gregbr549

I have a 105 9 speed front derailleur. I am thinking about changing to Ultegra so my whole bike will be Ultegra. What is the difference between a 9 and 10 speed front derailleur? Can I use a 10 speed on my 9 speed bike? I now have a clamp on. Can I use the existing clamp and buy a braze on?
Thanks for all the help,
Greg

sch

Previous posters have indicated no problems with such a change. Minor quibbles about cage width and such seem to make little practical difference to those with mid level bikes. You will gain very little out of the change, however as 10 spd offers not much more than panache or bling to the bike. Granted 9spd is so '00, it also is half the price of 10spd equipment on the retail level and is not arguably higher quality, better shifting, significantly lower in weight etc. All that aside it should be a straight forward changeover, bolt on so to speak to swap 10 for 9 spd. There is essentially no difference between 105 and Ultegra front der. 10spd gives you another single step over 9spd for those who can tell the difference in the 17-24mph range. Shimano makes a brazeon to clampon adapter.

Sheldon Brown

Right, assuming it's for a double crank. This would be a foolish waste of money, resulting in no improvement whatsoever.

If it's for a triple crank, the "10-speed" model is intended for a 39 tooth middle, while the "9-speed" model is optimized for a 42 tooth middle. You should choose based on the chainring sizes you use.

Sheldon "Save Your Money" Brown

HillRider

Sheldon, given the different "optimazation" of the two crank types, does it really make any difference in practical terms how they shift?

In the past, I've seen front derailleurs designed for 52T big rings (105, RX-100) used very successfully on cranks with 46T big rings (RSX) so I wonder if the 39T vs 42T "optimazation" really means anything.

Sheldon Brown

Using a front derailer with a big ring smaller than it is designed for doesn't usually cause shifting problems, but does generally increase the need for "trimming" the front derailer as you go back and forth in back.

The issue with triples is actually mainly based on the difference in size between the middle and big rings. My previous message was assuming the usual 52 tooth big ring, so there's a 10 tooth difference (52-42) for the "9-speed" version, and a 13 tooth difference (52-39) for the "10-speed" model.

The "10-speed" has the inner cage plate hanging down lower. This improves the shifting from the granny to the middle ring, because it is closer to the teeth of the middle ring.

If you install a "10-speed" triple front on a setup with a 52-42, you will have to mount it higher than normal to keep the inner cage plate from rubbing on the teeth of the 42. This extra height will cause deterioration in the 42 -> 52 shift.

Sheldon "It Matters" Brown

HillRider

Sheldon,

Thanks for the explanation. I wasn't sure if the difference was mechanical or marketing, as so much else is.

gregbr549

Thanks for the help. I have a 53/39 FSA double. I don't want to go to a 10 speed, I just saw some 9 & 10 speed Ultegra derailleurs on ebay and was wondering if a 10 speed would work on mine. which reminds me of another question. It states 130mm on it. What does that mean? What is the difference between a braze on and clamp on? Will a braze on fit on the clamp I have on my 105?
thanks again for all the help,
greg

DMF 

130mm refers to the BCD.

Braze-on uses a mounting tab that is already brazed to the bike frame. Clamp-on has an integral clamp to fasten it to the down tube.

Don't know. Are you using a clamp adapter?

See Sheldon's web site for a discussion of all this.

oldokie

What does BCD (bolt circle diameter) have to do with the front derailleur?

Al1943

I think you should stay with what you've got but if you're set on buying a new FD you need to replace your clamp-on with a clamp-on having the same tube clamp size.

I would be concerned with running a 10-speed double FD on a 9-speed drivetrain because the 10-speed derailleur is narrower and might require more trimming.

As for triple derailleur incompatibility, what Sheldon says fits with problems described in previous posts from others. Triple derailleurs designed for 52 or 53-39-30 triples don't seem to work well with 42t middle rings. But Shimano 9-speed triple derailleurs designed for a 42t middle ring seem to work fairly well with 39t middles.
My comments here are based mostly on what I've read, not personal experience, except that my wife's 9-speed Ultegra triple derailleur does work well with her 49-39-28 TA rings.

Al

Sheldon Brown

Strictly speaking it isn't the size of the middle ring, but the difference betwixt middle and large rings. Your wife's setup has a 10 tooth difference there, exactly what the "9-speed" model was designed for.

Sheldon "Difference, Not Size" Brown

Al1943

Yes, thanks for shaking that loose from my foggy memory bank.

wmelton

If I follow the logic correctly, then a 10-speed FD should also be used with a compact crank (50-34) on a 9-speed drive train, correct?

Sheldon Brown

No, this is a non-issue with doubles.

Sheldon "Doubles Are Easy" Brown