Quoted message said:8-speed cassette, no front derailleur
SRAM MRX Comp Grip Shift
Rear derailleur, chain and chain ring, clean and lubed
All components relatively new (11 months or less) - chain 1 month old
- 300 road miles per month (daily commuting in Chicago, all weather)
I am having a little trouble with my rear derailleur. I am hoping that
someone can take a minute to help me understand what is going on. I am
new to bike repair/maintenance, so don't assume that I know anything
at all. My goal is to learn more about repair/maintenance, so I can
eventually do most stuff myself, except for headsets.
My rear derailleur would not always shift properly when going anywhere
from 6 to 3 (one gear at a time). I had to go too far and then come
back; this workaround always worked fine. I could always upshift (1 to
8) perfectly. Could always shift between 7-8 and 1-2 fine, in either
direction. I visually compared this cassette with a brand new
cassette, and could not see any obvious wear difference between the
two.
My solution (which I blindly stumbled on in desperation) was to turn
the barrel shifter on the gear shift several turns counter-clockwise.
So I have two questions:
1. My understanding is, tuning the barrel shifter on the changer
changes the 'indexing' of the shifter, which essentially changes how
much the derailleur moves between cogs. Is this correct?
2. Also, is this the correct way to solve this problem?
TIA - J.
Maybe I can help. I'll try.
When you speak of gear numbers, the lowest gear (1) is next to the
spokes and the highest gear (8) is on the outside. In service, we
normally speak of "inside" and "outside" for clarity.
I believe you mean the changer moves freely (changer is neither twisted
nor broken and the control cable is both free and unkinked) but that the
'clicks' in your lever no longer correspond to the actual steps across
your cassette. Is that the problem?
If so, begin by ensuring your chain is oiled and each link moves freely.
If there was a recent trauma, sight the chain while backpedalling to
ensure there are no damaged or twisted links - each link should look
like every other in profile while backpedalling. Stop and cure a visibly
damaged chain before riding.
It's always nice to check the control wire. Modern bikes have a slotted
stop so the casing may be pulled out, leaving the wire slack. Pull the
casing back, wipe the wire looking for kinks or frayed areas and wipe
with oil before snapping the casing back in place. Check the under-bike
nylon guide for dirt/crud and add a drop of oil there as well. Note the
small piece of casing by the rear changer is prone to dirt/rust/kinks
more than other areas.
Change to high gear and get your head behind the changer by moving
either you or the bike. Is a line through the rollers vertical, i.e.,
parallel to the front sprocket? If bent, align it or get assistance with
that. A bent changer will not shift well and risks serious damage to
your wheel and/or frame.
If all that seems well, shift to one of the middle gears[*]. If the
changer is not exactly under the sprocket, it will be noisy. Your cable
setting coordinates the lever with the changer. Making the wire tighter
moves the changer inward, looser moves out. Turn an adjuster (either at
the lever or at the changer) until the changer lines up either visually
or audibly or both. If it seems well, go ride around the block and
ensure it's acceptable.
Assuming it was all OK before you turned an adjuster, it should be easy
to rectify. If you turned the adjuster because it was noisy after being
bent or damaged, you can reset the adjustment but the underlying problem
will remain. That's why I suggested you check for a bent derailleur
early. If it is bent, you risk shifting into the wheel with resultant
major (expensive) damage.
more gear and other bike advice is in our FAQ:
http://draco.acs.uci.edu/rbfaq/FAQ/index.html
[*] If you do not have a bike stand or cannot hang the bike for gear
service, ask a friend to stand on the left side of your bike, hold the
front brake tight and lift the bike by the saddle. This is not strenuous
and provides a convenient way to see what you are doing.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
