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Best front derailleur for half step plus granny
In article ,
Russell Seaton wrote: I am transferring my touring bike parts to a new frame. The new frame needs a 1.25" clamp on front derailleur. So my old 1991 Shimano Deore DX half step specific 1.125" clamp on front derailleur won't fit. My chainrings are 48-45-20. Half step plus granny. Rear cogs will be 9 speed 12-34 cassette. 1. Which current front derailleur will best handle the 3 tooth difference between the 48 and 45 chainrings and still allow the use of the 20 tooth granny with the largest 4 or 5 rear cogs without dragging the chain on the derailleur cage? 2. I know a double front derailleur will handle the half step very well. But how would it work with the 28 tooth difference in chainrings? 3. Is there any way to change clamps on my old front derailleur? Can I buy any cheap Shimano front derailleur and easily change clamps? I feel your pain. If you can't find something from, say, Rivendell, then my recommendation is to get a road front that doesn't have the deep inner plate, and extend the plates toward the rear. Most derailleurs have steel plates (IIRC) so it's fairly easy to braze or weld extensions. There will probably be some that argue against the 1/2+Gr arrangement, but I'm with you -- there are nice things about this arrangement. Good luck -- and let us know how it works out! -frank -- |
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#2
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Best front derailleur for half step plus granny
Russell Seaton wrote: I am transferring my touring bike parts to a new frame. The new frame needs a 1.25" clamp on front derailleur. So my old 1991 Shimano Deore DX half step specific 1.125" clamp on front derailleur won't fit. This, I think, is what really screws you when it comes to a half-step. My chainrings are 48-45-20. Half step plus granny. Rear cogs will be 9 speed 12-34 cassette. 1. Which current front derailleur will best handle the 3 tooth difference between the 48 and 45 chainrings and still allow the use of the 20 tooth granny with the largest 4 or 5 rear cogs without dragging the chain on the derailleur cage? 2. I know a double front derailleur will handle the half step very well. But how would it work with the 28 tooth difference in chainrings? If it weren't for the clamp issue, these work great just like your Deore DX: http://cgi.ebay.com/ws/eBayISAPI.dll...m=3685486 553 http://cgi.ebay.com/ws/eBayISAPI.dll...m=3685712 205 3. Is there any way to change clamps on my old front derailleur? Can I buy any cheap Shimano front derailleur and easily change clamps? I doubt it. Many of the f-ders have half the clamp as part of the derailleur itself. You could look for the model of Suntour Cyclone f-der with the totally removable clamp. Maybe you could replace it with a custom clamp. I don't know if I've ever seen a 31.8 Suntour Cyclone. All I've seen were 28.6. My Cyclone is not the removable clamp model. Let me know if you have trouble. I have a cheapo Suntour front der that I bent (modified) the cage on that I would sell you if you got desparate. It would probably work for you. It has a 31.8 clamp. I use it with a 46-42-26 front. It works, but is not perfect. (This is not the Cyclone.) |
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Best front derailleur for half step plus granny
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#4
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Best front derailleur for half step plus granny
Russell Seaton wrote:
=20 My chainrings are 48-45-20. Half step plus granny. Rear cogs will be 9 speed 12-34 cassette. 1. Which current front derailleur will best handle the 3 tooth difference between the 48 and 45 chainrings and still allow the use of the 20 tooth granny with the largest 4 or 5 rear cogs without dragging the chain on the derailleur cage? Virtually any modern "double" type front derailer will work for=20 half-step-plus-granny. 2. I know a double front derailleur will handle the half step very well. But how would it work with the 28 tooth difference in chainrings? This may require some experimentation, may also require some surgery to=20 the cage. See: http://sheldonbrown.com/derailer-adjustment An anomymous poster asked: Help me out here. I thought the biggest difference between a double and triple front changer was the range of motion (side to side) available. That is to say, I don't think there would be any difference between a front derailleur for a half-step granny and any other triple set-up. Am I mistaken? Yes, you are. =20 It's been a few years since I ran a half-step granny, but doesn't the half-step make things better, not harder? I mean, with only a 3 (I used to run a 4 t diff back in the day), you can mount the changer lower and closer to the center ring without the outer cage hitting the the outer