jgf310

My 6703 front derailleur stopped working on a ride a few days ago. I figured the cable had a few broken strands that were causing it to hang up - as this is usually what the problem is. The left shifter seems to destroy cables, I think because the bend is too tight.

Anyway, I took the cable off - and it was fine. Without the cable in place I shifted through the range a few times and everything seemed fine with the shifter.

I put the cable back on.

When I shift up - from the smallest chain ring to the middle and then to the biggest chain ring, everything seems fine,

But, when I shift down: trying to go from the big to the middle ring.., it jumps down - with al lot of force and a very loud clunk - to the smallest chain ring

It doesn't seem like there is too much tension on the cable - I made it hand-tight with the cable guide and the shifter set for the smallest chain ring. If anything, now that I am operating it there is a slight amount of slack in the cable at that position.

Like I said - the shifter seemed to work.., but I also don't see any problem with the derailleur...

Does anyone have any suggestions?

jgf310

So I thought I might have made a thread about this problem before - and I found it:

https://www.bikeforums.net/bicycle-m...l#post16056733

i have replaced this shifter a few times...

It's not exactly the same behavior - because in the present case, the shifter will move the derailleur down.., it just goes all the way and misses the middle chain ring

Crankycrank

Like your older post mentioned try flushing and lubing the shift lever mechanism and report back. Try the easy stuff first and at least eliminate the "needs lube" issue before moving on.

Andrew R Stewart 

I'll also mention that Shimano road triple ft ders that were controlled by a STI lever were known for the way rapid down shift der cage movement. So much so that many road bike started to come with seat tube mounted chain derailment guards, as well as many after market ones being sold too. Andy

jgf310

I just finished doing that - took both the derailleur and the shifter off.., de-greased them thoroughly and re-lubricated them.

I put them back on the bike and gave it a try...

What happens is that it still shifts up to bigger rings normally.., but when i try to shift down from the big ring, it doesn't stop at the middle ring, but instead goes all the way. If anything it does it with even more force now that it is clean - the whole bike shakes on the stand as the spring goes right to the limit.

My conclusion is that the little pawl, or whatever, that is supposed to stop the motion at the index position, has failed.

I can't find any new 6703 shifters anywhere, so I bought the best-looking used one I could find on ebay - $175.., ouch!

This failure node is a little different than in the past - back then, it wouldn't shift down at all when it failed - but I guess the root cause is probably the same.

But hey - this one has lasted since 2013!

Going forward I will change the groupset. I don't really want a triple anyway...

It's a 2007 Roubaix, but I think it's still worth rehabilitating.

Crankycrank

Well booger. I like to recommend these Gavenalle Shifters if you've never heard of them. Not for everyone but cheaper, more reliable, serviceable and easy to change to various speed cranks and cassettes than the standard brifters for futureproofness. Shifters – Gevenalle They have a video or two showing them in action.

masi61

I highlighted something in your description of the setup could be your mistake. Not sure if you remember this or not or if you looked up any of the Shimano 6703 pdf setup documents but do you remember the orange setup block that comes with a new triple front derailleur? This is actually pretty important for proper operation of the triple. You insert the setup block against the spring in the parallelogram and it pushes the cage out ~5mm or halfway between the "granny" ring and the middle chainring. With the shifter in the "granny" position you can then pull the slack out of the cable (while making sure that the adjuster barrel is not bottomed out but has both (+) and (-) capabliity. Once you snug down the cable, you can remove the setup block (or 5mm allen wrench if you don't have the block) and test the shifting. Now I can't absolutely promise that this will cure your problem but since you already seemed to have verified that you have no broken cable strands and also that the shifter can click through the 3 chainring settings (when tested with no cable set up yet) - I would suggest you give this a try. It worked for my Dura Ace 7703 and a couple other Shimano triples I have worked on. When done like this, the down shift is no longer abrupt and you can tell it helped because the trim clicks become more usable and there is no overly tight feeling anymore either. I'm curious to know if this trick might resolve your issue - good luck!

jgf310

well.., mine is green.., but even though i actually installed this groupset and have had the derailleur off a few times.., i'm not exactly clear on how to use that thing.

in the directions, it seems to say to take it out _before_ attaching the cable...

masi61

AFAIK - it is not just packaging. It is a set up gauge! After you set your triple up this way, a lightbulb went off in my head and I no longer have this anxiety about triple shifters being "defective" because they're not. It is your setup!

