Chain always wants to go onto smaller ring

[geopat]

Advice please. My chain slips badly when pressure is applied when I'm on the large outer ring. I have a Shimano compact drivetrain. On the large ring it will not go into the lower gears without the chain slipping to the small ring or even slipping off the inside of both rings.

Can someone advise what I need to adjust to ensure the chain stays on the outer ring when shifting between high and low gears. Note there are no issues when moving the gears up and down on the small ring.

Many thanks in advance.

 

[Andy_R]

The chain is obviously scared of you and the power you are asking it to transmit. It feels inadequate, and unloved....or you could try adjusting your cable tension & hi/lo stops......(2 screws on the front mech that limit how far the mech can move)

 

[raleighnut]

Increase the tension on the cable a bit, if it was OK before Do Not touch the limit screws unless you know what to set them to (my guess is that the cable has stretched a tad)
Of course it could be your bike telling you not to cross-chain.

 

[bonsaibilly]

"On the large ring it will not go into the lower gears without the chain slipping to the small ring"
"Note there are no issues when moving the gears up and down on the small ring"

I'm confused, as these two statements appear to contradict each other?

Taken in context, the first statement suggests that "go into the lower gears" means moving on the rear cassette. But then you say there are no issues moving the gears up and down on the small ring, which I assume you mean to be the rear cassette too. But clearly there *is* an issue if the chain is slipping around up front when you shift the rear. Unless you have established with certainty that the rear setup is not responsible for the problem then I wouldn't be saying there are no issues with it.

It's possible you may have the upper limit screw on the front derailleur too tight, this would cause the derailleur cage to be too far inwards towards the frame when you were nominally in the higher front gear, which could have the effect of forcing the chain back down onto the small front ring.

How old is the chain?

bb

 

[Yellow Saddle]

Do a search on this site for a description of chain skating and chain skipping and then modify your question. I find it difficult to understand what's happening.

 

[mjr]

Do a search on this site for a description of chain skating and chain skipping and then modify your question. I find it difficult to understand what's happening.

^^ This.

At the moment, my guess is that the chain's slightly too short (so big-big is basically impossible and chain tension forces it to shift at the front) but I may have completely misunderstood what's happening. Photos of the front mech from above when the big-small, big-big, small-big and small-small gear combinations are selected may help rule out some obvious possibilities.

 

[geopat]

Apologies for the confusion. Big front, small rear is fine. No issues at all on small front.

Big front, large rear is the issue.

Hope this helps. Thanks.

 

[Ajax Bay]

When you're on the large chainring, do not use the largest 2 sprockets. Yes, just don't use them. While not riding, put the chain round the large chainring and the largest sprocket, what direction (use the hours of a clockface as metric) does the cage point?

 

[gbb]

In basic terms geopat, you're asking too much big to big. You should always be trying to achieve the straightest chain line possible...and big to big is the worst chain line you can achieve ( as well as small to small). You'll kill your chain and transmission quicker doing it.
Why do you ride big to big ?

What compact are you using ? 50/34 perhaps...if you find the 34 is not much good to you, leaves you spinning too fast, then perhaps consider replacing it with a 36, 37, 38, whatever suits your terrain better. As an example, I live in a flat area. My former bike came with a 50/34....which is useless around here so I spent most if not all my time on the 50t...now that will encourage you (wrongly) to use poor selections and a bad chain line...so I replaced my 34 with a 40t...perfection for me and my terrain and a much better range of usable gears.

My experience may not even remotely apply to you but is just an illustration of inappropriate gearing that encourages poor or limited gear selection...which might be why you're running big to big.

 

[Nigelnaturist]

I will put my tuppence in, whilst it is advisable not to use large/large ect it should work with undue short term effect (it does on my triple so it should on a double) unless the mechanics are at the limits of their design, as @raleighnut pointed out if it was working the hi/lo limit stops should be fine and it is likely to be wear in the outer cable (opposed to cable stretch as @Yellow Saddle has pointed out on many occasions) as @mjr pointed out the chain could be a bit short but again if the problem is new not likely unless the chain has been replaced and it being to short, if you can remove the chain link wrap around the large front and large rear and see how many whole links there are a (a link is an outer an inner link) there should be an overlap of 1-2 links.

 

[mjr]

When you're on the large chainring, do not use the largest 2 sprockets. Yes, just don't use them.

Depends how many you've got to start with... but even with only 5, I try to avoid big-big.

 

[mjr]

In basic terms geopat, you're asking too much big to big. You should always be trying to achieve the straightest chain line possible...and big to big is the worst chain line you can achieve ( as well as small to small). You'll kill your chain and transmission quicker doing it.

While not great, I think small-small is still usually less twisted than big-big on most bikes. It all depends on the BB axle length, chainset and rear wheel selections, though.

 

[geopat]

Apologies for the confusion. Big front, small rear is fine. No issues at all on small front.

Big front, large rear is the issue.

Hope this helps. Thanks.

Just for clarification I don't ride Big, big but at the moment my bike is an 11 speed instead of an 18 speed. If gear 18 is Big, smallest then I don't have gears 10 - 16 as the chain wants to always go on the small front chain ring in these gears or it comes off the chain ring altogether when pressure is applied.

 

[User6179]

Just for clarification I don't ride Big, big but at the moment my bike is an 11 speed instead of an 18 speed. If gear 18 is Big, smallest then I don't have gears 10 - 16 as the chain wants to always go on the small front chain ring in these gears or it comes off the chain ring altogether when pressure is applied.

Big chain ring bent maybe , take the chain off and use the mech as a guide to see , only way I can see your problem happening is if chain ring/crank is not lining up with the cassette at the back .

 

[User6179]

"On the large ring it will not go into the lower gears without the chain slipping to the small ring"
"Note there are no issues when moving the gears up and down on the small ring"

I'm confused, as these two statements appear to contradict each other?

I think when he is on small ring at front then everything works fine but when on the large ring on the front and tries to change up to an easier gear on the back then his chain drops onto the small ring on the front .