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SRAM XO Rear Derailleur Adjustment Issue

Tony S

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Okay, so I have this new used bike. Almost everything working great. Made some cockpit adjustments, took a spacer out of the fork, replaced a valve core. That's about it. Except one crazy thing that I can't figure out. Before I take it for professional attention, maybe one of YOU can give it some professional attention.

SRAM XO 11-speed rear derailleur. Problem description in next paragraph. Here are things I've looked into already: Played with the B-screw, setting it to spec (jockey wheel 12-16mm below the big cog, per the SRAM install manual) and back to where it was when I got it (more like 8 - 10mm). No difference. Limit screws are fine. Cable action is fine (not sticky). Chain looks pretty new. No significant stretch by ruler test. Not sure about cogset - can't be more than a year old, and by the looks of the rest of the bike, seems unlikely to have a ton of miles on it. Not sure if a bent hanger or cage would cause the problem (below). Don't have a device to check.

Here's the problem: As the derailleur climbs the cogs from smallest to largest, the cable tension appears to grow increasingly too tight. I.e., the further you climb the cogs, the more one click of the shifter causes the derailleur to want to overshoot the target cog and start moving toward the next one, causing noise, yadda yadda. Basically it's a problem on the top 3 or 4 cogs. If I reduce cable tension to the point that it shifts okay on the largest cogs, it is way too loose to shift properly on the smallest cogs. E.g., one index "click" at the shifter won't even come close to moving the chain from the smallest cog to the next-smallest one. The indexing is off somehow.

I have been using a stopgap measure to keep me riding while I futz with the issue. I'll describe it here only as a diagnostic: Tighten the cable one cog's worth. When I do this it basically works fine on the largest 7 or 8 cogs. Since I spend the vast majority of my time in that range it's getting me by, but it's not right and it bugs me.

Ideas?
 

skibob

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Just had similar problem with a new RD on my beater.

In my case it was solved by tightening the cable itself and then readjusting the b-screw (and hi also needed adjust in my case).

It seems likely the answer is in the b-screw and cable slack adjust somewhere.

I can't personally think of anything else that will cause this.

I suppose one other idea: have you taken all the tension off and checked the freedom of movement of the derailleur itself? If those hinges/springs were sticky I suppose I could see it behaving this way.
 

at_nyc

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You can check the straightness of the dropout and hanger by putting a ruler to it. (need to take the RD off the dropout)

I happened to have bend my hanger once. The "professional" device is just one big long rod with the right size bolt on one end. You can probably fashion one yourself.
 

Tom K.

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It's a bent hanger or derailleur, pretty much ANY time things are right at one end of the cogset, and "clicking" at the other end.

Pro Tip: Absent a Park Adjustment Bar, keep in mind that 99% of the time, things bend inward from being bumped. Almost never outwards. Eyeball it from behind, and give it an outward tweak if that appears to be the case.

I did this a couple weeks ago on a huge, remote ride where my bike had apparently been bumped a bit in the pickup truck. All perfect afterwards. I hate pickup truck tailgate racks.
 
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Tony S

Tony S

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Hey everyone: Thanks for all the great tips. I got it working passably, if not perfectly. Like many challenges, it appears to be a "layered problem," with several different causes joining forces. Biggest issue was that I forgot that the outboard limit screw actually has two functions: The first and obvious one is to stop the outward movement of the jockey pulley before it guides the chain past the cogset. It was performing that job fine. But it actually has another job, which is to establish a starting point for cable indexing. I moved it out about a mm, which did not affect shifting onto and off of the smallest cog noticeably, but it DID set up cable tension and derailleur travel to align better with cog spacing. I also ended up adjusting the b-screw to allow the jockey closer to the cogs. This actually put it even farther out of spec than it was originally, but it seems to work better. In the longer term I will look into the possibility of a bent hanger or derailleur.

Absent a Park Adjustment Bar, keep in mind that 99% of the time, things bend inward from being bumped. Almost never outwards.

Doh. Obvious when you say it. Makes total sense.

Question: When you straighten a hanger, how do you do it? On the bike? Using just your hands? Link to video or pics? (Back in the day we would just put a hand behind the bolt that affixes the derailleur and pull, but that was in the days of steel frames, yadda yadda. The hanger on this bike is beefy, and it's short, so there's not a lot of metal to put a gradual curve into. Also hard to apply leverage to just the hanger and not the derailleur body / cage.)
 

Josh Matta

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Always follow this procedure....

Check Hanger

take of shifter cable, (always set B screw and limit screws) with out shift cable on

Set B screw about a half of centimeter from the largest cog.

SInce you have SRAM derailler it will default to to smallest cogs. Adjust lower limit screw till it will start to shift to second cog, then back off till it doesnt

Push(by hand) the derail inwards to the biggest cogs, adjust till it start jump to second biggest, then back off slightly.

adjust the barrel adjust on the shifter a couple turns out from as loose as possible, giving you room to adjust with the barrel boths ways and not just more tenison.

reattach the Cable by pulling it as tight as possible.

readjust with barrel until the indexing is correct.

