Triban 3 Microshift front deraillieur rub in largest ring

[Ryanconway]

Hi, basically I've got a problem with the front deraillieur rub on my Triban 3 road bike when in the smallest chainring on the rear and the largest chainring up front.

I've tried setting this up myself about 4 times using this guide
http://www.btwin.com/notices/wp-content/uploads/2013/03/TRIBAN-3-MicroSHIFT-front-derailleur.pdf

I just cannot seem to make the dérailleur move far enough out! I have tightened the cable as tight as it will go (can't have it too tight or the shifter will be too hard to press) but I need just 1mm more clearance! and the only way I seem to be able to achieve this is by manually pulling the cable tighter from underneath the frame but this is only temporary as once I downshift and upshift back into (3rd gear) it has reset its position causing rub again.

Here is a photo of the problem



I would appreciate any help on this, as I'm clueless! Thanks.

[cny-man]

You don't say if the problem has always been there or developed recently, nor do we know if the bike is new or if the derailleur and lever are original equipment. That's important info.

If you can get the derailleur out far enough by pulling on the cable then logically the problem is not with the derailleur itself, but rather the lever is not able to move the derailleur far enough. The lever should not be harder to press when the cable is tightened. First make sure the shift cable housing is not too long, then disconnect the cable at the derailleur and check to make sure the cable moves very easily. Finally back off the outer limit screw perhaps a quarter turn and see if things improve. If you replaced the derailleur it may not be compatible with the amount of cable the lever pulls.

[DaveM]

Could be just the photo, but it looks to me like the derailleur is not parallel to the chainrings. If so, you need to correct that first and then redo all the other adjustments (cable tension and limit screws.) Check the height of the der. while you're checking angle as well.

[cny-man]

Now that I took a 2nd look I must agree, especially as the chain is rubbing at the front but has a gap at the rear. That should not happen in the large-small combo, where the chain is angled outward from the chainwheel.

http://www.parktool.com/blog/repair-help/front-derailleur-adjustments

[Ryanconway]

I think the angle of the picture makes it appear that way, I have adjusted height to around 1mm from the ring and the rotation is straight with the chain but the chain is so close that it rubs regardless of angle.

I had a look at your park tools link and noticed that you have to set indexing on the middle chainring? I assume this bike has indexing as its a triple and if so I haven't set it yet could this be why it won't go far enough?

And yes all parts are stock the bike came with it set like this

[cny-man]

...still missing two things - is the bike new and how/when did this problem develop?

[Ryanconway]

Bike is about a month old, the gears were set incorrectly and would not shift into the 2nd or 3rd cog when it arrived so I took it to halfords and he set them up in about 2 minutes but once I got it home I noticed that it did change now but in the largest chainwheel on the front it rubs the outside of the cage. This is only a problem in the largest gear front and smallest/2nd smallest back, all the other gears (when not cross chained) are fine.

[cny-man]

Thank you, that's the info we needed up front. Any time one describes a problem it's best to give as much background as possible. Too much detail can be confusing, but it's always safe to both describe the symptoms in detail and the timing and circumstances surrounding it.

This is clearly the Halford's responsibility. My understanding is that they do not necessarily offer the most expert service, so please ask for the head mechanic to properly adjust the front derailleur and look over the rest of the bike. That is a reasonable request given your frustrations at this early a point.

Again, even though I thought the derailleur might not be at the proper angle, the fact that you can move it properly out of the way of the chain indicates the problem is with cable pull or the lever.

[DaveM]

If the derailleur is aligned correctly, the next check is to make sure the outer limit screw is not too tight. This would prevent the cage from moving far enough out. If you can move it far enough out by pulling on the cable with your hand, then the limit is not the issue.

Next check the cable tension/indexing. You can check the indexing on the middle ring, but the real test is if it moves onto all three chainrings properly. Increasing tension on the cable should make the derailleur move farther out and stop the rubbing. But if this messes up the position for the other gears, there may be another issue.

Finally, check to make sure that the cable is anchored to the derailleur in the right place and following the right path. There is often a small groove that the cable to sit in when it is tightened by the clamp bolt and it needs to sit under the clamp bolt on the correct side (toward the center of the bike or toward the outside). If the cable isn't clamped in the right place, it changes the geometry so the the shifter doesn't move the derailleur the correct amount for each shift. It's not that rare for this to be installed wrong at the factory and the mechanic might have missed it if he did a very quick check of the shifting.

One last question. Does your shifter have "trim adjustments" (small half clicks that aren't meant to change gears but just move the derailleur over slightly to stop rubbing.) Some people get confused by these if they're not used to them and mistakenly think the shifting is not adjusted right.

If none of that finds the issue, you may have to bring it back in to a pro to tinker with unless someone else here can think of something.