Would you run a chainring this close to the chainstay?
#26
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So far, so good, on mine:
We have clearance, Clarence!
We have clearance, Clarence!
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FWIW; I had a modern sram crankset with sram BB that had about the same gap as the OP. It "walked" just enough to grind a quarter moon into the chainstay. It didn't take much. It was a new frame too.
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#28
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This is what I'm saying. In spite of all the detractors telling me I got it wrong, I wouldn't ride that bike with that clearance.
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You're more likely to have a crank spider arm or chainring bent enough to contact the frame, than the frame itself bending that much.
I ran my chainrings close to the stay on my old Vitus 979, which was like a springy piece of penne pasta, and the small ring never contacted the stay.
I ran my chainrings close to the stay on my old Vitus 979, which was like a springy piece of penne pasta, and the small ring never contacted the stay.
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#31
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mrmb if you're asking about it, I presume it's because you're concerned about the paintwork. No judgement here...I would be also. I guess I'd ask myself what the costs are in just spacing the chainring over a little bit. I think someone suggested gaining a mil or two with a crank spacer, or even a slightly longer spindle. I understand the concern about Q-factor, but I don't think your legs, knees, or body will notice an extra couple of millimeters (my fat bike has a 168mm spindle in a 100mm bottom bracket!). I think I'd personally spend the 30 bucks now (or less if you use a thin spacer) to know you won't have any problems in the future.
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I think the gap should be fine. The biggest risk is if you drop your chain between that gap, and have to extract it.
I'm trying to remember the mechanics of a trapped chain. It may be that it always happens on the middle/outer ring, and requires a smaller ring to pull the chain through.
In that case, it won't happen with the close small ring.
Perhaps what I'm thinking about is "Chain Suck".
Again, that may be more an interaction with outer rings than something that regularly happens with the inner ring.
I'm trying to remember the mechanics of a trapped chain. It may be that it always happens on the middle/outer ring, and requires a smaller ring to pull the chain through.
In that case, it won't happen with the close small ring.
Perhaps what I'm thinking about is "Chain Suck".
Again, that may be more an interaction with outer rings than something that regularly happens with the inner ring.
Last edited by CliffordK; 03-02-23 at 01:57 PM.
#33
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#36
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mrmb if you're asking about it, I presume it's because you're concerned about the paintwork. No judgement here...I would be also. I guess I'd ask myself what the costs are in just spacing the chainring over a little bit. I think someone suggested gaining a mil or two with a crank spacer, or even a slightly longer spindle. I understand the concern about Q-factor, but I don't think your legs, knees, or body will notice an extra couple of millimeters (my fat bike has a 168mm spindle in a 100mm bottom bracket!). I think I'd personally spend the 30 bucks now (or less if you use a thin spacer) to know you won't have any problems in the future.
#37
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Never thought of that. I'll give this a try once it's together.
#38
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The gap is actually UNDER 2mm. Just barely under 2mm.
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The paint wouldn't bother me - after all it will be covered in a layer of dirty chain lube - but creating a stress raiser in the chainstay isn't something I'd want to do if I could reasonably avoid it. Having said that, of course I've dropped chains and chewed up chainstays and they didn't break, but you never know ...
#43
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Got it all together and gave this a try today. Since it has low pressure, high volume tires (29 x 2.5 @ 30psi) all that really happened is the tires flexed and distorted some. I couldnt get any visible frame flex.