Tiagra 10sp, chain slips or jumps

[Tangled Metal]

Got a problem with my new bike. The Tiagra 10sp chain slips or jumps when the chain is running on the smaller rear cogs. This means I can only use the 2 largest rear cogs. It is worse as you change gears to the smaller rear cogs.

I'm not clued up on gears so need help.

Now looking at it logically I guess there's a tension issue on the chain. This means I need to make the rear derailleur straighten to pull the chain tighter.

Now I'm guessing the two small screws close together and lower down on the derailleur that are fairly flush with it are the upper and lower stop. These screws stop the chain being moved off each end of the cassette I think.

Above these is one, longer screw that's sticking out a lot. Is this what I turn to stop the chain jumping?

Now I know the above makes me sound hopeless but I've only done basic bike maintenance before and not done much at all with gears. Other than replace the simpler front derailleur. So help is needed.

[Brucey]

when you say 'new', how new is this?

it could be a stiff link in the chain, that'll make it jump....

to check for this, take the tension off the chain (by holding the mech forwards by hand) and turn the pedals backwards slowly. A stiff link should show itself...

cheers

[Tangled Metal]

I got it from planet x straight after Easter, that's about 2 weeks.

It is worse on the smaller cogs. By that I mean the largest two cogs nothing, third it almost.jumps when on largest chainring and does on the smaller chainring. Then the fourth biggest cog jumps, the next jumps a lot and I've yet to go into a smaller cog than that.

In my view this means something about the shorter distance around the smaller cogs allows for the chain to slip. Could be wrong, I'm trying to work it out.

[531colin]

Got a problem with my new bike. The Tiagra 10sp chain slips or jumps when the chain is running on the smaller rear cogs. This means I can only use the 2 largest rear cogs...............

If the chain is trying to jump onto the next cog, this is "ghost shifting" and is caused by the cable settling in with a bit of use. Try backing the barrel adjuster out 1/2 turn at a time and see if things improve.....if you count turns, you can always re-set it back where it is now. Correct cable tension is when its equally keen to change gear in both directions.

[Tangled Metal]

It's more like it's jumping within the same gear. Like it's moving around the cog by a tooth at a time. There is no change in the gear it is in.

[Spinners]

Is the cassette fully tightened?

A misaligned gear hangar?

[531colin]

It's more like it's jumping within the same gear. Like it's moving around the cog by a tooth at a time. There is no change in the gear it is in.

Quite. The chain climbs off the teeth for a split second, then goes back on, because the thing thats meant to steer the chain exactly to the cog (the cable tension) is wrong.
Or if its Brucey's stiff link, it will jump once every 2 turns of the pedals, or thereabouts, as the stiff link goes over the cog.
A properly adjusted gear won't slip unless you have worn the chain out in 2 weeks.

[Tangled Metal]

If that's the issue then it's a visit to a bike shop. Annoying! It's my only bike and I commute on it. Was hoping it's an easy job. Something like tighten or loosen a screw somewhere. A gear hanger is something I read about somewhere which said it wasn't a job for the inexperienced. Needs a special tool or knowledge I think.

[Tangled Metal]

It's more like it's jumping within the same gear. Like it's moving around the cog by a tooth at a time. There is no change in the gear it is in.

Quite. The chain climbs off the teeth for a split second, then goes back on, because the thing thats meant to steer the chain exactly to the cog (the cable tension) is wrong.
Or if its Brucey's stiff link, it will jump once every 2 turns of the pedals, or thereabouts, as the stiff link goes over the cog.
A properly adjusted gear won't slip unless you have worn the chain out in 2 weeks.

So how would that be fixed?

[531colin]

..............Now looking at it logically I guess there's a tension issue on the chain. This means I need to make the rear derailleur straighten to pull the chain tighter.

No. it can't be chain tension, and you don't need to "straighten" the mech.

......Now I'm guessing the two small screws close together and lower down on the derailleur that are fairly flush with it are the upper and lower stop. These screws stop the chain being moved off each end of the cassette I think.

labelled "H" and "L", the high and low gear limit stops.

..........Above these is one, longer screw that's sticking out a lot. Is this what I turn to stop the chain jumping?...........

Thats the "B" screw. Sets the clearance between the top jockey wheel and the cassette. pull the jockey wheel away from the cassette and you won't get crisp shifts.

[531colin]

It's more like it's jumping within the same gear. Like it's moving around the cog by a tooth at a time. There is no change in the gear it is in.

Quite. The chain climbs off the teeth for a split second, then goes back on, because the thing thats meant to steer the chain exactly to the cog (the cable tension) is wrong.
Or if its Brucey's stiff link, it will jump once every 2 turns of the pedals, or thereabouts, as the stiff link goes over the cog.
A properly adjusted gear won't slip unless you have worn the chain out in 2 weeks.

So how would that be fixed?

Cable tension is adjusted by the barrel adjuster, backing it out 1/2 turn or so at a time.
if there is a stiff link, first thing to try is working it with your fingers with a bit of oil. There is very little room for error once you set about 10 speed chains with a rivet tool.

[Tangled Metal]

Sounds like it could be a 10 minute job for an experienced bike techie or hour of cursing for me as I make it worse, followed by an hour at a bike shop to sort out.

[531colin]

Sounds like it could be a 10 minute job for an experienced bike techie or hour of cursing for me as I make it worse, followed by an hour at a bike shop to sort out.

About 2 mins to adjust cable tension on the stand, then a road check. Or just do it riding along, thats why they put cable adjusters on the downtube cable stops.