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+1 on what was just said about excessive elastic memory in the caliper seals pulling the pistons back too far back into the calipers - should only be enough to retract the pads off the disc a fraction.

And. like DEcosse, I've been around Hinckley triples and forums such as this, long enough to remember the similar issues with '05 - '06 S3s. Not to mention the brake issues with all variants of the 955 for years before then, but that's another story .....sigh...

As it's under warranty do as DEcosse says and push the shop for replacement calipers. Otherwise I'd pull the pads, push the pistons as far back as possible in the bores and clean very carefully the very front part of the bore surface. It's best to actually remove the pistons but of course it's a lot more work. Do not use anything overly aggressive on the bores. You'll also find that new pads will push the pistons back a little more so the pistons are operating in a cleaner section of the bore. The better feel after a couple of pumps is what leads many to think there's air getting in the system and leads to countless, often quite creative, brake bleeding attempts all to no avail. I've taken the liberty of scratching a small sketch and attaching it here to try and show what's happening.
 

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.....You won't get much exposed piston bore......
Agreed, however it is the small exposed section forward of the pistons that is the problem together with debris and deterioration of the piston surface just about where they meet the seals. It only starts to be used as the pads wear - that's why the OP is only now experiencing the problem. The pad wear over time is usually commensurate with the deterioration of the bore and piston surface over the same time and conspire to start the problem.

New pads will fix the problem for a while but of course this exposes more of the bore forward of the seals allowing the debris buildup/bore degradation to creep a little further back.
 

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Repeating myself here but it's not air in the system. Zip tying the lever back to the bars works not because it allows any residual air to move up and out of the line and up into the master cylinder, because there isn't any, it works because constant pressure allows the pistons in the calipers to eventually overcome the resistance of caliper bore/piston surface degradation and move forward that tiny bit extra so the seals don't have to over flex. Of course the problem reoccurs as the tiniest bit of disc run out pushes the pistons back just a little further or as the pads wear a little more.

Triumph seems to be repeating the problem that occurred with the first few batches of 1050 Speed Triples ('05-'06) and Tiger 1050s ('07) that necessitated the replacement of improperly surface treated caliper pistons (refer TSB # 381 as an example). What's baffling is that was with Nissin calipers, and this more recent Speed Triple RS problem, is with Brembo items. I suspect the surface finish/corrosion resistance limit specification Triumph issues with its procurement instructions is unusual and is difficult for the supplier to comply with or is just plain wrong.
 

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Can't believe the dealer is persisting with continually bleeding the system. IT IS NOT AIR IN THE SYSTEM. You can show them my posts from page 3 of this thread (see also the posts from DEcosse) where we're trying to explain what's occurring. Of course your dealer will claim they are the 'professionals' and dismiss us as know nothing keyboard warriors.

Must be frustrating for you as a new owner.

If you're competent enough to perform a pad change yourself you can try this (yes, yes I realise your pads are nowhere near worn out, bear with me).

Go to a well stocked parts/accessory store and see if you can discern which brand of pad has the thickest amount of friction material. You might be able to work it out by looking at specs online. Try SBS, EBC, Ferodo, Brembo. They are probably all the exact same friction materail thickness but if there is one a little thicker (even 0.25mm) buy them. Fit them and the problem will go away for quite a long time. Alternatively, but only do this if you're really competent and confident in what you're doing, you could try and fashion some stainless steel shims to go between the back of the pad and the pistons. You can get the shims from any car wrecker as many cars have these fitted as standard. You'll have to cut them to size of course so don't do this unless you understand what I'm trying to achieve.
 

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Found the "First Lever Pull feels soft" on the 959 Panigale Forum:

Pard posted: "My 959 is at the dealer and they noticed that the pistons at the calipers are not retracting after pressure is released as much as one would expect. They think this may be the cause of the soft brake feel. Ducati was informed of the finding and we await a reply."
The problem is actually the exact opposite - the pistons are not moving forward in the calipers the tiny fractional amounts needed to make up for the tiny fractional pad wear that occurs continually. As a consequence the seals, which have overly distorted (we're talking tiny fractions here), pull the piston back a little too far so the first pull has to push the piston out a little and then the second pull of the lever only has to push it by the requisite amount. Then the seals s-l -o-w-l-y retract the piston again but just a tad too far and so the cycle repeats.