After you tighten the cable with the cage offset slightly in toward the middle ring, you can then use your adjuster barrel to dial in where you want your trim stop to click into action or how many cogs you are trying to have rub free. For me I have no rubbing in 7 out of 9 cogs then do a half "trim" click so it does not rub in the 2 biggest cogs (mostly a big chainring thing, i.e. "big-big" combo).

jgf310

So I'm just getting a chance to look at this again. I got the new shifter, but thought i would give the old one a try using the "Pro-set Alignment Block".., as you suggest.
Yes - I agree that it is some sort of a setup aid...

I have not been able to figure out exactly how it goes in the derailleur, and I haven't been able to find any pics online.

I also note that if you look at this Shimano manual; https://si.shimano.com/pdfs/si/SI-5LX0B-001-ENG.pdf

Where the SIS adjustment section is.., it says to take out the alignment block, in the step _before_ attaching the cable...

If you look in the previous section, it indicates that the purpose of the pro set alignment block is to help get the _vertical_ clearance of the derailleur cage correctly set to between 1-3mm over the largest chain ring - by holding the cage out over that largest ring, so you can better see that the clearance is correct.

My vertical clearance is fine.

Anyway - like i said - i can't figure out the correct way to stick the alignment block into the derailleur - i see it's supposed to come in from the rear, with the little indent facing out.., but none of the ways i have tried that really look correct.

masi61

The “pro-set gauge” is the piece of tape that is applied to the outer front derailleur cage.

The “pro-set alignment block” is the one that offsets the cage slightly when you first pull cable when you are in the small chainring. The “pro-set alignment block” should have 2 little grooves in them that will nestle into the inside of the swinging parts (aka “parallelogram”) of the FD. To slide the pro-set alignment block in there you have to manually push the cage outward against the strong spring until you get enough daylight where the alignment block fits in there.

I’ve done this maybe half a dozen times over the last 10 years. I know this is how Dura Ace 7803, 7703and Ultegra 6503 and 6603 triple front derailleurs are set up. I have 2 sets of 6703 three by 10 drivetrains for future builds but have not finished setting them up yet.

Thanks for your reply to my suggestion. I’ll eagerly await your response to see if this works or not…

jgf310

I have tried to put the Pro Set Alignment Block into that space by moving the cage - it just never really looks "right"...

but anyway - I understand that the pro set gauge - the tape - is to measure the vertical distance between the cage and the chain ring. It shows that in the PDF manual that I linked above.

What I was saying, is that from the PDF manual.., it seems that the purpose of the pro set alignment block is to hold the cage out far enough, so that you can use easily the gauge (the tape) to see that the clearance is correct.., and not to pre-tension the cable.

The reason I think this is that in the manual, in the next step after setting the vertical clearance, it says to remove the proset alignment block before it says to attach the cable to the derailleur.

I do have a question though...

Do you think it matters whether there is a chain in place when testing the up and down movement of the front derailleur?

To make playing with this easier, i took the chain off. I can't think of any reason that the derailleur shouldn't stop where it is supposed to without a chain.., but maybe I'm wrong about that...

richosti

Getting front mechs right is one of the hardest things on a bike! The Ultegra has this problem often..

masi61

jgf310 when I looked again at the Shimano tech doc, the use of the set up block was explained as you described. I know I read somewhere that leaving it in place until after you pull the cable gives proper feel to the triple indexing without it feeling so tight when you shift to the big ring.

As to your question about setting it up with or without the chain - my preference would be with the chain in place so you have no surprises. Let us know how your final setup shifts.

Regards, from Bill.

Soody

End this nightmare, just switch to a friction shifter for the front, Lance style