Compact or Triple Crank?

[limewave]

Anybody riding mountain bike with a compact crank? If so, do you like it more or less than a triple and why? What are you gaining with the compact and what are you compromising?

I'm asking b/c the bikeshop guy just told me all xc racing is moving towards compact and that's what he recommended on my new bike. But I have never ever ridden compact on my xc bike. I'm a little nervous about it.

[Veronica]

I have a triple on my mtb, so take this with a grain of salt...

But I'd think about it the same way I did for my road bikes. What gear ratios do I need for my riding? Can I get something close with a compact? If I could, then I'd go with the compact.

Veronica

[SheFly]

I haven't heard of a compact for MTBs...

That said, I only use a double anyway. In most of our races/terrain here, there is no need for a "big ring". I find I can ride most anything, including a recent "dirt road crit" with just the double. This also provides more clearance for me with logs and rocks.

Like V said, think of the gears you will use. A triple is likely unnecessary (I take that back if you live in CA and are MTB riding in the hills!).

SheFly

[limewave]

I have no understanding of gearing. The numbers mean nothing to me--I just don't speak that language. I just go by how things feel. Maybe you guys can shed some light for me.

Right now I have a 9-speed
22-34-44 with 11-32 in the rear

What I'm lookin' at:
20/47 front
12-36 on the back.

[Veronica]

(I take that back if you live in CA and are MTB riding in the hills!).

SheFly

Yeah, I don't think I could give up my little ring on my mtb. I think I spend 90% of every ride in it.

Veronica

[jessmarimba]

I know the bf seriously dislikes the idea of 2x10 gearing for mtb. In his opinion, it's moving that way because that's what companies are making, and not b/c that's what people really want. But I'm sure it depends on where you're riding (and who you ask - but he's been riding for eons, so it's not like he's not in bike shape).

Personally, I wanted to go 1x9 before I got hurt and lost most of my leg strength. I was spending the majority of every ride in the same 2-3 gears. But...now I'm very happy with a triple

[bellissima]

limewave, are you sure is a 20/47? it seems like a very odd number, most double cranks ( what you call compact) start at 24 for the small ring and go up to 44 for the big ring. A size 47 will be too big on a mountain bike. A 20 teeth granny gear would be super easy (too easy) and a 47 would be too hard. Using a double really depends on the area you ride and you level of fitness. Here in SoCal most of the fast racers are using doubles and really like them, but you must consider that they don't use the granny gear at all so having it make no sense and they tend to ride bigger gears anyways.

[laura*]

limewave, are you sure is a 20/47?

I think she typoed: The El Mariachi specs say 27-40.


I wouldn't apply the term "compact" to any of the mountain doubles. If anything, they are the opposite of compact. Here are three types of mountain double:

1) A 22-32-44 crankset with the 44 tooth ring removed (and possibly replaced with a bash guard).

2) Like above, but with the middle ring replaced by a larger ring at the factory - perhaps 22-36.

3) True doubles meant for use with wide range 10 speed cassettes. SRAM seems to like the ratios 26-39 and 28-42. The FSA crank on the El Mariachi splits the difference at 27-40.

---

In the 2000-oughts, the MTB industry settled on a 22-32-44 crank with a 9 speed 11-34 (or 11-32 for flat landers) cassette as optimal. The problem is that a lot of gear ratios are duplicated. There might only be 13 distinct ratios.

With the change to 10 speed cassettes, it is possible to provide nearly the same lowest to highest range while eliminating many duplicates by using 2x10 gearing. I'm not sold on this though - this change does lose the lowest and highest gears!

I think SRAM has a (old) patent on cranks with 1:1.5 ratio chainrings. They found that this jump provides for smooth easy quick shifting. (26 times 1.5 is 39!) This wasn't useful until the 10 speed generation 'cause the 1.5 ratio is just a bit too big for narrower range cassettes.

Shimano's DynaSys ratios also claims better shifting than before.

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The 3x9's lowest gear (22:34) is gone from the 2x10 system. The 3x9's next lowest gear (22:30) is almost the same as the 2x10's lowest gear (26:36).

