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  1. #1
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    2x10 and 3x10 crank...what's the difference

    Other then the obvious third ring is that a difference in the cranks...are the chain rings in the 2x10 crank actually positioned so that they would fall in between the 3x10 rings (i.e. the inner ring is physically further away from the frame and the outer ring is closer to the frame?)...or they exactly the same...

  2. #2
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    On some 2 x 10 cranksets, they use a different bolt pattern that may limit your chainring and/or bash ring options.

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    Quote Originally Posted by JQHansolo View Post
    are the chain rings in the 2x10 crank actually positioned so that they would fall in between the 3x10 rings (i.e. the inner ring is physically further away from the frame and the outer ring is closer to the frame?)

    Yes

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    Quote Originally Posted by JQHansolo View Post
    Other then the obvious third ring is that a difference in the cranks...are the chain rings in the 2x10 crank actually positioned so that they would fall in between the 3x10 rings (i.e. the inner ring is physically further away from the frame and the outer ring is closer to the frame?)...or they exactly the same...
    Yes, 2X10 and 3X10 chainlines are set up specifically for the number of rings. For a 3X10 the chainline is set off of the middle ring, for a 2X10 the chainline is set off of a point exactly between the two rings. So basically the small ring is further from the frame and the big ring is closer on a 2x10, not by a whole lot, it's only a matter of a few mm's. But it does make for more usable gear combinations, i.e. reduces cross chaining, and reduces gear ratio overlaps, i.e. front and rear gear combinations that are nearly identical, which are inherent in any tripple ring set up.

    So yeah they are different, and in some ways the 2x10 is more efficient.

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  5. #5
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    One thing 2x10 offers is a more efficient chainline. It matters more than people give credit for. 3x10 system or 3xanything always will be a bit skewed in the extreme ends of the rear cog. When I set up an old road bike I played with the chainline. I was using a Phil Wood bottom bracket. It allows you to move it right to left a few millimeters either way. It was amazing the difference you felt when you found the sweet spot on the chainline. It is most apparent if you have some rollers to test it on.

    So for me, after switching to 2x10 on the road bikes, I am doing it on the mountain ones as well. I live up in the high country, 7,000' so I have to climb hills, lots of them. In fact I think there is some perverse physics going on here. I seem to always be climbing, never descending. I do keep a spare front crank with higher gearing for when I take a trip to the lowlands (like when there is snow everywhere and I want to ride) and want more top end. It only takes a few minutes to swap it out.

  6. #6
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    Quote Originally Posted by bt View Post
    I've heard 3 ring cranks actually have a better chainline when used in 2 ring config. than 2 ring specific cranks.

    Am I heard wrong?
    Yes you are wrong. Nothing changes in the 3x by taking 1 ring off. You can't change how they are mounted.

  7. #7
    bt
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    I've heard 3 ring cranks actually have a better chainline when used in 2 ring config. than 2 ring specific cranks.

    Am I heard wrong?

  8. #8
    bt
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    Quote Originally Posted by mucky View Post
    Yes you are wrong. Nothing changes in the 3x by taking 1 ring off. You can't change how they are mounted.
    I'm aware you don't change the position of the cranks when you remove the third ring but my point is that the remaining two rings are in a better position than a 2x specific crank.

    I could be wrong.

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    Quote Originally Posted by bt View Post
    I'm aware you don't change the position of the cranks when you remove the third ring but my point is that the remaining two rings are in a better position than a 2x specific crank.

    I could be wrong.
    The inside ring on the 3x is still farther in than on the 2x, creating more angle as you shift down. The 2x inner ring is better. The 3x middle ring is better than the outer of the 2x. The bigger benefit of the 2x is the efficiency. In the 3x, you have a lot of wasted gear ratios as they repeat themselves. Far less with the 2x

  10. #10
    bt
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    leaving wasted gear ratio efficiency out of this discussion, could it be true that the small ring on the 2x being further outboard makes it even worse than the small ring on a 3x since both are too far out to begin with?

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    My experimentation with the Phil Wood bottom bracket proved it to me. I put C-Record parts on an old Colnago Mexico. I wanted to still ride i,t so I used the 1 generation Ergo shifters and a Campy Moscow wheelset. So nothing was lining up when I put it together. Finding a variety of offset sizes in old campy bottom brackets is an exercise in finding the Ark of the Covenant. So I bit the bullet and got a Phil Wood. The way it mounts allowed for the movement left to right. I looked at Sheldon Brown's web page for wisdom on chainline, which got me in the ballpark. But moving it a couple of millimeters made it just ride better.

    Well, when I got the compact crank on the CX-1 the experience was similar. So I have been slowly changing the herd-o-bikes to 2x10. It just seems more efficient to me. With all the same, comparing my Dura Ace triple equipped (before I changed it) Litespeed. It was 3 mph slower on the rollers over 25 miles. After I swapped to the SRAM Red compact crank, it went up 2 mph. Now it could be a placebo halo effect, but it does seem to be more efficient to my legs.

