Bicycle Mechanics - Shimano 105 front derailleur and 10 speed cassette question.

Let me first admit my amateur level when it comes to understanding bicycle mechanics. If I happen to say something stupid please forgive me. :)

I have a Cannondale R800 double with a 10 speed cassette with, Ultegra rear derailleur, and a 105 front derailleur.

No matter how much I adjust the front derailleur the chain always scrapes along the front derailleur either on the first gear or the tenth gear of the rear cassette. If I compensate for the first gear it scrapes on the tenth gear and vice versa.

When I did dome searching on the Shimano website I only see the 105 components working with a 9 speed cassette. My question is was the 105 front derailleur designed to work with a 10 speed cassette?

I should mention that the bike has all of the stock components, so I didn't think that non-compatible components would be installed, but I just can't seem to get it right.

Thanks for your help in advance.

Depending on the length of your chain stays, you might be able to set up the front derailleur to not scrape the chain when using the middle ring and the full range of the cassette. On your R800, I doubt that is the case. In the little ring and big ring, you really shouldn't be cross chaining (using the inside ring up front and the outside cog in the back or vice versa) that much anyway so don't worry about a little rub in those gears. I've always been happy with a little rub in the small/small combo, at either end of the cassette when using the middle ring, and the big/big combo. The chain rub itself is more of an annoyance than a real concern anyway unless it's rubbing very badly in which case, the chain would be derailing (and that would be a much bigger issue).

Depending on the length of your chain stays, you might be able to set up the front derailleur to not scrape the chain when using the middle ring and the full range of the cassette. On your R800, I doubt that is the case. In the little ring and big ring, you really shouldn't be cross chaining (using the inside ring up front and the outside cog in the back or vice versa) that much anyway so don't worry about a little rub in those gears. I've always been happy with a little rub in the small/small combo, at either end of the cassette when using the middle ring, and the big/big combo. The chain rub itself is more of an annoyance than a real concern anyway unless it's rubbing very badly in which case, the chain would be derailing (and that would be a much bigger issue).

Thanks for the info! Yeah it only rubs slightly. Thanks for letting me know that slight rubbing is OK. I was afraid that it may be damaging the derailleur. I also spoke to someone at Cannondale who explained that there's a half click for the front derailleur that I didn't know was there for the 9th and 10th gear. That seems to help. I recently read that small/small or big/big should be avoided so thanks for reinforcing that. I'll avoid those combos or at least use them at a minimum in the future.

When I did dome searching on the Shimano website I only see the 105 components working with a 9 speed cassette. My question is was the 105 front derailleur designed to work with a 10 speed cassette?

Boosheet. 105 is 10 speed now, in fact you can even use a 9 speed (FD-5500) with a a 10 speed drivetrain no problem. Adjustment is the key here. Also, make sure you ain't crosschaining (bib/big, small/small).

Boosheet. 105 is 10 speed now, in fact you can even use a 9 speed (FD-5500) with a a 10 speed drivetrain no problem. Adjustment is the key here. Also, make sure you ain't crosschaining (bib/big, small/small).

The rubbing only occurs in these gears big/big small/small. Why is crosschaining bad or to be avoided? Still learning so forgive my ignorance.

The rubbing only occurs in these gears big/big small/small. Why is crosschaining bad or to be avoided? Still learning so forgive my ignorance.

These two gear combinations are hard on the chain since it's angularity (and the side load on it) is at the maximum. Chain wear is accelerated for no benefit as the same gear ratio is available in other combinations with out the downside.

The general rule is to avoid big-big or small-small for any crank/cassette configuration, not just 10-speed. Front derailleur rubbing in these gears is almost unavoidable but not a problem since you shouldn't use them anyway.

The general rule is to avoid big-big or small-small for any crank/cassette configuration, not just 10-speed. Front derailleur rubbing in these gears is almost unavoidable but not a problem since you shouldn't use them anyway.

Got it. Thanks for clearing that up.