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Problem with fitting chain rings

acacacac Posts: 348
edited 21 April in MTB workshop & tech
Hi all I have a Cannondale rz 120.
Fitted hone cranks, but I can't fit a chain ring on the middle or a granny ring.
As the cranks are to close to the swing arm.
How can I solve this any help pls thanks
play hard ride hard
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Posts

  • JBAJBA Posts: 2,625
    What chainset have you fitted and what bb?
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Bird Zero Mk1 ¦ Giant Revolt Advanced 2 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • acacacac Posts: 348
    Shimano Hone
    Xt m8000 bottom bracket.
    play hard ride hard
  • acacacac Posts: 348
    Picture

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  • steve_sordysteve_sordy Posts: 1,990
    It looks like you need to move and/or add spacers on the bottom bracket to get your chainline correct. The middle ring should be directly in line with the middle gear on your cassette.
  • acacacac Posts: 348
    I've already got two bottom bracket spacers on I didn't what to add more spacers.
    The gears run prefect.
    play hard ride hard
  • acacacac Posts: 348
    I have a 38t single ring on it at moment.
    I am thinking of buying xt m8000 cranks.
    But don't know if they will fit.
    Because of the chain rings will be to close
    play hard ride hard
  • The RookieThe Rookie Posts: 27,747
    edited 22 April
    You need to be able to replicate whatever was originally fitted in terms of the chainline, get the same chainline and the same sized rinks must fit!
    So what year/what was the original chainset?
  • acacacac Posts: 348
    edited 22 April
    It was 2013 Cannondale rz120 .
    I brought the frame from eBay new old stock .
    It it came in a box with a label saying warrety on it.
    play hard ride hard
  • acacacac Posts: 348
    edited 22 April

    I think the original chainset was SRAM s8000.
    play hard ride hard
  • The RookieThe Rookie Posts: 27,747
    I've found various cranks fitted, all triple and none seem to cause an issue, from Deore to S1000.
    Apparently it's a BB30 shell but comes with BSA adaptors, so maybe its an issue with your adaptors, or maybe it has a longer shock fitted so the chain stays sit lower.
    I'd start by measuring the effective shell width (to the inside face of the two bearing houses) which should be 75.5mm. In addition to that measure the chainline from the centreline of the frame to where the centreline of the middle ring would be, that should be circa 50mm.

    Maybe the frame is defective (so warrantied) and the BB shell is wrong?

    That's all I can think of.
  • steve_sordysteve_sordy Posts: 1,990
    When you look at the bike from the rear, is the rear triangle in line with the centre line of the bike? If isn't the bike could be bent. Not sure what can be done about that. I don't know, just not sure.

    If it is OK, consider accepting that the bike has something not quite right about it. Then go 1x and fit a wider range cassette.

    I'm sure you would not have bought the bike if you thought the frame was a warranty reject, did the eBay seller make that clear? If so you may have a claim.
  • acacacac Posts: 348
    edited 23 April
    I going to do some measurements.
    It is a bb30 bottom bracket, I fitted BB FSA adapter and fitted xt 8000 bottom bracket.
    The gear are spot on.
    The chain looks like it is straight when in 6th gear.
    I think it's some thing to do with the swing arm.
    The seller on eBay was Cycling Sports Group UK.
    They are supplyer for Cannondale.
    I may ring them see if they come up with anything.
    It's 11 speed
    play hard ride hard
  • acacacac Posts: 348
    edited 23 April
    I had a measure it's 51mm where the ring is now on the outer.
    If I could get a ring on middle how the cranks are on now it would be I think bout 41mm.
    The is to be able to move crank set out more bout got two spacers on even if I put one more spacers on it won't be a enough.
    play hard ride hard
  • steve_sordysteve_sordy Posts: 1,990
    If your outer front ring is in line with the middle of the cassette, then it is too close to the frame, which is your problem. For a 3x set of rings, the middle gear should be in line with the middle of the cassette. (See my post on 21st Apr).

    At least you know know exactly how far over you need to move the crankset! (The distance between the middle and outer rings).