    Now your experience may be different, but then if we where all the same, there wouldn't be the variety of frames and gruppos out there, each with a devoted set of followers.

  12. #12
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    Quote Originally Posted by bt View Post
    leaving wasted gear ratio efficiency out of this discussion, could it be true that the small ring on the 2x being further outboard makes it even worse than the small ring on a 3x since both are too far out to begin with?
    I'm not sure what you mean by "both are too far out".

    Anyway, the 2x will be better. It will offer a better overall line. The 3x will be better on the 1st and 2nd cogs, and then the angle of the chain will increase as you shift down. The 2x is a little more centered to the cassette. There is a little angle to the chain in the 1-3 cogs, evens out 4-6, and gets a little more angle 7-9/10.

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    I just found this thread when searching on Yahoo for this topic, hence it's resurrection.

    I have read through everything here but am still not 100% on 2x10 setups.

    Are 2x10 setups meant to allow shifting throughout the entire cassette on either chainring? Or are you supposed to change chainrings as you move up or down the cassette?

    Also, in regard to the chainrings, ignoring the distance between the two rings, are they centered in relation to the cassette? In other words, is the chainline offset from the inner ring to the big cog equal to the offset between the outer ring and the small cog?

  14. #14
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    Quote Originally Posted by komekomegaijin View Post
    I just found this thread when searching on Yahoo for this topic, hence it's resurrection.

    I have read through everything here but am still not 100% on 2x10 setups.

    Are 2x10 setups meant to allow shifting throughout the entire cassette on either chainring? Or are you supposed to change chainrings as you move up or down the cassette?

    Also, in regard to the chainrings, ignoring the distance between the two rings, are they centered in relation to the cassette? In other words, is the chainline offset from the inner ring to the big cog equal to the offset between the outer ring and the small cog?
    A 2x crank lets you use more of the cassette with each ring. Using the small/small combos are still not recommended.

    Big/big is fine on most crankc, especially the triples without the outer ring.

    No current mtb crank has a chainline that centers the rings on the cassette (135/142 hub width) as they should for a "proper" chainline. The double-only cranks are better than a triple, but still worse (further outboard) than the triple with the outer ring removed and all are WAY outboard of a proper chainline.

    Current triple chainline is 50-51mm
    XTR 2x Race: 48.8
    XTR 2x Trail (3x w/o outer ring): 46.8
    Cassette (proper) chainline: ~45mm
    Last edited by shiggy; 08-14-2012 at 07:01 AM.
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  15. #15
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    Thanks for the reply Shiggy. Answered my question perfectly.

  16. #16
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    Quote Originally Posted by bt View Post
    I've heard 3 ring cranks actually have a better chainline when used in 2 ring config. than 2 ring specific cranks.

    Am I heard wrong?
    I agree with this. I think the chainline from a converted 3x setup using the small and middle ring positions works very well and benefits from being slightly inboard of the dedicated 2x setups.

    I tend to use the small ring as just a bail gear, and being slightly farther inboard makes for a better chainline with the gears I actually use with the small ring (mostly 1 & 2, sometimes 3). The middle position ring (now the "big" ring) is also in a better position for using the whole cassette. So basically I use my bike like a 1X setup except for the few times I need to granny grind up something, and this chain-line works better than if it were pushed farther out.

    Also, the heaviest loads I put on my chain are when I am climbing, and this happens on the lower end of my cassette. I'm usually just topping off some DH speed in the highest gears of my cassette.

    Contrary to what some people think (including myself until a few years ago) the chain-line on many newer 3x cranks are already pushed outboard, so the small and middle positions are actually not THAT far off what you find on dedicated 2X setups. Just a tad inboard.

    Now, it you are talking about using the middle and outer rings from a 3x setup, that IS a pretty bad chainline.
    15mm is a second-best solution to a problem that was already solved.

  17. #17
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    Quote Originally Posted by Odessa434 View Post
    I've heard 3 ring cranks actually have a better chainline when used in 2 ring config. than 2 ring specific cranks.

    Am I heard wrong?
    This exact question was asked and answered already.

    In short, it depends on how you approach your use of the two rings.
    15mm is a second-best solution to a problem that was already solved.

  18. #18
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    Thank you Shiggy and Kapusta. IMHO some of the posts in this thread should be rehashed to a new sticky topic as there seems to be some misinformation about the differences between double and triple cranks and their chain lines floating around and a search often produces tons of fluff.

    I have converted a (9sp) SLX triple to a 28-40T double with 2x10 XT rings and I like the new chain line a lot. I ride in the small ring most of the time and only shift to 40T in fast sections and downhills, the 28T ring is almost like a 1x9 setup for me (with a 11-34 cassette and 650b wheels). But, when I cross the chain to small/small, the chain rubs slightly against the 40T's shifting ramps so I see how moving the rings a few extra millimeters outboard would help in this scenario if one really wanted to ride all 9 gears in the rear with the small ring (I don't).

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