dirtydozen

Hello,

I have bought a second-hand road bike in early june, tarmac SL4 with shimano 105 5700 groupset, with a triple 50-39-30 crankset. FD is compatible with this.

Since I have it the FD isn't working properly, 3 different bike shop took a look at it, but none managed to index the FD, I tried aswell with no success. 4 people that know about roadbikes failing to index a FD.. there is a weird thing going on.

The main problem is downshifting from the big ring to the middle ring, I have 2 choices : either I can downshift easily but 50-11/13/15 are rubbing, or nothing is rubbing but I have to be high in the cassette to downshift / I have to downshift to the little ring and then upshift onto the middle ring (clearly this kills the momentum I have at the bottom of a climb).

I have now ridden 5 500km (3 500ish miles), but I just can't stand it anymore.

I was thinking about changing the big ring, middle ring, cassette, chain and FD.

I would like to get a 53T ring but I don't think any FD can have enough capacity to do 53T to 30T, and going 53-39 is not possible since I love doing hard climbs (39 is too much for me in those climbs) and changing the lever is expensive.

Do you guys have any ideas on what can I do ? (about fixing the current set up or thinking about a new set up)

Here are some photos of the FD when the chain is on the middle or big ring (I know it's dirty but when everything was clean it wasn't working either, now I live in a small flat it's hard to find a place to clean the bike and use chemicals)

https://ibb.co/vv5mDcq
https://ibb.co/hZNxGGV
https://ibb.co/jzf2Lnq
https://ibb.co/Y2NrkzX


Thank you for your time, I really appriciate it.

ARider2

First thing I would do is clean the chain, cassette and chainrings really well. From the pictures it looks like sandy grit on the drivetrain and I find in extreme cases it can cause chain suck and it less extreme cases it can slow down shifting. The next thing I would do is adjust the front derailleur by rotating it clockwise so the rear part of the cage is slightly inboard which I find can help with downshifting. Also make sure the bottom of the cage is in the correct position in relation to the top of the chain rings.

andrewclaus

The FD appears in the photos to be a few mm too high. It should clear the large chain ring by 1 to 2 mm. I agree with the 1 to 2 degrees of rotation.

As a last desperate measure before you replace parts, I would try "modifying" the FD cage. Use adjustable wrenches to bend the outer plate a fraction of a mm, see if you can get the right clearance in the right spot, and still retain shift quality. I've done that on cheaper bikes and components, and would never do it on someone else's or a client's bike.

AeroGut

The DR is also positioned slightly higher than necessary. I would try dropping it down a few mm and see if that helps, especially when combined with an optimum angle as mentioned by others.
Basically, just start from scratch as if you were installing it for the first time and setting the height and angle and setting up the indexing. Sometimes that works better than trying to make minor tweaks to an existing position.

dirtydozen

Alright thanks for your input guys, I will try this and I will let you know how it works! When I tried to index it myself I didn't change the position of the FD, I assumed the LBS checked that already..

Thanks for your input! Yes I know it's a very dirty drivetrain, but sadly I live in a small flat with no balcony/courtyard, I can only do a good wash/use chemicals every couple of months at a friend's house. I had this shifting problem when everything was super well cleaned, so the dirtiness of it all isn't causing the problem, even though I agree with you it's clearly not helping.

Clearly the position seems wrong, thanks!

CargoDane

Bring a bucket or two of soapy water and a brush and do it on the street. You don't need to do it inside or on a balcony. People also wash their cars or motorcycles in the street.

Eggman84

When cleaning anything outside,(even with "biodegradable" products) try to make sure your wash/rinse water goes to a sanitary ewer that leads to a wastewater treatment plant and not the storm sewer, which leads to those overrated bodies of water like lakes and rivers. Though I am guilty of washing my car and bikes in the driveway with water running off to the storm sewer. so who am I to preach. Just a thought we can all try to be easier on the environment.

CargoDane

No different than washing it on a balcony. But point taken.

dirtydozen

@cubewheels @andrewclaus @AeroGut @ARider2

I changed the position of the FD as you guys suggested and it worked flawlessly for a 2h30 ride, thank you very much!
I can't believe the 3 LBS couldn't figure this out.. one of them didn't even realize my shifter has a trimming position for each ring
Thanks again, its actually the first time i experience smooth 105 and i'm very pleased, comming from old soras

Reynolds 

Glad BF helped you solve this problem.
The first thing I do when trying to fix FD issues is to check the FD is as near the big ring as possible without touching it. This solves many problems with only 2 adjustments, FD height and cable.

ARider2

Good to hear you got it working properly. It always feels great when you solve a problem like this especially one that eluded your LBS.