Ultegra 12-27T 9 Speed Cassette - Will it fit?

superkenners

Have got myself a new set of Fulcrum 3's for my Spec Allez, just wondering what sort of cassette would be best/fit them.

I have a Tiagra groupset on it at the moment with the short cage rear derailleur, seems a bit of a squeeze to get onto the 25tooth on my current stock cassette (11-25T), wondering if I am asking for trouble fitting a Shimano Ultegra Cassette 6500 9 Speed 12-27T on the new wheels to use, alternative seems to be 12-25T.

Cheers

ChrisSA

What is your chainset size? Unless your chain is very short I cannot see how a 25T is a squeeze.

I've run a 28T on the back with a Tiagra RD-4400 and a 50/34 chainset without problems.

Select a cassette that fits in with your capability and the profile of your ride.

SDK2007

Nice - I'm planning to get some Fulcrums 3's for my Allez.

A 12-27 cassette should fit fine.

superkenners

I'm running a 50/34 on the front, it might be my chain is a bit short as I dropped a few links out of it when I replaced the old one (though this was due to the fact that the chain it came with was shorter than the chain I replaced it with).

Looking to do more sportives, thought 12-27 would be better than a 11-25 as bit easier on the hills, can keep it on the 50 rather than dropping down then.

AndyI

The Tiagra short cage mech will work with a 27t sprocket at the back, but you need to bear in mind the "chain wrap capacity" which is 31. You get that number by subtracting the smallest chainring size from the largest, and the smallest rear sprocket from the largest and adding the reults. So, 50 -34 = 16 and 27 -12 = 15. 15 plus 16 = 31 ergo, it will work fine! To get the correct chain length there are various methods but the simplest is to remove the chain and wrap it around the largest chainring and largest sprocket without going through the rear derailleur. mark where the links meet and add one full link ( ie. two half links) . That will give you the correct chain length. If in doubt there are some very good free videos on the web which take you through how to do it.

superkenners

Cheers AndyL, great tip!

ADIHEAD

Superkenners wrote:

I'm running a 50/34 on the front, it might be my chain is a bit short as I dropped a few links out of it when I replaced the old one (though this was due to the fact that the chain it came with was shorter than the chain I replaced it with).

Looking to do more sportives, thought 12-27 would be better than a 11-25 as bit easier on the hills, can keep it on the 50 rather than dropping down then.

Just remember you'll wear the chain out much quicker, possibly causing failure if you ride cross chain - ie. big front ring to big cassette ring The chainline should be kept as straight as possible, ie. avoid last 2 big rear cogs when on the 50, smallest 2 rear rings when on the 34 to avoid the chain being strained

See under the heading of 'Chainline Criss-Cross Gears' on this link: http://www.sheldonbrown.com/gear-theory.html