sprocket wobbles

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9/3/2020 2:10 PM

so i got a used bike to fix and resell, sprocket was worn out so i fit a brand new one. i tighten the crank bolts and sprocket runs nice and even, then i tighten the sprocket bolt and sprocket starts to wobble/is pulled into an uneven position by the sprocket bolt. what’s wrong here? is the crank arm bent (eclat tibia)? am i just dumb?

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9/3/2020 3:24 PM

if you tighten the bolt and that action causes the sprocket to wobble then something somewhere needs a washer to keep the sprocket from pulling out of alignment when the bolt is tightened..

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9/3/2020 10:02 PM

pnj wrote:

if you tighten the bolt and that action causes the sprocket to wobble then something somewhere needs a washer to keep the sprocket from pulling out of alignment when the bolt is tightened..

it turns out im just dumb, this has been discussed here at length already. it must be the crank arm and i’ll need to file down a spacer so that i can fill the extremely tiny uneven gap between sprocket bolt and sprocket

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9/5/2020 6:06 AM
Edited Date/Time: 9/5/2020 8:00 AM

rokrok33 wrote:

so i got a used bike to fix and resell, sprocket was worn out so i fit a brand new one. i tighten the crank bolts and sprocket runs nice and even, then i tighten the sprocket bolt and sprocket starts to wobble/is pulled into an uneven position by the sprocket bolt. what’s wrong here? is the crank arm bent (eclat tibia)? am i just dumb?

Having experienced something similar to you my money would be a warp in your sprocket. My old one seemed perfectly straight but would always spin in an off axis manner. I refused to beleive it was the problem until the sprocket folded in on itself from the stress of the chain while peddling

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9/5/2020 6:38 AM

Flip the spacer around-if it is the "top hat spacer", put the wider part between the sprocket and the frame, and make sure the spacer doesn't show through the sprocket on the other side but sits pretty flush..

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9/5/2020 8:35 AM

rokrok33 wrote:

so i got a used bike to fix and resell, sprocket was worn out so i fit a brand new one. i tighten the crank bolts and sprocket runs nice and even, then i tighten the sprocket bolt and sprocket starts to wobble/is pulled into an uneven position by the sprocket bolt. what’s wrong here? is the crank arm bent (eclat tibia)? am i just dumb?

yarders91 wrote:

Having experienced something similar to you my money would be a warp in your sprocket. My old one seemed perfectly straight but would always spin in an off axis manner. I refused to beleive it was the problem until the sprocket folded in on itself from the stress of the chain while peddling

not sure, i sat it on a perfectly flat surface and it seemed fine (unless the error is minimal). the crank arm on the other hand wasn’t as the angle between spindle and crank arm is not 90 degrees but off by ca 0.5-1 degree

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9/5/2020 8:43 AM

dave lawrence wrote:

Flip the spacer around-if it is the "top hat spacer", put the wider part between the sprocket and the frame, and make sure the spacer doesn't show through the sprocket on the other side but sits pretty flush..

yea i checked that and that is fine, there’s nothing in between sprocket and crank arm and sprocket should sit perfectly tight against it, however since the angle between spindle and crank arm is not a perfect 90 degrees but off by ca 0.5 degrees the sprocket cant possibly sit tight. i’m now considering getting a spline drive sprocket so i can avoid the sprocket bolt altogether. still sucks since i wanted to sell the bike and trusted the quality of the eclat tibia cranks

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