What if you want to go lower than 27T with Shimano Ultegra? - Page 2

Originally Posted by gclark8

Just for the record I checked my new bike.
It has a 76 degree seat tube
40mm bb drop (650c wheel)
Triple chainring, 30/42/53 Sugino 9 speed
Cassette 12-25 9 speed HG-50
Front Derailleur FD-443
Rear Derailleur RD-6500 Ultegra
Chain HG-93 Ultegra

With the chain on the 30 (small) I can select the 25, 23, 21 tooth sprockets, no problems, however the 19 will fowl the bottom of the derailleur cage. Using a straight edge, I estimate a 28 small will be ok on my bike, a 26 small may work on a bike with a slacker (73 degree) seat tube, it won't work on mine.

The engineering PDFs from Shimano are all on frame design and set-up. Not the published service and parts files Richard is referring to.

Also it would be more productive for the original poster for Richard, Ozark Bicycle Service, and I to agree not to comment on each others posts from this point in time.

Originally Posted by gclark8

Yes, Try-Bike, not Tri-bike. Fair go, I'm over 55!!

Originally Posted by sergen

My bike has full ultegra components - brakes, FD, RD, triple hollowtech chainring and a 12-15 CS6600 cassette.

I know that Shimano's official line is to not go any lower than a 27 but recent forum users have suggested that this is just Shimano being conservative and that the rear derailleur could probably handle a 29T sprocket. Indeed, given that I never cross-chain I wouldn't have to worry about getting a new chain to cope with 52x29. I simply wouldn't use that ratio.

But since Shimano don't manufacture a sprocket any lower than 27T, what cassettes are available on the market that would allow me to get a 30x29 gear? I'm obviously looking for something that would not cause shifting problems with Ultegra components.

Many thanks

Originally Posted by Ozark Bicycle

Good one!
What shifters are you using?

Originally Posted by gclark8

SL-R440 Shimano.

I can start a seperate topic on the project or e-mail you the parts list.... Its a Sprint Distance Tri bike for oldies, it was fininshd on Tuesday, see: http://www.cyclingforums.com/t302530...n-offence.html

Originally Posted by sergen

My bike has full ultegra components - brakes, FD, RD, triple hollowtech chainring and a 12-15 CS6600 cassette.

I know that Shimano's official line is to not go any lower than a 27 but recent forum users have suggested that this is just Shimano being conservative and that the rear derailleur could probably handle a 29T sprocket. Indeed, given that I never cross-chain I wouldn't have to worry about getting a new chain to cope with 52x29. I simply wouldn't use that ratio.

But since Shimano don't manufacture a sprocket any lower than 27T, what cassettes are available on the market that would allow me to get a 30x29 gear? I'm obviously looking for something that would not cause shifting problems with Ultegra components.

Many thanks

Originally Posted by Ozark Bicycle

I prefer to read upright!

Anyway, I know what you were saying in your prevoius post and, IME, this is not wholly correct. So long as the chain will clear the bottom rear cross bar of the cage(clear enough?) on the 2 or 3 largest rear cogs, all is well. Those are your climbing gears. Why stay on the inner ring when the same gear is available on the middle ring?

The true limitations in the minimum usable size of the inner ring are 1)FD capacity, which can usually be slightly exceeded 2) the shape of the inner cage. Shimano will usually spec a min chainring size which, again can usually be slightly exceeded. In this case, we are exceeding FD capacity and recommended min chainring size by 2T.

Bottom line on using a 28T inner on an Ultegra Triple: it works. A 26T would be a bit dodgy on an STI road triple with a 52T outer and a 24T will probably be impossible.