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  1. #1
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    Shimano SLX M660 vs M670 crank?

    Hi all, I'm rebuilding my drivetrain and decided on a mix of SLX and XT components. I wanted to try 2x10 but do some road riding to get to trails, so I decided to stick with the 3x10. After a lot of reading, the SLX crank seems like a pretty good bang for the buck. Is there any difference between the M660 and M670? Jenson has the M660 (without BB) for $89 and Chain Reaction has the M670 (with BB) for $170. Is there any reason to choose one over the other?

  2. #2
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    Nearly the same arms, and the M670 is for 10sp, I would go with M660 as it also works with 10 speed.

  3. #3
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    There is also a 10 speed version of the M660, that's what Jenson is selling minus the BB (there is a -10 on the arms by the part number). I am not aware of any significant performance gains between either and I prefer the M660 look.

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    Thanks for the info!

    As a follow up: The 3x10 is a 42/32/24 setup. I've got 26" wheels and I ride mostly XC with a few steep hills (no real mountains near me). Is there any reason to go with a 11-36t cassette? Or will I be OK with 11-34t? I searched for this beforehand but it seemed a lot of questions dealt more with 2x10.

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    It's hard to judge if you would need the 36, I am larger, 215 or so and ride a 5" trail bike with a 24/36/bashguard crank and 11/34 in the rear and I have not missed the 36th, I climb mostly in 2nd gear which I believe is a 30 tooth. What are you riding with now and do you feel the need for the lower gearing?

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    Quote Originally Posted by RSabarese View Post
    I prefer the M660 look.
    True, I hate the new Shimano designs, The old M950 and M750 cranks were very nice to look at IMO.

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    I'm 6'2" and 180 lbs and ride a hardtail bike. Right now I've got a 42/32/22 crank with an 11-32 cassette. I don't really do a lot of extended climbing, maybe on a trip or two a year but that's about it. Otherwise things are relatively flat. I ran the numbers through Sheldon Brown's gear calculator and think I'll be OK with the 11-34 with the new 42/32/24 crank. Looks like the 11-36 would give me more climbing advantage but I honestly don't think I ever go all the way down to the 22/32 combo that I have now.

    P.S. I'm kind of a see it to believe it person, so running those numbers through the gear calculator really showed me the merit of a 2x10 setup. I'll keep that in mind for further down the road...

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    First of all you need to know if your BB is compatible with the SLX crankset. Otherwise you need to buy a BB too.
    If you will use a 3 chainrings crankset I believe that you wouldn't need a 36-11 cassette. Usually, the riders only used this type of cassette when they use 2 chainrings crankset...

    Cheers

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    Thanks, I'm going to go with the 11-34t. It looks like I'm gonna need the BB as well. I called the mfg and the bike has a 73mm English threaded frame, so the SM-BB70 used with the SLX cranks should fit.

  10. #10
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    According to Shimano site SM-BB70 is the correct one...

    During the assembling of the crankset, it's necessary to be careful with the spaces... The frame with 73mm you should use only one spacer... I think... Please read the manual, they have all explained...

    Cheers

  11. #11
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    Thanks again for the confirmation, I'm fanatical about reading/following manuals so I shouldn't have a problem there

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    OK here I go again, the engineer in me has to ask lots of questions...
    I'm trying to match a front derailleur to the M660 crank and want to make sure I get the right chainline spec. I read that it would be a good idea to go with a better/stiffer/more robust front derailleur, so I was looking at the Shimano XT-M780 FD. Its chainline spec is 48.8mm while the M660 crank specifies a 50mm chainline. Is the difference negligible?
    The SLX M670 front derailleur specifies a 50mm chainline, should I call it good enough and go with the SLX FD instead of the XT? I was going to assume that it's all Shimano 3x10 components so they should all work, but figured it's easier to ask now than have problems later.

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