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Problems shifting after replacing chainrings

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Problems shifting after replacing chainrings

Old 09-30-18, 12:30 PM
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El Gato27
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Problems shifting after replacing chainrings

Hello,

In the process of rehabing a 2004 Sirrus. The chainrings were in poor condition so I decided to look for some at the local bike co-op. Was lucky enough to find three matching Sugino rings. I installed them and now I have trouble shifting onto the small ring. I noticed the gap between the middle ring and the small ring is bigger than the large to middle ring. All rings installed with the labeling towards the outside.

Any suggestions?


Thank you.
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Old 09-30-18, 12:47 PM
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Do the spacers have a shoulder? If so, is the shoulder seated in a corresponding counterbore in the crank arm or chainring?

As a last resort, you can file the spacers thinner.
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Old 09-30-18, 06:45 PM
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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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Old 09-30-18, 07:55 PM
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Originally Posted by Andrew R Stewart View Post
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. Andy
This,

I re-installed the middle OEM ring and noticed the "shift aids", shifted fine from middle to small ring. The OEM middle ring does have a couple of bent teeth. I'm thinking of just getting a replacement crankset, but most are for a ~120 spindle length, I have 110. Still looking. Or maybe just move the large ring to the middle position and ride it as an 8 speed, pretty flat where I'm at.
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