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Old 04-16-14, 10:07 PM   #1
vredstein
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Rings on DA 7410 crank

I picked up a 7410 crank set at a swap meet. I'm not sure if they have the original rings. The big ring is labeled "Shimano SG" and "B-53", all marked on the outer side of the ring and with a grove running around the circumference of the ring beneath the teeth. The inner ring is mounted with no markings on the outer side. On the inner side it is marked "Shimano SG", "TL", "B-39", and a "V" mark positioned right at the crank arm (3rd pic). The inner ring has a "shelf" on both sides running around the perimeter of the ring below the teeth (2nd pic). As mounted, the shelf on the on the inside is about 1/2 mm higher than the shelf on the outside. Is this the correct orientation? Are these original DA 7410 rings? IMO, the condition of these rings is excellent, but I'd appreciate a second opinion. Thanks.
Edit-After removing the rings, I see the ring nut groove on the inside of the bolt holes of the small ring, so it was correct.
Attached Images
File Type: jpg ringcondition2.jpg (98.9 KB, 19 views)
File Type: jpg innershelf.jpg (98.8 KB, 17 views)
File Type: jpg SGV.jpg (98.3 KB, 18 views)

Last edited by vredstein; 04-16-14 at 10:14 PM.
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Old 04-17-14, 03:29 AM   #2
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they don't look too bad, but IME, an opinion from looking at a pic is worthless. for me, either the chain skips or it doesn't. if it does, i buy a new chain and cogs, and if it STILL skips, i buy a new chainring. other's will have different opinions and no doubt you'll hear them.
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Old 04-17-14, 03:53 AM   #3
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Wow, they're pretty damn mint for 7400! Those are totally DA rings; look how smooth all the edges of the chainrings are. Pretty sure those surfaces are rough on a nice shiny tricolour chainring.

I bet the cranks aren't even scuffed, huh? If they are, these rings would have to be replacements.

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IME, an opinion from looking at a pic is worthless.
Bah. Those chainrings are like 1/4 used, max.
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Old 04-17-14, 10:18 AM   #4
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Many seem to see the way the engineers modified the tooth profiles to make it shift just a tiny bit quicker as if they are worn down ..
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Old 04-17-14, 10:27 AM   #5
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The mounting orientation is correct and the chainrings are "matched". The corresponding "B" on both rings means they are made to work together. And yes, Shimano rings are mounted so the engraving faces outward on the big ring and inward on the smaller one.
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Old 04-17-14, 10:18 PM   #6
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Quote:
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Wow, they're pretty damn mint for 7400! Those are totally DA rings; look how smooth all the edges of the chainrings are. Pretty sure those surfaces are rough on a nice shiny tricolour chainring.

I bet the cranks aren't even scuffed, huh? If they are, these rings would have to be replacements.




Bah. Those chainrings are like 1/4 used, max.
Drive side arm is scuffed to a high gloss. I only picked them up because I needed a 172.5 mm, square taper set to replace my current Suntour Cyclone 170's. $40, probably cheaper than I'd get them on Ebay.
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Old 04-18-14, 07:46 PM   #7
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These cranks were anodised rather than clearcoated like the 7700s, right?
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