On Wednesday, August 7, 2019 at 12:36:34 AM UTC-4, wrote:
On Tuesday, August 6, 2019 at 9:34:51 AM UTC-5, Sir Ridesalot wrote:
Why did the rear derailleur cable routing get moved to under the chainstay?



In the OLDEN days, shifters were mounted on the downtube up by the headtube. Or on stem shifters either side of the quill stem. AND there was a clamp on guide at the bottom of the downtube that directed the shift cables (cable only for the rear derailleur, not the housing) to their respective derailleur, front and rear. See the eBay picture below.

https://www.ebay.com/p/Suntour-Gear-...45941129&rt=nc

https://www.ebay.com/itm/Suntour-gea...0AAOSwY7ZdF-pv

https://www.ebay.com/itm/Shimano-28-...AOxy IMhRGUOt

The long groove piece was for the rear cable. The bare cable from the shifter went into the groove/trough and was directed along the TOP of the chainstay to the cable stop at the rear of the chainstay, where a cable housing then formed the loop to the rear derailleur. And the other side of this clamp on piece directed a piece of cable housing from this clamp on up to the front derailleur. This was how cables were routed on bikes before someone invented the under bottom bracket guides bolted to the bottom of the bottom bracket. Under bottom bracket guides made of slippery plastic probably work better than the old clamp on guide contraption.

I have bicycles that have brazed on cable guides that are located on top of the bottom bracket shell. The radius of the rear gear cable is greater and the loop is smoother on the bicycles with the cable stop on top of the chain stay.

It looks like the move to under the chainstay was just to save time and money in t he manufacturing process. Having the cable guides under or through the bottom bracket sure does expose them to a lot more crud though.

Cheers