- Joined
- May 27, 2021
- Messages
- 1,027
- Age
- 63
- Location
- Coquitlam British Columbia Canada
- Bike
- 2009 ST1300
So I've gone back to the brake hydraulic schematic and wrote up how I understand the system thus far. I'll ask the questions here and just copy and paste my description below it so as to show what I already [think I] know. In google search for more specifics I came across an instance where someone wound up locking up the rear seems like in a downhill braking circumstance, not all is clear what all the factors were but I wonder if it's possible that the rear can get light enough that strict lever braking can effect enough SMC force to lock up the rear? Wonder if anyone had that experience on a 13. I imagine it would have to be a non-ABS to even know.
I'm mainly interested in specifically how the SMC, Delay Valve and Proportioning Control Valve output pressures rise [and / or hold or drop off] in proportion to rising input pressures. If anything more can be known about these components.
ST 1300 Brakes – Interpreted
There are three master cylinders capable of providing hydraulic force.
There are two other fluid controlling components in the hydraulic system.
There are three caliper assemblies, each housing three pistons. Each caliper has two separate hydraulic circuits, one for the centre piston, and one for both outer pistons. Caliper operation may occur as either centre piston actuation, simultaneous outer piston actuation, or a combination of both.
Brake Pedal MC – The Brake Pedal MC provides hydraulic force equally to the Delay Valve and the Rear Caliper Inner Piston.
The Delay Valve transfers force from the BPMC in sequence via two outputs; the first connects to the SMC input, then through a hub style connector over to the Front Left Caliper Centre Piston. The second connects to the Right Front Caliper Centre Piston.
The Secondary Master Cylinder transfers force through the Proportioning Control Valve to the Rear Caliper Outer Pistons. The source of SMC output force can originate from either plunger activation caused by left front caliper shift, or from the Delay Valve primary output fluid passing between the SMC plunger lip and cylinder bore.
I'm mainly interested in specifically how the SMC, Delay Valve and Proportioning Control Valve output pressures rise [and / or hold or drop off] in proportion to rising input pressures. If anything more can be known about these components.
ST 1300 Brakes – Interpreted
There are three master cylinders capable of providing hydraulic force.
- Front MC [Lever Actuated] – The Front MC provides hydraulic force directly and equally to the two outer pistons of the front two calipers. This is the only simple hydraulic circuit and operates in isolation from all the other components. However, while the right caliper is mounted in a conventional manner and remains stationary upon activation, the left caliper will shift CCW and actuate the secondary master cylinder [SMC].
- Brake Pedal MC – The Brake Pedal MC provides hydraulic force directly and equally to the Delay Valve input and the rear caliper inner piston.
- Secondary MC [Front Left Caliper Movement Actuated] – The Secondary MC provides hydraulic force through the the Proportioning Control Valve [PCV] to the two outer caliper pistons.
There are two other fluid controlling components in the hydraulic system.
- Delay Valve – The delay valve receives hydraulic fluid from the Pedal MC and through the first output port, transfers it to the SMC input port. A jumper brake line at the SMC input port transfers unrestricted Pedal MC fluid along to the Left Front Caliper centre piston. As Pedal MC hydraulic pressure increases, the Delay Valve will transfer hydraulic pressure through the second output port to the Right Front Caliper centre piston.
- Proportional Control Valve -
There are three caliper assemblies, each housing three pistons. Each caliper has two separate hydraulic circuits, one for the centre piston, and one for both outer pistons. Caliper operation may occur as either centre piston actuation, simultaneous outer piston actuation, or a combination of both.
- The front right and rear calipers are mounted in a stationary position.
- The front left caliper is mounted in a manor such that as the caliper activates and engages with the rotating disc, the caliper shifts and depresses the plunger of the Secondary Master Cylinder.
Brake Pedal MC – The Brake Pedal MC provides hydraulic force equally to the Delay Valve and the Rear Caliper Inner Piston.
The Delay Valve transfers force from the BPMC in sequence via two outputs; the first connects to the SMC input, then through a hub style connector over to the Front Left Caliper Centre Piston. The second connects to the Right Front Caliper Centre Piston.
The Secondary Master Cylinder transfers force through the Proportioning Control Valve to the Rear Caliper Outer Pistons. The source of SMC output force can originate from either plunger activation caused by left front caliper shift, or from the Delay Valve primary output fluid passing between the SMC plunger lip and cylinder bore.