# 9100 mechanical rear shifting issues



## thumper8888 (Apr 7, 2009)

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?


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## MMsRepBike (Apr 1, 2014)

I've seen a common problem cropping up from those doing it themselves: the length of the housing entering the rear mech.

This mech and previous designs do not work the same. If you try to put a loop or large piece of housing, you'll end up with your problem.

So how long is your housing? It should be about this long:


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## thumper8888 (Apr 7, 2009)

MMsRepBike said:


> I've seen a common problem cropping up from those doing it themselves: the length of the housing entering the rear mech.
> 
> This mech and previous designs do not work the same. If you try to put a loop or large piece of housing, you'll end up with your problem.
> 
> So how long is your housing? It should be about this long:



God I love the internet when questions like that actually get smart, knowledgeable answers. Even if that doesn't help me, it def will help someone else. But sure, I'll shorten in tomorrow and see if it helps. I did notice that it works differently and cut the loop unusually small after mocking up the movement a couple times, since the mech does work so differently.
The frame is much different from the one in your photo, and I can't tell but it looks like my loop almost follows the same arc if you think about where the cable is inside your frame.
The main point I'd guess is the angle it goes into the mech... I don't think theyre significantly different but it won't take 10 minutes to cut one a couple inches shorter and check it.
thanks much for the idea.


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## thumper8888 (Apr 7, 2009)

This is the loop I've got BTW....


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## rcb78 (Jun 15, 2008)

It's not the frame and based on the pic it's not the loop. You said internally routed bars? I haven't worked with a broad variety of brands, but of those I do have experience with, every single one made the shifting worse.
I just installed 9100 on my Tarmac and arguably the frame routing is worse than yours, but mine shifts perfectly into all gears. I did cross the cables up front and used all the nosed ferrules, with the exception of not using the metal ferrule at the derailleur, I don't like o-ringed ferrules. Also, make sure all your housing cuts are clean and detailed. I've run into plenty of cabling jobs where the only thing causing problems was inconsistent technique.
On really nasty installs I do use the special shimano cable grease, that stuff can sometimes help when nothing else does.


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## thumper8888 (Apr 7, 2009)

rcb78 said:


> It's not the frame and based on the pic it's not the loop. You said internally routed bars? I haven't worked with a broad variety of brands, but of those I do have experience with, every single one made the shifting worse.
> I just installed 9100 on my Tarmac and arguably the frame routing is worse than yours, but mine shifts perfectly into all gears. I did cross the cables up front and used all the nosed ferrules, with the exception of not using the metal ferrule at the derailleur, I don't like o-ringed ferrules. Also, make sure all your housing cuts are clean and detailed. I've run into plenty of cabling jobs where the only thing causing problems was inconsistent technique.
> On really nasty installs I do use the special shimano cable grease, that stuff can sometimes help when nothing else does.


Yeah, it's not the loop. Damned aerofly riser bars... the riser brings one more bend into the equation. I went through it all again, made some minor cable end cleanups and installed another coated Shimano cable and .... its better but still sometimes hangs up a bit.....
It was like this last time, mainly worked ok in the house but on the road, not so well.
I feel pretty sure the cables, housings, ferrules are as good as they're going to get. the bars may be a bend too far for 9100.
Im willing to bet, at this point, their spring on the rear mech is softer than 9000...


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## rcb78 (Jun 15, 2008)

I asked the guys at Shimano about this, the spring in the RD-9100 is actually stiffer than the 9000, that's part of the Shadow design and originated from the need to overcome cable friction on mucked up mtb cables.


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## thumper8888 (Apr 7, 2009)

rcb78 said:


> I asked the guys at Shimano about this, the spring in the RD-9100 is actually stiffer than the 9000, that's part of the Shadow design and originated from the need to overcome cable friction on mucked up mtb cables.



That's good to know, thanks much.
I guess now I will place the blame on specialized and the excessively sharp angles for that cable's bends, particularly where it exits near bottom of downtube.


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