New chain issues

Brookert

Brookert

Brookert

Soldato
Joined
13 Dec 2010
Posts
4,219
I've got a brand new SRAM 9 speed chain to replace a very old stretched one. The problem is, when I cut it to approximately the same length as the old one (taking into account the stretch), the highest gear causes the chain to rub on the derailleur when on the lowest front chain ring.

Take another link out you say? Well when I do that, it's too tight in the lowest gear and highest on the front chain ring. The derailleur leg is fully extended and causing resistance.

Any suggestions?
 
As in smallest cog front and smallest cog back. The chain rubs against itself from the cassette to the derailleur. This suggests it's too slack.

Take a link out and that problem is solved. Put it in largest front and largest rear and it's then too tight.

Is it just asking too much to expect the extremes to work. Odds are you'd never use those gear combos, at least the lowest ones.
 
Brookert said:
As in smallest cog front and smallest cog back. The chain rubs against itself from the cassette to the derailleur. This suggests it's too slack.

Take a link out and that problem is solved. Put it in largest front and largest rear and it's then too tight.

Is it just asking too much to expect the extremes to work. Odds are you'd never use those gear combos, at least the lowest ones.
Click to expand...
Ah right I get you. You can sometimes rotate the mech to prevent this. At least I can on my shimano da rear mech.
 
Is it a sram rear mech?

Shimano always have about 2 fingers clearance between the chain and the jockey wheel in the smallest cogs.

If you set sram that way it ends up top short in big and big. You could adjust the B screw inwards to sort of ghetto tighten it in that gear but that could knock out the gear change elsewhere.

Realistically you should ride small and small so should cause any issues..

Is the chain going between the two jockey wheels and dnot going oer the tab that is between them?
 
for next time, even now :-
Count the links when you replace the chain, just lay it in a serpentine with 10 links a turn, or, if you have the spare bit from last time, you know how much to cut.

my derailleur arm is near vertical when I have biggest front and smallest rear.

I've not yet seen a benefit from rotating the mech/rd itself, even though my latest mech offers that, since it is not modifying the spring tension.
 
I'd always advise to size it yourself as it could be too short before.

Generally big front and small rear would give vertical cage on most bikes, newer 11 speed road bikes it's slightly more cage back. Single ring setups look silly in the smallest as it has to cope with the big dinner plate low gear.

The B screw is only for setting the distance between the lowest gear and the jockey wheel. Top little tension and you'll hear the jockey wheel ride on the cog
 
Also despite it being called chain stretch, chains don't actually stretch, but the inner links wear which in turn increases the pitch. So basically if you old chain was the correct size just use the same about of links with your new chain are before :)
 
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