At the other end, the 3x9's highest gear (44:11) is also gone from the 2x10 system. The 3x9's next highest gear (44:13) is comparable to the 2x10's highest gear (39:11).

And of course, those of us who are thrilled to use a 29er 36 tooth 9-speed cassette to provide an even lower gear on a 26er - well, we're left out in the cold.

---

Do you need the extremes of gear ratios? Do you need to zoom down a highway to get to a monster climb?

[Aggie_Ama]

DH just put 2X10 on his Specialized S-Works Hardtail, loves it. I wish my Epic was 2X10. Why? I spend very little time in my big ring with the smaller cogs in the back which is what you lose the most. So less weight and eliminates parts I am not using. I would only need those for one race I am targeting training for that has a large road element to it. If I can save enough I will be adding a hardtail 29er with a double on it to my fleet. As Laura said, there is redundancy in the gearing that is taken away with 2x10.

Many of my Cat 1 friends are running 1x10 now, yes even several women.

[Becky]

I'm running a mock 22-32 double on my 26er, since I currently have the big ring "limited out". I can't say that I miss the 44 at all- I just don't use it. For me, the shifting gets a little weird when I'm in the 22 and the higher-geared half of the cassette, but I think that's a quirk of my particular frame. I will likely move to a 22-34 or 24-36 combination, and replace the largest ring with a bash guard.

Can you try out a double-equipped bike before committing to it?

[laura*]

I wish my Epic was 2X10. ... So less weight and eliminates parts I am not using.

I think this is an exciting time for bicycle drivetrains! In the past (or since Shimano invented HG gears) the emphasis was on simply providing enough ratios. Now in the 10-speed era the focus is on the quality of the shifting.

SRAM is rumored to be working on a whole line of two speed internal geared hubs. I could see them introducing a single chainring 2x10 system that gets the "10" from a cassette, and the "2" from the hub. SRAM hasn't been a big name in hubs - this way they may get more of their product on a bike.

Two speed cranks already exist, but they are expensive and rare. Currently bottom bracket standards are in flux. I could see Shimano making a cheaper two speed crank that uses a new bottom bracket design. That would be an alternate way to 2x10 gearing. Shimano's big enough to push through a change to frames' bottom bracket shells. This crank would keep buyers locked to Shimano's cranks.

Note that this is the first year of 10 speeds on lots of mountain bikes. (Last year's XX was for racers.) It might be a while before the optimal configuration is found.

[limewave]

After reading everyone's responses, I'm pretty excited to try the 2x10.

[Reesha]

I would think switching from little ring to big ring and back and forth would be a fairly big jump. Potential for cross chaining? I don't know. I like the smoother shifting of my triple...

[Aggie_Ama]

The large ring on the 2x10 is not usually as big as the large ring on a triple so it would be more like shifting little to middle. The little ring I think is a little bit bigger. But if you play around with a gear ration chart you will find a lot of combinations in a triple are duplicates. I believe the bottom line is with a double you lose your biggest gear (hardest effort in big ring) and maybe your absolute granny.

Not for everyone but I think you may like it Limewave since you are a racer and have said you liked the more aggressive bikes anyway. Have fun!

[tzvia]

There is so much overlap in gears that you only loose a couple of the highest gears if your 44 gear fell off and left you with 32/22. No biggie. 2x10? If you already have a 3x9, you don't have to go the full 2x10 route (cogset, shifters, crankset), you can do a 2x9. I did so on both my MTBs, by removing the 32 and 44, and putting a 36 on the middle position. I then chose to put a bash guard on in place of the 44 but that's optional. I still have all my low gears, and lost the highest gear (which I can't remember ever using). I then adjusted the front derailleur stop to prevent it from going far enough to throw the chain to the now missing 44 chainring. Tada! 2x9 for a little elbow grease to remove the crankset and remove chainrings, a bashguard and chainring.

So now I am either climbing or I am not, just two choices up front. The chainline is improved, there is less slack chain in the lower gears as I removed two links (no longer need to wrap around a 44 ring) and there is a bashguard protecting my calves from being sliced open by a spining chainring in a wreck. I've been riding this way since about this time last year and I will never go back to a triple.