ultegra sl chainset & tiagra bb...........problem??????

SIMON1978

hey guys, any ideas on my problem, just fitted an ultegra sl double chainset on my work/training bike which has tiagra groupset on. Since fitting it when i am anything past halfway down the rear sprocket and in the small ring at the front the chain is catching the big ring on the way round, i cant for the life of me work it out, is the tiagra bb cupset compatable withe ultegra chainset or is there something else which may be wrong, cheers guys :roll:

andyrr

Is it defintely the same chainring combo on the oldl/new chainsets ?

SIMON1978

No sorry i forgot 2 say that the old tiagra chainset was a compact and the ultegra sl is a standard double!!

topdude

Most likely it is just down to the Ultegra big ring being thicker in profile than the tiagra one was. So the chain rubs on the inside of the big ring when on the smaller rear sprockets.
I have had this to varying degrees with various chainsets.