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Cage width question

Old 02-26-21, 11:19 PM
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etherhuffer
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Cage width question

I have built up several vintage frames with no problems at all. Sugino front triple, RSX front derailleur. Did a Surly Long Haul Trucker with Deore front derailleur and get rub at high and low gears. Are varying derailleurs of varying speeds more or less narrow? I have all 7 and 8 speed on all my stuff. The Surly has long chain stays, which should minimize rub, not make it worse. Any ideas?
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Old 02-27-21, 08:03 AM
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Front derailleurs intended for friction shifting tend to be narrower than those used with indexed shifting because with friction shifting you can eliminate rub by trimming the derailleur after the shift. Front indexed shifting relies on ramps and pins to facilitate the shift, and a wide cage eliminates the need for post-shift trim.
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Old 02-27-21, 03:01 PM
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What shifter does the LHT have for the front? 9 speed cranks have the rings slightly closer together so the matching 9 speed ft der doesn't have to travel as far. So for the same cable pull the 9 speed ft der cage will move less. With a friction ft shifter one just pulls the lever a tad more. Plus there's a difference between road and MtB 9 speed cable pull/der cage movements. With an indexed shifter one has to match up the intended gear counts with ft ders and shifters of the same intended use (MtB w/ MtB and road with road). Andy
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Old 02-27-21, 03:59 PM
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With indexing, front derailleur width is specific to the brand and the number of cogs on back. With friction, use trim. Check your chainline and derailleur alignment too.
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Old 02-27-21, 04:57 PM
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Originally Posted by JohnDThompson View Post
Front derailleurs intended for friction shifting tend to be narrower than those used with indexed shifting because with friction shifting you can eliminate rub by trimming the derailleur after the shift. Front indexed shifting relies on ramps and pins to facilitate the shift, and a wide cage eliminates the need for post-shift trim.
Could be that deore derailleur.. Try a road one.
Is ithe shifter the limit or the derailleur?
Can you push the derailleur by hand past the rub?
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Old 02-28-21, 06:39 PM
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Thanks all. Sugino compact triple in front. Sora shifters 3x8 indexed. Deore FD I tried an Alpina and RSX FD but the tails with chainstay. I have done this same build on several other bikes, the oversize tubing sort of limits what I use, and the seat-chainstay angle.
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Old 03-01-21, 10:06 AM
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Well, if the FD cage has a screw, and not a rivet, in the back that connects the outer cage to the inner cage, you can put a washer in there and spread it if the chain is barely rubbing no matter what you do.

I have done this “enhancement” many a time when I wanted a skosh more clearance for the chain.

John
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