On Tue, 6 Aug 2019 07:34:48 -0700 (PDT), Sir Ridesalot
I was looking at a couple of my old bicycle frames with the rear derailleur
cable routed along the top of the chainstay. I'm curious now. Why did the
rear derailleur cable routing get moved to under the chainstay?
My guess(tm) is that someone tried to use their bicycle as a ladder.
They stepped on the right rear chainstay, tripped over the derailleur
cable, crash landed, and sued everyone involved. In honor of this
event, the bicycle manufacturer probably moved the derailleur cable to
a less hazardous location to avoid further litigation.
Topic drift follows...
Some manufacturers may have decided that locating moving parts in the
"mud zone" is somehow a great idea. Here is a Specialized Stump
Jumper with both the drailleur cable and the rear brake positioned for
maximum exposure to mud, rain, dust, rocks, gravel, tar, etc.
Extra credit for using rather small rear brake pads.
I would normally guess(tm) that such a brake location would not matter
because disk brakes are at approximately the same height above the
ground and presumably will be exposed to an equal amount of road
rubbish. My guess(tm) is the difference in brake pads, where the
softer pads in rim brakes tend to collect more abrasive road debris
than the harder and self cleaning pads used on disk brakes.
If you look at the rims, you might notice that there is more gouging
and wear on the rear rim, than on the front. This is backwards from
normal wear, where the front rim tends to show more wear because of
higher grip pressure. Most of the wear on the rear rim seems to be
from rocks and debris imbedded into the rear brake pads.
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