rough feeling smallest sprocket

[e-rider]

I've noticed that when using my smallest sprocket the gears feel quite rough. If I change up to the next one it improves and up one more it's silky smooth!

The gears are all set correctly and everything works perfectly so why does the small cog (12T) feel so bad. I know that small sprockets are less tolerant of poor chainline but in the large chainring the chainline is pretty good. And, on my mtb the smallest cog is an 11T and that feels pretty good!

any ideas?

 

[Jonathan M]

Smaller sprockets mean the links have to curve around the smaller circumference, so it will just be the chain not "liking" being curved in such a tight diameter. In fact I'm sure that I read somewhere (here, C+, or somesuch) that smaller sprockets are less efficient due to this.

 

[Mr Pig]

Or it could just be worn.

 

[ufkacbln]

As a tendency wear would cause jumping as opposed to simply feeling rough

 

[Mr Pig]

As a tendency wear would cause jumping as opposed to simply feeling rough

It can just cause the gear to feel rough too though. However usually when you fit a new chain.

 

[accountantpete]

Best bet is to turn the bike up and slowly rotate the pedals whilst observing how the chain settles on the sprocket - it might give an idea as to the problem.

 

[jimboalee]

Smaller sprockets mean the links have to curve around the smaller circumference, so it will just be the chain not "liking" being curved in such a tight diameter. In fact I'm sure that I read somewhere (here, C+, or somesuch) that smaller sprockets are less efficient due to this.

This is one of the weirdest things in cycling. Smallest sprockets always feel roughest.
I will agree with Jonathan, and add that the smallest has less teeth engagements.

I changed from a 12-23 to a 13-25 and the 13 is smoother than the 12. About the same as the 13 on the old cassette.

It's something that must be lived with. I haven't found a way of lessening the roughness of a 12 or less sprocket.

 

[02GF74]

This is one of the weirdest things in cycling. Smallest sprockets always feel roughest.

they cannot be as smooth since the chain is made of short links as opposed to say a totally flexible rubber belt.

the rough ness is related to the cog diameter and link distance so for smaller cogs the chain jerks more

 

[Perfect Virgo]

A very interesting post. I have just fitted a new cassette and new chain, at the same time as replacing both wheels. Like the OP I have things set up pretty accurately and the larger sprockets are nice and smooth but the 13 and 14 are noisy and engage less smoothly. The old worn components had presumably "settled" into place with each other.

That said, I lopped almost 10 minutes off my 40 mile loop. So, a definite efficiency gain!

 

[02GF74]

I have just fitted a new cassette and new chain, at the same time as replacing both wheels. Like the OP I have things set up pretty accurately and the larger sprockets are nice and smooth but the 13 and 14 are noisy and engage less smoothly. The old worn components had presumably "settled" into place with each other.

noiseness, shouldn't do that - how old is you rear shifter? when the shifter spring starts to go, it has less tension to pull the chain onto the smallest sprockets, eventually failing to move them altogether.

also clean you gear cable.

 

[Mr Pig]

also clean you gear cable.

Take the chain off and move the rear dérailleur in and out with the shifter. Look carefully at how it moves, look down from above and see how it lines up with the gears. It should snap crisply into the correct positions when moving on both directions. If it's sluggish or fails to line up then clean/replace the cable. Assuming the dérailleur itself is clean, well lubed and not too worn.

Also keep an eye on the plastic guide on the underside of the BB, if you have one. It can get chewed up and snag the cable.

 

[Perfect Virgo]

Thanks for the replies chaps. The derailleur is a 105 from the late 80s and in pretty good shape but I plan to overhaul it and lube the cable next.

 

[Perfect Virgo]

A careful re-check of the high adjustment limiter revealed it was fractionally too low. Secondly, I tightened the tension aduster screw where the derailleur bears against the frame as the top jockey wheel was a little too far forward. Nice smooth changing now.