Strange Scratch on NDS Shimano 105 Crankarm
04-10-23, 01:52 PM
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Strange Scratch on NDS Shimano 105 Crankarm
I just noticed this bare metal line on the NDS arm of my Shimano 105 5700 crankset. Any idea what would cause this or what it could mean. I'm not racing criteriums with this bike, so it didn't happen in a lefthander.
04-10-23, 02:05 PM
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It's evidence of use. You might have scratched it before cleating in, or in non-riding handling, or maybe you have an enemy who keyed your bike but really wasn't that mad at you.
Either way, stop obsessing and enjoy your bike and accept that wear and tear is part of the joy.
Either way, stop obsessing and enjoy your bike and accept that wear and tear is part of the joy.
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04-10-23, 02:07 PM
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Actually, the only reason I even think about it is because I had read something awhile back about Shimano cranks delaminating, although I believe those were DuraAce cranks.
04-10-23, 02:24 PM
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04-10-23, 03:47 PM
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Looks like a typical scrape from any of a hundred different causes. The only bikes I've seen without them are the new ones the showroom floor. Nothing to worry about or get some of these. J&L Silicon Bicycle Crank arm Boots/Protectors*2-For Shimano,FSA,Sram,Campagnolo | eBay
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04-10-23, 04:37 PM
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look at how and where the bike is parked or stored.....
i'd suspect that a pedal from a neighboring bike did that...
and if you race that bike... jumping on and searching for a pedal with a cleated shoe can cause similar marks...
i'd suspect that a pedal from a neighboring bike did that...
and if you race that bike... jumping on and searching for a pedal with a cleated shoe can cause similar marks...
Last edited by maddog34; 04-10-23 at 04:40 PM.
04-10-23, 05:24 PM
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Dura Ace & Ultegra but apparently 105 is immuned. There's other fun stuff, see https://www.instagram.com/thanksshimano/?hl=en.
04-10-23, 05:31 PM
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That looks like the hit you might get pedaling over and not quite clearing a speed bump.
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04-10-23, 06:05 PM
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Run a sharpie over it and it's gone.
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04-10-23, 07:36 PM
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That is not delamination, that is scraped on something. If I had to guess I would say walking the bike up a curb, but could be a a number of different things. If it really bothers you, you can gently file it and buff it, but it's just cosmetic.
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04-10-23, 07:58 PM
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Lots of plausible explanations have been offered, and they all fall under the category of "riding your bike." Stuff happens, and that scrape is not structural.
04-10-23, 08:00 PM
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I like the Sharpie idea. It's worth a shot.
04-10-23, 08:46 PM
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Thanks for everyone’s suggestions of cause, but I honestly don’t think any of those situations occurred. It’s just odd that the scratch or whatever it is runs the length of the bevel on that portion of the crank arm.
If it wasn’t for my recollection of problems with other Shimano cranks (but not the 5700 series), I would have already had a Sharpie to the line/scratch/scrape and wouldn’t have mentioned it.
If it wasn’t for my recollection of problems with other Shimano cranks (but not the 5700 series), I would have already had a Sharpie to the line/scratch/scrape and wouldn’t have mentioned it.
04-10-23, 09:27 PM
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It is easy to scratch a crank and also easy to forget about it. I don't worry about it on any of my cranks generally. My Ultegra 6800 cranks have similar scratches and yeah it sucks but it shows I have ridden the bike a bunch. Those things happen sometimes unintentionally and sometimes we just get lazy and do something we shouldn't and something happens I have been there so many times and it comes back to bite me in the arse but in some cases I may not be thinking fully clearly or am just so tired and just want to be done or maybe I had an issue with a bike and just said screw it and threw it down (I don't throw bikes but I do sometimes treat my stuff a little rough if I am mad at it!)
04-11-23, 03:06 AM
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04-11-23, 05:36 AM
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https://www.practicalmachinist.com/f...ean-it.398187/
If someone is really worried about it
https://www.foreinnovations.com/product_p/pen_black.htm
If someone is really worried about it
https://www.foreinnovations.com/product_p/pen_black.htm
04-11-23, 07:19 AM
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04-11-23, 07:52 AM
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Or simply stop obsessing.
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
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04-11-23, 11:22 AM
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04-11-23, 11:31 AM
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And the 6800, most of the photos I've seen have been of the 6800 failing, then the 8000's, correct that the 5700 is of a different construction which doesn't have this issue
04-11-23, 06:47 PM
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Keep a high cadence. "Persistence of vision" will make it disappear! 
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