Lastly please for the love of spaggetti monster use a cable end and crimp it down HARD.
 
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Tony S

Tony S

I have a confusion to make ...
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Set B screw about a half of centimeter from the largest cog.

Interestingly, this is where I ended up, but it's way closer than SRAM recommendation (15mm). So, your advice is spot on for my case.
P.S., I have done this before. Like, before you were born, Josh.:beercheer:
 

Tom K.

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But it actually has another job, which is to establish a starting point for cable indexing.

Question: When you straighten a hanger, how do you do it? On the bike? Using just your hands?

To your first point. Not really. The outer limit screw only affects the outer limit. Honest.

To your second point, I shift the bike into a gear that puts the derailleur cage roughly vertical, then pull on it gently. It's best to "tease" it out with multiple little and quick tugs, not one big pull where you actually see/feel movement. Then check out alignment from behind. It's surprisingly easy to see whether your cage angle is vertical or slanted.

Have fun!
 

Philpug

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Hmm. It does say 11 speed on the shifter carapace.

Good, it does go to 11
Spinal_Tap_-_Up_to_Eleven.jpg
 

at_nyc

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Question: When you straighten a hanger, how do you do it? On the bike? Using just your hands? Link to video or pics? (Back in the day we would just put a hand behind the bolt that affixes the derailleur and pull, but that was in the days of steel frames, yadda yadda. The hanger on this bike is beefy, and it's short, so there's not a lot of metal to put a gradual curve into. Also hard to apply leverage to just the hanger and not the derailleur body / cage.)
Best if you can borrow a Park tool specific for that.

But, if you get your hands on that tool, you realize you can make one yourself! The tool is just one long rod with a derailleur bolt at one end.

You do need to take the derailleur off, because the tool needs to bolt into that same hole the derailleur bolt goes.Once you screw it in, you got tons of leverage to push and pull on that rod, which bends the hanger.

I hope your hanger is steel, not aluminum. Al don't bend well.
 

Tom K.

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Best if you can borrow a Park tool specific for that.

Agree 100%, or just buy one. I bit the bullet over 20 years ago. I only use the thing a couple times a year, but it's amazing how a bike that is shifting "OK" can improve once you dial it in the Park Bar of Wonder!
 

at_nyc

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I was lucky a friend does volunteer work in a recycle-a-bike workshop so have access to a lot of tools. Though that was the first time I had a need for a tool I I hope not to use too often. (hanger was bent way out of alignment from a high speed crash, so was my collarbone :()

I worked the rest of the night helping out in their workshop and had gone back to help out from time to time.
 
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Tony S

Tony S

I have a confusion to make ...
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Biggest issue was that I forgot that the outboard limit screw actually has two functions: The first and obvious one is to stop the outward movement of the jockey pulley before it guides the chain past the cogset. It was performing that job fine. But it actually has another job, which is to establish a starting point for cable indexing.

To your first point. Not really. The outer limit screw only affects the outer limit. Honest.

Hmm. If the cable is clamped to the derailleur already, then yes, it doesn't matter. But it seems to me that if you're starting out fresh with the cable anchor screw completely loose, then it makes a lot of difference.

Let's say the distance between cogs is 5mm, and let's say that shifter pulls enough cable to move the derailleur 5mm with each "click." If I start out with the outboard limit screw adjusted so that the jockey pulley is perfectly under the smallest cog, and clamp the cable based on that, we can say that the starting position is 0mm inboard, second position is 5mm inboard, third position is 10mm inboard, etc. On the other hand, if my limit screw is off at the start, and my position is more like 1mm inboard, then I'm going to be off by 1mm on all the cogs.
 

Tom K.

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Hmm. If the cable is clamped to the derailleur already, then yes, it doesn't matter. But it seems to me that if you're starting out fresh with the cable anchor screw completely loose, then it makes a lot of difference.

Let's say the distance between cogs is 5mm, and let's say that shifter pulls enough cable to move the derailleur 5mm with each "click." If I start out with the outboard limit screw adjusted so that the jockey pulley is perfectly under the smallest cog, and clamp the cable based on that, we can say that the starting position is 0mm inboard, second position is 5mm inboard, third position is 10mm inboard, etc. On the other hand, if my limit screw is off at the start, and my position is more like 1mm inboard, then I'm going to be off by 1mm on all the cogs.

Fair points.

But really, no matter where the limit screw is set, you're never going to get the cable clamped perfectly when you first cinch it down.

That's where fine tuning with the barrel adjuster on the shifter itself comes in. Just set that about 1/3 of the way out, and you'll have room to tighten or slacken the cable perfectly for precise indexing.

Seriously, if your cable tension is correct, you could actually remove the limit screw and it would have zero effect anywhere but your smallest cog.

Back to your original point: Any time I've had good shifting at one end of the cassette that progressively deteriorates as you shift to the other end, it is a misaligned deraileur and/or hanger.
 

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