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Old 09-17-12, 09:39 AM   #1
Joel_l
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XTR dyna-sys shifting issues

Hi,

I recently upgraded my mountain bike ( 2004 Enduro Expert ) to new XTR and XT components. I'm using,

All 10 speed dyna-sys
XTR SL-M980-A shifters
XTR FD-M980 front derailleur
XTR RD-M985-SGS rear derailleur
XT 11-36 10 speed rear cassette
XT FC-M780 triple crank 42-32-24

The rear works perfect. When it comes to the front derailleur, I can't find a spot where it works for all shifts. If I'm on the smallest cog, I can't shift from the middle ring to the smallest chain ring. If I adjust so that works, then, if I'm on the biggest cog, I can't shift from the middle ring to the largest chain ring. When I set it up so that while on the biggest cog, I can shift from the middle to biggest chain ring as a starting point, then go back to the smallest cog and try to shift to the smallest chain ring, it fails again. If I adjust the front so that it will finally shift to the smallest chain ring ( low side adjustment ), then when I'm on the biggest cog and shift from the middle chain ring to the smallest chain ring, the chain will fall off to the inside half the time. I have things working better by rotating the front derailleur so that the back end of it is slightly more towards the frame than the front. Seems happy here, but not close to following the spec'd setup. I know these are the extremes and I would not be typically riding here. I do how ever expect it should shift properly, and accept that there will be noise while in certain gears. Any thoughts?

Thanks

Joel
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Old 09-17-12, 09:52 AM   #2
mechBgon
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Ok, two things to start with:

1. when you sit on the bike, the suspension squats and will change the effective approach of the chain, bringing it through the FD higher. Notice how the outer plate of the FD has a "kick-down" step stamped into it... well, if you're on the small cogs in the rear, the chain may actually be coming in below that step until the bike squats. So verify your shifting setup with a test ride, it can change how a suspension bike shifts.

2. corrolary to #1 there... it's not common to be using the smallest cogs in the rear, and then try to punch down to the granny ring in the front. That's like shifting your pickup truck into 5th gear and then dropping the transfer case to LOW. I mean, technically it would be nice for it to work when demanded, but in your real-world usage pattern...? Not very likely you'd do that one except by accident. So I would a) verify the FD height and alignment respective to the chainrings, b) set the lowgear limit screw for slight clearance in low-low, c) adjust the cable to achieve slight-to-none clearance in middle-ring/largest-cog, and d) adjust the highgear limit screw for slight clearance in big-ring/smallest-cog.
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Old 09-17-12, 09:53 AM   #3
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I'm not a shifting/derailleur expert - i.e., I can put 'em together, and follow the documentation and get it pretty close, but I'm not someone who does it regulary and can provide "off-the-top-of-the-head" advice.

However, I will say that if I follow Shimano's step by step instructions clearly detailed in their PDF's I get it close enough that the mechanic I have check my stuff over will test my work for a minute and place the bike on the floor. Essentially, I've got it close enough that it's ready for the floor - and test rides.

Last year it was a Surly Long Haul Trucker with Deore XT. Got the front working I would say at about 90% in the combos you mentioned.

So seriously, http://techdocs.shimano.com Give it another try...

=8-)
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Old 09-17-12, 09:55 AM   #4
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Quote:
Originally Posted by mechBgon View Post
Ok, two things to start with:

1. when you sit on the bike, the suspension squats and will change the effective approach of the chain, bringing it through the FD higher. Notice how the outer plate of the FD has a "kick-down" step stamped into it... well, if you're on the small cogs in the rear, the chain may actually be coming in below that step until the bike squats. So verify your shifting setup with a test ride, it can change how a suspension bike shifts.

2. corrolary to #1 there... it's not common to be using the smallest cogs in the rear, and then try to punch down to the granny ring in the front. That's like shifting your pickup truck into 5th gear and then dropping the transfer case to LOW. I mean, technically it would be nice for it to work when demanded, but in your real-world usage pattern...? Not very likely you'd do that one except by accident. So I would a) verify the FD height and alignment respective to the chainrings, b) set the lowgear limit screw for slight clearance in low-low, c) adjust the cable to achieve slight-to-none clearance in middle-ring/largest-cog, and d) adjust the highgear limit screw for slight clearance in big-ring/smallest-cog.
I've noticed that Shimano's documentation has the "suspension" caveats stamped all over 'em lately...

=8-)
__________________
4000+ wheels built since 1984...

Disclaimer:

1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
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Old 09-17-12, 10:09 AM   #5
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That's an area I actually noticed, seems that little step just misses the chain. I have the derailleur as low ( 1mm from teeth ) as the minimum spec says. It does seem to work better when I'm on the bike then when the bike is on the stand. Only issue there is, what about when the rear is locked out? Given the way the chain line goes, having the derailleur rotated slightly seems to help and not cause any " extra " noise. I have a ride this Wednesday, I'll see how it does on the trail.

Thanks

Joel


Quote:
Originally Posted by mechBgon View Post
Ok, two things to start with:

1. when you sit on the bike, the suspension squats and will change the effective approach of the chain, bringing it through the FD higher. Notice how the outer plate of the FD has a "kick-down" step stamped into it... well, if you're on the small cogs in the rear, the chain may actually be coming in below that step until the bike squats. So verify your shifting setup with a test ride, it can change how a suspension bike shifts.
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Old 09-17-12, 10:10 AM   #6
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I'll go back and see if I missed anything in Shimanos notes on suspension bikes.

Thanks

Joel

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Originally Posted by mrrabbit View Post
I've noticed that Shimano's documentation has the "suspension" caveats stamped all over 'em lately...

=8-)
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Old 09-25-12, 10:08 AM   #7
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So I finally got the bike out for a ride this morning. Everything worked fine. I ended up leaving the front derailleur set so it is rotated very slightly tail end towards the frame. That seems to help the middle to small ring shift while on the small cog even with the rear shock locked out. I can cause a problem by waiting until I need to be up on the pedals and smashing hard before I shift. Then the front derailleur just pumps until the load lightens up and then will shift. Overall things worked well. The clutch setup on the rear that is supposed to reduce chain slap seems to do its job. I do notice the drivetrain get noisier faster when dirty then the old 9 speed setup.

Joel
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