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 Post subject: 2012 Red FD auto shift
PostPosted: Sun Mar 31, 2013 4:24 am 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1697
Location: Santa Cruz, California, USA
In my very rough race today (Copperopolis for you NorCal folk) my FD made some unwanted down shifts.

I have ridden some rough roads on this Red setup before but not as this level of roughness as its been on the bike less than a year.

I could have been accidentally bumping the lever with my hand.
Or it could have been gravel hitting the exposed shifter cable on the down tube.
Or there's something in the mechanism that causes unwanted downshifts when you hit sharp bumps.

Anyone experienced this problem?


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PostPosted: Sun Mar 31, 2013 10:16 am 
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Joined: Fri Dec 24, 2010 9:37 pm
Posts: 560
Location: it's raining, it must be uk
i've had the same a few times on very rough bits of road, i'm pretty sure i haven't hit the lever, i think the ratchet/whatever in the shifter gets jarred free and releases tension

mine are 2010, probably same as 2012 aside from cosmetics


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Posted: Sun Mar 31, 2013 10:16 am 


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PostPosted: Sun Mar 31, 2013 6:53 pm 
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Joined: Sun Mar 27, 2011 8:16 pm
Posts: 425
Had the same experience with Force and Apex.


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PostPosted: Sun Mar 31, 2013 6:58 pm 
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Joined: Wed Feb 15, 2012 1:53 am
Posts: 45
had this problem with red 2011 with the titanium front mech, no problem with new sram red though!


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PostPosted: Sun Mar 31, 2013 10:00 pm 
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Joined: Tue Feb 01, 2011 6:53 pm
Posts: 17
I would just switch to the new Yaw derailleur (its what I did) and I had no issues at Copperopolis yesterday... With the exception of my headtube and stem nuts rattling free. :roll: Riding from the downhill segment to the finish line with free spinning stem (hand tightening it constantly while I rode) would have been funny if wasn't so terrifying.


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PostPosted: Mon Apr 01, 2013 12:54 am 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1697
Location: Santa Cruz, California, USA
I have the Yaw FD already. Not sure how a different derailleur would prevent it.

Riding that downhill with a loose stem would make it extra exciting... like the truck with cattle trailer coming up that we met on our first lap.
When there's no other traffic on that road I kind of enjoy it.


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PostPosted: Mon Apr 01, 2013 4:18 am 
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Joined: Tue Feb 01, 2011 6:53 pm
Posts: 17
Oops read the first line and that overrode what you wrote in the subject line. The only thing I can think of for rear shifting is make sure that there is no slack in the line and if you are not already running compression-less housing you should consider making the switch. Although that will just make the shifting better and has nothing to do with auto-shifting.

On that first climb, the guy in front my had his rear-derailleur detonate...I think Copperopolis is just bad for equipment. That truck-trailer was really hauling ass and the spray from the asphalt/gravel is what I think cut my finger, although honestly I didn't notice the cut till the 2nd loop.


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PostPosted: Mon Apr 01, 2013 4:22 am 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1697
Location: Santa Cruz, California, USA
Sorry, unclear: FD = Front Derailleur. I was suddenly in the small ring when I had been in the big ring. Rear shifting was fine.


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PostPosted: Mon Apr 01, 2013 4:59 pm 
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Joined: Thu Jun 09, 2011 4:10 pm
Posts: 274
My wife's bike does this occasionally with very hard efforts on her DA 7900 equipped Ruby. I actually got her to reproduce it in the trainer - the frame is flexing enough move the derailleur over and dropping the chain.


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PostPosted: Mon Apr 01, 2013 9:10 pm 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1697
Location: Santa Cruz, California, USA
This wasn't under hard effort. In fact it happened a couple times while I wasn't pedalling. But it was always on the bumpy parts of the course.

Having ridden a Vitus 979 for years I am familiar with frame flex induced ghost shifting. But this is on a Cerveo R3SL and I weigh 145 lbs. I'm not flexing this frame much even when pedalling hard.


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PostPosted: Sat Apr 06, 2013 11:35 am 
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Joined: Sat Jun 13, 2009 4:02 am
Posts: 1960
Location: NoVA/DC
If your cable tension is too high, or your high limit screw is too far in, then the shifter may juuust barely be clicking into position for the big ring, allowing it to slip out of position when jostled.


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Posted: Sat Apr 06, 2013 11:35 am 


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PostPosted: Sat Apr 06, 2013 2:36 pm 
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Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1697
Location: Santa Cruz, California, USA
Good point, thanks. What is the ideal cable tension?

It could also be that the shifter was just barely clicked into poisiton in the big ring because of me- I sometimes don't push it all the way. I discover that when the chain rubs the front derailleur cage in the small cogs. I think it's because I spent so much time on Shimano 7800 which has a much lighter action (and shorter lever throw for FD upshifts).


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