On Thursday, August 8, 2019 at 8:55:47 PM UTC-4, jbeattie wrote:
On Thursday, August 8, 2019 at 1:39:57 PM UTC-7, AMuzi wrote:
On 8/8/2019 2:54 PM, Tom Kunich wrote:
On Tuesday, August 6, 2019 at 7:34:51 AM UTC-7, Sir Ridesalot wrote:
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?

Cheers

Andrew told us about when it happened but not why. The rear derailleur cable was moved when the downtube friction shifters were moved to Shimano Brifters in the 70's.

Running the cables under the downtube gave the cables a cleaner run from the head tube to the under bottom bracket plastic runner.


First modern under-BB guides were steel, mid 1970s.
First nylon gear plate was Vitus in 1979.
First integrated shifter was Shimano 1990, followed by
Campagnolo Ergo a year or so later.

With the Vitus, the cables were structural. https://tinyurl.com/y4kh5o3g It was the first cable-stay frame design and ensured that the tubes would not separate in the event of epoxy failure.

-- Jay Beattie.

Seeing as the headtube joints were in front of the downtube shifters, how would shifter cables keep the frame together if a doubtube or toptube joint failed at the headtube?

Cheers