No rear brake again

[Martynbradley]

When I bleed the brake it take at 4 of 5 pumps of rear brake to get air out, that to me suggest air is up by the modulator and when air comes though its a lot.
In my opinion air is being drawn into system when the bike is stood for a long time and I think it could be aluminium washers used on the bangos to the modulator.Why the didn't use copper washers as this is the prefered for bangos as they create a better seal.
Also could it be not that they didn't torque bango bolts on modulator properly on some bikes ?

 

[RUN666]

Anything is possible, really! Since I'm still unsure of the real cause of this problem, I'll wait and see if what I did changed anything. If not, then I'll really look for the source of the problem: loose washers (that'll be easy to check...), overheating around the ABS unit... or some other nonsense!

In the meantime... I'm driving!

 

[atomsplitter]

The only way to get air into a 'sealed' system is if the system is under vacuum. That means if the system is below atmospheric pressure it can draw air in thru sealing surfaces, however if that were the case, under pressure it would leak fluid out unless the banjo is acting like a check valve (it doesn't). When the system is filled and vented (purged) it should be at atmospheric pressure since the reservoir cap is removed to add the fluid. If you're getting 'lots' of air out then there is something else going on like inadequate purging. If you're using a vacuum pump to draw fluid from the reservoir (most power bleeders) you may be moving air around the system. The ABS module only bypasses fluid back to the reservoir (i.e. lower caliper fluid pressure) in pulses so the tires don't lock up. The ABS modulator doesn't do anything if the speed sensors aren't calling for activation.

 

[Mighty Mouse]

Coming from a non mechanic although I live vicariously through Turbo200R4, Kevin and Journeyman. My 2020 GT was bled before I bought it new as the dealer realized there was a brake problem. I have had my GT bled 3 times since then and it’s right at the point where I will be going in for my 4th bleed. All three times my brakes have gone out was summer days over 90 degrees in the backroads with me “laying the wood” to my Rocket for around 2 hours. Each time my brakes went out after around 2 hours and I noticed my seat was uncomfortably hot. Touching the rear passenger pegs burnt my hand the 3rd time it happened. There is no doubt in my mind at 88 degrees today if I hit it hard on the backroads for over an hour what’s left of the rear brake would be gone. Just for info I use 85 to 90% front brake and just feather the rear in turns to bring the rear down. My pads are good. Makes no sense but that’s the way it is.

 

[RUN666]

As long as your gonads are still functioning, everything's fine... But if what you're saying is true, then I don't see any other solution than to "air-condition" the ABS module !

 

[Davey]

My 2020 bike had recall for new large master 18 month ago, thought it was getting a bit spongy again towards the end of last summer,but after 4 month storage,no back brake again,thought that Triumph had finally fixed it with recall, but now back to bleeding myself again.

Same here on my 22 plate been bled twice since recall

 

[TURBO200R4]

Coming from a non mechanic although I live vicariously through Turbo200R4, Kevin and Journeyman. My 2020 GT was bled before I bought it new as the dealer realized there was a brake problem. I have had my GT bled 3 times since then and it’s right at the point where I will be going in for my 4th bleed. All three times my brakes have gone out was summer days over 90 degrees in the backroads with me “laying the wood” to my Rocket for around 2 hours. Each time my brakes went out after around 2 hours and I noticed my seat was uncomfortably hot. Touching the rear passenger pegs burnt my hand the 3rd time it happened. There is no doubt in my mind at 88 degrees today if I hit it hard on the backroads for over an hour what’s left of the rear brake would be gone. Just for info I use 85 to 90% front brake and just feather the rear in turns to bring the rear down. My pads are good. Makes no sense but that’s the way it is.

ok my friends this is a perfect account of MY THEORY about the air in the rear brake cylinder getting hot and expanding and displacing the brake fluid
now what we need is to do another run and with a thermo gun stop in a safe place and check the heat on the abs unit and the rear brake cylinder and if it is 5 to 600 degrees then i will buy into the boiling fluid theory.
another test would be when they bleed the brakes and you have a good firm pedal make your run and see if it stays good pedal.
going out on a thin limb here and still need a lot of testing.
my MY THEORY is that the rear wheel cylinder seals has a lip on them that allows the seals not to leak fluid but is able to suck air because the springs are not strong enough to return them all the way out so they suck air into the rear cylinder.
every one has theory's triumph has had a bunch that has not worked so i will not be disappointed if mine does not work. and remember this is just one opinion.

 

[stingray]

ok my friends this is a perfect account of MY THEORY about the air in the rear brake cylinder getting hot and expanding and displacing the brake fluid
now what we need is to do another run and with a thermo gun stop in a safe place and check the heat on the abs unit and the rear brake cylinder and if it is 5 to 600 degrees then i will buy into the boiling fluid theory.
another test would be when they bleed the brakes and you have a good firm pedal make your run and see if it stays good pedal.
going out on a thin limb here and still need a lot of testing.
my MY THEORY is that the rear wheel cylinder seals has a lip on them that allows the seals not to leak fluid but is able to suck air because the springs are not strong enough to return them all the way out so they suck air into the rear cylinder.
every one has theory's triumph has had a bunch that has not worked so i will not be disappointed if mine does not work. and remember this is just one opinion.

One thing is the new bike is completely different than the first gen. Almost every single part and design is different. It's hard to compare an apple to an orange.

Also Brake fluid doesn't have to get that hot to boil. Look at the wet boiling points. That is just the industry minimum testing standard of allowed water at 2.4% or so. If you have more water than the allowed minimum the boiling point goes even lower. If your theory of the air entry is correct just imagine how much moisture is being absorbed from the humidity in the air. Since most of us don't live in a desert.

 

[stingray]

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.

 

[TURBO200R4]

One thing is the new bike is completely different than the first gen. Almost every single part and design is different. It's hard to compare an apple to an orange.

Also Brake fluid doesn't have to get that hot to boil. Look at the wet boiling points. That is just the industry minimum testing standard of allowed water at 2.4% or so. If you have more water than the allowed minimum the boiling point goes even lower. If your theory of the air entry is correct just imagine how much moisture is being absorbed from the humidity in the air. Since most of us don't live in a desert.

First of all i am not talking about my 07 it has been perfect since i have owned it all i have done is change pads and flushed a couple of times i was talking about the 2020 gt in the thread that has been bleed three times and ready for the fourth time.
you seem to be dead set about boiling brake fluid with out even testing the what heat the brakes are getting up to .
you seem to be knocking my ideas when i am the only one that has offered some tests to try to get to the bottom of this brake problem.
if any one wants to test whether the brake fluid boiling is the problem then they should put in new fluid bleed the brakes till they have a frim hard pedal then take it out and try to get the fluid to boil.
how would any one solve the brake problem with out doing some testing
if i had a bike with that problem i would be running those test till i found the problem.
one guy said that he install dot 5 fluid so with new fluid he should measure the temp and t ry to get us some information.
true i live in the desert which brings on the heat but we do not have a lot of humidity til june and july in the rainy season but i am relying on info from others on the rocket site to form a theory
i think that it would be great if some one proved me wrong and they found the brake problem but it is not going to happen without testing.