Bicycle Mechanics - FT Der capacity problem.
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I am looking for a 28.6 ft der to complete a couple of Deore 7 sp groups. The pickings are slim to say the least. All the MTB ders I've found are for 42-44 tooth chainrings max. I have a 46 and 48 tooth. Would a road triple work? They have thumb shifters so indexing isn't a problem, their friction fronts. I would like to keep the BP set up, which is why I'm thinking about a road der. Thanks
08-17-06, 08:07 AM
yes of course it will work. a campy one would work. a shimano, a suntour. friction loves diversity.
08-17-06, 01:37 PM
I have exceeded the maximum chainring size a little bit and discovered no issues. A derailleur designed for 44t will work for 46 or 48 in friction mode no problem. I have an XT front designed for 46-48t that I use with a 52/42/30 crank and it's indexed. Front derailleurs are a pain but friction sure softens the setup.
08-17-06, 03:36 PM
I think most Shimano road FD's are designed for 50T-56T big ring but I've seen cross and touring bikes with 46T and 48T big rings equipped with road FDs. Conversely, I run a 46T big ring on my MTB with FD designed for 42-44T big rings. So for 46-48 you can probably use either MTB or road FD.
I went the opposite way, with a Shimano Titlist front derailleur, whose cage is curved optimally for something like 52-42, on a 45-42. It looks a bit weird and demands a bit of extra trimming, but works fine.
I have a nice Deore crank that's 48-36-26. Most ft ders have a capacity of about 22 teeth, so that shouldn't be a problem. My big concern was going from a road crank with the 52/53 tooth large chainring to a smaller touring type 48 tooth. I will be using barcons or thumbies.
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