Cassette Change Questions

jcfitz7 Posts: 3
edited July 2013 in Workshop
Hello All,

I looked in the FAQ and didn't find an answer to my question so I thought I could ask here.

I ride a 2011 Specialized Secteur Sport Compact Double, stock.

The current drivetrain is a 50x34 ring with a 12-25t 9-speed cassette. The front derailleur is Sora and the rear is Tiagra with Tiagra STI shifters. It's a good set-up for me on the flats and on slight uphill grades.

However, on downhills I would like a little more low gear and on steep climbs I really struggle to keep my cadence up. I'd like to change the cassette to something in the 11-30t range (11-32? 11-34?) but I don't want/need to change out the rear derailleur unless it's unavoidable. I do understand that I may need a longer chain.

So, has anyone else made this type of switch? What is the largest # of teeth that the current derailleur will be able to accomodate? I do understand the principal of drivetrain capacity but I also know that many people have said that they have exceeded recommended capacities by a few teeth and not had any issues. I do not want to get into a situation where there are inaccessible gears in certain combinations.

I have looked in the Specialized Archive and I can not tell if the stock derailleur in 2011 was long cage or short cage but I suspect it was short cage. I do not have the bike in front of me at the moment so I can't check til Monday.

What does anyone think?

Thanks in advance for all of your thoughtful responses,

Jason Fitzgerald