Joined: Feb 2012
Posts: 19,353
Likes: 5,471
From: Rochester, NY
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
John has it right. You can see the ring bolts' ends sticking proud of the middle ring's inner face. I strongly suspect that this ring is backwards. Also the teeth on this ring are not centered on the ring, but are offset to one side. In this case that side is, incorrectly, closer to the large ring.
But there's other issue likely at play. First is still about the rings c-c dimensioning. It looks like that middle ring is thinner then the OEM was and thus it's teeth sit even further toward the large ring. Perhaps playing with thin (..6mm thick ?) spacers between the middle ring and the spider' arm tabs faces will better center the middle ring's teeth between those of the large and the small ring. The second issue is that the OEM rings likely hade shift aids, tooth sculpting/shapes that better allow the chain to climb off the current ring and thus shift onto the next smaller ring. These Sugino rings look to not have this feature.
So what to do (besides better spacing)? One would be to source more modern rings with said shift gates. Another is to file off the tips of pairs of teeth at 4 or 5 locations around the middle ring (and create what Shimano called "W-Cut" back in the early 1980s). Make sure that the ft der position and adjustment is spot on. And lastly remember to soft pedal when shifting the ft der. Andy
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AndrewRStewart