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Frankenbrakes and brake improvement discussion

God help me, I just read all 29 sections of this topic. There's a lot of discussion, mostly earlier, of fluid leakage in Shimano calipers, but exactly nothing substantive regarding cause/cure. This triggered by @canadmos report recently.

Anybody got a defensible model for the cause of fluid leaks in contemporary Shimano calipers/
 

slimshady

¡Mira, una ardilla!
Dec 20, 2007
2,563
660
La Plata, Argentina
God help me, I just read all 29 sections of this topic. There's a lot of discussion, mostly earlier, of fluid leakage in Shimano calipers, but exactly nothing substantive regarding cause/cure. This triggered by @canadmos report recently.

Anybody got a defensible model for the cause of fluid leaks in contemporary Shimano calipers/
It has been discussed before, if not in this thread somewhere else in the forum. The ceramic pistons cannot withstand the pressure and start developing micro cracks, which firstly allow air to get into the circuit and ultimately lead to oil leaking over the pads.

EDIT: this happens on SLX calipers and above, since those brakes have ceramic pistons. From Deore and below all you get is the ovalization of the master cylinder's bore as a result of a combination of the softer aluminum MC material and the plastic piston deforming under the ServoWave mechanical advantage.
 
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Bike078

Monkey
Jan 11, 2018
327
154
It has been discussed before, if not in this thread somewhere else in the forum. The ceramic pistons cannot withstand the pressure and start developing micro cracks, which firstly allow air to get into the circuit and ultimately lead to oil leaking over the pads.

EDIT: this happens on SLX calipers and above, since those brakes have ceramic pistons. From Deore and below all you get is the ovalization of the master cylinder's bore as a result of a combination of the softer aluminum MC material and the plastic piston deforming under the ServoWave mechanical advantage.
From what you've read or experienced, does the micro cracking thing happen to most shimano brakes with ceramic pistons?
 

slimshady

¡Mira, una ardilla!
Dec 20, 2007
2,563
660
La Plata, Argentina
From what you've read or experienced, does the micro cracking thing happen to most shimano brakes with ceramic pistons?
It all boils down to how hard you are on the brakes. Most of the XT/SLX sets I've seen here are used for XC/trail bikes, so the bite point changes are the first fail you notice as a result of the MC's bore deforming. But several of my friends riding DH, Enduro or just hitting hard on the brakes ended up with leaking calipers. Seems like the finned pads help postpone the unavoidable, which suggest temperature is a key factor on the micro cracks development.
 
It all boils down to how hard you are on the brakes. Most of the XT/SLX sets I've seen here are used for XC/trail bikes, so the bite point changes are the first fail you notice as a result of the MC's bore deforming. But several of my friends riding DH, Enduro or just hitting hard on the brakes ended up with leaking calipers. Seems like the finned pads help postpone the unavoidable, which suggest temperature is a key factor on the micro cracks development.
The difference in use would perhaps explain why I haven't had significant issues with brakes in my Diatech -> Magura Julie (ugh 'cause shims) -> XT -> SLX evolution; I have experienced occasional minor pump-up with the SLX but zero leakage.

Edit: Caliper piston cracking could conceivably be from thermal, rather than mechanical, stress. Hard to talk about without seeing a few failed pistons...
 
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Bike078

Monkey
Jan 11, 2018
327
154
I have a set of lightly used slx brakes coming my way. We'll see how they hold up.

My m615 deore brake lever (rear) would move farther away from the bar a bit when it got hot (even when it was new). Then it got worse, to the point where you could barely squeeze the lever. The front brake has been OK so far.
 

slimshady

¡Mira, una ardilla!
Dec 20, 2007
2,563
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La Plata, Argentina
I have a set of lightly used slx brakes coming my way. We'll see how they hold up.

My m615 deore brake lever (rear) would move farther away from the bar a bit when it got hot (even when it was new). Then it got worse, to the point where you could barely squeeze the lever. The front brake has been OK so far.
That bite point variation is different than the one I'm describing. Yours seem to involve to air in the circuit. It expands faster than oil when heated and moves the lever away from the bar. If the MC bore was deformed the bite point would be inconsistent, with the lever hitting the bar regularly.
 

Bike078

Monkey
Jan 11, 2018
327
154
That bite point variation is different than the one I'm describing. Yours seem to involve to air in the circuit. It expands faster than oil when heated and moves the lever away from the bar. If the MC bore was deformed the bite point would be inconsistent, with the lever hitting the bar regularly.
Bleeding didn't fix the issue. I still have the brake. Will see what can be done.
 

slimshady

¡Mira, una ardilla!
Dec 20, 2007
2,563
660
La Plata, Argentina
The difference in use would perhaps explain why I haven't had significant issues with brakes in my Diatech -> Magura Julie (ugh 'cause shims) -> XT -> SLX evolution; I have experienced occasional minor pump-up with the SLX but zero leakage.

