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-   -   105 front derailuer upgrade? (https://www.bikeforums.net/bicycle-mechanics/918827-105-front-derailuer-upgrade.html)

sbslider 10-21-13 07:06 AM

105 front derailuer upgrade?
 
My Tiagra front derailleur broke, so I am looking to get a replacement. I have a 9 speed shimano drive train, and was wondering if a 105 would be an appropriate upgrade. My main concern is will the 105 cage be narrower and cause chain rub since it is made for a 10 speed set up.

Also, I presently have only two chain rings up front, but am considering adding a third as long as I am getting a new front derailleur. Any reason this would be a bad idea?

demoncyclist 10-21-13 07:12 AM

A 10s front derailleur will have a slightly narrower cage. Rubbing tends to be dependent on a number of factors, so we can't give you a yes or no. Any available Shimano 9s road derailleur will work. As for the triple, you would need a triple specific derailleur (the cage is different) and a triple compatible shifter for that to work, then you would need a triple crankset and bottom bracket. Seems like an expensive thought.

sbslider 10-21-13 07:19 AM

thanks for the note. My shifter and crankset are already set up for a triple, I think I just need the chain ring. This is a 2011 cross check.

demoncyclist 10-21-13 07:43 AM

So you definitely will need a 9s triple FD to make that all work.

Delmarva 10-21-13 08:01 AM

How will performance be improved by going to a more expensive 105 derailleur? If there isn't much I don't see an upgrade. Just spending more.

sbslider 10-21-13 09:11 AM


Originally Posted by Delmarva (Post 16177916)
How will performance be improved by going to a more expensive 105 derailleur? If there isn't much I don't see an upgrade. Just spending more.

Your response is why I was asking the question. My main reason for thinking an upgrade would be appropriate is the original broke after 16 months of use. The cage broke at the corner where the inner plate and horizontal piece meet in the front. Possibly my bad, but I don't know anything specific I did to cause it. It appears stress from shifting from the big ring to the small ring caused the stress and break. I thought/wondered if a higher quality part would be less susceptible to this happening again.

Delmarva 10-21-13 01:22 PM

Ok. Look at the construction of those units and see if there is any significant difference that would make the 105 stronger. I would be surprised if there is. The inner plate would be stressed on and break on upshifts I would think. Because it is unusual for a front unit to separate like that I think you need to look at other possibilities. What is the chain wheel range.

bobotech 10-21-13 01:53 PM

Heck as far as I can tell, the difference between my Tiagra and 105 front derailleurs is pretty much just the finishes involved. The cages look all the same.

sbslider 10-21-13 01:55 PM

Chain wheel range: Not sure if this answers the question, but the chain rings I have are 48 and 36.

techsensei 10-21-13 01:59 PM

I believe the only material difference between the Tiagra and 105 front derailleurs is the inner link of the parallelogram; it is stamped steel on the Tiagra, and cast aluminum on the 105. The cast links on the 105 should...at least in theory...make it stronger/stiffer.

Spld cyclist 10-21-13 04:49 PM

It could be seen as a downgrade, but I recently bought a Sora triple FD due to the same concern - 9 speed drivetrain and the narrower cage width that 10 speed FDs have. I wasn't sure this was a good idea because it's a cheaper part, but I've been very happy with shifting on the Sora. Don't know how durable it will be, but at that price, I wouldn't mind just buying another one if it ever fails (unless it falls apart in no time, but I don't think that will happen).

sbslider 10-22-13 06:35 AM

thanks for the inputs all, I think for the short term I am going with J.B. Weld and see how that goes. Costs $0.00 since I already have it, but it does add a fraction of a gram . . .

FastJake 10-22-13 07:54 AM

Your front derailer breaking is rare. I don't think I've ever had one break, but the pivots can wear out over time, and the cage plates can get worn down if you ride in gear combos that rub. Did you possibly jam the chain in there really bad?

If going to a triple, you will definitely want a triple FD. Since yours is broken now would be a good time to replace it. Go with Sora/Tiagra/105, whichever you want, there shouldn't be any significant differences between them. I would try to find a 9-speed which is a wider cage and have less tendency to rub.

sbslider 10-22-13 08:47 AM

for sure 9 speed when I get one, thanks for the feedback fastjake

joejack951 10-22-13 09:01 AM


Originally Posted by sbslider (Post 16180770)
thanks for the inputs all, I think for the short term I am going with J.B. Weld and see how that goes. Costs $0.00 since I already have it, but it does add a fraction of a gram . . .

Don't bother. There's no way you are going to JB Weld your front derailler back together. There simply isn't enough contact area to make a sufficiently strong bond.

Buy a Sora 9 speed front derailler and be done with it. If you want to move to a triple and have a crankset that has the mounting points for an inner ring, you'll also likely need a new bottom bracket to correct the chainline (assuming a square taper crank) as well as the triple version of the Sora derailler. You won't notice the "downgrade" and neither would you notice the "upgrade" to 105, other than the frustration of dealing with a 9 speed chain in a 10 speed front derailler (quite likely to rub).

sbslider 10-22-13 09:15 AM


Originally Posted by joejack951 (Post 16181214)
Don't bother. There's no way you are going to JB Weld your front derailler back together. There simply isn't enough contact area to make a sufficiently strong bond.

You may be right, but it is already done. If it last a couple weeks while I shop for a new part it will be worth it. If it lasts longer than all the better.

Not sure what you or the other poster mean about getting a new bottom bracket, but I have not really looked closely at how the chain line would be for that new small ring. If you can suggest some reading on this I would appreciate it.

joejack951 10-22-13 09:35 AM

http://sheldonbrown.com/chainline.html

sbslider 10-22-13 09:50 AM


Originally Posted by joejack951 (Post 16181334)

thank you


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