Record–I am replacing my front DR on my P2K. It is now Ultegra (I am replacing it with DA, and moving the UL group over to my road bike). I have already screwed up by ordering the wrong FDR. I assumed, wrongly, that whether it was braze on or clamp didn’t matter–that the DR would just bolt on to either the clamp on clamp or the braze on clamp. Monk was wrong, and will have to return it.
Meanwhile, I want to order the right one. So which is the right one, as they seem to come in different mm’s. Here is the bikenashbar site:
Which item # do I want (and don’t tell me the Campy!)
Thanks, but is there a measurement or part number I can take off the existing Ultegra 9spd (I am going to 10spd, but the part number may be instructive).
BTW–good restraint on not mentioning Campy in your response.
What does thamm measurement relate to? DOes it matter, since I am not actually going to braze it on, just remove the DR itself and put the new one on the same brazed on clamp?
I am not at all sure on that, I may be wrong and stating the size for a 25mm post. You need to check with someone who knows. All my bikes have braze on. I have not worked in a shop for at least 10 years.
Theoretically speaking, why would the DR itself change, just because the diameter of the tube changes–that would only seem to effect the curvature of the braze on fitting, which is not changing or being replaced.
I thought sizes were for clamp diameters only… And that braze-on was a single part (i.e. braze-on goes with braze-on clamp). And the one’s with sizes just include a seatpost clamp, which you won’t need if you are replacing, instead of building from scratch…
According to Shimano, there are 4 part numbers
braze-on double
clamp-on double
braze-on triple
clamp-on triple
So any size must be a clamp band diameter
If you want double, braze-on, Ultegra 6600 (10spd) it is part #FD-6600-F
(F = braze-on, B = band, 6600=double, 6603 = triple)
P2K’s have a braze on already in place for the front der. (at least the one i built yesterday does). Its called a “braze on” as a hold over from the old days, and is basically a pre-aligned tab for the front der. The clamp size is based on the outer diameter of the lower part of the seat tube, and ranges from 1 1/4"(31.8) to 1 2/5" (34.8mm). You can find this dimension by taking a caliper to the outside of the seat tube where the front der. would mount. The product # you’ll need is SH-FD7800B.
I “think” you are correct. P.S. neither the 2K or P3 are round at the point where the clamp/braze on goes, and I think they have developed a special mounting fitting, but it seems that since that part is already in place, and I am just hanging the DR itself to it. I shouldn’t matter which of the braze on’s I get, but I don’t want to screw up twice.
#SH-FD7800V
Click for more pictures Braze on with Clamp 34.8mm More rigid for faster shifting under higher loads. The new Dura Ace front derailleur boasts wider and reinforced pivots and a super-strong cage. Narrower cage to accommodate the new Shimano 10-speed chain. 75 g For 28.6 or 31.8 clamp size us SH-FD7800. For Braze on use item SH-FD7800B.
#SH-FD7800B
Click for more pictures More rigid for faster shifting under higher loads. The new Dura Ace front derailleur boasts wider and reinforced pivots and a super-strong cage. Narrower cage to accommodate the new Shimano 10-speed chain. 75 g For 28.6mm or 31.8mm clamp size use SH-FD7800. For 34.9mm clamp with derailleur use SH-FD7800V.
braze-ons and clamp-ons are not the same. you need braze-on for your p2k, this is a certainty. any real braze-on front deraill. will work.
however, nashbar has their descriptions all f*cked up, but just get a braze on only. you may need to call them to figure out if they have even the foggiest idea of what they are selling.
(there is one exception to this–not applicable to your p2k: in that you can mount a braze-on front der. on a clamp-on frame. then you must buy a special clamp, also made by shimano, that the braze on front der. attaches to that can covert it to a clamp on front der. You cant go the other way: you cant convert clamp on to a braze on unless you own a machine shop and can build custom alloy parts).
