How much chainring to chainstay clearance do I need?

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  • How much chainring to chainstay clearance do I need?
  • Premier Icon JoeG
    Subscriber

    My On-One Fatty was delivered today! 😀

    It comes with a single ring crank, and I’m pretty certain that I need a double. So I ordered a Race Face Evolve 24-36-Bash and put it on. It fits. 🙂 But there is only about 1 mm (the thickness of a zip tie) of clearance between the chainring and chainstay. 😯

    Would anyone be comfortable with so little clearance on their bike?

    I’m leaning toward getting a 34 tooth ring instead…

    ska-49
    Member

    My yelli screamy with a 34t has the same clearance. I’ve been running it like this for a few months. Not had any issues (touch wood).

    druidh
    Member

    Have you moved all the axle spacers to the drive side?

    Premier Icon wwaswas
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    Any chainsuck will kil the stay 🙁

    richpips
    Member

    You could always mod a bit more clearance.

    Premier Icon mtbfix
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    I ran a ring with about 3mm gap on an Inbred and the ring rubbed when out of the saddle. I guess I’d be looking for 5mm to mitigate against any issues.

    Premier Icon JoeG
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    Thanks, all.

    ska49 – good to hear that.

    Druidh – I installed it stock per this. I could move spacers, but then the crank arms would be offset from the frame centerline. While I appreciate that this won’t be noticeable when riding, it would drive me crazy knowing that the cranks aren’t centered. So if someone else had built the bike and not told me, it would be fine. Since I know, no. Good idea, though.

    wwaswas – I’m switching the bike to a Simano Shadow+ rear der. That should make chain suck a lot less likely. And the chainstays are effin’ huge square things! I can’t remember the last time I had chain suck on my regular bike, but its 8 speed.

    rich – yes it would have to be a biiiig BFH. As above, the stays are huge.

    mtbfix – I’d guess that the Fatty stays are a lot bigger than the Inbred, so less likely to flex IMO. We’ll see when I ride.

    richpips
    Member

    Seriously though I had a frame with little clearance, and the ring did cut the stay. I guess I’d give it a whirl before taking any “remedial” action.

    rob jackson
    Member

    How does a shadow plus cut down on chain suck

    bigdugsbaws
    Member

    How does a shadow plus cut down on chain suck

    The clutch makes the cage much harder to pull forward compared to a conventionally sprung mech so it tends to free the chain when it starts to suck.

    PeterPoddy
    Member

    My 853 Inbred had precisely 2.5mm of clearance when new. (It was exactly the thickness of a HT2 spacer)
    Chain suck was almost uncontrollable and despite me changing rings 3 times in a year at the first sign, it gnawed through the chain stay. One it was so bad I had to remove the cranks to get the chain out.
    I had a new stay put in that didn’t have the S bend in it. I lost 2-3mm of mud room but gained a lot of chain room.
    4 years later the new stay is virtually unmarked and I can leave middle rings until they are utterly shot.
    Why O-O have this blinkered fixation with mud room, at all costs, I can’t imagine. And super short head tubes, but that’s a different story.

    Old stay, one year old

    IMG_5531 by PeterPoddy, on Flickr

    New stay after I had it changed

    IMG_7251 by PeterPoddy, on Flickr

    You can see the different profile of the new stay here. Far more more sensible

    IMG_7254 by PeterPoddy, on Flickr

    I’m still running the exact same cranks, mechs and wheels.

    Premier Icon JoeG
    Subscriber
    Slogo
    Member

    get a bb spacer. your not going to notice 2.5 or 1 mm.

    You could off center your cleats if using spds by 2.5mm to help too.

    another 853 inbred (22/36)

    after

    Premier Icon JoeG
    Subscriber

    Damage 😯

    Hmm, that repair looks a lot like something Ragley would do. 😉

    Premier Icon JoeG
    Subscriber

    Slogo – you’re using logic that makes sense. I can’t live with knowing that the cranks are off center as I said above. It may not make sense, but…

    druidh
    Member

    JoeG wrote:

    Slogo – you’re using logic that makes sense. I can’t live with knowing that the cranks are off center as I said above. It may not make sense, but…

    The whole point of the axle shims is to make the chainline fit. Are you currently running half on the drive side and half on non-drive side?

    Premier Icon JoeG
    Subscriber

    druidh – I installed the crank the way RF recommended, with spacers in the following configuration:

    NDS 1 mm Spindle spacers – 1 (factory installed on spindle)
    NDS 2.5 mm BB Cup spacers – 1
    DS 2.5 mm BB Cup spacers – 2
    DS 1 mm Spindle spacers – 2 (factory installed on DS crank)

    Per the RF pdf cited above, the crank clearance should be within 0.2 mm of each other.

    So, I took my digital caliper and measured from the pedal side face of the crank to the seat tube. They were only 0.06 mm* off! 😯 :mrgreen:

    I then used the highly scientific and very repeatable method of sticking a finger between the crank arm and chain stay and determining that they are the same distance as well. 😀

    *I do realize that my measurement accuracy is probably not even that good. Even slightly different paint thickness on the two sides of the seat tube would affect the measurement this much, FFS. And I doubt that my caliper was held perfectly square, etc. Bottom line is that the crank is centered within a pretty small tolerance.

    On my Nic there is something silly (like 1 mm) between ring and chainstay. Never had any problems as the drivetrain is in good nick.

    The chain has to get sucked round before it can get jammed ‘twixt ring and frame, there needs to be wear or misalignment before that happens.

    Premier Icon superstu
    Subscriber

    Those mod jobs are really impressive!

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