serpico7

Considering converting from a compact double to a triple, partially for slightly wider gearing (though my current gearing is pretty wide at 30-101 gear inches), but mostly because I find that my sweet spot on flattish terrain is in the high 50s to mid 70s, so I am constantly switching chainrings (because my gearing is so wide, the large ring can't be used with the largest cogs). I figure with a 39t or 42t middle ring, I can stay in that ring for most flats/rollers. Also, I'd get the benefit of more closely spaced gearing, so I can maintain a steady cadence.

Am I nuts? I suppose I could use some of the larger cogs with the large ring on the compact double if I used a long-cage RD, but I'd still be cross-chained. And I figure the shifting on the triple will be at least as good as the compact double because the jumps between rings are smaller. The conversion probably won't cost much money because I'll buy used components and sell my compact double components, and I figure I can do all the wrenching myself.

If I want to use an Ultegra 6603 crank, do I just need to get a Shimano 6600 bottom bracket with the right threading for my frame (not sure if it uses English or Italian - it's an Orbea)? Or does the Ultegra crank come in English/Italian varieties (guessing this isn't the case, but want to confirm)?

DMF 

No you're not nuts.

The cage length has nothing to do with max. cog size.

Before you start asking specific questions about how to do it, first provide more info about the components on your bike. Otherwise the only answer is, "It depends".

oilman_15106

If I want to use an Ultegra 6603 crank, do I just need to get a Shimano 6600 bottom bracket with the right threading for my frame (not sure if it uses English or Italian - it's an Orbea)? Or does the Ultegra crank come in English/Italian varieties (guessing this isn't the case, but want to confirm)?

Bottom bracket is where you make the English/Italian threading determination. Make sure the bottom bracket also has the correct spindle length for a triple crank arm.

serpico7

Yes, I know. But the cage length does have something to do with whether or not you can use big-big or small-small combos (or how close to those combos you can get).

Currently, I have Ultegra 6600 double components, and an FSA SLK compact crank (with MegaEXO bottom bracket). Looking to swap brifters, crank, bb, front and rear derailleurs to Ultegra 6603.

Proximo

Spindle length doesn't apply in this case. The FC-6603 triple crankset shares the standard BB-6600 outboard bearing bottom bracket with FC-6602 double crankset.

DMF 

No it doesn't. The length of the cage affects *only* how much slack the tension arm can take up. What you're talking about is the affect of chainline variance - nothing to do with the dérailleurs.


Only the left brifter needs to change if you can find just the one.

6600 is a Hollowtech II design where the axle is of one piece with the drive-side crank. There is no bottom bracket per se - just external bearings. The bearings are the same for double and triple. Just install what comes with your new crank. Threading is probably English, but do some research.

Dérailleurs FD-6603 (-B or -F as appropriate), RD-6600-GS.

serpico7

Sure it does, for the reason you just stated - the longer cage can take up more slack. That means you can use a longer chain, which means you can use big-big combo (or big-2nd biggest cog), and still take up the extra slack so that you can use small-small (or small-2nd smallest cog).

Note that in my first post I mentioned my gearing range - though it's not explicit, that gearing range on a compact double means I have a very wide cassette (in this case, 13-30). Wide cassettes present a chain wrap issue, hence my mention that simply switching to a long cage RD might address part of the reasons I am considering converting to a triple.

Of course one of the problems with simply using a long-cage RD is that even if I could stay in one ring for the flats, I'd be cross-chaining a lot. With the middle ring on a triple, I'd have my "flat land" gears on one ring and a straighter chainline.

Thanks for the bb info - that's all new to me.

DMF 

Nope. Think about it.

N.b. that the standard method of determining chain length doesn't take the dérailleurs into account at all. You wrap the chain big-big (without going through the RD) and add two. When changing from double (53/25) to triple (52/25) one can use the exact same chain, even though the max. amount of slack increases (27T to 33T) and RD changes from short to long cage.


Cross-chaining is simply a function of the physical relationship of the rings. The configuration of the RD does not affect it.

serpico7

I don't disagree with this. I think you are misunderstanding my post(s). Let me try to be clear - on a double setup, if one uses a very wide cassette, chain wrap can be a problem. The sole purpose of the long cage is to wrap more chain than a short cage can wrap. See https://www.sheldonbrown.com/deakins/lowgears.html - scroll down to "Cross-Chaining - The rest of the story".

Yes, of course. My point was that even if I could easily make use of all the gear combos by using a long cage RD, I'd still be contending with cross-chaining for my "flat-land" gears if I decided to stay with the compact double.

DMF 

Yeah, that makes sense. A wide cassette introduces more slack.

For a Shimano road double (53-39) the delta ∆ is 14T. The short cage RD can handle the widest road cassette that they sell, 12-27 or ∆13T. Your compact (50-34?) is ∆16T, and your cassette is ∆17T. That's out of spec for the short cage, assuming you use it all (i.e. crosschain).

So you should be running a long cage, but doing so won't solve the problems you have with your compact. If you go to the triple, think in terms of a 12-25 or even 11-23 cassette. You'll thank yourself.

serpico7

Actually, to preserve my current granny gear (~30 gear inches - and I use it!), if I go with a triple crank with a 30t small ring, I'd need to use a 27t cog, so I was thinking 12-27, or maybe even using my 13-30 for a 26 gear inch granny.

DMF 

For steep climbing I use a 12-27, but 11-23 for more reasonable stuff. It's also possible to customize Shimano cassettes.

fmw

I wonder, then, why Campagnolo recommends medium RD's with cassettes with 29 tooth gears but not those with 25 or 26 tooth gears?

For the OP, I prefer triples to compact doubles personally but I think doing this conversion may be an expense that doesn't really net you much. I ride a triple and a couple of compact doubles and do fine with either setup. The triple is a little more efficient for me and more flexible but the compact double works just fine. Personally, I wouldn't worry about it. I think you will get used to what you have.

I'm not a fast rider. One thing I do, however, is change out the small chain ring on the doubles from 34 to 36 tooth. That lets me spend more time on the small ring at higher speeds and that improves efficiency a little for me. That with a 25 or 26 tooth cassette works out almost as well as a triple for my kind of riding.

DMF 

We were discussing that in another thread. The short cage should be able to handle 29T - assuming that all other dimensions than cage length are identical to the medium - but apparently the tension arm can't swing fully so it can't handle the extra slack from the wider cassette.

Al1943

I like that idea too but the OP says he needs a 30" gearor lower and he can't get there with a 36t chainring. A 36/30 combination is 32.4 gear inches.

serpico7

Right. I want it all - low-end gearing, but also a chainring that gives me most of my "flat-land" gears, so that I'm not constantly shifting rings or cross-chaining gears. This is why I'm thinking a triple conversion might be in order.