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froymot

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Reply with quote  #1 
Hey guys
Ive built up this marin single speed around some old custom built wheels i had lying around but, i'm having an issue with the chain skipping on the sprockets when pedalling under heavy load, fast, hard, trying to wheelie for example.

ive experienced this before with worn out chains & or sprockets but my issue here is that all of the drive train is brand new.

up front i have a 3/32 32T - then a 3/32 18T freewheel on the rear. the chain was a new kmc 3/32 1x which i swapped with a kmc 8 speed (pictured) when i started having the issue to try and diagnose. This however made no difference.
the tensioner i'm using also pictured is specified as suitable for the purpose and i have the spring tension/ angle of the jockey wheels correct according to its own instructions.

I have the chain line adjusted as straight as i can get it (see spacers) but this too has made no difference. 
the next guess i'm thinking to make is a ridgid non spring type tensioner but i dont see how or why the one fitted should be inappropriate as i see similar designes on trials bikes ect which i would have thought get even more torque through the drive train.

Any ideas anyone!? ANY help would be awsome I appreciate your time folks!
regards Tom [smile]






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OneLessCar

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Reply with quote  #2 
How do you know its not the rear hub causing the problem?
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froymot

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Reply with quote  #3 
thanks for looking mate!
Im not 100% on what you mean by the rear hub causing the problem?
are you suggesting that the rear hubs free wheel is skipping?
if so its a separate unit wound on to the hub which is also new.
it spins nicely and dosent sound to have damaged teeth if it where to be that skipping.
i just want to rule everything else out before i try a new freewheel too [tongue]
thanks for the response [smile]
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Fairnooks

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Reply with quote  #4 
The only thing I can think of is the tension device might be flexing or binding just a little, enough to offset the chain enough to ride up a cog tooth and skip. Can you mount a camera on the frame and try to capture the incident? Otherwise change one adjustment or component at a time and test test test. Maybe put a regular derailleur on and set it in line with the limit screws to rule out the tension device. Look for any slight twists or bends in the hanger as well that might be causing enough misalignment for skipping under pressure.
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bmxboy

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Reply with quote  #5 
Check your chain sight and the chain tension i had the same problem with my ss cyclocross bike it might help
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soup

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Reply with quote  #6 
I am in no way a single speed afficianado. With the hills around here ( everywhere uphill from everywhere else )
<Mode:Yorksireman>
... three miles to school, uphill both ways, in't snow
<Mode : off>
gears are very necessary.

However putting on my engineering hat I can't help suspecting the jockey wheels on your tensioning device perhaps under load one or the other (the bottom one especially) is binding up causing the tensioner to straighten out meaning the chain goes over less of the rear sprocket causing the 'jump'.
  Check the jockey pulleys are running free and easy under load and that the width of the tensioning device is right (though the width does look OK in your pics.
Nice looking build by the way get this'jumping' sorted and get it dirty.


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scram

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Reply with quote  #7 
Hey Marco, Good to see your posts. Hope the new career is treating you well. I wish I had become an electrician like I wanted as a kid. Working for the state now. OK, but desk work gets old. Be well. Seems like the dying days of BMFU. Your timing was excellent, no doubt.


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