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Caliper Piston Pitting 1000SP

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FrozenSP View Drop Down
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    Posted: 20 Nov 2022 at 16:13
Not been too happy with the rear brake performance for a while, even after switching to braided lines, so decided to rebuild the caliper. 
I believe it's a Brembo P09, and the brakes have been delinked.

Managed to get one of the pistons out, the other is pretty stuck in, will take it to a garage with an air compressor to see if they can blow it out. 

The piston which has come out is pitted around the edges;





I'm reasonably sure that the pitting occurs past the seal, but I should still replace these right? 

Don't seem to be the easiest thing to find these days; my usual brake part supplier, Ducatipaddy, has this to say about them - "These pistons are currently unavailable. I don't know whether more will be made at this stage."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ranton_rambler Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 06:33
When I rebuilt all 3 callipers on my Spada, the big pistons were harder to find. Try a few more places - HMB, Stein Dinse, Teo Lamers etc.
Also, the mountings are the same as P08 if you’re really stuck.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote russellp Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 09:16
Gutsibits are showing one (only) in stock
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Post Options Post Options   Thanks (0) Thanks(0)   Quote russellp Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 09:21
HMB showing them in stock
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Barry Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 10:12
Niks Euro Bits have one (according to eBay) and Gutsibits have one (according to online stock). Worth a call in both cases, but (potentially) sorted!

https://www.ebay.co.uk/itm/352867897337

As others have said, if you're totally stuck, a P08 caliper fits to the rear - my 1000SP has P08's all round. A common "mod", I gather, during the various years when the 09's and parts were unavailable.

edit: just read the O/P again - "brakes have been delinked". Well, there you go then. The rear, with original caliper, wasn't designed to be doing that job on its own. Did the person de-linking attend to the Master Cylinders, or use the originals? Is the 'proportioning valve" still in the system? Not to say that those pistons don't need some love, of course, but if you're unhappy with the rear brake performance, you might have some other components that deserve attention. HTH. 



Edited by Barry - 21 Nov 2022 at 10:15
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FrozenSP View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FrozenSP Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 11:05
Thanks for the suggestions! Gutsibits do only have one in stock, but got a pair from Niks Euro Bits SmileShould be sorted

Originally posted by Barry Barry wrote:

edit: just read the O/P again - "brakes have been delinked". Well, there you go then. The rear, with original caliper, wasn't designed to be doing that job on its own. Did the person de-linking attend to the Master Cylinders, or use the originals? Is the 'proportioning valve" still in the system? Not to say that those pistons don't need some love, of course, but if you're unhappy with the rear brake performance, you might have some other components that deserve attention. HTH. 

It's got a PS15 cylinder on the rear, which I think is larger than the original? 
No clue regarding the proportioning valve, I'd have to guess not though. It's a kind of interesting set up, the rear is straightforward with a braided line from the cylinder meeting a copper line along the swingarm which enters the caliper. 
The front has a single braided line to the right caliper, which then has a copper line over the mudguard to the left caliper. Seems unusual to not just have a braided line to each of the calipers straight from the cylinder, but they're strong enough 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Barry Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 11:29
PS15 rear? Not 100% sure (without pulling up the parts list), but I think PS15 rear was as original.

Others may know better, but I think the general advice is - when de-linking - OEM front PS12 need to be changed for a front PS15 (to operate two calipers instead of one). By the same logic (which may be flawed), an original rear PS15 (operating two calipers) would need to go down in size? (to PS12?) - scratchig my head on recollections here - The Guzzi Bible (Guzziology) will surely have guidance on the subject if you feel the need to check what you have vs. what you "should have".

Definitely worth checking that the 'proportioning valve' is no longer in the mix - can't see my 1000SP from here, but I'm sure as that this component is visible on the LH side frame, aft of the side panel.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stevex Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 12:45
I've de linked my LM2, PS13 rear, PS15 front. 
You can get alloy anodised pistons for the P09 calipers:


Edited by Stevex - 21 Nov 2022 at 12:49
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 13:23
I used teflon ones 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 14:18
The original master cylinder would be the 15, but for a single caliper should be changed to a 12. Again the front one should be changed the other way.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dukedesmo Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 17:12
When I rebuilt the brakes on my LM2, all the pistons were corroded with the chrome flaking off in places. I replaced them all with alloy pistons & new seals and the brakes now work much better and with no drag as per before. 

A (very) small side benefit is that they weigh less too...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 26 Nov 2022 at 16:59
Originally posted by FrozenSP FrozenSP wrote:

No clue regarding the proportioning valve, I'd have to guess not though.

If still present, and if it's the original, the rubber thingy inside (looks like a grommet) will have given up a long time ago, so the proportioning action will be gone, and so it will basically function as just a manifold block to link all the pipes together. Guess how I know. Big smile

Took mine apart once to find out it was shagged.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote FrozenSP Quote  Post ReplyReply Direct Link To This Post Posted: 27 Nov 2022 at 15:34
Alloy pistons, fresh seals, and all back together. 
Pedal feel still isn't great, but the brake is definitely stronger! Maybe I'm trying to compare it to a modern brake too much, or maybe it is that the cylinder is incorrect. Either way, I'm happy enough with it now
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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2022 at 17:26
Originally posted by FrozenSP FrozenSP wrote:

Alloy pistons, fresh seals, and all back together. 
Pedal feel still isn't great,


No it won't be, until it's been used, the pads bedded in and the pistons properly pumped up. Until then the seals pull them back a bit when released. I think this is true of most if not all hydraulic brakes. When the car had new pads and rotors couple of years ago, took two weeks for the pedal to go hard! OK I don't regularly commute in it or anything, but even so. Big smile




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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jools Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2022 at 18:18
With the master cylinder not the correct size (for a de-linked system), you'll never get a decent amount of 'feel' at the pedal. I have exactly the same problem on my G5, which I've lived with ever since I got the bike some years ago. 

Many moons ago, I converted my T150V to front disc brake after an amusing flirtation with a 10" Yamaha double-sided drum brake from a TZ350A. As Meridan Triumph master cylinders were unobtainable at the time, I used one from a Norton Commando, in my naivety reasoning that it would be more or less the same thing. The resultant 'feel' was best described as somewhere between oak, mahogany, and ironwood!
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