• This topic has 24 replies, 14 voices, and was last updated 9 years ago by jja37.
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  • 104 BCD Raceface ring won't fit Shimano crank??
  • idenry
    Free Member

    My LBS is building up a bike for me and has just told me
    the Raceface single ring I was gonna put up front won’t fit the Shimano crank
    as new Shimano cranks aren’t 104 diameter anymore.

    So they’re saying I either just use a standard middle ring or buy a new crank.
    Saying even a Saint ring won’t fit the crank, which is a basic Deore jobby.

    I’ve trawled web and can’t find any reference to similar problems, anyone else had this??

    z1ppy
    Full Member

    No idea about the not being a 104 BCD thing but most non-orignal (even other model shimano) chainrings tabs need a little tickle with a file to fit shimano spiders , unless there the original model too. Your LBS probably aren’t interested in filing down a brand new chainring though (unless the BCD thing is correct)… I’ve been filing down chainrings tabs to fit, without issues for years and will continue to do so (some ppl prefer to file the spider).

    honourablegeorge
    Full Member

    Think some 2×10 cranks have odd BCDs, and some SRAM 1x ones, but most Shimano cranks should work just fine.

    “What crank is it?” is probably the question to ask here.

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    idenry
    Free Member

    Cheers, he actually showed me the bits and said they used to just file them down but now the actual bolt holes don’t line up and are different diameter. So Shimano not 104BCD.

    I put a Middleburn ring on an XT crank a few years ago but they’ve changed apparently – just seems odd I can’t find evidence of others having the same problem, must be plenty of folk who’ve put a single ring on a Shimano crank.

    idenry
    Free Member

    honourablegeorge – it’s a Shimano FC-M622. Doesn’t give the BCD on Shimano’s site.

    kayak23
    Full Member

    Shimano slx crank here with a single blackspire ring, no issues.

    z1ppy
    Full Member

    FC-M622, do indeed have a 96/64 BCD apparently, seems counter-intuitive after producing 104/64 for so many years.
    (Shimano document says the same)

    idenry
    Free Member

    kayak23 – is that a newish crank?

    kayak23
    Full Member

    Yeah, the newest slx.

    idenry
    Free Member

    Thanks z1ppy. That’s pretty conclusive then. Seems SLX and XT are 104 so looks like I need an(other) upgrade!

    cheers.

    honourablegeorge
    Full Member

    Hmm. It’s for 650 and 29er wheels, you see. Clearly needed a new BCD

    “Shimano Crankset FC-M622 40/30/22 175mm schwarz – Crank. New Dyna-Sys compact 3-speed crank with 40-30-22 teeth for 27.5 – or 29-inch wheels.”

    idenry
    Free Member

    It’s a cheapo crank too, why make that a weird size?
    Mainly to bugger up my day and mean I don’t get to ride my new bike home I guess.

    warpcow
    Free Member

    It’s 29er specific (seriously, according to Shimano).

    PJ266
    Free Member

    Surely so the 30t chainring can fit as normal, rather than have the little tabs to space it out as per the raceface 30t 104bcd chainring?

    Makes sense to me… Though it is annoying.

    Pyro
    Full Member

    Odd that it’s the BCD that’s the issue, it’s normally the middle ring tabs that cause the problems. Shimano changed their cranks from 90mm to 88mm ID a while back, So aftermarket rings will be baggy on Shimano cranks but should fit.

    idenry
    Free Member

    Found a thread that explains a bit….

    http://forums.mtbr.com/shimano/bash-rings-new-96mm-bcd-pattern-m782-cranks-876969.html

    and ends with a possible solution – Blackspire doing 96mm single rings

    http://www.blackspire.com/SNAGGLETOOTH-96BCD-Chainrings

    Now need to find a decent price with shipping.

    cheers_drive
    Full Member

    Fell foul of that one recently. Asked Works Components who said they’d have new 96bcd ones before end of year

    deadkenny
    Free Member

    honourablegeorge – Member
    Think some 2×10 cranks have odd BCDs, and some SRAM 1x ones

    SRAM have certain 2×10 cranks that are 120/80 bcd. Really annoying when I discovered that.

    However a lot of their cranks also have replaceable spiders and you can get ones with 104bcd, and their 1x spider is available 104bcd. Plus you can get spiderless/direct-mount chainrings that don’t need the spider at all.

    As for the middle ring file off thing, I found that was the case with a triple if trying to fit a single ring to the middle. The single rings were designed for single spiders and needed tabs or crank filing down slightly.

    spyke85
    Free Member

    I’m buying a chainset to run a single ring on. What’s best to get, Deore or SLX? Double or triple?

    sillyoldman
    Full Member

    Deore or SLX will work fine. Triples give better chainline in the middle ring position without having to faff with spacers.

    Just make sure you get one with a 32T middle ring to avoid the odd BCD issue of the OP.

    idenry
    Free Member
    carlos
    Free Member

    spyke85 – Member
    I’m buying a chainset to run a single ring on. What’s best to get, Deore or SLX? Double or triple?

    Just bought this – http://www.merlincycles.com/shimano-slx-m670-10-speed-triple-chainset-58295.html to do exactly that after my old XT crank finally required replacing.

    Went for triple as the chain line is a little better and for the money you can’t go wrong imo

    butlerjamesp
    Free Member

    RF only seem to do a 104, 110 and a 130 bcd chainring.

    jja37
    Free Member

    It’s so people can now run a 28t narrow wide – once chainring makers do like they did for making 30t fit on 104 bcd cranks. cool. great thinking

Viewing 25 posts - 1 through 25 (of 25 total)

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