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Slow rider on fast wheels
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Hi guys, thanks for all the advice on my saddle problems the last time.

I encountered another problem. Recently, I changed to another wheelset, and noticed the bike behaved differently in terms of trimming and chainrub. When I shift to the smallest chainring/smallest cog combo, and try to do trimming i.e. slight upshift of the front derailleur, it made things worse. Not only did it not reduce the chain rub sound, there would also be additional rather loud clanging sounds that occurs a few times in quick succession, for every crank revolution. It does get audibly loud during higher revolutions of the crank.

Chainrub also occurs in the smallest chainring / second or third smallest cog, but trimming worked when in these combinations.

This never happened on my previous wheelset, where only the regular chain-rub sound was heard, and trimming did work when I am in the smallest chainring/smallest cog combo. Chain rub was not so noticeable too on the next few cogs.

Upon closer inspection, I found that the sound occurs when the chain 'bounces' i.e. vibrates near the front derailleur, a few times for every turn. It is as if the chain is having difficulty latching onto the front chainring at certain spots. The chain did not jump to a different cog though, it stays in the same cog when the vibration happens.

Can anyone please let me know if this is a tuning/setup/chain problem, or it is also a natural occurrance as part of the 'undesirable gear combo' of small chainring/small cog? How do I resolve it?

I am using a Giant TCR Composite 3, with Full Ultegra 10 speed and Mavic Ksyrium SL3.

Thanks in advance!
 

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First, you should avoid the small/small combination

theychosenone said:
Hi guys, thanks for all the advice on my saddle problems the last time.

I encountered another problem. Recently, I changed to another wheelset, and noticed the bike behaved differently in terms of trimming and chainrub. When I shift to the smallest chainring/smallest cog combo, and try to do trimming i.e. slight upshift of the front derailleur, it made things worse. Not only did it not reduce the chain rub sound, there would also be additional rather loud clanging sounds that occurs a few times in quick succession, for every crank revolution. It does get audibly loud during higher revolutions of the crank.

Chainrub also occurs in the smallest chainring / second or third smallest cog, but trimming worked when in these combinations.

This never happened on my previous wheelset, where only the regular chain-rub sound was heard, and trimming did work when I am in the smallest chainring/smallest cog combo. Chain rub was not so noticeable too on the next few cogs.

Upon closer inspection, I found that the sound occurs when the chain 'bounces' i.e. vibrates near the front derailleur, a few times for every turn. It is as if the chain is having difficulty latching onto the front chainring at certain spots. The chain did not jump to a different cog though, it stays in the same cog when the vibration happens.

Can anyone please let me know if this is a tuning/setup/chain problem, or it is also a natural occurrance as part of the 'undesirable gear combo' of small chainring/small cog? How do I resolve it?

I am using a Giant TCR Composite 3, with Full Ultegra 10 speed and Mavic Ksyrium SL3.

Thanks in advance!
The Ksyriums likely have a little different dish than your old wheels, which puts the cogset in a little different position. You will need to adjust the trim on your rear derailleur. I suggest following the trimming instructions on the Park website at http://www.parktool.com/repair/readhowto.asp?id=64. You also should not have to do any "trim" adjustments on normal shifting. If you get this set correctly, the indexing should be fine.

The clanking, etc. you are finding is probably due to the chain hitting the pins on the front chainrings. Front chainrings have ramps/pins to help shifting. In the small/small combination the angle can be so severe that the chain will catch those pins. Some cranksets (FSA) may even have this problem in the second cog. Most manufacturers will tell you to avoid the extremes on both ends as the chainline is too steep an angle.

So, while you may have been able to get away with it on your old wheelset, you probably can't (and shouldn't) with your new Ksyriums.
 
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