Front derailleur tweaked - got a couple of other questions

[Llewellyn]

So I’m feeling quite smug and pleased with myself after having built up my frame after it came back from a respray. I’m feeling quite pleased with myself because by and large I have no mechanical skills whatsoever, so to be able to finish this without having to concede defeat and walk into the LBS with my tail between my legs and ask them to finish the job for me is quite an achievement. It took me far longer than any self-respecting bicycle mechanic would have taken but I had fun and learnt some things along the way.

Anyway, the front derailleur shifts well but the chain rubs against the outer cage slightly when it’s in the big ring/smaller cogs combo. It probably needs about 1 or 2mm more clearance for it to run nice and quietly. Is there a way I can bend the cage slightly to get the clearance I need or is it a matter of adjusting the derailleur until it stays clear? It’s a 9 speed Ultegra set up and the FD is a braze-on. I’ve swapped the 53T chainring for a 50T TA ring and as a result the FD is at the bottom of the mount on the frame so it can’t go any lower.

Should I take it to an LBS and get an expert to tweak it that last little bit?

[bismo37]

Can you give the derailleur outer limit screw (H screw) another 1/4 to 1/2 turn to allow the cage to move outward just enough to get rid of the chain rub without the chain falling off? I wouldn't bend anything.

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

[Peter P.]

I'm assuming the same parts were used successfully on the same frame before repaint?

Follow the link provided by bismo37 or even better yet, pony up some cash and buy the essential Park Tool Blue Book of Bicycle Repair.

Some tricks: Align the outer cage so it's in the same plane as the outer chainring. The gap between the lower edge of the outer cage and the tips of the large chainring teeth should be 1-3mm.

There should be a minimal gap between the chain and the inner cage of the front derailleur when the chain is in your lowest gear; just enough so there's no chain rub.

The rest comes from the Park Tool link provided, or just buy the book.

Occasionally, the advanced mechanic will bend the cage but for the most part it's not necessary with today's well designed front derailleurs.

[oldpotatoe]

So I’m feeling quite smug and pleased with myself after having built up my frame after it came back from a respray. I’m feeling quite pleased with myself because by and large I have no mechanical skills whatsoever, so to be able to finish this without having to concede defeat and walk into the LBS with my tail between my legs and ask them to finish the job for me is quite an achievement. It took me far longer than any self-respecting bicycle mechanic would have taken but I had fun and learnt some things along the way.

Anyway, the front derailleur shifts well but the chain rubs against the outer cage slightly when it’s in the big ring/smaller cogs combo. It probably needs about 1 or 2mm more clearance for it to run nice and quietly. Is there a way I can bend the cage slightly to get the clearance I need or is it a matter of adjusting the derailleur until it stays clear? It’s a 9 speed Ultegra set up and the FD is a braze-on. I’ve swapped the 53T chainring for a 50T TA ring and as a result the FD is at the bottom of the mount on the frame so it can’t go any lower.

Should I take it to an LBS and get an expert to tweak it that last little bit?

When in small ring and lowest cog is back(biggest cog), make sure the inner portion of the FD cage is really close to the chain..adjust with limit screw. shimano says 0.0 to 0.5mm..close.

Make sure cable is tight. shift to big ring and smallest cog(highest gear) and adjust limit screw so FD outer cage is about .5mm away and outer cage is aligned with chain. Also make sure FD outer cage is about 1mm above big ring.

[Llewellyn]

Thanks for the help - I'll give these a try. On further inspection it appears that the genuine Shimano chanring has a narrower profile than the TA ring (when viewed from above) and I think this could also be part of the problem. Also with the 50T ring I have to put the FD right at the bottom of the mounting plate and even then there's still a large gap between the bottom of the cage and the chainring (around 5mm) which is clearly more than is ideal.

I think I need to swap back to the Shimano 53T ring. Bummer, I really liked the 50

[cachagua]

I have the utmost respect for those who like their equipment the way the factory made it, but I'm a big fan of bending front derailleur cages.

I often bend the outer plate of the cage outboard at the bottom very slightly. And as others have written, it's best to adjust the height so you just clear the large chainring. The effect of bending the outer plate, then, is that when the chain attempts to overshift, it's caught by the narrower, upper part of the cage -- because it's riding the top of the chainring's teeth. And when it engages the teeth and sits down in its usual position, there's a little more room for rear shifting, and for chainring flex, than if the cage plate were vertical.

Full disclosure: I have been fired from working in a bike shop because I took too much time repairing bikes. (It was my first bike shop job; it was not my last.) I like to labor over details. I am in no way putting this out as the only method, or the right method, for getting your bike to work -- just one option.

[DRietz]

Assuming you didn't change the limits when you took it off or put it on, try adding more tension to the cable...

[bart998]

Make sure the cage is parallel to the chainrings and did not get angled a bit when you mounted it on the frame.

[Llewellyn]

I took the 50T ring off and swapped it for the original 53T Shimano one, moved the derailleur up a bit to compensate, lined it up it shifts like a charm. It's a shame to lose the 50T ring but it's just not going to work smoothly if I leave it on there.

A couple of little other issues have come up which I hope the gallery might be able to help with. I can get the chain to shift smoothly on all the cogs on the cassette except for the two largest ones. When I shift it from the 3rd largest cog it skips over the 2nd largest on to the largest cog, and the same when I shift down. I hope my explanation makes sense. I've tried twisting the adjuster to every imaginable setting and nothing seems to help. Any ideas?

And my front Dura Ace brake has a little circular washer about 3mm wide that slips into the top of the barrel adjuster. The cable housing then slips inside the washer. But the washer keeps coming out. Can I put a bit of Loctite in there to keep it in place? Any other solutions that I haven't thought of.

[oldpotatoe]

I took the 50T ring off and swapped it for the original 53T Shimano one, moved the derailleur up a bit to compensate, lined it up it shifts like a charm. It's a shame to lose the 50T ring but it's just not going to work smoothly if I leave it on there.

A couple of little other issues have come up which I hope the gallery might be able to help with. I can get the chain to shift smoothly on all the cogs on the cassette except for the two largest ones. When I shift it from the 3rd largest cog it skips over the 2nd largest on to the largest cog, and the same when I shift down. I hope my explanation makes sense. I've tried twisting the adjuster to every imaginable setting and nothing seems to help. Any ideas?

And my front Dura Ace brake has a little circular washer about 3mm wide that slips into the top of the barrel adjuster. The cable housing then slips inside the washer. But the washer keeps coming out. Can I put a bit of Loctite in there to keep it in place? Any other solutions that I haven't thought of.

Shifter 'speed' match the number of cogs? 10s shifter, 10s cogset, for example?

First click of the shifter actually shift the RD to the second cog? Put chain on smallest cog(highest gear), turn barrel adjuster all the way in, attach cable tight, shift, and adjust pulley chain to be centered on 2nd cog..continue up cogset.

[Llewellyn]

First click of the shifter actually shift the RD to the second cog? Put chain on smallest cog(highest gear), turn barrel adjuster all the way in, attach cable tight, shift, and adjust pulley chain to be centered on 2nd cog..continue up cogset.


Thank you so much. I tried it this way and had it sorted in about 2 minutes :banana:
You've saved me a trip to the LBS. Time that I can actually spend riding!! Thanks again.

[oldpotatoe]

Thank you so much. I tried it this way and had it sorted in about 2 minutes :banana:
You've saved me a trip to the LBS. Time that I can actually spend riding!! Thanks again.

happy to help, thanks for the note.