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I'm having the same issues with 9100 rear that I had with 7900 back in the day... the spring doesn't seem strong enough to overcome the cable friction on a frame with a lot of cable bends due to internal cable runs.
The 7900 springs are a known issue now, and in part that's why Shimano moved to coated cables and slicker outer casings to get friction out.
The shifts to larger cogs are fine, but the shifts to smaller ones take at least a couple of seconds and sometime 10-15 seconds, and make a lot of noise as the spring slowwwlllyy wins the tug of war.
Adjustment doesn't help, just moves the problem down a cog and keeps it from shifting into largest cog going the other way
I have run three sets of cable for the rear now, starting with shimano uncoated inner and jagwire outer, which I immediately regretted. Now Ive run the Shimano coated cables twice.... and there's no improvement.
The bike has a fair amount of bends in the cable run, but just the standard stuff -- internal for the bars, out to the downtube, uncoated inside the downtube, out just before BB, under BB back up to chain stay, uncoated for a stretch to the rear loop.
With 7900 I moved the same group from a Noah Ridley to a 1st gen Venge, same issues with both, then the other shoe dropped and I figured it out....threw up my hands after a half dozen cable swapped and plumbed in Di2.
This time, its exactly the same symptoms on an Allez Sprint.
My first guess is that Shimano has gone back to a weaker spring in search of that "lighter shifting effort" that I don't recall ever wanting...
On the other hand, I might be screwing up.
Has anyone out there among the early adopters of 9100 seen this, or seen a build with a lot of bends where it wasn't an issue at all?
The 7900 springs are a known issue now, and in part that's why Shimano moved to coated cables and slicker outer casings to get friction out.
The shifts to larger cogs are fine, but the shifts to smaller ones take at least a couple of seconds and sometime 10-15 seconds, and make a lot of noise as the spring slowwwlllyy wins the tug of war.
Adjustment doesn't help, just moves the problem down a cog and keeps it from shifting into largest cog going the other way
I have run three sets of cable for the rear now, starting with shimano uncoated inner and jagwire outer, which I immediately regretted. Now Ive run the Shimano coated cables twice.... and there's no improvement.
The bike has a fair amount of bends in the cable run, but just the standard stuff -- internal for the bars, out to the downtube, uncoated inside the downtube, out just before BB, under BB back up to chain stay, uncoated for a stretch to the rear loop.
With 7900 I moved the same group from a Noah Ridley to a 1st gen Venge, same issues with both, then the other shoe dropped and I figured it out....threw up my hands after a half dozen cable swapped and plumbed in Di2.
This time, its exactly the same symptoms on an Allez Sprint.
My first guess is that Shimano has gone back to a weaker spring in search of that "lighter shifting effort" that I don't recall ever wanting...
On the other hand, I might be screwing up.
Has anyone out there among the early adopters of 9100 seen this, or seen a build with a lot of bends where it wasn't an issue at all?