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Discussion Starter · #1 ·
When my chain is on the big front ring and big ring in the back (its a double, 12-25 ) if i backpedal when stopped or roll the bike backwards the chain jumps to the small ring on the crankset. I've tried adjusting the barrel on the rear derrailleur no luck, LBS couldn't fix the problem. I know not to use this combo with the chainline issues, but sometimes i'm just in that combo. It was working properly and the only thing I changed was a 50t ring to a 51t for the front then this problem started. LBS said live with it or change back to 50t, I'm sure there is a solution. Any help would be appreciated,thanks.
 

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rlrj said:
When my chain is on the big front ring and big ring in the back (its a double, 12-25 ) if i backpedal when stopped or roll the bike backwards the chain jumps to the small ring on the crankset. I've tried adjusting the barrel on the rear derrailleur no luck, LBS couldn't fix the problem. I know not to use this combo with the chainline issues, but sometimes i'm just in that combo. It was working properly and the only thing I changed was a 50t ring to a 51t for the front then this problem started. LBS said live with it or change back to 50t, I'm sure there is a solution. Any help would be appreciated,thanks.
Avoid the big ring, big cog combination....It's called cross-chaining...

as Andrea said, just don't do it...you can find a similar gear by using the small front ring... if I tried big/big on my bikes, they would most likely have the same problem as yours..just say no:D
 

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Discussion Starter · #4 ·
that situation happens on a couple of routes I ride (big ring-big ring) and it never jumped off before so I'm sure there is a solution as opposed to ignore it and it will go away. 1 rt. theres a stop light at the top of a pretty steep incline and when stopped and then backpedal to get the pedal in position to start( it is only 1/2 turn of the crank) again the chain jumps off to the small ring and it never did this before.
 

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Discussion Starter · #5 ·
Dave Hickey said:
Avoid the big ring, big cog combination....It's called cross-chaining...

as Andrea said, just don't do it...you can find a similar gear by using the small front ring... if I tried big/big on my bikes, they would most likely have the same problem as yours..just say no:D
I know your supposed to avoid that combo, and I only ride like that for maybe .25 mile, its just got me frustrated because the chain never jumped for the 3 years I've owned this bike and its setup.I changed 1 thing 50t to 51t front ring now this. I'm 50 change is hard(lol).
 

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Discussion Starter · #7 ·
Andrea138 said:
It shouldn't matter if your chain length was OK in the first place, but if it was close to being too short w/the 50t, then you may need to add a link w/the 51.
thanks I'll give that a try.
 

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Chain condition?

rlrj said:
I know your supposed to avoid that combo, and I only ride like that for maybe .25 mile, its just got me frustrated because the chain never jumped for the 3 years I've owned this bike and its setup.I changed 1 thing 50t to 51t front ring now this. I'm 50 change is hard(lol).
While I would agree with the others that you would want to avoid that chain angle, I also find myself in the big-big combo sometimes. However, I don't find myself backpedaling when stopped or rolling the bike backwards in that situation; it's a purely temporary combination when I know I can crest the hill without shifting to the small chainring.

That said, it may be that your old chainring had some wear on the teeth and that the chain was worn to match. If your chain is elongated more than 1/16 inch in 24 links (12 inches original length) then that might be the problem. I would suspect that issue more than your chain being too short.
 

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I'm just curious - why / when do you pedal backward or roll your bike backward? I sat here thinking for a bit about when I'd perform those maneuvers. My answer is never. I never backpedal, and if I have to move my bike backward at a rest stop or even in the garage, I always pick it up to move it.
 

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you've got some good ideas here...

don't do it any more...
use the small ring/smaller cog combo
or...
instead of pedalling backwards, why not hit the front brake while stopped, and lift the back wheel off the ground and pedal if forward?
sometimes i'm puzzled by what people bring in to the shop and also what they post about on the internet. weird...
 

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Discussion Starter · #11 ·
if you read the post, I don't pedal backwards, just 1/2 turn to reposition my pedal to start again. thanks for your help, give my regards to Mensa International. (last 2 posts)
 

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LOL! Hey noob sauce We're only trying to help, and all I did was ask a question that your original post didn't answer. If you read most of the responses above they generally say, "Don't do that." Speaking of Mensa, are you the president?
 

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Small/small and large/large are both to be avoided as they are cross-chaining which causes excess wear to the entire drivetrain. Shimano now encloses a (somewhat confusing) chart of gears that may/will cause noise and other unpleasant symptoms with their front-derailleurs. I enclose a copy below. I would suggest you have your derailleur-hanger's alignment checked at your local bike-shop. It's fast and easy and easy to fix if it's off. The tool costs $70, so most individuals don't have one - and most shops do.

Here's the Shimano FD-noise chart:

 

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Discussion Starter · #14 ·
Mr. Versatile said:
LOL! Hey noob sauce We're only trying to help, and all I did was ask a question that your original post didn't answer. If you read most of the responses above they generally say, "Don't do that." Speaking of Mensa, are you the president?
I'm noob sauce to posting but not to cycling or life. No, just a member like you.
 
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