chain rub on 105 front derailleur

cristiofpopa

Hello,
Sorry if this has been already discussed, I couldn't find any topic for my exact problem.

My issue is this: I have a shimano 105 5800 drive train and no matter how I tune my cable tension I get chain rub on the front derailleur. First I tuned the tension for the small chain ring - big cog, but then in the big chain ring - small cog the chain touches the outer derailleur plate. So I put in a little bit more tension until there was no rubbing, This resulted in the chain touching the inner derailleur plate when in small chain ring - big cog (actually there was touching in the biggest 3 cogs, not only the last one).

The limits screws are correctly set, I already checked. The derailleur is also correctly positioned, in accordance with the shimano manual (1-3 mm above the big chain ring and parallel to it). I am also aware of the trim positions of the 105 derailleur and this is not the problem, I always shifted to the lowest/highest limit.

Did anyone experience a similar issue? Do you have any idea what might cause this issue?

Thanks in advance,
Cristi.

imafatman

cristiofpopa wrote:

First I tuned the tension for the small chain ring - big cog, but then in the big chain ring - small cog the chain touches the outer derailleur plate. So I put in a little bit more tension until there was no rubbing, This resulted in the chain touching the inner derailleur plate when in small chain ring - big cog (actually there was touching in the biggest 3 cogs, not only the last one)

It may be bike specific in terms of the geometry of the chainline but In my experience it's practically impossible to get zero chain rub across every possible gear combination. Since the inner side of the derailleur comes with a rubber strip I tend to adjust my gears so that the inner FD rubs slightly when I'm at the top most gears in the rear, I don't hear/feel it and I don't spend that much time in the top 2 gears so it works for me.

The tolerances on the front derailleur seem incredibly tight to the point where I have to get it <1mm against the outside but it will still then rub on the inside. I can't see that this problem can be solved on my current bike as I have spent a long time trying to solve.

Would love to hear some suggestions though!

Andymaxy

Use your trim there's 4 different FD position, learn it.

webboo

Andymaxy wrote:

Use your trim there's 4 different FD position, learn it.

Did you read the first post, he says it’s not an issue with trim adjustment.

Andymaxy

Webboo wrote:

Andymaxy wrote:

Use your trim there's 4 different FD position, learn it.

Did you read the first post, he says it’s not an issue with trim adjustment.

I skimmed it, let's be honest who reads word by word.

webboo

:roll:

imafatman

Andymaxy wrote:

Webboo wrote:

Andymaxy wrote:

Use your trim there's 4 different FD position, learn it.

Did you read the first post, he says it’s not an issue with trim adjustment.

I skimmed it, let's be honest who reads word by word.

Eugh skimmed milk is horrible stuff. I don't know how anyone could drink the stuff, might as well drink water.

bobones

If the chain is touching the inner plate when in small chain ring and large cog then you should loosen the limit screw because there is no tension on the cable at this point and the limit screw determines the position of the cage. The outer limit should also be adjusted in big chainring/small cog so that outer plate barely clears the chain. You can also fine tune the rubbing by rotating the cage slightly. I prefer to have little or no noise in big/big combinations and can tolerate some rubbing in small/small as I don't use that combination at all.

cristiofpopa

Thanks all for your input.

bobones wrote:

If the chain is touching the inner plate when in small chain ring and large cog then you should loosen the limit screw because there is no tension on the cable at this point and the limit screw determines the position of the cage. .

Well I think that might be related to my problem, because there is still some tension when in small chain ring biggest cog. The lower limit is ok, because if I slightly push the derailleur with my hand it will go until the limit and there will be no rub.

But if I remove all the tension for this position, I'll get rubbing in the big chain ring small cog, because I don't have enough tension for the derailleur to stay at the outer limit.

Could the derailleur spring be too weak? Is there any way to check that?

jermas

Have you set the converter correctly by checking the angle of the cable as it enters the derailleur (Shimano tool Tl-FD68)? Is the cable correctly routed around the clamp bolt?
Also make any adjustments when the shifter is in the lowest trim setting - not the low setting.
Although an inline adjuster isn't essential, fitting one can save a lot of frustration setting cable tension. Sram ones are good and stay locked in position.
As mentioned above, a very slight chain rub with the inner plate when the bike it set small chainring / largest cog is acceptable.

cristiofpopa

Thanks for the tip jermas, I wasn't aware the cable must be clipped at a certain angle. I'll check the manual about that.
I do have an inline adjuster, that is how I modify the cable tension.

I'll let you know if I manage to sort this out.

cristiofpopa

Hello. Sorry for the late reply, but I only had time this last weekend to try what jermas suggested. And it worked, the problem was indeed the cable angle. I moved the cable to the other side of the clamp bold and now everything works us expected.
Thanks again for the tip jermas.

jermas

Thanks. Glad to have helped.