Dual Diagonal Brake System Question
Thread Starter
Former Moderator
Joined: Jul 2005
Posts: 4,634
Likes: 28
From: West Virginia
John,
If our system worked that way then one of the front brake bleeders would relieve pressure from the primary piston, and the other front bleeder would relieve the secondary piston. There would be a difference in pedal feel when you bled the two front brakes. This doesen't happen, the brake pedal goes to the floor easily when bleeding either front brake. <<< Wrong, after rereading John's explanation above I see he is correct.
I'm pretty sure that our primary and secondry pistons are mechanically connected so that the brake pedal directly moves both pistons, the system doesn't rely on hydraulic pressure to move the secondary piston. <<< Wrong again, they're mechanically connected after the return springs completely collapse.
Most real race cars have a completely separate front and rear brake system. Two master cylinders are acted upon by a moveable bias bar that changes how much brake pedal force is applied to the front and rear master cylinder allowing you to adjust the brake bias, usually from a cockpit adjustable knob.
If our system worked that way then one of the front brake bleeders would relieve pressure from the primary piston, and the other front bleeder would relieve the secondary piston. There would be a difference in pedal feel when you bled the two front brakes. This doesen't happen, the brake pedal goes to the floor easily when bleeding either front brake. <<< Wrong, after rereading John's explanation above I see he is correct.
I'm pretty sure that our primary and secondry pistons are mechanically connected so that the brake pedal directly moves both pistons, the system doesn't rely on hydraulic pressure to move the secondary piston. <<< Wrong again, they're mechanically connected after the return springs completely collapse.
Most real race cars have a completely separate front and rear brake system. Two master cylinders are acted upon by a moveable bias bar that changes how much brake pedal force is applied to the front and rear master cylinder allowing you to adjust the brake bias, usually from a cockpit adjustable knob.
Registered User
Joined: Apr 2004
Posts: 311
Likes: 0
From: Ellicott City
Rob,
I found another diagram. This one appears to be for/from Lexus. Here is a link. It has much better diagrams - Brake diagrams
John
I found another diagram. This one appears to be for/from Lexus. Here is a link. It has much better diagrams - Brake diagrams
John
Registered User
Joined: Jun 2005
Posts: 7,261
Likes: 1
From: The Blue Ridge
Rob,
Unless a resident expert on S2k brakes speaks up, I think we need a sacrificial MS to find out. Since the shop manual say not to open one and just replace the entire assembly, I would assume you won't get one back together after opening it.
That has been my experience with many things, because I have to know how they work
Unless a resident expert on S2k brakes speaks up, I think we need a sacrificial MS to find out. Since the shop manual say not to open one and just replace the entire assembly, I would assume you won't get one back together after opening it.
That has been my experience with many things, because I have to know how they work
Thread Starter
Former Moderator
Joined: Jul 2005
Posts: 4,634
Likes: 28
From: West Virginia
John,
That Lexus brake article is very detailed and the explanation of "Leakage in the Primary/Secondary Circuit" makes it clear why the pedal goes soft when a leak occurs. When either circuit fails, much of the brake pedal stroke is used to compress the failed circuit's piston return spring.
This quote is an understatement:
Thanks for looking it up for me.
Rob
That Lexus brake article is very detailed and the explanation of "Leakage in the Primary/Secondary Circuit" makes it clear why the pedal goes soft when a leak occurs. When either circuit fails, much of the brake pedal stroke is used to compress the failed circuit's piston return spring.
This quote is an understatement:
Stopping distance is increased signigicantly, however, when operating on only one circuit."
Rob
Joined: Jan 2003
Posts: 6,337
Likes: 1
From: Gods Speed #57 Lemons #77
Originally Posted by robrob,Dec 21 2008, 08:38 PM
John,
That Lexus brake article is very detailed and the explanation of "Leakage in the Primary/Secondary Circuit" makes it clear why the pedal goes soft when a leak occurs in either circuit. When either circuit fails, much of the brake pedal stroke is used to compress the piston return spring.
This quote is an understatement:
Thanks for looking it up for me.
Rob
That Lexus brake article is very detailed and the explanation of "Leakage in the Primary/Secondary Circuit" makes it clear why the pedal goes soft when a leak occurs in either circuit. When either circuit fails, much of the brake pedal stroke is used to compress the piston return spring.
This quote is an understatement:
Thanks for looking it up for me.
Rob
I think that is the part that is over looked. When you experience brake failure at a single caliper you will have *SOME* brake function for the diagonal/parallel portion however brake pedel feel and actual brake function will be compromised.
thanks guys! 
Registered User
Joined: Aug 2002
Posts: 48,203
Likes: 10
From: Lewisville, TX
One thing that may have been overlooked is that in order for the computer to know something is wrong with a caliper, there has to be a speed indicated by the speed sensor. If no speed is present, there is no need to engage its "emergency" plan. Since I'm unable to bleed my brakes at speeds fast enough to confirm this, you will have to take my word. 
Thread
Thread Starter
Forum
Replies
Last Post
trackrabbit21
S2000 Under The Hood
8
Aug 11, 2015 11:14 AM