Chain/ derailleur issue.

[LarryDuff]

My son tells me that on his 105 equipped bike when he is in the small ring and using the smallest 3 or 4 cogs the chain is touching and rubbing against the part of the chain thaix coming through the lower jockey wheel. Pic attached. Anyone any ideas as to what could be causing this?
P.s. the gears have recently been serviced

 

[Paulus]

It could be that the indexing needs a tweak, maybe to tighten the cable a little bit. Is the shifting nice and crisp across the cassette?

 

[LarryDuff]

It could be that the indexing needs a tweak, maybe to tighten the cable a little bit. Is the shifting nice and crisp across the cassette?

Doesn't feel as crisp as it did just after the service.

 

[faster]

The correct answer is to just not use those combinations of gears, but if he insists on riding the bike like that, shortening the chain may help although you must be certain that the chain is still long enough to work when using the largest gears at the front and back.

 

[Sharky]

Could we have a photo of the RD when on a big/big combination please.

 

[PeteXXX]

It could need a twiddle on the B screw..

 

[Ajax Bay]

Take a (one inch) link out of the chain, provided that when the chain is cross chaining in large large the RD cage is still wrapping chain eg pointing to 7 o'clock (or higher), say (as @faster but with chain shortening as the primary thrust).
The cassette looks like 11-30 so with a compact chainset, the RD should have sufficient capacity.
Also agree with @PeteXXX that a turn or two of the b screw would be a good idea (but not related to the OP issue).
Edit: OP has shared large/large image since this post: the chain is only just long enough (but cannot wrap in small/small, likely because the RD has a short (SS) cage).

 

[presta]

the gears have recently been serviced

Did this service involve fittting a new chain? It looks like the chain's too long, and it's likely to be if it was fitted straight from the box without cutting it to length. Don't shorten it without checking that it'll still go over the two big ones first though, unless you want your gears wrecked.

 

[Dogtrousers]

B-screw was my first thought, because I didn't read the OP properly and I thought it was fouling on the biggest sprocket. But then I looked at the pic and it's not like anything I've ever experienced. It does look like the chain might be too long, but as @presta says be very careful if you shorten the chain because a too-short chain is dangerous, so make sure it's long enough to accommodate big-big. Riding in little-little should work with no problem other than maybe a bit of noise on a properly set up drive train.

 

[LarryDuff]

Could we have a photo of the RD when on a big/big combination please.

 

[Ming the Merciless]

That is big small

 

[LarryDuff]

That is big small

D'oh!! Of course it is.

 

[LarryDuff]

That is big small

Sorry for the delay in the pics but he is 7 timezones away

 

[faster]

It's not really my area of expertise, but the chain length looks pretty good to me. I'd certainly be wary of taking a link out.

Could this be a short cage derailleur with not enough capacity for such a large cassette? The model numbers on it will confirm.

I'm still of the opinion to live with it and just not use those gears!

 

[craigwend]

It's not really my area of expertise, but the chain length looks pretty good to me. I'd certainly be wary of taking a link out.

Could this be a short cage derailleur with not enough capacity for such a large cassette? The model numbers on it will confirm.

I'm still of the opinion to live with it and just not use those gears!

This >>>>. Could this be a short cage derailleur with not enough capacity for such a large cassette?