Chain rub on smallest cog ??

[fr188]

Hello, am building up a Carlton Pro , when the chain is on the smallest cog on the cassette it rubs on the chain stay, any suggestions?
I'm running a ultegra 9 speed 25/14 cassette, I'm thinking it could be the smallest cog of 14 is too big for the limited space / I will try a 25/12 cassette when it arrives , that could be the answer maybe, I've set the limit on the rear derailleur to stop at the 8 th cog just incase the chain jams up, any thoughts.

 

[raleighnut]

A picture would be useful however I assume you mean the seatstay as opposed to the flat chainstay. Has the frame been 'coldset' from 126-130mm.

 

[fr188]

Yes sorry, it's the seat stay I've not cold set this bike as the distance is 128 mm

 

[fr188]

Well I should know if it is when I get the new smaller tooth cassette & post the results

 

[raleighnut]

Well I should know if it is when I get the new smaller tooth cassette & post the results

It looks like a 12 top gear might just clear to me, it is tight running more modern gear on old frames though, I run an 8 speed on a very similar frame (531c Raleigh Road Ace )

 

[ColinJ]

I think you are right - the smallest sprocket is too big. A similar problem is discussed HERE.

 

[fr188]

Yes I think I'll try the 12 tooth cog though I liked the idea of a the small cog being 14 as there's less jump gaps in the gearing, as it would be rare for for me to be riding on the 12

 

[Tigerbiten]

A tooth increases/decreases a sprocket/chainring radius by 2mm.
So going 14->12 will drop your chain by 4mm.

Top gear tends to be around 4:1 so if you drop your cassette by 2 teeth then by dropping your chainrings by 8 teeth will give you the same range of gears .........

 

[raleighnut]

This is the 'back end' of my 531c Worksop Raleigh (built by the same fellas) with a 12-25 rear Dura-ace cassette albeit 8 speed but the same spacing as the 9 speed Dura-ace cassette, wheel is a Shimano 10 speed with spacers behind the cassette.

 

[fr188]

That's a better photo, the chain rubs at the small bump where the rear dropout & seatstay are brazed together

 

[fr188]

Changed over to a 25/12 cassette, works a treat!
Yeah 14 tooth cog was just too big for the space available.