Converting my 11-25 to 11-27

PennState - 2010-04-19 4:47 PM My opinion would be the 12-27. I think you have am upcoming Ironman, and you will need the extra hill gears moreso than the 11 on the downhills. In general Ironman is about conserving energy and not pushing flats and downhills. Good luck

ADollar79 - 2010-04-19 7:53 PM How many times do you wish you had one more easy gear during a race?
How many times do you wish you had one more hard gear during a race?

The reality is the 99% of us would benefit more from the 27 than the 11.  The 27 will let you spin your legs rather than trashing them.  That will help you more on the run than the .5 mph your gain for 300 ft on the downhill. 

KathyG - 2010-04-19 8:41 PM Buy a 11-28 and get best of both worlds. I bought that cassette when Sram first came out with it in Fall of '07 to use for IMLP. It may be tricky to get older 10 speed to shift right due to the specs of Shimano stuff back 3-5 years ago the difference between high and low gears would work for 12-27 spread not greater. I was able to get it to shift well on my road bike and at times on my tri bike but sometimes I could either get the 11 or the 28 but not both so I'd always opt to adjust shifting so I 'd get the 28.

Oldteen - 2010-04-19 9:31 PM Spinning out top gear issue comes up a lot in cycling BBs- 11t vs 12t is pretty meaningless in distance events.  In typical 53t big ring, cadence of 105rpm is roughly 38+ vs 41+ mph respectively.  Honestly- on 40mph downhills you are prob better off tucking tight with those pedals level & coasting to conserving energy.  And if you are worried about maintaining 38 vs 41mph on the flats solo in 112mi bike leg, you should be getting off the damn computer & talking to Johan Bruyneel

KathyG - 2010-04-19 5:41 PM Buy a 11-28 and get best of both worlds. I bought that cassette when Sram first came out with it in Fall of '07 to use for IMLP. It may be tricky to get older 10 speed to shift right due to the specs of Shimano stuff back 3-5 years ago the difference between high and low gears would work for 12-27 spread not greater. I was able to get it to shift well on my road bike and at times on my tri bike but sometimes I could either get the 11 or the 28 but not both so I'd always opt to adjust shifting so I 'd get the 28.

Kido - 2010-04-20 12:57 PM I will get us back on point...

HOWEVER, let's pretend I wanted to do what I originally asked.  COULD you replace the last two rings on the 11-25 with the 24 and 27 from the 12-27 and have it work?  Anyone try it.

Kido - 2010-04-20 12:00 PM

once again, good advice from you!

I did not know of a 11-28.  I will look into that.  However, I don't think it's important enough to drop money on.  I have been cool on even the steepest stuff around here (12% in a lot of places) with my 27 and compact crank.  I can stand up on the rare and crazy steep stuff (up to 20%).

rkreuser - 2010-04-20 9:09 AM

Jim, according to Shimano and the LBS (when I checked 2 years ago), 11-28 isn't recommended - even though you can do it under some circumstances - the issue is the 28. Couple reasons - the shifting (as documented above), plus if you don't change the chain to a longer chain - in some cases - you can break the derailleur by accidentally shifting into 52-28. Not that you ever would on purpose, but it's a consideration.   

Lastly - due to the gearing gaps in an any of these bigger cassettes, you might end up missing that sweet-spot gears for the flats. On my 12/27, I'm missing a 22mph, 92rpm gear on when in my big ring. Gotta switch to small ring and run it way over at the bottom of the cluster, which is pretty cross-chained. I miss that gear. But you likely won't know that until you try it. And the chances of it being a gap you notice are bigger, obviously, on 11-28.

Just more for your brainz to think about.

gvey - 2010-04-20 3:00 PM

I'm assuming you're using Shimano?  Aren't the cassettes set up with the largest THREE cogs as one piece?  I know all my cassettes are.  Maybe the higher end cassettes (DA?) have separate cogs for the whole cassette but the largest three on my Ultegras are one piece.