Panthers007

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.

Happy Trails!


* Not just seasoned mechanics might be reading this, you know?

cs1

Forgive me if I don't quote your, lengthly, OP. That is good news. Wish it wasn't XTR but regular old Deore, it's a lot cheaper. Thanks for the news.

Panthers007

Your welcome - I decided to post it as a short story. LOL. I'd never read anywhere of this being attempted. Hope it comes in handy.

The XTR cost me around $40, and the Trek came with a Deore FD-M570. That thing didn't work with the stock parts. I'm guessing Trek bought a shipping-container of them and had to put 'em somewhere...

Chris_W

You can also go in the other direction without too many problems - using a front derailleur listed as needing MORE teeth on the large chainring than you are using.

On my racing bike, I'm currently using an Ultegra triple front derailleur to shift between my "super compact" crankset: 28 and 46 tooth chainrings. It works quite well, even though the minimum size of large chainring that Shimano want you to use with a road FD like that is 50 teeth. However, it certainly could be better, I would use a MTB or trekking FD if possible, but I haven't found anything suitable with a braze-on fitting, which is all that this frame will take. On my touring bike, I'm using a Deore LX trekking model rated for a big ring of 46-48 teeth to shift between a 26-42 double crankset. That works fine, which is why although I could get something rated for 42 teeth, I have no reason to. I believe some cyclocross riders use 34-46 chainrings on compact crankset, and so again use road FD's outside of their official capacities.

You might wonder why I'm using such weird chainring sizes, but the answer is that I like the range of a triple crankset without the hassle of having three rings. These chainring combo's paired with 10 rear cogs of the right size (11-26 on the racer, 11-28 on the tourer) gives me an awesome choice of gears, plus a simpler and lighter drivetrain than with a triple (lighter than a standard double, in fact, because of the small chainring sizes).

HillRider

Chris W is correct that a road front derailleur will work quite well with a smaller big chainring. Shimano's RSX cranks came 46/36 or 46/36/26 and my son's Trek 1220 fitted with the RSX triple came OEM with an RX100 road fd intended for a 52Tring. It shifted fine.

As to using a MTB fd on a road crank, it will shift but the fd will have to be higher above the big ring than optimum.

Panthers007

You are right. I have this one set at approx. 4mm over the 52T ring to be sure. It work very nicely. But anything would when compared to the Deore that came as stock.

Thanks for both of your input. I wonder if Shimano will notice this some day. I sure won't be buying any of their stock if they don't.