Rear derailleur...which screw to adjust?

[Mazz]

Shimano tiagra rear derailleur. On small chainring and smallest/highest gear at back (ok, I rarely use this combination), the chain rubs against the mech body.

Which screw needs adjusting so there's some clearance between chain and mech? Thanks.

P.s
Gears indexing seems reasonable enough.

 

[screenman]

There is never a need to go on those two, it puts to much bend in the chain for one thing.

 

[Paulus]

Small to small is not a good combination,
but from the photograph, the chain could be a link too long to pull the rear derailuer down enough.

 

[All uphill]

Small to small is not a good combination,
but from the photograph, the chain could be a link too short to pull the rear derailuer down enough.

Too short?

Too long, methinks.

 

[roubaixtuesday]

Yeah, shorter chain, not screw adjustment required.

But check big/big is OK before riding.

 

[Paulus]

Too short?

Too long, methinks.

Indeed, my mistake. Edited now.

 

[Mazz]

Yeah, shorter chain, not screw adjustment required.

But check big/big is OK before riding.

Big-to-big is fine.

I purposely made the new chain 2 links longer than the previous one, because the new cassette had 2 lower gears than the previous cassette. Maybe 1 extra link would've sufficed.

 

[roubaixtuesday]

Big-to-big is fine.

I purposely made the new chain 2 links longer than the previous one, because the new cassette had 2 lower gears than the previous cassette. Maybe 1 extra link would've sufficed.

Sorry, check big/big *after* you've shortened the chain was what I meant.

Because if too short, it'll rip the drivechain apart under load.

 

[Ming the Merciless]

Maybe 1 extra link

It’s always an even number because of the alternating inner and outer plates.

 

[Mazz]

It’s always an even number because of the alternating inner and outer plates.

I see what you mean. The 2 ends of the chain wouldn't join up otherwise.

 

[Gunk]

I always set the chain length small cog to small chain ring, it should be tight enough to just tension the derailleur, that chain looks too long.

 

[raleighnut]

There is never a need to go on those two, it puts to much bend in the chain for one thing.

I used to inadvertently use that combo when coming home from work, Glenfield Rd. starts off pretty steep but then flattens off gradually until after a mile it's level but being a bit tired after a 12hr nightshift I'd just click another gear on at the back until the 'clattering' started then it was a 'whoops' and select the middle cog moment. Bike didn't seem to mind too much but then it's only a 3x7 set up on the old Ridgeback (52-42-30 with a 13-28 on the back)

 

[Mazz]

I always set the chain length small cog to small chain ring, it should be tight enough to just tension the derailleur, that chain looks too long.

Thing is, if I remove a paired link, is there a risk the chain will become too short and cause damage, like @roubaixtuesday says?

 

[Gunk]

Thing is, if I remove a paired link, is there a risk the chain will become too short and cause damage, like @roubaixtuesday says?

Firstly I would check how tight it is on the large chain ring to large cog, also check how stretched the rear mech is, if there is some capacity, then I would shorten the chain slightly. It won’t need much, just enough to stop it running on the jockey wheel.

 

[richardfm]

Thing is, if I remove a paired link, is there a risk the chain will become too short and cause damage, like @roubaixtuesday says?

If the chain has a quick link remove it and check the chain length big-big without being through the derailleurs. To be the right length it will appear to have one more link than it needs.
Method 4 on this page https://www.parktool.com/en-us/blog/repair-help/chain-length-sizing
Other methods are available.