This may have been covered somewhere before, but I couldn't find it if it was. So here's the question - right now if we want a R700 compact drivetrain we're locked into the 50/34. I would want some additional low end gearing but also the flexibility of climbing in a spinning gear (since I'm old and mostly weak), so could I easily change the cassette from stock to an 11-27?? I'd be looking at 11-12-13-14-15-17-19-21-24-27 and use Ultegra componentry. So it would come down to removing the stock 16 cog and adding the 11 in its place (from a stock 12-27). How easy is this and is it costly for someone (i.e., LBS or other builder, not me) to accomplish this?
Thx for any info and opinions on this minor alteration in stock cassette/gearing.

you can ditch the 16t cog, your lbs should be able to order an 11t cog for you.

This may have been covered somewhere before, but I couldn't find it if it was. So here's the question - right now if we want a R700 compact drivetrain we're locked into the 50/34. I would want some additional low end gearing but also the flexibility of climbing in a spinning gear (since I'm old and mostly weak), so could I easily change the cassette from stock to an 11-27?? I'd be looking at 11-12-13-14-15-17-19-21-24-27 and use Ultegra componentry. So it would come down to removing the stock 16 cog and adding the 11 in its place (from a stock 12-27). How easy is this and is it costly for someone (i.e., LBS or other builder, not me) to accomplish this?
Thx for any info and opinions on this minor alteration in stock cassette/gearing.
Maybe you know what gears you need, but if you haven't considered just using the 12/27, do so. I've raced many times with my biggest gear being a 50-12 with no problem. You probably don't need that 11. - TF

To convert a 10sp 12-27 to 11-27, you'll need a 12t next to outer cog, an 11t outer cog, and an 11t lockring. It's an easy thing to do, all you need is a lockring tool and chain whip to hold the casette.

Myself, I don't have a need for an 11 cog for my 50x34 compact, but I'm not racing criteriums.

Thx for good input all, I don't pull that hard on the flats, but with an FSA 36/50 (actually SI crankset) I have found myself spinning on downhill sections with the 12-27 (in the 50-12) and having to coast with no power output due to loss of gearing. It wouldn't be used a ton cuz I have no sprint, but I hate spinning around when I could be generating something maybe with the 11. Sheldon Leonard's gain ratio chart would give me an 8.8 in a 50-11 vs an 8.1 in the 50-12. OK, so I'd need the 11 lockring also and just slide in the 11 and remove the 16, sounds doable.

I have found myself spinning on downhill sections with the 12-27 (in the 50-12) and having to coast with no power output due to loss of gearing.

110 rpm in a 50/12 is 35 mph, at which speed most people are faster in a tight tuck than they are sitting up and pedalling. Also, in a tuck they are resting, so they are better able to tackle the next climb after that rest.

BTW, who is Sheldon Leonard as it relates to bicycles? I thought he was a hollywood mobster, or something like that.

Oooops, I meant Sheldon Brown. I only know 2 Sheldons, must've picked the wrong one! Yeah I guess coasting is a good option, I'm never spinning at 110 for very long (if at all) so it's not a speed thing, more a comfort thing. Figured a 50-11 would a slower spin with more efficient power transfer on "milder" descents compared to 50-12.. I don't think I'd ever be using a 50-11 routinely, 'cept maybe on my Angliru climbs. It was just the loss of the 16 cog would probably not be missed at all in the 34 and probably not missed much in the 50 either. And I'd be gaining a bigger "cruising" gear on those minor descents where I could still pull instead of coast. Probably a minor advantage at best, like I said more a comfort thing. Sorry about that Sheldon thing. Too many Clif blocs I guess.

It's easy to do but you'd be giving up a better cog, probably the 16, to make room for the 11.

Al

Maybe true for the 50 chainring, wouldn't miss the 16 in the 34 at all -- but I think my ideal setup might be a 52-36 with a 12-27. I'm just kicking around the idea of using the existing Shimano compact where we're locked into the 50-34 and trying to play with the rear cassette to get as close to the "ideal" setup as possible. Using the 11-27 might be as close as I can get.

You're not "locked in" to 50x34. Lots of companies make different size chainrings for 110mm BCD cranks. Stronglight and FSA for example.

50/36 with 12-27 or 12-25 sounds better to me, but you've got to go with what's right for you.