Linked Brakes

[tbloor]

Morning Everyone,

I've bought a 1999 ST1100 at 150,000km. I don't know if I'm missing something, but when the bike is on the center stand, I roll the rear wheel and squeeze the front brake, but the rear just keeps rolling. I'm assuming this means the linked braking system is no longer working. The rear and front operate separately, and have plenty of bite and the pads are fresh. Is it worth reinstalling this system? I'm presuming that isn't an easy job.

Thanks!!

 

[Mike M.]

None of my st1100's have linked brakes and ABS. I think if your bike does not have ABS then it most likely also does not have linked brakes.

 

[Alberto]

My bike doesn’t have linked brakes, but if I remember correctly, the rear brake is activated by a secondary master cylinder on the front fork, and it only engages under load, when you’re braking while moving.

 

[ST1100Y]

I think if your bike does not have ABS then it most likely also does not have linked brakes.

His avatar clearly shows a post '96 ABS-II/CBS...
But who knows if a PO has either neglected or disabled the CBS circuit...
I'd get a w/shop manual and go though the checking procedures one by one...

 

[tbloor]

Thanks guys, it is indeed a 1999 model with TCS and ABS. The under load part is interesting, I have no idea how to safely engage that! . As I said the braking feels solid, but not sure if this is a known issue with aged bikes.

 

[tbloor]

Interestingly I asked Gemini, and this was the response. If anyone can confirm based on not being an AI, that would be great. “
There’s often some confusion about how the Linked Braking System (LBS) on the ABSII models (post-1996) actually triggers. Here’s the breakdown:


• Fork Compression: The rear brakes do not activate simply because the forks are compressed under load or braking dive. The system is torque-reactive, not suspension-sensitive.


• The Pivot Mechanism: Activation requires the front wheel to be spinning. When you grab the front lever, the left-side caliper "swings" on its pivot due to the friction/torque against the rotor. This mechanical movement is what strokes the secondary master cylinder mounted on the fork leg.


• On the Center Stand: If the bike is stationary, pulling the front brake will not engage the rear. Without the "drag" of a spinning rotor to move that left caliper bracket, the secondary master cylinder stays static.


• Testing/Bleeding: This is why you can't test the linked functionality while parked. To bleed the system properly or test it on the stand, you have to manually unbolt/pivot the left caliper bracket to simulate that rotational torque.


TL;DR: No rotation = no link. Static fork compression does nothing to the rear circuit.”

 

[Uncle Phil]

ABSII (1996 and later) is the only model of those years with linked brakes (the other model is the standard).
The quickest way to know is look at the front fender - the ABSII has a two piece and has fork 'protectors' built into the front fender.
You will also see 'plumbing' across the top of the front fender.
The wheels will have sensor rings front and back but someone could have done a wheel swap.
Also over here, the turn signal indicators are half way down the speedo cover on ABS bikes and up in the light bar for the standards.

 

[tbloor]

Yep that's definitely what I have. I'm going to assume that the linked brake system is operating when both wheels are turning, unless there anyone knows any easy way to test it when static, without pulling it apart! Thank you gents to everyone who has already helped me confirm this.

 

[Ryan_B]

I don't know how the ST1100 is, but the ST1300 you can actually squeeze the secondary master cylinder with your hand and it will engage the rear brakes. You basically lay down next to your bike when it is on the center stand, you can kick the rear wheel with your foot and cycle the secondary master cylinder with your hand (it is mounted on the front left caliper and pivots forward). It only moves like 1/8th an inch, but it will stop the back tire immediately.

Picture borrowed from the internet:


Ryan

 

[Uncle Phil]

Yep, when I clicked on your avatar and got a good look at the front end of your beautiful blue (my favorite color of) ST1100, it is definitely a ABSII. If the ABS is functional, the ABS lights should come on when you turn the key on and then go out after you start rolling. If it has a problem, they will blink and you can retrieve the fault code.

 

[Andrew Shadow]

Rotating the left front caliper upward on its pivot point will cause the activation of the SMC enabling it to be tested when stationary.
I would suggest a good cleaning and lubricating of all of the pivot points and moving parts to ensure that everything is able to move freely. Might as well do the same for the entire brake system if you aren't sure what condition it is in.

From the Honda service manual;

 

[Alberto]

Yep, there are pictures of SMC on my neighbours st1100, it linked to caliper via movable bracket