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  1. #1
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    Converting my 3x10 to 2x10 question?

    I purchased a used bike a while back that was set up as a 3x10 with an XT M781 (3x10) front derailleur and 24-36-Bash. When I recently got the bike serviced, they told me to get a 2x10 front derailleur in order to prevent chain rubbing and to enable for proper shifting throughout all the gears.

    Assuming I'm ok with with the range of gears with a 24-36 set-up, would I need to get a native 2x10 crankset as well as front derailleur? My XTR shifters can adjust between 2x and 3x so that shouldn't be an issue.

  2. #2
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    It is probably fine as is. Adjust the outer limit screw to stop the derailleur from going too far. Have you had chain rubbing problems?

  3. #3
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    Before I took the bike in, I was having shifting issues but not chain-rubbing issues. The mechanic said in order to get it shifting properly, there would be rubbing in the middle ring unless I got a 2x10 front mech.

  4. #4
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    Try dialing in your shifting before you spend any money. I don't care enough to change my bikes' drivetrain setups, but I believe best practices is to use the middle and small positions for a 2x setup with a triple derailleur and shifter. Do you have trouble shifting up or down?

    If you have a burning need to spend more money, a new front derailleur might help. But you shouldn't actually need it to make this work well.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  5. #5
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    When you think about it, what they are telling you makes no sense. They are basically saying 3x drive trains can't be set up to shift correctly. The fact that the big ring has been removed has no affect on shifting performance.

  6. #6
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    The bike shifts fine now. Yeah Eric, it doesn't make much sense except I thought there may be some rubbing do to cross chaining with when in the middle ring up front and high gears in the back. I'll just tinker with it for now and see what happens.

  7. #7
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    It does make sense. If you understand true 2x systems. A true 2x crankset is centered so that you can use all 10 gears on the cassette without cross chaining (or rubbing) on the front derailleur. A 3x crankset can't do that. It will rub because you cross chain. The two cranksets are built differently with different ring offsets. Also, a 2x FD has a slightly wider cage to help allow for the range of gears. You need both to not have any rubbing.
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  8. #8
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    Quote Originally Posted by eric1971 View Post
    It is probably fine as is. Adjust the outer limit screw to stop the derailleur from going too far. Have you had chain rubbing problems?
    Quote Originally Posted by AndrwSwitch View Post
    Try dialing in your shifting before you spend any money. I don't care enough to change my bikes' drivetrain setups, but I believe best practices is to use the middle and small positions for a 2x setup with a triple derailleur and shifter. Do you have trouble shifting up or down?

    If you have a burning need to spend more money, a new front derailleur might help. But you shouldn't actually need it to make this work well.
    Quote Originally Posted by eric1971 View Post
    When you think about it, what they are telling you makes no sense. They are basically saying 3x drive trains can't be set up to shift correctly. The fact that the big ring has been removed has no affect on shifting performance.
    these gentleman are spot on and making the change is no issue performance wise.

  9. #9
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    Do not know for sure about 2x crankset, but I was under the impression that positions of the chainrings on them (smallest one and the next one in size) are exactly the same as on 3x cranksets. Chainline measurements are different, but it's because of the way chainline is measured.

    However, after converting from 3x9 to 2x9 and using old 3x front derailleur for about a year I changed my 3x FD to 2x for the following reasons -
    1. it was a time to change FD anyway
    2. 2x FD seats lower, and there is much less chance to drop chain (due to the frame design of FS bike I could not lower 3x FD)
    3. the cage on 2x FD is wider or it's design is different, so it accommodates 2x setup better

    Now I can use the whole 11-34 9 speed cassette without any rubbing, and it was not possible with 3x FD before.

  10. #10
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    I just installed my 2x9 specific crank yesterday keeping my XT M771 3x9 front derailleur. No issue. I get all gears with no derailleur rub. It is possible!
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