FD grinding...LBS says there is nothing you can do
 

I started out on a bottom level road bike with a triple. Great for a beginner, but the constant grinding of the FD was driving me crazy. I understand the whole cross-chain issue and it makes sense on a wide triple. Now I have had 105's (double) on my last two bikes and both had issues on the big-big rings. Took it to my LBS, which is a very good shop, and the mech said if he makes the big-big grind go away it will grind on the big-small. Is he FOS or is this the truth? Seems kind of rediculous to have a drive system that doesn't allow you to use all the gears properly.

I very rarely use the small cogs on the cassette, so should I just set it up to run smoothly on the big cogs?

He's correct.

:twitchy: He speaks the truth. Look up the gear ratio you get on the big-big combo, and find the small-big combo that gets close to it.

All true. This should be a short thread. There is no excuse for big/big or small/small, especially on a triple, in everyday life.

Crap. My dilema is that my most comfortable gears are big ring in front, and then the biggest 3-4 rings on the back (I could probably do without the 3 smallest rings all together). The only time I shift to the small ring up front is when going up a steep hill. So would it make sense to adjust the FD so that it sits a little to the inside so that it doesn't grind in the big-big gears?

Also, my buddy has an Ultegra FD he has offered to give me. Would that make a difference? Somebody has to make a FD that works on all gears.

I guess I wasn't clear. I have a double now, not a triple (fixed the original post). And it still rubs. So even on a 105 double, the big-big is going to rub?

Depending on a lot of factors it is usually possible to configure it to keep out the chain rub....but this is affeccted by the stiffness of the drivetrain and the frame, cable system/housing stiffness, etc...

I can usually find a way to make it work but I usually have to cheat it to the big/big getting a tiny bit of run in the 53x11....but let's face it I don't use that gear very often and when I do I am usually hurting too much or going to fast to care about chain rub. The big-big - while not recommended as it does put a lot of stress on the chain and leads to premature chain and cog wear - is an easy quick bailout for small kickers around here while racing or in groups. Being able to use it can mean using an 11-23 in a race - giving you back nice gear stepping in the middle where it counts and still giving you that 23 for a small kicker on the course.

switch to sram rival or force. the big ring is made to be compatible with all gears on the 10speed cassette. I mentioned this in the Big Ring Syndrome thread:

+1

Even on a double cross chaining will cause unnecessary wear on your cassette, chain and chainrings. As others have indicated, there is purposeful overlap in you gearing so that you do not need to use the big big or small small combos. You should be able to get proportional gear increases by skipping those combos. It is by design even though it seems like you got short changed when you realize your 10sp only has 9 useful gears or less if you have a small frame.

I like that, but it would cost more than my whole bike to upgrade to SRAM. One my next bike I will definately investigate.

If you are riding using the big ring and the biggest 3-4 cogs in the rear you are doing it wrong.

Those same happy gears will be found off the middle and further down the cassette and will give you a far better and more efficient chain line.

You should punch in the stats of your drive into a gear calculator and see where your gears overlap and where those best combinations are.

Maybe I've been doing it all wrong (only been riding for about 7 months). I have been trying to stay as much as possible on the big ring. Using the small ring has only been a last resort when going up hills (the shift of shame). So, instead of using the big-big combo I should be using a small-medium combo?

Then why did shimano redesign 7900/6700/5700 so you can ride big/big with no rub? I'm sorry, but that's BS. It will wear out your chain faster, but other than that there is no reason you cant use the whole cassette with the big ring these days if you dont get FD rub. Chain life is pretty short with 10speed chains anyways, even more so if have a compact, so why even worry about it?

Cross chaining in the small/small combos is another matter though, since your chain may hit the big ring due to the chain angle.

To stop people like the OP bringing their bikes back to the LBS repeatedly to have something fixed when it's not even broken.

Just because a bicycle will shift into those bad combinations does not mean that they are supposed to work this way... every derailleur system that uses standard chain rings and a modern spaced cassette has a fair amount of overlap.

A good rule for running a triple as efficiently as possible is to use the 4 low cogs with the small ring, you can run the full range off the middle, and run the 4 smallest cogs with the big ring and that will give you access to pretty much every gear you have available to you.

A double will forgive you a little more for cross chaining but there is still no good reason to run a big/big combination.

i've been riding an even shorter time than you, but on my triple (which for my purposes is essentially a double, i've never had to use the small cog) i almost ALWAYS stay in the middle cog on the front and use the 3 or 4 smallest cogs in the back and haven't had any issues. now that my fitness is improving i am finding that middle cog in front and smallest cog in back just isn't cutting it for some of my sprints, and going up to the large front cog makes me have to shift to the larger ones in the back and i get that chain rub on my FD. but i just ordered a double crankset that has a slightly larger "small" cog than the middle one on my current setup so i hope that works out... i got it for a hell of a cheap price considering it's a new-in-box 105 crankset.

you mentioned someone offered to give you an Ultegra FD... even if you don't need it, why not take him up on the offer and give it a shot? it's worth trying at least.

I remember when I felt like that when I rode a triple.

Yes.

You can play with this...http://www.sheldonbrown.com/gears/

How about the very slight chain rub I hear while in the middle ring and largest rear cog? I have that problem on both my triples, and it's why I don't like indexed front derailleurs. I don't know if there's way to adjust that out.

Yes

Or to allow people who have the fitness to climb rollers in 50/25 or 53/25 the ability to climb short hills in the big ring without taking the time to shift to the small ring, then back up and down the cassette as soon as they crest the hill.

bingo!! as others have said yes cross chaining is an issue with even doubles. sometimes yes you can get it to work but that just depends on a few things including the frame (length of chain stays) but it is still not recommended. dont be afraid to shift up front when needed. if your FD is tuned correctly this shouldnt be an issue.

Probably both. Either way it's not good for your bike and it shouldn't be done often.

Wait, so both Shimano and SRAM design their FDs to allow you to crosschain, but it's bad for your bike? Funny, I thought running worn out chains is what damages your drivetrain:o

Excessive wear is bad for your bike. Crosschaining causes excessive wear. I don't even know why we're arguing about this.