ring like you would if you had a 10 t or 12t diff, no? Modern "triple" front derailers have an inner cage plate that hangs down = much lower than the outer one. This is to facilitate the upshift from=20 the smallest ring to the middle. They also generally have a more 3-dimensional outer cage plate to reduce = rubbing when clueless riders cross chain the small/small combinations. Sheldon "There Is A Difference" Brown +---------------------------------------------+ | If your bike has drop handlebars, but you | | rarely or never ride on the drops, it=92s a | | sure sign that your bike is not properly | | fitted or is not properly adjusted! | | See: http://sheldonbrown.com/handsup | +---------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide http://captainbike.com http://sheldonbrown.com |
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Best front derailleur for half step plus granny
I asked:
Help me out here. I thought the biggest difference between a double and triple front changer was the range of motion (side to side) available. That is to say, I don't think there would be any difference between a front derailleur for a half-step granny and any other triple set-up. Am I mistaken? Sheldon replied: Yes, you are. So, do all (most) modern double and triple FDs have the same range of motion side to side? I would have expected that some double FDs wouldn't have enough travel for a triple. Sheldon continues: Modern "triple" front derailers have an inner cage plate that hangs down much lower than the outer one. This is to facilitate the upshift from the smallest ring to the middle. Ah.... so do I understand correctly.... This lower inner cage plate would become the limiting factor for how low you can mount the FD so it will clear the middle chain rain when the cage is over the outer chanring. And given the huge difference in the lower edges of the inner and outer cage plates, this would leave you with the FD too high for effective shifting from the outer to middle chain rings. Did I get that right? -- Dave ============================================== "It is impossible, or not easy, to do noble acts without the proper equipment." Aristotle, Politics, 1323a-b, trans Jowett ============================================== |
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Best front derailleur for half step plus granny
Russel and Sheldon, can you guys reconcile the following?
Russell Seaton wrote: I really need a front derailleur shaped like a triple, to handle the capacity between the outer and inner chainrings, [snip...] Sheldon wrote: Virtually any modern "double" type front derailer will work for half-step-plus-granny. Russell, I'm assuming that you are concerned about: a) the chain draging on the connector bolt that runs between the 2 sides of cage when on the granny or b) clean shifts from the granny up to the middle Sheldon, thanks for the clarification in your other post. -- Dave ============================================== "It is impossible, or not easy, to do noble acts without the proper equipment." Aristotle, Politics, 1323a-b, trans Jowett ============================================== |
#7
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Best front derailleur for half step plus granny
Jeff Wills wrote:
To the OP: I recall that the Shimano Deore and Deore XT front derailleurs came in both "half-step" and "alpine" versions in the late 80's. I *think* there was one that featured an endless-band clamp that was adaptable to 1 1/4" seat tubes. I can't recall if there was one with *both* a half-step cage *and* an endless band clamp... Yes (I had the Deore 31.8mm variety on a Cannondale touring bike) but it looks a lot like a typical road double front derailler. but I'd bet that one of the old-guard bike shops could get one from Euro-Asia if they ever existed. I can't say for sure, though. |
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Best front derailleur for half step plus granny
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#9
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Best front derailleur for half step plus granny
Jeff Wills wrote:
Benjamin Weiner wrote in message news:40e218f2$1@darkstar... Yes (I had the Deore 31.8mm variety on a Cannondale touring bike) but it looks a lot like a typical road double front derailler. Ah, so... I kind of figured it would be used on a Cannondale. As to it "looking like a typical road double front derailleur"... whaddaya wanna bet the cage is longer? I managed to dig it up, and I think we're both wrong. The cage is about the same length as a road double, and oddly, the inner plate is deeper than a road double. It looks similar to the type of FD that came on early mountain bikes with 48-38-28 rings. |
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Best front derailleur for half step plus granny
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