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Old 03-27-11, 06:27 AM   #1
th2dge
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Help me figure out why my Front Derailleur is being a pain.

Hey,

I got the following problem: The chain rubs against the front derailleur on the biggest front chain ring. The rubbing is really slightly and only when you put force on the pedals while riding. Nevertheless, this needs to be fixed. Because I'm a person that rather tries to understand the mechanics than bring it away for service I decided to mess with it.

Now here's the deal: I got the mechanics pretty much down from watching video's and a few hours of adjusting the FD. I found out that my FD just refuses to go outward any further. The limit screw has no use because I need to practically take it out in order to even get to the biggest chain ring.

Because I felt like I was doing something wrong I decided to completely remove the front derailleur and start from scratch. I got it to shift smoothly again but the problem of the slight rub against the FD remains no matter what I try.

So basically, the setting for the FD to go outward is maxed out and it refuses to go further no matter how much tension I put on the cable. Limit screw is already maxed out.

I'm using stock parts with the FD being: Shimano C-051. I can't find much info about it other than one site saying its compatible with 6/7 speed. According to this site (its in German but you should be able to make out the parts) I can pretty much make out that I have an 8 speed.

Anyone with some clear insight as to what is going on?

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Last edited by th2dge; 03-27-11 at 10:01 AM.
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Old 03-27-11, 07:00 AM   #2
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check for bb play
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Old 03-27-11, 08:45 AM   #3
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I believe the derailleur in question is a Shimano Tourney FD C501 and is perfectly capable of handling a triple crank set-up on anything up to an 8 speed rear cassette.

If after watching all those online videos and mucking around for a couple hours you still haven`t got it set up properly - really suggest you just take it to a shop. Its normally a 10 minute operation and I suspect you just overlooking something. Exactly what it would be hard to figure out without actually seeing the bike.
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Old 03-27-11, 10:10 AM   #4
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Quote:
Originally Posted by reptilezs View Post
check for bb play
Yes, there is indeed a very slight play when I put down some pressure. This does indeed seem to be why it nudges just slightly and rubs the FD. It doesnt really feel like play though but more like a "bending". I don't know how to fix that other than shifting the FD slightly outward.

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Originally Posted by Burton View Post
I believe the derailleur in question is a Shimano Tourney FD C501 and is perfectly capable of handling a triple crank set-up on anything up to an 8 speed rear cassette.

If after watching all those online videos and mucking around for a couple hours you still haven`t got it set up properly - really suggest you just take it to a shop. Its normally a 10 minute operation and I suspect you just overlooking something. Exactly what it would be hard to figure out without actually seeing the bike.
How did you end up with Shimano Tourney FD C501? The specs write Shimano C-051 and the FD itself actually reads 050. I'm confused.

I included two pictures that show where it rubs against the FD and the position of the FD and limit screws.
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Old 03-27-11, 10:53 AM   #5
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follow the steps on the park tool site for fd adjustment. start from step 1. if you can get more clearance by drawing the exposed wire then you need more cable tension.
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Old 03-27-11, 11:15 AM   #6
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Things flex, all things on all bikes.

If you were to take any bike and put it against a wall so it couldn't roll and stood on a pedal to tension the chain, you'd find the top of the chainring moves outward with respect to the FD cage.

The flexing can be in the crank, BB, chainring, or just as commonly at the base of the seat tube as the BB shell twists slightly under the load. It's 100% normal and unavoidable, though movement due to bearing play can and should be eliminated.

Usually this isn't a problem, because before using the highest gear at high pedal pressure most folks have already shifted to a lower gear moving the chain inboard a bit.

But, if you ride in outer/outer under high load, adjust the outer limit and cable tension to move the cage out far enough to clear. This may cause trim issues using the large chainring with more inboard rear sprockets, but unless your FD system allows trim is a decision you have to make and adjust for accordingly.
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Old 03-27-11, 12:04 PM   #7
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Quote:
Originally Posted by FBinNY View Post
Things flex, all things on all bikes.

If you were to take any bike and put it against a wall so it couldn't roll and stood on a pedal to tension the chain, you'd find the top of the chainring moves outward with respect to the FD cage.

The flexing can be in the crank, BB, chainring, or just as commonly at the base of the seat tube as the BB shell twists slightly under the load. It's 100% normal and unavoidable, though movement due to bearing play can and should be eliminated.

Usually this isn't a problem, because before using the highest gear at high pedal pressure most folks have already shifted to a lower gear moving the chain inboard a bit.

But, if you ride in outer/outer under high load, adjust the outer limit and cable tension to move the cage out far enough to clear. This may cause trim issues using the large chainring with more inboard rear sprockets, but unless your FD system allows trim is a decision you have to make and adjust for accordingly.
Thanks a lot for this clarification. This absolutely makes sense on my bike. It inspired me to start over again but with more clearance in mind for the highest gear. I managed to clear more space for the front high gear. It doesn't shift as smooth down as it first did but I don't run hills so I'm always on high gears so it's a tradeoff I'm willing to make. The rear sprockets hesitate a lot now but this might be due to me messing around all day.
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Old 03-27-11, 12:11 PM   #8
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Quote:

How did you end up with Shimano Tourney FD C501? The specs write Shimano C-051 and the FD itself actually reads 050. I'm confused.

I included two pictures that show where it rubs against the FD and the position of the FD and limit screws.

Its called a simple typo and should have read
Shimano Tourney FD C051. Didn`t think it would be that much of a challenge to figure out. Anyway - if you look at the Shimano tech documents - thats the way the derailleur is speced. Really doesn`t matter how anyone else wants to represent it.

The difference between a FD C050 and a FD C051 is pretty straight forward. A FD C050 is designed for a 42/34/24 crankset and a C051 is designed for a 48/38/28 crankset.

Last edited by Burton; 03-27-11 at 06:12 PM.
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