#1
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Front mech problem
Fitting a new front mech yesterday (Deore) and I left the recommended
2mm gap between the outer cage and the big ring. Trouble is when trying to move the chain to the big ring the inner cage catches on the teeth of the middle ring. So I had to lift the mech about another 4mm so it could clear it. It seems to work OK but I wondered if anyone else has had this problem or what might cause it. Andy |
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#2
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Front mech problem
andyforse wrote:
Fitting a new front mech yesterday (Deore) and I left the recommended 2mm gap between the outer cage and the big ring. Trouble is when trying to move the chain to the big ring the inner cage catches on the teeth of the middle ring. So I had to lift the mech about another 4mm so it could clear it. It seems to work OK but I wondered if anyone else has had this problem or what might cause it. Shimano front mechs intended for triple chainset use are generally optimized for a 10 tooth difference betwixt the large and middle chainring. If you're going for a much smaller jump, as with a (yuck!) half-step-plus granny setup, you'll get better results with a "double" type front mech. Sheldon "Decimalization" Brown +----------------------------------------------+ | Music expresses that which cannot be said | | and on which it is impossible to be silent. | | --Victor Hugo | +----------------------------------------------+ 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 |
#3
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Front mech problem
andyforse wrote:
Fitting a new front mech yesterday (Deore) and I left the recommended 2mm gap between the outer cage and the big ring. Trouble is when trying to move the chain to the big ring the inner cage catches on the teeth of the middle ring. So I had to lift the mech about another 4mm so it could clear it. It seems to work OK but I wondered if anyone else has had this problem or what might cause it. Andy I think the newer Deore FD is designed to work with a difference of 12T between the big ring and the middle ring (ex. 44-32-22). Older cranksets often have 42-32-22 or 44-34-24. I had the same problem after I replaced the FD. In my case, lifting the FD another 4mm didn't work very well. I had to replace the big ring. |
#4
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Front mech problem
The chainrings are 22-32-42. Getting a 44 big ring just might be the
answer. I think I'll wait till it wears out or stops working first though. Thank you both for the advise. Andy |
#5
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Front mech problem
Shimano front mechs intended for triplechainset use are generally opti
ized for a 10 tooth difference betwixt the large and middle chainring. If you're going for a much smaller jump, as with a (yuck!) half-step-plus granny setup, you'll get better results with a "double" type front mech. Sheldon "Decimalization" Brown "Yuck"? And here I thought you were my friend :-3( May you have the wind at your back. And a really low gear for the hills! Chris Chris'Z Corner "The Website for the Common Bicyclist": http://www.geocities.com/czcorner |
#6
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Front mech problem
andyforse wrote in message ... The chainrings are 22-32-42. Getting a 44 big ring just might be the answer. I think I'll wait till it wears out or stops working first though. Thank you both for the advise. Andy I'm running Deore front with 22-32-42. Lifted the cage to clear, angled it 'just so', and have zero problems shifting, well, that aren't related to the (now) badly worn pivots on the mech (have to overshift a little, but it worked fine for most of the year it lasted un-worn....). Shaun aRe - Deore mech shortly to be replaced by an XT _conventional_ swing type which will hopefully wear better than the awful top swing types........). |
#7
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Front mech problem
Those pivots do wear pretty quick don't they.
I'll get the XT myself next time, but I'm not sure if the conventional swing will work with the Marin Rift Zone I'm riding. Whats the difference between the two? Andy I'm running Deore front with 22-32-42. Lifted the cage to clear, angled it 'just so', and have zero problems shifting, well, that aren't related to the (now) badly worn pivots on the mech (have to overshift a little, but it worked fine for most of the year it lasted un-worn....). Shaun aRe - Deore mech shortly to be replaced by an XT _conventional_ swing type which will hopefully wear better than the awful top swing types........). |
#8
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Front mech problem
andyforse wrote in message ... Those pivots do wear pretty quick don't they. Yup! 12 months average so far ;-( I'll get the XT myself next time, but I'm not sure if the conventional swing will work with the Marin Rift Zone I'm riding. Whats the difference between the two? 'AFAICR', the non-conventional ones were designed to bring the clamp band lower on the seat tube to allow their use on certain full suss designs where a higher band wouldn't have a place to fit (clamp band is below the mech cage on these). The conventional ones have the clamp band higher than the cage. The 'conventional' low end Shimano (Altus? - dunno!) front mech I am currently using just to keep the chain in place on the single front ring on my FrankenBeater (commute bike) was still working (although not fantastically) after about 8 years of constant use and abuse. The one that replaced it (Deore top-swing) lasted less than 1 year before the pivots were so worn it wouldn't shift unless I had all week to wait.......... Opinions I have solicited as to the comparative longevity of the two _types_ (not 'levels') seem to back up my experience(s). This is OK for me, as I have enough room on my (HT) seat tube to mount the cage under the top tube, if I so desired. You probably aren't so lucky, if your bike is an FS Marin, but I can't picture the bike's design clearly enough. Shaun aRe |
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