    Check to see if there are any spacers on the non drive side of the BB that can be moved over to the drive side. If that does not move the ring far enough then get some more spacers! There is plenty of thread in the frame and the BB to allow for this.
  • acacacac Posts: 348
    edited 23 April
    I have got more spacers didn't think I should put more then two on.
    If I put one more spacers on it not enough bot if I put two more on it would be enough.
    That be four spacers didn't think should put four on to many then have to redo the gears.
    Wouldn't that change the chain the line by about 5mm it make it bout 56mm?
    Not sure
    play hard ride hard
  • The RookieThe Rookie Posts: 27,747
    edited 24 April
    The middle ring should be at circa 47.5-50mm. 41mm is right there your problem.

    Root cause could be in the frame, the adaptor, the BB or your install.

    2 spacers are 5mm, so will move chainline by 5mm obviously.

    You're going to do a lot of measuring to see if the frame is even useable IMO.

    Width of shell, is it central, adaptors etc.
  • acacacac Posts: 348
    I have tried to fit a 32th ring on the middle.
    32th fits fine, bout wouldn't be able to fit any thing bigger.
    If I buy xt m8000 cranks will I be able to use a bigger ring then 32th.
    Thanks
    play hard ride hard
  • The RookieThe Rookie Posts: 27,747
    No, XT cranks give the same chainline (based on the same bearing location). your incorrect chainline is going to increase drag and reduce chain life as well.

    This may also cause leg issues if you have the cranks offset by 6-10mm from the saddle.
  • acacacac Posts: 348
    Don't know what to do now.
    I can't move cranks out any more, and I can't fit new cranks unless I have 32th.max
    play hard ride hard
  • acacacac Posts: 348


    play hard ride hard
  • steve_sordysteve_sordy Posts: 1,990
    I guess that you have now found out why the box it came in was marked "warranty". :'(
  • acacacac Posts: 348
    Yep may be the frame been giving me a headache since got it.
    Only had one choice on headset as it headshox head tube to be able to fit 1/18 forks. never mind.
    But it rides nice.
    play hard ride hard
  • The RookieThe Rookie Posts: 27,747
    I'd start by measuring it carefully and trying to figure where it's out of whack, BB shell looks central on the downtube, how wide is it, what is the width to the inside of the bearings cups (should be 75.5mm) photo's aren't going to help us to help you, facts are.
  • whyamiherewhyamihere Posts: 7,336
    It may well be BB30A, where the A means asymmetric. These are 73mm wide, with the BB shell shifted 5mm towards the non-drive side. To use this with a non-Cannondale crankset, you'd need something like this: https://wheelsmfg.com/bottom-brackets/cannondale-bb30a/bb30a-outboard-abec-3-bb-for-24mm-cranks-shimano-black.html

    You can see on the Wheels Manufacturing one that the non-drive cup is a lot narrower than the drive-side cup, which corrects the chainline. You can confirm this by measuring the BB shell and whether it is offset towards the non-driveside.
  • acacacac Posts: 348
    I think I been giving wrong information sorry.
    I measured chain line again
    Where the ring is now on the outer tabs it's 57mm,
    If ring was on the middle it would be 50mm.
    I put it in second gear and back pedal the chain jumps to 3nd gear.
    Do same in first gear,
    I guess the chain line is way out.
    But the gear work perfect.
    The BB is bb30 68 shell.
    I guess if I got xt cranks 50mm cranks I only be able to use 32th max..
    Sorry for been a pain and wrong information.
    play hard ride hard
  • acacacac Posts: 348
    Bearing cup to bearing cup is 72mm.
    play hard ride hard
  • steve_sordysteve_sordy Posts: 1,990
    Are you sure that the rear triangle is in line with the centre-line of the front triangle?
  • acacacac Posts: 348
    Sorry not sure what you meen I think it is.
    It looks all central.
    play hard ride hard
  • steve_sordysteve_sordy Posts: 1,990
    If it is central, and it doesn't need to be far out to cause a problem, then the issue is at the bottom bracket.

    For example, if the rear axle was heaved over to the drive side by 5mm, would that fix the problem?

    That has just sparked an idea! Have you got the cassette in the correct place? Is there any way that could be shifted over? That would help with the chain line.
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