Having installed a Shimano Ultegra Hollowtech II crankset and the corresponding Hollowtech II bottom-bracket on my (former) Trek FX 7.5 hybrid, I ran into a problem. This particular hybrid thinks it's a mountain bike. This due (in this instance) to it's needing a top-pull front-derailleur. A top-pull front derailleur means the cable that operates the derailleur is coming down the seatpost from above. Bottom-pull is where the cable comes from under the Bottom-bracket*. Usually. And this presented a problem: Finding a top-pull FD, that could handle the 30-39-52 and the 22T difference, was just about impossible - according to the specs I read in each candidate for a FD.
The derailleurs that could handle this size chainrings were made for road bikes, as was the crankset. It was an attempt to convert a hybrid to, in this situation, behave as a road bike. So a trick I tried was to run a pulley underneath the FD on the seat-tube - to reverse the cable direction. All is fine - until I installed a Shimano Ultegra FD and attached the cables. I could get the Ultegra FD (triple model - FD-6603) to go, with minor difficulty, from the small to the medium chainring. But it didn't like the idea of going to the large. After a substantial period of time, it would. But it then refused to go from large to the medium chainring. Adjusted cable-tension, reset the high - low adjustment-screws. Still it would not, in varying patterns (no large to medium, large to medium - no go to small, etc). So I finally conceded that this thing hates me! LOL. So I started looking for another FD.
As I said - all the front-derailleurs that were top-pull models were made for mountain bikes. This means they had specification for a maximum large ring for between 44 and 48T. The Ultegra was 52T. As I was sorting through specs on every FD out there - nothing met the criteria I had set for the bicycle. But then I remembered something - Shimano also claims the Ultegra rear-derailleurs are given a max-tooth on cassettes as being 27 (28?) teeth on the large cog of a cassette. I was running Ultegra RD's, and heard from people who were doing the same, with cassettes of up to 32T. With zero problems being reported. So...
I had a Shimano FD-M961 XTR front-derailleur living, brand-new, in a box for a rainy day. It is a dual-pull unit. It has a 34.9mm clamp - yay! And it was snowing. The XTR FD-M961 is given, by Shimano, a max of 48T. So what the hey - I put it on. Luckily it had a 34.9mm clamp. As my Trek also is 34.9mm on it's seat-tube it was easy. But would it work? It did and does. Only minor adjustments to the high-low screws and one click on the cable tension adjustment on the shifter itself (SRAM Attack 9spd.). Operates perfectly.
So if you run into a Shimano MAX claim in their ad-copy, disregard same. I can testify that it is working happily, with room to spare, on a 30-39-52T crankset. May this nugget of information come in use to you. With the prevalence of hybrid bikes selling out there, you may well run into people with the same problem. And the Shimano FD-M961 XTR FD will work perfectly.
Anyone have another good FD to suggest? I'm sure the XTR can't be alone regards being low-balled by Shimano. Anyone else have stories/information on attempting this sort of project on a hybrid? What worked for you? People are, by nature, tinkerers. Tinkerer + Hybrid = Innovations & Change.
* Not just seasoned mechanics might be reading this, you know?