Can a non boost crank be used on a boost frame?- Mtbr.com
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  1. #1
    dmo
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    Can a non boost crank be used on a boost frame?

    Im thinking of gettimg a new bike with a 148 boost rear and want to be able to use the parts from mynold bike which is non boost. Is there a way to.use the non boost crank? DO I need a new BB and/or chainring? Can a 6mm offset chainring be used with a boost crank?

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  2. #2
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    I think the offset differential is actually 3mm and you're limited on chanring size. Many frames are okay, but not all. Not a ton of people do it, so it might be hard to find info on your (new) particular bike other than just trying it. You're chain line will actually be better on the larger gears.

    Can you actually put a spacer on it and secure it properly?

  3. #3
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    As said, it's only 3mm. You might get away just fine until time to replace the chainring, at which time you could get the "boost offset" one (3mm). Many companies like wolftooth and 1up make stuff like this. There are possibly other solutions too, like spacing your cranks a little further out on the drive side. Typically, most cranksets run some spacers on the ND side. On my boost frame, I'm using my old wheels with 3mm boost spacers on each side, so my cassette with my non-boost crankset is exactly where it was on my old frame.
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    If your frame will clear it the regular crankset will afford a better chain line. If not enough clearance, some companies make an offset chainring. I think Wolftooth Components makes one, but there are others I can't remember off the top of my head.
    Edit*** was typing the same time as Jayem posted lol.

  5. #5
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    What BB and crank-chainring are you currently using?
    I took a Race Face Next crankset off of a non-boost bike and moved it over to a boost Giant Trance with no issues (I did the same with my wife's boost Yeti). I put a boost specific chainring on from Absolute Black with no issues.

    In the case of RF, the non-boost chainring has 6mm of offset. The boost version has 3mm of offset. I was under the impression (probably incorrectly, but it hasn't affected my application) that there is no boost or non-boost specific crankset and that chainring offset is the determinant. Regardless, the short answer is yes.

    As to whether or not you need a new BB, that's impossible to tell without knowing what you currently run and what you are looking to get.

  6. #6
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    I run non-boost rings/crank on my boost bikes because it slightly favors the lower gears where I do the large majority of my pedaling anyway. If there is sufficient clearance between the ring and chain stay and the chain and tire knobs, it'll work well. From Wolftooth:

    "With the 3mm outward cassette move, one might think that a chainline move is imperative (chainline is how far the front chainrings are from the centerline of the bike). However there are actually only 3 situations where a a boost spaced chainring, 3mm further out than "standard", is required. For other situations, a non-boost ring might work well or even better for you!"

    https://www.wolftoothcomponents.com/...and-chainrings
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  7. #7
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    Quote Originally Posted by MSU Alum View Post
    I was under the impression (probably incorrectly, but it hasn't affected my application) that there is no boost or non-boost specific crankset and that chainring offset is the determinant.
    Sometimes that's true. Sometimes it's not. Some cranks, like the pre-12spd Shimano ones, absolutely are different from each other. Shimano did it with the crank spiders on those cranks.

    Race Face is an interesting case (at least on their cranks with 30mm spindles), because they can switch between boost and non-boost many different ways. You can do it with different chainring offsets. You can do it with different spindles. You can also do it with the crank spider.

    As to whether you can use a non-boost chainline on a boost bike, that depends on the bike. I have a bike where that is not possible due to frame clearance.

  8. #8
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    Quote Originally Posted by Harold View Post
    Sometimes that's true. Sometimes it's not. Some cranks, like the pre-12spd Shimano ones, absolutely are different from each other. Shimano did it with the crank spiders on those cranks.

    Race Face is an interesting case (at least on their cranks with 30mm spindles), because they can switch between boost and non-boost many different ways. You can do it with different chainring offsets. You can do it with different spindles. You can also do it with the crank spider.

    As to whether you can use a non-boost chainline on a boost bike, that depends on the bike. I have a bike where that is not possible due to frame clearance.
    Yeah, (and to lone rager's point) I just checked the Truvativ Descendent 6K that came with my Trance 29 (boost) and it has a 6mm offset ring! I swapped it out with a RF Next SL with a 3mm offset and a spacer and it works fine...I think I'm now firmly in the "do whatever it takes" camp.

  9. #9
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    One thing that hasn't been mentioned yet is that if you're running 2x, you probably won't be able to adjust the front derailleur so that the chain doesn't rub when you're in the lowest gear if you use a non-boost crank on a frame with boost spacing. At least that was my experience.

  10. #10
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    Quote Originally Posted by BroomWagon View Post
    One thing that hasn't been mentioned yet is that if you're running 2x, you probably won't be able to adjust the front derailleur so that the chain doesn't rub when you're in the lowest gear if you use a non-boost crank on a frame with boost spacing. At least that was my experience.
    What is this 2x you speak of?


  11. #11
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    Late to the party on this, but here's my $0.02

    You don't NEED boost chainline unless you're running PLUS tyres, that is the absolute only reason to move your chainline out from the old 51mm. Otherwise, 148 now puts the chainline in a much better (although still not perfectly centrered) position compared to 135/142. I run my 150x12 rear with old Shimano 3x cranksets and use the middle and inner positions for my rings running 2.5"< on my trail bike. On my plus bike I use the middle and outer spots because if not then tyre clearance is none existent.

    As others have said, the only real issue you might run into is if the CS yoke is very wide, it might restrict how big a ring you can run, but you definitely do not need boost cranks and chainline for setups running <2.6" tyres.
    Quote Originally Posted by Harold
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