Brake Cable Pull Ratios

[Lelandjt]

I posted this on RBR and got no responses. Maybe there's some Campy or Sram guys here who know:


Shimano has gone through 3 generations of brake cable pull:
1. 8, 9, and 10 speed shifters with external shift cables pulled the least cable (Gen 1).
2. 10 speed shifters with internal shift cables pulled more cable (Gen 2).
3. 11 speed shifters pull even more cable (Gen 3).

Which pull ratio is Sram closest to? I'm guessing Gen 2.
Which is Campy closest to? I'm guessing Gen 1.
Have Sram or Campy changed their cable pull over the years?

My own experience is that there is a very noticable difference between the generations. I had a bike pieced together with free parts that combined Gen 1 brakes with Gen 2 levers and they were very wooden feeling. Sharp, solid response but required a hard squeeze to stop. Mountain V-brakes required adapaters to work with Gen 1 & 2 levers but not with Gen 3, though the pads must sit closer to the rim than with a MTN lever. TRP mini Vs have a very sharp action with Gen 3 levers but still have sufficient power.

[stormur]

Next thing is pull curve : progressive ( more sqeeze bigger pull ratio ), regressive and passive.

AFAIK Campa is progressive, Sram passive, Shimano (gen3) regressive.

[BRM]

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[Lelandjt]

Next thing is pull curve : progressive ( more sqeeze bigger pull ratio ), regressive and passive.

AFAIK Campa is progressive, Sram passive, Shimano (gen3) regressive.

Good point. You're using "regressive" to mean that as you go farther into the lever travel it pulls less cable for each millimeter of lever movement, right? This would seem like a good design so you can set the pads wide with extra clearance, then the lever quickly brings them to the rim, followed by more and more power (leverage). It's how Shimano mountain cable levers used to be designed (Servo-Wave) and how most of their mountain hydro disc levers work.

What doesn't make sense is that anyone would design a lever that pulls more cable per mm of lever movement as it gets deeper into the travel, which depending on your terminology you're saying either Campy or Shimano do. This would require the pads to be set close to the rim because the initial lever squeeze doesn't move them much and then as you pull more (cuz you want more pad pressure) your leverage diminishes making the brakes feel less powerful. Unless the calipers are designed for this curve an have their own curve built in that negates it?

Thanks for the info and a thoughtful answer.