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My trusty old CF racer was stolen the other day, and I'm looking for a replacement. I saw this bike at PlanetX and was intrigued. It's a full carbon bike with (last years) Ultegra components for a very reasonable price ( < $2k). It comes with a compact crankset and a short-cage dérailleur. The largest cassette it can accommodate is 11-28, which would give me a lowest gear of 34-28.

Not bad, and the same as I had before. But I live in the Alps and I frequently find myself in the lowest gear well before I hit the steepest parts of the hills, so I would like to have a lower gear, if at all possible.

I spoke to the vendor, and they said that it would (at least in theory) be possible to put on a medium-cage dérailleur and an 11-30 cassette. But I was wondering if it would be possible to have a smaller chainring in front instead. Can you get smaller than 34? Or would that not fit?

At some level I'm contemplating putting on a triple instead, but that seems like going back to the 20th century...

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You're talking about the 6800 range, right? According to Shimano, there exists an 11-32 cassette in that range. That on its own might help. But your reason for not going to a triple sounds like its based on testosterone, by the way, especially for where you live. –  PeteH Jun 18 at 8:30
    
Compact doubles give you pretty much the same range as a triple though, especially with an 11-32, + less mechanical problems, better chainlines and easier shifting. –  7thGalaxy Jun 18 at 8:36
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@7thGalaxy a compact will give you 34, a triple will give you 30, so when you say "pretty much the same" you're talking 10% or so difference. And I've never had an ounce of trouble on my triple - and that's the bike I ride on tours and long journeys. Where do you get your data that triples suffer from more mechanical problems? –  PeteH Jun 18 at 8:45
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My triple was always a faff to maintain and clean, and the gear changing between the inner ring and the middle ring could be tricky, when I switched back to a compact double I found I needed so much less work. Yes, 10% difference, but you'd never run a 11-32 on the back with a triple, you're more likely to run 12-27. With a 52-42-30, and a 12-27 you get about the same range as a 50-34 with a 11-32. –  7thGalaxy Jun 18 at 9:00
    
Actually, @Pete, I was looking at a bike at PlanetX, and they refuse to change the deraillleur to a medium-cage one, which would be required in order to accommodate the 32T sprocket. I suppose the real solution is to buy it through an LBS. I went to my LBS, and was wowed by a nice-looking Scott. But it's almost twice as expensive as ordering on-line. –  Popup Jun 18 at 12:03

3 Answers 3

up vote 2 down vote accepted

The smallest chainring that will fit on a compact double 110 BCD is 33t and they are quite hard to find ( Only TA or custom chainwheel manufacturers make them).

IMHO, what would be a true triple replacement would be something like a 11-30 with a 30/48.

Unfortunately, the 94 BCD cranks are almost all old MTB triples.

The problem with putting a large range cassette on that bike is compatibility with the Ultegra 11 spd shifters. I know Shimano 9spd is interchangable between road and mtn, but I'm pretty sure that is not the case 11 speed deraillers. Shimano does sell an 11-32 with that groupset Ultegra 6800, so they must think the medium cage derailler can deal with it.

http://www.chainreactioncycles.com/us/en/shimano-ultegra-6800-11-speed-road-cassette/rp-prod108686

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I'm picking this as my preferred answer, even though all answers were pretty similar. –  Popup Jun 30 at 11:25
    
What I did in the end was to go for a medium-cage derailleur and an 11-32 cassette. The place where I'm getting it won't sell me the Shimano medium-cage derailleur, so I'm going for SRAM instead. –  Popup Jun 30 at 11:27

If you are concerned about fashion or being ridiculed by cycling snobs, go for a compact double with as large a rear cassette as you can find. You can easily get a 32-tooth rear cog for most groupsets and may even be able to fit 11-34 if you're willing to go with something 3rd party.

If you actually want to be able to climb hills more easily, go for a triple as PeteH suggests. You will be faster and your knees will thank you in years to come.

While SRAM seem to be moving away from triples entirely, providing some super-wide cassettes for mountain bikes (but not road bikes AFAIK), both Shimano and Campagnolo offer a range of modern triples for road bikes.

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I don't mind being ridiculed... Until Monday I rode on a bike with down-tube shifters! (But it had street-cred, by virtue of being one of the first CF bikes available.) –  Popup Jun 18 at 12:11
    
down-tube shifters are hardcore ;) –  7thGalaxy Jun 18 at 12:59

Assuming that the ultegra hole-diameter is 110mm you won't get anything under 33 on the smaller chainring. That's why I'd recommend going for a medium cage dérailleur with the 11-30 cassette.

As you said, getting a triple would be 20th century... :D

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Yes, that sounds like the most reasonable solution. Honestly, if I could get a triple I would. –  Popup Jun 18 at 12:09

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