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Chain rubs on front derailleur.

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Chain rubs on front derailleur.

Old 07-10-05, 02:12 AM
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Chain rubs on front derailleur.

I saw this question posted before but if wasn't really addressed.
I have a Specialized Epic with a Strong Arm crank on the front. When I step on the right peddle and crank the whole crank and cog unit "flex" out by about 2mm. You can see the whole unit bend. When this happens the chain is carried with the cogs and rubs against the front derailleur. There is no derailler product out there that allows for 2mm of headroom on a 27 speed bike. Maybe 1/2 a mm at most.
I think perhaps the cranks are just not built for people of my weight (180lbs).
However, I want to know what my options are. I've tried adjusting the front derailleur in every direction. It won't work. I basically can't use my upper bracket at all. The cogs flex so far that 7 of the 9 top gears don't work (if I want any of the gears on the middle cog to work without grind).

I find this annoying that my 27 speed bike is essentially a 9 speed bike as a result. I feel is a manufacturing issue but have not had any response from Specialized.

As posted before, it doesn't matter how you adjust the front derailleur, the issue is with the crank and cogs. Is flex expected? How much is normal? Can you reduce the ammount? Is a better crank and cog set in order? Can any set handle the stress a 180lbs rider is going to put on them when stomping hard on the peddles?

Thanks for all your help!!!

Conrad D. Seaman
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Old 07-10-05, 04:49 AM
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I ended up switching to a saint crankset from my stock specialized when I found one cheap locally. I had the same crank and it was a bit too flexy for me. Zero flex on the new setup and I'm an awfully big guy (220). Some cranks are just GOING to flex a bit and some of the flex is going to be the frame flexing as well. So basically you can:

1. Get a stiffer crank setup and hope it fixes your problem.
2. Live with it once you see the price for a stiffer crank setup.
3. Improve your technique so you're spinning instead of mashing.
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Old 07-10-05, 11:46 AM
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Thanks Geopolitical. This is rather what I figured.
I don't think there is much I can do in terms of 'technique'. I'm not perfect, but even when I'm riding on the road and just spinning the chain still rubs (without much effort on my behalf). This has caused me to pedel mostly with my left foot as it doesn't flex and rub then. Not exactly fine form.

Overall I must say I'm a bit dissapointed in the specialized crank set. I'd expect a more robust piece of gear on a bike designed for technical cross country riding and some pretty big bumps.

Conrad
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