ziconater

I'm hoping someone might know the answer to this. I run a Shimano 5700 groupset on a Tek Madone, but the front derailleur is Tiagra. I have been fighting with this front derailleur now for two years, and I'm fed up with adjusting and cleaning it just so I can have a have way decent shift.

So.... I'm going to replace with a 105 front derailleur. My question is-- do you know if I can use the new 5800 front derailleur with my 5700 shifter, or do I need to stick with a 5700 front? I heard that the new 5800 front is supposed to be a nice improvement (lighter/smoother shifting) from the older version, so I was wanting to take advantage of this.

Thanks

cpach

It would probably work OK, but the cage is a little thinner for the thinner chain, so I wouldn't necessarily expect it to shift better, and it may be more prone to rubbing in extreme gear combinations.

I'm surprised that you're having such problems with your Tiagra derailleur. For what it's worth, my anecdotal experience is that 5700 FDs work fine.

Bill Kapaun

Before you swap, have you tried raising it 2-3mm?
Sometimes it helps and sometimes......

Andrew R Stewart 

ziconater- I agree with cpach in that I wouldn't expect a significant difference in the SHIFTING between a 105 and the Tiagra. But I do have a few questions/comments.

First is what actually is the issue you are experiencing? Is it that the chain won't catch when shifting up to the large ring, or not derail off and onto the small ring? Or does the ft der do these actions well enough but you've got chain rub that you can't trim away? Does the chain jam onto both rings when shifting (chain suck of sorts)? How worn is are the parts? If the bike was clamped in a repair stand and you were shifting the ft der would it shift much better then when actually riding? How about when you pull on the cable directly (which might require some finagling if there's that damned internal cable routing)? Is there any friction in the cable route? If the cable is detatched from the der will the lever index through all it's catch points?

All this is independent in the assessment from the der's position on the frame WRT the rings or it's movement range, both of which also have to be within a narrow range of properness.

Lastly I would also ask how you're coordinating the shifting when you're riding? Do you soft pedal for the stroke or two it takes to allow the chain to lift up and over?

This issue, poor front shifting, is a common complaint that often is more the rider then the bike/parts/adjustments. But what is really going on in your case is any one's guess without in person assessment. I assume you've tried to have a shop work on this problem, having been frustrating for two years. If so did they tell you anything, make any difference, actually test ride the bike while you watched? Have you ridden with a friend how can watch what you do when you shift and then give you feed back?

"Throwing" new parts at a problem can often fix the issue when it's a hardware one (worn out, poorly adjusted, wrong compatibility) if but for the reason that the new part is starting it's install at a base line point without the "baggage" of the previous understanding. But if the shifting issue is the rider's cause then the problem will continue. Andy.

ziconater

The problem is that it becomes very stiff to shift up to the large chain ring. I have replaced the cable and removed the derailleur, cleaned it out throughly with solvent, and lubed it. It's a definite improvement, but after a month or so, it goes back to being very sticky/stiff to shift up to the large chainring. I've owned 105 and Ultegra front derailleurs before, but never dealt with this issue, and have been riding now for over 15 years on three different road bikes. I could never tell a difference from 105 to Ultegra, so I bought this bike with the 105 Group.

It may just be a defective part, so my thinking is just to replace it. I think I'll go with the suggestion by 'cpach' and just get a 5700 front derailleur.
Thanks

Andrew R Stewart 

When you say "sticky/stiff" are you talking about the der's pivots or the cable? And is this problem also present on the down shift to the small ring? generally one's hand strength is stronger then the der's return spring, so a sticky parallelgram pivot will be more problematic in the down shifting direction. Does this bike use internal cable routing? Is your sweat strongly acidic? Are the cables stainless steel? Have the bikes you've had before had the same cable routing? Andy.

ziconater

Andy-
I beleive it's the pivots, because when I clean the derailleur, it makes shifting from the 34 to 50 easier (less of a strain).

On a side note: I tried out a bike today with the 5800 groupset, and was amazed at how much lighter it was to shift both the back and front derailleurs. Meaning, if I shift from 11t to 12t, for example, or 34t to 50t up front. It's NOT more accurate, just very effortless. On my bike, I have replaced cables and housing in the past, but maybe that's part of the problem as well. What do you recommend I use next time I replace my cables/housing? I'm getting the impression that this could also be part of the problem. Oh, and btw, it's not my shifters that have the problem. Without cables attached to them, they shift without effort.
Thanks