ishi

First time adjusting front derailleur and all I’ve done so far is dig the hole I’m in even deeper.
When I started the front derailleur wouldn’t shift to the smallest cog; the outer cage of the derailleur only lightly scratched the chain whilst it was in the middle cog. However, after doing what a beginner does best, I’ve made the situation worse. When in first gear, the chain is still not pushed enough by the outer cage - only a light scratch. Furthermore, when shifting up from first to second gear; the inner cage goes so far and pushes the chain from the first cog onto the third cog.

As I said, I am a beginner without much experience of adjusting derailleurs. Can I somehow go back to square one and try again, or should I go to a nearby mechanic?


if further clarification or pictures are needed, please ask. Any help or tips is greatly appreciated!

Bill Kapaun

Did you do anything else, like changing the crank or Bottom Bracket (BB) or????
Of the top, it sounds like a mismatch between the two.

grumpus

What did you do to change the adjustment so it doesn't work? Setting the front derailleur is one of the more fiddly adjustments on a bike but it's usually not hard starting from scratch if that's what's needed.

FBinNY 

Some understanding of FDs will help.

In low (inner) the cable is slack, and position is controlled by the inner limit. In high (and middle on triples) the FD is hanging on the cable, so trim is done that way. The high limit's ONLY job is to prevent overshifting on that side.

That knowledge drives the process of setting up and adjusting.

Start (before attaching cable) by setting the lower limit so the cage's inner plate just clears in low (inner/inner). Now set the upper limit so it shifts crisply but not beyond, when pushing on the arm. Do multiple shifts to dial this in.

Then attach the cable leaving minimal slack, but no tension in low. Now shift to high using the lever and fine tune trim by adjusting the cable.

When dialing in, you MIGHT need to back off the inner limit a hair for a crisper shift.

NOTE - this is MY method, but there are other equally sound ways. The key to respect the functions of the two limits and cable trim.

Camilo

Go online and find a good video on FD adjustment, preferably for a triple. Follow each step,step by step, starting at step one (which is usually no cable, adjust height and alignment and limit screws. Don't skip any step.

ishi

Thanks everyone for the incredibly helpful comments! None of the videos I watched beforehand had covered triple FDs, so your knowledge about them really helped. I had misunderstood the cable tension adjustment, and it now works (kind of).

My FD is weirdly shaped, in that the back end of the cage is far higher than the front (the front is 2mm above the cog), and I can’t seem to tilt it. This results in that when the rear gear is higher, i.e the chain is “lower”, the chain is rubbing on the underside of the outer cage (and won’t shift down).

Is there something else causing this, should I be able to tilt it, or do I need to install a new FD? Perhaps one shouldn’t downshift without being at the biggest cog?

FBinNY 

The last tiltable cage FD in memory was the Simplex of over 50 years past.

FDs no longer have tiltable cages. The cages are curved to match the chainrings they're designed to work with, ie. 53t for road, or 46t for mtb.

When you use smaller chainrings than expected you get the effect you're seeing. You can also get this if the seat tube is steep, or the braze-on tab positioned poorly.

This can be especially problematic with triples and small inners. The assumption is that you won't use the innermost chainring with the outer rear sprockets.

Kai Winters

Assuming the front derailleur is a proper match for the crankset..
First make sure the front d is in the correct position...the spacing between the outer guide and large chain ring is correct then the guide plate is parallel to the big chain ring.
Then follow FBinNY's info.
I don't attach the cable until the front d is correctly spaced and the space between the inner plate and inner chain ring is adequate when the rear d is in the easiest gear. Then I attach the front d cable, make sure the front d shifter is in the correct position, attach the cable and so forth.

fishboat

https://www.parktool.com/en-us/blog/...railleur-works

https://www.parktool.com/en-us/blog/...eur-adjustment

maddog34

Front derailleurs are made to fit not only the Radius of the Chainrings, but also the ANGLE of the Frame's Seat Tube... A dedicated and specific Triple Front der. will also have a LONGER CAGE that will nearly touch the Frame's Chain stay when adjusted to the correct height, and also follow the Chain ring Radius fairly closely..

it sounds like you have an INCORRECT front derailleur on your bike, in more ways than one.
the proper Front Derailleur will also have all the odd shapes and ridges in place to correctly and quickly shift the chain.

eddy m

All those procedures work great for adjusting new derailers, but the cage gets bent out of shape whenever you drop the chain. Try squeezing the cage to make it narrower, and try pinching the front of the cage. Almost any derailer with enough throw and a long enough cage will work with any chainring. The curvature of the cage is not that critical. Also, get a chain keeper on the down tube to prevent chain drops, then it's easy to adjust so that it always shifts to the small ring.
If none of that works buy a new derailer. Also a chainkeeper.

em