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crank spider contacting chain on singlespeed

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crank spider contacting chain on singlespeed

Old 07-16-13, 08:42 PM
  #1  
sirtirithon
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crank spider contacting chain on singlespeed

I just had my bike converted to single speed. Crank is a Shimano XT M785 and chain ring is a stainless shimano 32T. I'm running a Surly 18t in back. Love the ratio. I noticed the chain is slightly contacting the crank spider though and has worn off the finish a bit. Is this a problem? I am having no performance issues it appears to be cosmetic at this point but as the chain wears down or the teeth on the chainring could it become a problem? Can I solve this by installing chainring spacers between the spider and chainring? Or am I just making an issue out of nothing? Thanks!












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Old 07-16-13, 09:03 PM
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No, it shouldn't be a problem as long as the chain stays properly seated as it passes over the spider.
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Old 07-16-13, 09:12 PM
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Originally Posted by JohnDThompson View Post
No, it shouldn't be a problem as long as the chain stays properly seated as it passes over the spider.
It appears to be properly seated as it goes around. No skipping issues. The spider is literally flush with the chainring. It looks like it is getting full tooth engagement when the chain passes over this area.
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Old 07-17-13, 12:35 AM
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If it BECOMES a problem, and you like the gear combo, you'll have to swap ring and cog; BikeCalc.com says 36/20 is pretty much identical.
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Old 07-17-13, 12:44 AM
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You won't have to swap the cog, just file a chamfer onto the spider where it contacts.

- Joel
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Old 07-17-13, 05:04 AM
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The chain will likely wear itself a recess on the spider. If you'd like you could take a Dremel tool with a drum-shaped tool and finish the job yourself. If your chainline permits you could also use "chainring spacers" to shim the ring away from the spider until the chain clears it.
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Old 07-17-13, 10:13 AM
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Spacers will foul up your chainline. I'd pull off the crank and spend a few minutes with the bench belt sander.
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Old 07-17-13, 10:40 AM
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Originally Posted by dsbrantjr View Post
The chain will likely wear itself a recess on the spider...
Maybe consider using an economical chain till it does and really it won't take long...
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Old 07-17-13, 10:55 AM
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Originally Posted by tomacropod View Post
You won't have to swap the cog, just file a chamfer onto the spider where it contacts.

- Joel
That's essentially what Ofmega/Avocet did to accommodate a 41T ring on their 144mm BCD spider:

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Old 07-17-13, 11:38 AM
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yea, File off the needed clearance, from the end of the crank spider .

Might want to have the crank off the bike to do a good job..
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Old 07-17-13, 12:15 PM
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Thanks for the advice! I am going to take it by the LBS and try a set of 2mm chainring spacers between the chainring and spider and see if that gives enough clearance. I have a Surly SS kit in the rear so I can easily adjust the chain line to keep it straight afterwards. This would also benefit me by gaining a couple more MM's clearance at my chain stay for the chain as its a bit close anyways.
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Old 07-17-13, 01:13 PM
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I have a Surly SS kit in the rear
some tweaking of axle spacers and wheel re-dish could move the chainline on the hub over ,
were it not a single- speed-on- a- Cassette hub, conversion..
clearance at my chain stay for the chain as its a bit close anyways.
You mean the dropout end, at the back, right?
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Old 07-17-13, 07:57 PM
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Update. Went by the LBS and they installed 4mm spacers and new bolts. Worked great! Adjusted the spacers in the rear for the new chain line and all is good now! Thanks guys!!! Hope this helps someone else if they run into this issue.






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