Front Derailleur problems, chain coming off.

[idlecyclist]

Not sure if I am missing something, but i cant seem to get the Front Derailleur shifting properly.
I'm running a ten speed compact 105.

I set the Low limit with no cable attached, chain on the small front gear and largest rear gear. 1mm gap, no rubbing, all is good.
Then attach the cable, Chain on the Big front gear and smallest rear gear and i adjust the High Limit to a 1mm gap. A few test shifters with the chain still in the rear small gear and all is fine.

But if I then put the chain back in the largest rear gear, the front derailler wont shift far enough out to shift from the small front ring to the big!
To get it to shift I have to let the High Limit out a bit, but by doing this the gap is now to big when on the small rear gear and the chain comes off.

I just cant seem to get it right. I've sort of got it on a unhappy medium at the moment.
Am i doing something wrong, or missing out something that i should be doing, or am i just going to have to live with it!

Thanks in advance for any help

 

[Milkfloat]

Don't set it with the chain on the largest rear cog, this is not something you would do when actually cycling (changing to the biggest front ring whilst on biggest rear).

You could also check with front derailleur alignment.

 

[idlecyclist]

Cheers Milkfloat, that does make sense.
But is that the correct way to set it up, or a compromise?

 

[Ajax Bay]

I set the Low limit with no cable attached, chain on the small front gear and largest rear gear. 1mm gap, no rubbing, all is good.
Then attach the cable, Chain on the Big front gear and smallest rear gear and i adjust the High Limit to a 1mm gap. A few test shifters with the chain still in the rear small gear and all is fine.

But if I then put the chain back in the largest rear gear, the front derailler wont shift far enough out to shift from the small front ring to the big!
To get it to shift I have to let the High Limit out a bit, but by doing this the gap is now to big when on the small rear gear and the chain comes off.

Am i doing something wrong

We're doing a bit of guessing here and there are some potential anomalies in your description.
1) I suspect that when you attached it, you have not got the cable properly taught, and it needs to be. You might like to try setting the low limit screw to chain touching or close (r than 1mm) (small chainwheel (cw) to large sprocket) then attach the cable tightish, and then let the lower limit screw off a bit - should allow the cage to 'relax' and off the chain (and the cable will be taught).
2) As @Milkfloat has said, you'll never be in the large sprocket wanting to change to the large cw. So once you've set the top gear line, change to a middle sprocket at the back and test the small cw shift to large. Adjust the upper limit screw as necessary.
3) Then try it on the road.

 

[Heisenberg71]

As ^^^^^^^
Big ring / big cog is giving you a false impression of what the high adjustment needs to be. Also as above, check your cable tension

 

[Big John]

When in doubt Youtube's always worth a look. A picture paints a thousand words, etc, etc..

View: https://www.youtube.com/watch?v=Ea03ChN-7Vg

 

[idlecyclist]

Cheers guys, good advice, especially the video.
My cable tension is OK, i did adjust using the barrel adjusters.
I think, as has been said, im trying to get it working on a gear combination i would never use, so not worth worrying about.

Anyway, after riding for a few days since adjusting, the gears are shifting nicely and no more chain drop off (touch wood) so i think i was maybe being a bit to fussy.

 

[Deleted member 1258]

Have a read through this.

http://www.parktool.com/blog/repair-help/front-derailleur-adjustment#article-section-2

 

[Ajax Bay]

As you can see ^^^^^^ @dave r , he's sorted it. Welcome to the thread.