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Tacking on to what I posted the other day, I think I have a theory on these brake issues. It's just a theory, combining what everyone has said, the fact that my bike has been sitting for months and has seemingly way worse brake issues, and some things my mechanic has said.

The air in my system and the initial soft feel of our brakes on daily use may be the same issue. Nicspeed mentioned it in their post above, the brake system is allowing a tiny amount of air in, without leaking brake fluid. This happens at the master cylinder, which according to my mechanic can let air in without leaking fluid if the seals have a failure. This tiny amount of air is enough to cause the initial squeeze of the brake handle to be soft, but then is "bled" out (either through the leak source or into the fluid reservoir) resulting in subsequent squeezes being more firm.

If the system is allowed to sit unused over time, this tiny amount of air builds up behind the master cylinder and causes what I had, a complete brake failure. Bleeding the system fixes the issue temporarily but does not completely solve the issue.

To me this also explains why our mechanics and dealerships can "fix" the problem by repeatedly bleeding the system in the shop, only for it to come up again on the streets.

Triumph really needs to step up and fix this, but I have no idea how to get them to do that.
 

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Exactly what happened to me. I left the bike parked at the airport for about a week and after that the first pump went all the way down almost touching the grip. Second a little less travel and so on till “normal” operation.
 

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I contacted Brembo USA seeking a seal kit for the master cylinder. Triumph only sells a whole new master:

“Unfortunately Brembo does not offer the rebuild for late model masters.* For any new masters Brembo only offers rebuild for them direct through the OEM manufacture.* In this case if Triumph does not sell it, it’s not available.* I can confirm an upgraded master to a 19 RCS or 19 RCS Corsa Corta will provide a much better feel.”

Brakecrafters.com sells a master cylinder rebuild kit but they label as “1999 -2017 speed triple”. I doubt all of those years share exact piston and seals. But I’ll try it and get back to y’all.
 

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Well it’s been a couple months since the dealership replaced the master cylinder and about 500 miles. The double pull is coming back. Not as bad as it was but I assume it will continue to soften on the first pull the longer I ride.
So replacing the master cylinder is only a very temporary fix.
 

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I received the master cylinder rebuild kit from brakemasters.com. I've not completely torn down my master cylinder yet. But, from the outset, the dust seal in the new kit doesn't match the existing dust seal at all. Size and shape is wrong. The other parts may fit, but I'm not going to tear apart my master cylinder to find out.

Jason Wess, above, confirms what I was afraid of. Even if we get a new OEM master cylinder installed, it will start to fail soon after install.

Looks like the Brembo rep may be right. The only solution is to replace with a 19RCS or RCS Corsa Corta.
 

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I am 100% convinced of what Terry, Steve and Decosse have said. It's the calipers pistons seals retracting the piston. People here have reported master cylinder been replaced, another the ABS pump and many multiple bleeds with different techniques, but to no avail. I will go the route of cleaning the pistons and lubricating, before replacing the seal.
 

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Red, I'm guessing you're pretty savvy mechanically so will risk proposing you try something normally frowned upon.

Remove and clean the pistons and caliper bores as you plan. Lube the seals with brake fluid and get the pistons started into them. Now (and this will elicit cries of no, no a thousand times, no) lubricate the piston and/or caliper bore with brake grease. Be aware most brake grease brands will carry a notice clearly stating "do not use on internal caliper piston". I suspect it's because most are silicon based and incompatible with all brake fluids apart from DOT 5.0 (which is silicon based). For that reason I suggest Permatex Ultra Ultra Disc Brake Caliper which is approved for use a caliper piston lubricant.

Of course any kind of grease on the forward part of the piston will attract dust and debris so this may exacerbate piston and bore wear (this is why calipers used on rally cars incorporate a gaiter between the face of the piston and the bore entrance) so be aware of this.

Another perhaps more radical option is to flush the brake system clean and then refill with DOT 5.0. Being silicon based it has a higher level of lubricity and may allow the piston to edge forward through the seals in the tiny infinitely fractional amounts needed to make up for the continuous tiny infinitely fractional amounts of brake pad wear that occur all the time. DO NOT MIX DOT 5.0 BRAKE FLUID WITH WITH ANY OTHER DOT VARIANT.

Do not attempt to follow these suggestions if you're still jousting with the dealer over this issue as a warranty matter. And only do this if you're confident in what is trying to be achieved and are willing to monitor the situation with an educated mind.
 

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I still think there may be multiple issues here. After having a mechanic bleed the brakes and letting the bike sit unridden for 5 months, I had a lot of air in the system. When bleeding the brakes last week, it looked like a shaken bottle of coke bubbling in the bleed lines. 5 months ago, they were working great, though softer than what I would prefer.

So, there is definitely air getting into my system. Mechanic says everything points to air getting in at the master cylinder based on where the air bleeds from. But, may be the caliper seals and the air is just slowly traveling up to the master.
 

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@terry, thanks for the suggestion and no worries, I assume ALL responsibility. I had right hand surgery for carpal tunnel syndrome last week, so down for 8 weeks. Then, I am having the left hand one done, so it will be a while before I tackle this and report back.
@specbebop, if air is getting in, there has to be a leak somewhere, is my guess.
How are you bleeding your MC, with a vacuum pump or straight hand pump???
The vacuum pump will pull little air bubbles coming through the threads, not the brake line system, so a false positive.
 

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I'm guessing that this problem is some sort of manufacturing defect as it seems to affect only 2016 and newer models. I've never had this problem with my 2014 S3R, even after it sat for two months after my rotator cuff surgery in March. Last week just for grins I bled the master cylinder and not a single air bubble showed itself.
 

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After research about all the bubble issues, most conclusions come to manufacturing areas that can hold microscopic that cant seem to bleed out. Rough casting areas and position of reservoir bubbles cant escape. This is not my opinion just what ive read. I will be changing to a Magura unit, great customer service and all there units are cnc’d for no rough casting and they have high quality control. Now if my money tree would start blooming i will absolutely buy it. Again this is all based on multiple research especially on the racing end where brakes are huge concern both bike and car.


Sent from my iPhone using Tapatalk
 

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Called the dealership today. They were going to follow up with Triumph to see what the next step is. We’ll see what Triumph says since master cylinder replacement didn’t work.
 

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Dealer called yesterday. Triumph has a new bleed procedure that involves removing the calipers and pushing the pistons back in. Asked me to drop my bike off so they can have it. Apparently Triumph now realizes this is an issue. They are asking for pictures of how far the first pull is compared to the second pull.
 

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That sounds like the same "fix" that brembo recommended for the same issue on a different bike.

Interested to see the outcome...
 

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Dealer called yesterday. Triumph has a new bleed procedure that involves removing the calipers and pushing the pistons back in.
This is painful to follow.

And at risk of sounding like a broken record because I've said it so many times before it'll never work because it's not air in the system.

Call me cynical but I wonder if the 'new' bleed procedure is actually a rehash of TSB # 78 first issued back in 2005?
 

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Picked up my bike this morning. Brakes felt firm first pull. Rode for an hour. Dealership kept it for a couple of days before I picked it up and rode it too. Time will tell but so far so good.
 
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