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Crank Arm Chain Scuff: Go or No Go?

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Crank Arm Chain Scuff: Go or No Go?

Old 04-09-20, 09:19 AM
  #1  
BFisher
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Crank Arm Chain Scuff: Go or No Go?

I've got this Sugino Mighty Competition crankset here that I used very briefly in the past, but has been sitting in the bin for years. Thinking about using it again, but this damage to the inner arm gives me pause. I'll defer to the experts. Would you ride these? Note the bike doesn't get the bulk of my mileage, no serious climbing. I'm inclined to think they'll be fine, but am short on experience with this. Pics:









Thanks in advance for any wisdom.
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Old 04-09-20, 09:24 AM
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I am not an expert, but I play one while on the internet.
I would file that off, sand it with emery cloth, polish it and use it.
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Old 04-09-20, 09:36 AM
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In the third photo it appears like there is a crack in line with the "171" stamp. If so, a crack will keep going deeper with load unless you blend it out completely and the only why to ensure it is gone is with a non destructive test (liquid penetrant, ultrasound, etc.) which would likely cost you more than it is worth t salvage an already damaged crank.

I't won't fail immediately, but if it does in the middle of a hard climb 50 miles from home.......I wouldn't use it.
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Old 04-09-20, 09:39 AM
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I've never seen one so bad.

If it's cracked, it's trash.
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Old 04-09-20, 09:40 AM
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Originally Posted by trailangel View Post
I am not an expert, but I play one while on the internet.
I would file that off, sand it with emery cloth, polish it and use it.
Yeah, what he said.
I can't see a crack, but maybe you could verify this in person. Filing/sanding might reveal one way or the other.
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Old 04-09-20, 09:52 AM
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I don't see a crack, just clean and ride if I had em.

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Old 04-09-20, 10:00 AM
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Originally Posted by bikeaddiction1 View Post
In the third photo it appears like there is a crack in line with the "171" stamp. If so, a crack will keep going deeper with load unless you blend it out completely and the only why to ensure it is gone is with a non destructive test (liquid penetrant, ultrasound, etc.) which would likely cost you more than it is worth t salvage an already damaged crank.

I't won't fail immediately, but if it does in the middle of a hard climb 50 miles from home.......I wouldn't use it.
I do see how it looks that way in the photo, but in person I see no evidence of a crack.
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Old 04-09-20, 10:56 AM
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Yeah just sand it out. No big deal, I've used worse!
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Old 04-09-20, 11:15 AM
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I don't see a crack. You want to sand and polish it to get rid of any stress risers. Do it a and ride.
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Old 04-09-20, 11:49 AM
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The "Mighty" Sugino Mighty Super/Competition, easily one of if not the best in the business, every bit as tough, strong and beautiful as any.

Sand, polish and ride.
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Old 04-09-20, 11:49 AM
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Originally Posted by BFisher View Post
I do see how it looks that way in the photo (it blows up quite well), but in person I see no evidence of a crack.
On my big screen the photo is 2-3 times normal and the crack (if it is a crack) appears to be at the back edge propagating both ways from the corner. At a minimum I would do better than the naked eye and either look at it with a magnifying glass or a clear blown up photo image. Maybe clean a few of the burrs away first for a clearer picture.I might be a little anal as my background is in Aeronautical Engineering and cracks are the root of all evil.

If it does break, think of which part of you anatomy hits the top tube first and how important is that to you.

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Old 04-09-20, 12:12 PM
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Originally Posted by bikeaddiction1 View Post
If it does break, think of which part of you anatomy hits the top tube first and how important is that to you.
Thankfully when my crank snapped I missed the top tube all together. Since I was standing on the crank at the time, my foot when right to the ground, and stopped. Unfortunately the rest of me was still going about 16mph. But thankfully the bike when left and I went right (ish).
Unfortunately there was some kids at a play ground near by who saw the whole episode - "DANG! DID YOU SEE THAT?!?!" ... yea.... sort of......
Thankfully I was not in traffic, or near a hard curb. Unfortunately ORIGIN8 would only sell me a crank at cost as a replacement. -- I think I should of sued......



just say "no" to ORIGIN 8's cheap crap

Probably about 2 years of riding. UNGLAUBLICH!!

Last edited by mrv; 04-09-20 at 12:13 PM. Reason: speeling is hard
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Old 04-09-20, 12:20 PM
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oh, sorry. to the original post's question - I dunno man. I dunno.
The SUGINO assembled to the bike in the first pic I posted has a slight nick in it from clipping the front derailleur. After hitting the deck once, I keep thinking I'm not going to use it.
Probably for you're mighty mighty SUGINO - I just don't think it's worth the risk and hassle. Maybe if you never stand on them, it'll all be fine. (I've only seen one rider who never stood on her pedals. I asked her why and she almost knocked me in the head with the chip on her shoulder... whatever..)
Heck - even the MIGHTY Grant Peterson says change you're handlebars every 15 years as a matter of safety.
I know SUGINO cranks are pricey. I understand. I just paid a lot for a set of VELO ORANGE cranks for my new GUNNAR. It's a lot of money.

cheers.
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Old 04-09-20, 12:24 PM
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Originally Posted by mrv View Post
Thankfully when my crank snapped I missed the top tube all together. Since I was standing on the crank at the time, my foot when right to the ground, and stopped. Unfortunately the rest of me was still going about 16mph. But thankfully the bike when left and I went right (ish).
Unfortunately there was some kids at a play ground near by who saw the whole episode - "DANG! DID YOU SEE THAT?!?!" ... yea.... sort of......
Thankfully I was not in traffic, or near a hard curb. Unfortunately ORIGIN8 would only sell me a crank at cost as a replacement. -- I think I should of sued......



just say "no" to ORIGIN 8's cheap crap

Probably about 2 years of riding. UNGLAUBLICH!!
Wow, glad you weren't hurt. Too bad about the witnesses. In the photo of the broken crank arm, the dark flatish area on the outboard side looks like a crack and the jagged area was what was remaining when it snapped. The issue with a crack on the crank is the cyclic loading will help the crack propagate so it is usually not a case of will the crack grow, but how fast will it grow.....if there is a crack.
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Old 04-09-20, 12:31 PM
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I'll add another voice to the sand-polish-assess crowd. I would not ride it as is, but a crack will reveal itself very quickly with a little sanding or filing -- and if it's cracked, set it aside.

I sanded a divot out of a Sugino AT crank that I use daily, but I also had to retire a gorgeous SR Royal crank that was definitely cracked after some light filing.
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Old 04-09-20, 02:08 PM
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Thanks again for all input. Concerns are definitely valid and taken seriously. I took a needle file to the area and then hit it with a Dremel wire brush. The area looks smooth, and most importantly, crack free. Will post a pic later.

Plan is a go, and I've swapped the set in.
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Old 04-09-20, 03:31 PM
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After some smoothing out:


I have a bit more to do here, but am relieved at the result. Close inspection, including magnification, put me at ease. Thanks again for the responses.

Cell phone shot of its new home:
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