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In article <
[email protected]>,
Barnard Frederick <
[email protected]> wrote:
>ESS says...
>
>> I have a new road bike with Shimano Tiagra front and rear Derailleurs.
>> When I am in the lowest cog in the rear and the lowest cog in the front
>> the chain rubs the front Derailleur. The manual says you can use the
>> left shifter to move the Derailleur just a bit to ease the noise but not
>> shift into the top cog in the front. When I do this it seems to move the
>> front Derailleur too much. Any thoughts on why this might be? Can I
>> adjust the indexed shift? Any help would be appreciated.
>>
>> Ethan
>
>Not only is it rubbing your front derailleur the wrong way, it is also
>very hard on your drivetrain. Don't use that combination, or the big
>ring, big sprocket combination. Ever. With a 9 speed system, I try not
>to use any but six gears for any chainring. The smallest six go with
>the big ring, and the largest six go with the smallest ring. You may be
>able to use all nine with the middle ring, but you may hear a little
>extra chain chatter even then. Assuming that everything is pretty well
>adjusted, a good way to tell when you are trying to use rear gears
>outside of the comfort zone of the chainring you are on is when the
>noise level from the chain goes up.
It's a bike, use it. The cross-chaining stuff is another often
repeated bike shop myth with no real evidence that it causes
any real damage to the bike. I cross-chain whenever I find it
convient and my stuff doesn't wear out any faster than anybody
elses.
The only research I've seen says that chain angle doesn't matter
at all across the range of a typical 9 speed cluster. However,
this research also says that for a given ratio if you can get
that ratio in bigger gears, vs using smaller gears then it's more
efficient.
Since there are slightly better gears available on a triple that
don't cause noise you might as well use them. With modern bikes
with short chainstays and indexed shifting, you can't really use
all the gears anyway as the derailers don't have enough leeway
for the larger angles that a short chainstay requires. So the
"damage" crosschaining does to your gears in mostly the rubbing
on the derailer and that fundementally can't be fixed since you
can't lengthen the chainstays or widen the derailer cage.
While your bike may have 24, 27 or 30 gears, there are many
duplicates or gears so close in ratio that you can't
differentiate them. At best you likely have 14 or 15 distinct
gears.
_ Booker C. Bense
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