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Front derailleur hitting chain - drivetrain to extreme??

by Brannonc4
Sat, Sep 19, 2015 18:49
2

I recently purchased a Trek Madone 2.1 and after a few weeks of riding and cables stretching etc I took it to the local bike shop to get the derailleur correct because it was hitting the chain on the big ring, the guy played with it for a while and told me that it would never be perfect because the drivetrain is at too much of an angle 39 .. so I can be in certain gears but not others 102 . Is there any way of getting round this?? I find it odd Trek creating a bike that will not shift into some gears without hitting the chain!!. If I can get any advice id be extremely grateful.

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Chuck | 9 years ago
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Pretty common and nothing to get worked up about. As sergius says you shouldn't really need to use every single permutation of front and rear, so if some of the more extreme ones cause the chain to rub then take the hint and change gear 1

IMO it's not helpful to think in terms of having (nFront x nRear) gears, because some of those are effectively pointless or unusable.

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sergius | 9 years ago
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Unless you have an auto-adjusting groupset like Di2 or I think the SRAM ones, you will always need to do some trimming in certain gears.

Realistically, you "shouldn't" be using say the smallest three cogs on the cassette when in the small in the front. Just like you "shouldn't" use the largest three cogs on the cassette when in the large on the front. It's not to say you can't, it's just not recommended. I read somewhere that cross-chaining like that can cost you about 5% of your power output.

On the Tiagra groupset on my other bike, I'm constantly having to micro adjust the front derailleur (trim it) to prevent chain rub. On my Di2 bike it does it automatically which is lovely.

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