No rear brake again

[TURBO200R4]

I just have a hard time trying to see the Brembo Stylema pistons are sucking air. Of all the bikes running them the new gen R3 is the only one having problems.

I have the same calipers on my KTM 1290 Super Duke and have never had to bleed them.

you make a great point about just the rockets having this problem
something for me to consider.

 

[stingray]

DOT 5 brake fluid is not compatible. Maybe you meant DOT 5.1 instead?

No testing? What do you mean boiling some brake fluid under pressure at different wet levels? I don't think any of us has the laboratory to do that. I trust the testing already done. Even Triumph is now saying its just normal degassing. Did you see that? What causes degassing of brake fluid besides temperature?

We have a design problem not a air intrusion problem. The gas comes from the excessive heat where the components are located.

 

[stingray]

you seem to be dead set about boiling brake fluid with out even testing the what heat the brakes are getting up to

lol, my brakes have to be pumped up before even getting the pads warm. so it's not heat from the calipers.

 

[TURBO200R4]

DOT 5 brake fluid is not compatible. Maybe you meant DOT 5.1 instead?

No testing? What do you mean boiling some brake fluid under pressure at different wet levels? I don't think any of us has the laboratory to do that. I trust the testing already done. Even Triumph is now saying its just normal degassing. Did you see that? What causes degassing of brake fluid besides temperature?

We have a design problem not a air intrusion problem. The gas comes from the excessive heat where the components are located.

Well i once needed info about atf so i put a pan of atf on an outside stove and found it was steaming and breaking down at 250 degrees so yes i try to find answers.
yes i should have typed DOT 5.1 i will try to be more careful when typing for you. sorry i typed info instead of information.
i can clearly see what we have is a failure to communicate probably my fault especially cause i think you already have made up your mine about the cause of the problem. so i will quit wasting my ime

 

[BiKenG]

same here. I've worked on hydraulic systems for over 40 years. Our Rocket 3 is a modulator controlled ABS. No pump is involved as there are also no abs valving at each wheel. It is all done through trapping and relieving pressure in the modulator. You are the hydraulic pump. The modulator either allows you through or not. I just hate to see this erroneous information being spread around.

I apologise for my first post being critical, but the above needs correcting. An ABS system works by relieving the hydraulic pressure to the brakes, allowing the wheel to turn again and then re-applying pressure from a pump, until the electronics decide the wheel is locking again and the pressure is released and re-applied again - repeatedly. That is the pulsing you feel in the brakes when the ABS system operates.

It's a long time since I was running Honda UK's Technical Training Centre, but the basic modus operandi of ABS systems has not changed since, only the electronics get fancier and the only way the system can re-apply pressure is by using a mechanical pump built-in to the modulator to pressurise the fluid back to the brakes. There is no way the manual operation of the pedal/lever can do this as it would simply move progressively to the end of its stroke and then no more brakes possible. The pump is required to re-apply the pressure so the manual pedal/lever remains essentially static and hence the ABS fuse is the largest single fuse, so it can handle the ABS pump. The R3 Owners Handbook I have seen however completely mislabels the fuses. Well done Triumph.

Another point concerns 'linked brakes'. Originally introduced by Moto Guzzi IIRC but soon taken up by Honda and others. There were various methods to attempt this in the early days, some entirely mechanical. Nowadays it can all be done electronically. The ECU (usually dedicated to the ABS) has complete control of what pressure goes where, so it's a simple matter of programming that decides which brakes are operated by which pedal/lever. However it's controlled and operated, some systems operate the front as well as the rear brakes when the rear pedal is pressed and some the other way around. I've used both and not really a fan of either.

The R3 Owners Handbook states that operating the rear pedal has no effect on the front brakes, but that pulling the front brake lever will also apply some pressure to the rear, albeit varying according to lever pressure and possibly speed - all controlled by the ECU. I see no reason to doubt any of that explanation and it seems entirely likely to me that when stationary, application of the front brake will have no effect on the rear. So might be hard to prove they're linked, but as I said, I see no reason to doubt the explanation in the Owners Handbook.

I've not ridden an R3 yet, but I plan to do so in the next few days, so be interesting to see how the brakes feel.

 

[BiKenG]

I can add a little more to the 'Linked brakes' saga.

In the early days, Honda were one manufacturer to cause the front brakes to also be operated by the rear brake pedal. The reason for this was because in the US, there was a tendency for riders to NOT use the front brake due to the misguided belief that the front would lock up and better to just use the rear brake. Any competent biker knows the nonsense of this, but no-one said the US had the best riders. In fact, I have heard of this appalling practice actually being taught to learner riders.

So in direct response to this poor riding, Honda designed their linked brake system to ensure even the incompetent rider would still be applying both brakes, i.e. safer braking.

Over the years things have changed and all big bikes now have ABS, so such poor bike control is not the problem it once was.

 

[RUN666]

To follow up on my post from March 17th: after bleeding the brakes and replacing the brake fluid with DOT 5.1, the rear brake pedal remained very firm for a ride of about 200 km, then it started sinking again...
I had the same problem on my Ducati SFV4, but in that case, the cause is known: the brake line runs alongside the exhaust, causing the brake fluid to boil, generating air bubbles. The only solution is an annual bleed. However, once bled, the pedal remains very hard for a long time.

I just checked the routing of the brake line on the Rocket, and it turns out it goes under the engine casing (almost integrated into it) before going to the ABS unit. So the DOT fluid gets very hot... I'm going to try to isolate this section of the line during my next work on the bike. We'll see...

 

[Gregger]

same here. I've worked on hydraulic systems for over 40 years. Our Rocket 3 is a modulator controlled ABS. No pump is involved as there are also no abs valving at each wheel. It is all done through trapping and relieving pressure in the modulator. You are the hydraulic pump. The modulator either allows you through or not. I just hate to see this erroneous information being spread around.

Your statement got me a little confused. I always thought there was a pump built into the ABS system. Doing a little Google search this was confirmed. In most cases, the pump motor drives one or more plungers (pumps) in the hydraulic block to replace the fluid/pressure bled off during braking which has locked a wheel. It is one of (usually) 4 components in an ABS system.

Wikipedia puts it like this;
Pump - The pump in the ABS is used to restore the pressure to the hydraulic brakes after the valves have released it. A signal from the controller will release the valve at the detection of wheel slip. After a valve releases the pressure supplied from the user, the pump is used to restore the desired amount of pressure to the braking system. The controller will modulate the pump's status in order to provide the desired amount of pressure and reduce slipping.