About ghost shifting -
* Are you friction-shifting? Some (myself included) find it
difficult-to-impossible to avoid ghost-shifting on 8 speeds and
above but are happy friction shifting 7 speed or fewer.
* Are you referring to skipping under load? A worn chain and cassette
will do that.
* What exactly do you mean by "ghost shifting"? My typical
ghost-shifting scenario was I'd downshift approaching a stop sign or
traffic light. All would be well. I'd stop, then upon starting up,
when I'd put the drivetrain under load it would skip to the next
higher gear with a BANG. The basic reason is Hyperglide is designed
to make shifting easy, so that the chain can happily ride on two
sprockets at once (during the shift) without clattering. So you
friction shift and - lacking any clattering to signal that you're
not 100% centered on the new sprocket - think you're fine. You
stop, and once you go to start and there's a big load on the drive
train it jumps to the small sprocket.
* If you're index shifting and it skips on every shift are you sure
you've got things adjusted properly?
As for gear charts: the basic idea is, convert the chainring / sprocket
combinations to Gear Inches (i.e., the equivalent "high-wheeler" wheel
size). An example: 52x14 feels like -- essentially is -- the same* gear
as a 48x13 for the same wheel. They both translate to 100* gear inches.
With a 17" wheel, a 54x9 would give you the same* 100 gear inches.
[*rounded to an even integer, that is]
The calculation for gear inches is #teeth on the chain ring / number of
teeth in back * wheel diameter in inches. It's away of quantifying the
"feel" of the gear for comparison purposes. You can also do it French
style: instead of converting to the size of the wheel, you convert to
"development" which is the circumference: how far the wheel travels for
one rotation. A lower gear gives more mechanical advantage / travels
less per rotation / is the equivalent of a smaller diameter wheel.
Once you know what the values are, you can lay them out in parallel rows
or columns and visually see how they lay out. Some gear calculators do
this with charts, others leave it as numbers and let you compare. Part
of the idea is to see how the gears overlap. Sometimes two different
chainring/sprocket combinations come out to the identical or nearly
identical gear. Sometimes the shift from one to the other is huge.
When you cross from a large to a smaller chain ring if you want to get
to the next gear in sequence a chart can show you how many shifts you
need in back to adjust for the shift in front.
On 3/21/20 1:33 PM, aeroperf wrote:
And for ghost shifting…
Check your hub. It should be designed for your rear cluster. An
8-9-10 speed hub is slightly shorter than an 11 speed hub, and an
11-speed hub can be used with a 10-speed cluster but requires a small
ring spacer.
If you have a 10-speed hub and you’re running an 11-speed cassette
with one gear removed, that might put things off enough to cause
ghost shifting, because the distance between the 11-speed gears is
slightly less than the distance between 10-speed gears. For Shimano
the spacing is 2.35mm for 10-speed to 2.18mm for 11.
But it is also possible the rear derailleur is set up a little off of
where it should be.
-
--
Steve Palincsar
Alexandria, Virginia
USA
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