This is getting tiresome.
 

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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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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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That's the issue. I lube piston seals with a mixture of ester oil and ceramic particles, applied with a thin brush and very little quantity. Be careful don't touch pads and rotors with that. No more spongy lever
Interesting concoction. It must reduce the seals grip on the pistons just enough that they can slide forward in the infinitesimal increments needed to accommodate pad wear yet provide sufficient hold that the seals still distort fractionally and so retract the tiniest amount needed to avoid pad/disc drag. Reassuring that you're addressing the root cause and not blindly assuming it's air in the system as many do.

Ceramic particles eh? Where on earth do get ceramic particles or do you grind up an old toilet fixture?
 

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Can you remember if the Street Triple R pistons you used had a black finish? Using Daytona/Street Triple R 675 pistons with the black coating was the fix a few years back but I didn't mention it in this thread because I thought the '16 and on Speed Triple Brembos might be different. I have no idea what the black finish was, some referred to it as a 'teflon like coating' but no one really knew. Might be worth investigating fitment dimensions.
 

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UPDATE:
Finished the left side caliper pistons cleaning and lubrication. Bled the system twice, starting at the master cylinder and it feels 100% better, but no solid. I wasn't able to ride, so tomorrow will be revealing to see if the first pull is sift or not. Will report again tomorrow.
Red Baron, I suspect you're going to be pleasantly surprised at the results of your efforts, at least until the Permatex Ultra Brake Parts Lubricant moves from between the seals and the pistons. Did you consider trying to rustle up some of the 'hexagonal boron nitride' concoction that trisonico told us about a couple of pages back? He was insistent it worked for him and continued doing so well after he did the job.
 

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Because the pistons were pushed way back in the calipers to allow removal so wiping (cleaning) the slightly corroded surface debris and allowing them to move a little further forward toward the disc surface. The problem will likely return as your pads wear fractionally.
 

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Baron, way back in this thread I tried to explain what I believed to be happening to cause this soft initial pull. I was never happy with the clarity of my explanation nor with my clumsy drawn diagram.

Your experience with the SS pistons confirms the criticality of the piston surface finish. If it's too rough the piston cannot move forward in the infinitesimal steps required to compensate for the same infinitesimal amount of wear that is continually occurring on the pad. If the pads wears 'x' then the piston has to slide through the seal by 'x' also. If it doesn't this results in the seal (and piston) retracting away from the rotor 'x' further than required when pressure is released and hence the soft initial pull. Of course there isn't always a soft initial pull because eventually 'x' will increase to the point the seal's elasticity will overcome the friction between it and the piston's surface allowing it to move forward that amount. I wish I had the graphic animation skills to develop a short animation of what I'm convinced is occuring, my 2D drafting expertise is sadly lacking and 3D is way beyond my skillset.

I'm following your, and Jeevs, endeavours to resolve this with interest. In the meantime you may find this thread about piston over-return of interest.
It's from an engineering forum and written by enthusiasts more eloquent than myself so better able to explain it all.

 

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There are plenty of other calipers that will fit. You might want to consider 675 Daytona calipers or the pistons at least. Fitting 675 Daytona pistons to Street Triples with the soft initial pull issue was a fix a while back but it was a particular year and part number that worked. It was even an official Triumph fix and covered by a Tech Bulletin but only ever attended to by dealers if the customer complained.

Have a look at this thread where champ87 says he fitted 675 Daytona pistons to a Sprint to cure what he called a 'sticky' piston issue. Different calipers of course. He might know the part numbers and if they fit Brembo as well as Nissin.

 

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Cheefkeef just posted some excellent 675 caliper piston/seal info in the thread I just referenced.

 
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