bike is on the work stand the gears operate perfectly.

 

 

 

I'm riding a Scott Genius mc 20 (dual susser)with a mix of LX and XT if that matters.

 

 

 

Any suggestions?

 

 

 

 

[Sacrosanct]

First: Get those cables replaced!

If your chain is new and you have an old(er) or worn chainwheel and cassette/cluster you will have problems when the chain is under pressure.

 

I'm no expert, but when you replace your chain it's best to replace the cassette/cluster as well. My advice would be to use 2 chains and swop them every 100km or every other ride so everything lasts a little longer...

 

[Capricorn]

i had something similar happen, turned out to be the derailleur cable tension. ?But hopefully the more knowledgeable can give their opines.

[TooManyMatts]

Its been a long time since anything has been changed - except the cables. Those were done recently.

[Sacrosanct]

Whip out the vernier scale and measure the teeth on the cluster to see if they differ on the gears.

[quickdraw]

Sounds like your cable housing is too long/short between the front and rear triangle.

When the bike is on the stand the gears will shift smoothly but when you sit on the bike the rear shock compresses and the section of housing that runs between the front and rear flexes(not sure if that is the correct term) and affects the tension on the inner cable causing your gears to jump up and down.

 

To cut a long story short - try running a longer housing and check that the cable routiing is correct.

quickdraw2009-08-11 12:22:22

[Speeddemon]

I do not know much about this sort of things but could it be the tensioning spring in the deraileur ?

[TooManyMatts]

Quickdraw may have hit the nail on the head. This problem started recently and it happens that I changed my gear cables recently... Sounds like too much of a coincidence. I'll go have a look.

[Sacrosanct]

You are Baffled,

I am dumbstruck,

and he is flabagasted!

Good luck man...

Sacrosanct2009-08-11 12:20:54

[Speeddemon]

Sounds like your cable housing is too long/short between the front and rear triangle.

When the bike is on the stand the gears will shift smoothly but when you sit on the bike the rear shock compresses and the section of housing that runs between the front and rear flexes(not sure if that is the correct term) and affects the tension on the inner cable casuing your gears to jump up and down.

 

To cut a long story short - try running a longer housing and check that the cable routiing is correct.

 

So obviouse  !!!

[droo]

+1 for cable routing. Deflate or detach your shock and check how your cables behave through the whole travel range. If they're going to kink or pull or do anything silly you'll be able to spot it before you cut the housings.

[TooManyMatts]

yeah It looked like a little too much cable in the wrong place (from the bars to the frame). I'll see how it goes on Friday.

 

 

 

Thanks guys

[Johan Bornman]

 

 

I'm no expert' date=' but when you replace your chain it's best to replace the cassette/cluster as well. My advice would be to use 2 chains and swop them every 100km or every other ride so everything lasts a little longer...

 

[/quote']

 

You are right about the former and wrong about the latter.  Poor advice cost people money.

[Guest Big H]

Just a thought...... were you able to measure the cassette with you vernier and compare it with the chain. If you were able to accurately measure the cassette along the curve you may be onto something revolutionary!!!!!!!!!