Edit: Caliper piston cracking could conceivably be from thermal, rather than mechanical, stress. Hard to talk about without seeing a few failed pistons...
I even confronted a local Shimano fanboi devolved into a sales representative about this a while ago, and he LITERALLY went like


 

slyfink

Turbo Monkey
Sep 16, 2008
5,809
1,600
Ottawa, Canada
It all boils down to how hard you are on the brakes. Most of the XT/SLX sets I've seen here are used for XC/trail bikes, so the bite point changes are the first fail you notice as a result of the MC's bore deforming. But several of my friends riding DH, Enduro or just hitting hard on the brakes ended up with leaking calipers. Seems like the finned pads help postpone the unavoidable, which suggest temperature is a key factor on the micro cracks development.
So at this point, I'm thinking of replacing my XT calipers with Zee calipers. This is the logic I'm following: I'm assuming that the mechanical advantage of the M785 levers is less than that of the M-640 levers. If I pair the M785 levers to M640 calipers, I will loose a little peak force of an M640 system, but it will be more than the M785 system. This will also preserve the pistons and seals on the M640 caliper, which I also assume is more robust than the M785....

This is the least-cost solution right now, and gives me time to figure out if I prefer a Magura MT Trail system, a Magura MT5 system, a Hope E4 system, or a Shi-Gura system with my M785 levers and MT5 calipers.

Hmmm
 

slimshady

¡Mira, una ardilla!
Dec 20, 2007
2,563
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Most of the SLX/XT/Zee calipers/levers are basically the same. Some small bits change, such as screws and pivots, and the oil reservoir's cap. But the cast molds are the same.
 

slyfink

Turbo Monkey
Sep 16, 2008
5,809
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Ottawa, Canada
Most of the SLX/XT/Zee calipers/levers are basically the same. Some small bits change, such as screws and pivots, and the oil reservoir's cap. But the cast molds are the same.
Saint then? Though Jozz posted a link to a sweet deal on Maguras in my other thread, which I may jump on once I get a credit card number...
 

Bike078

Monkey
Jan 11, 2018
327
154
Anybody tried the superstar alpine evo rotor? They're likely made in China or Taiwan and I found the same rotor under different brand names (e.g. Sagmit) on local online sites at cheaper prices. There are a lot more cut-outs (?) on the disc compared to Shimano ice-tech rotors though.
 
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Inclag

Turbo Monkey
Sep 9, 2001
2,326
46
MA
Zee levers are nothing like the newer slx, xt, Deore etc. Those levers are similar to the prior generation Shimano brake levers which went the way of the dodo bird several years ago.

My Zee levers are leaking like sieves from the isolator unit diaphragm and main piston since there's all sorts of mineral oil that collects around the hinge and inside of the lever blade. I'm going to swap to my Deore levers as there is no visible leaks, but am just wondering if a dead simple and inexpensive m396 lever may be worth trying. I've got some pretty large hands so I'm not too concerned about the ergonomics
 

velocipedist

Monkey
Jul 11, 2006
293
293
Cloudland Georgia
Materially speaking that makes sense:
heating up to 30% of Temperature of melting (Tm) or straining to 30% of ultimate tensile strength can give rise to eventual failure, the caveat being that for these microscopic flaws to propagate into cracks and failure requires cyclical fatigue to 30%.

While ceramic has a higher Tm than most metals, its HCP (hexagonal close packed) crystal lattice tends to be much less ductile and more brittle than the FCC (face centered cubic) or BCC (body centered cubic) of most metals.

Titanium being HCP would make for an interesting experiment to compare with ceramic. Alas lacking access to laser sintering printers, a thought experiment is all I can do.


It all boils down to how hard you are on the brakes. Most of the XT/SLX sets I've seen here are used for XC/trail bikes, so the bite point changes are the first fail you notice as a result of the MC's bore deforming. But several of my friends riding DH, Enduro or just hitting hard on the brakes ended up with leaking calipers. Seems like the finned pads help postpone the unavoidable, which suggest temperature is a key factor on the micro cracks development.
 

Nick

My name is Nick
Sep 21, 2001
14,401
2,917
behind you, don't wait up.
Zee levers are nothing like the newer slx, xt, Deore etc. Those levers are similar to the prior generation Shimano brake levers which went the way of the dodo bird several years ago.

My Zee levers are leaking like sieves from the isolator unit diaphragm and main piston since there's all sorts of mineral oil that collects around the hinge and inside of the lever blade. I'm going to swap to my Deore levers as there is no visible leaks, but am just wondering if a dead simple and inexpensive m396 lever may be worth trying. I've got some pretty large hands so I'm not too concerned about the ergonomics
Want to try an old set of 755 levers which last forever? I'd imagine they'll connect right up to a typical shimano line/ fitting?
 

local717

Monkey
Apr 11, 2010
258
16
Mt.Gretna/Lancaster
Apologies in advance if I've missed this confirmation, but curious about running MT7 calipers with my M8000 XT lever. I ran Magura Gustav and Louise for many years but have acquired a few sets of XT's in recent years. I'm now starting to experience the Shimano inconsistency so many have explained. So before I go ordering parts I wanted to confirm that a MT7 caliper will work with a M8000 XT lever? Thanks!
 

marshalolson

Turbo Monkey
May 25, 2006
1,439
73
Apologies in advance if I've missed this confirmation, but curious about running MT7 calipers with my M8000 XT lever. I ran Magura Gustav and Louise for many years but have acquired a few sets of XT's in recent years. I'm now starting to experience the Shimano inconsistency so many have explained. So before I go ordering parts I wanted to confirm that a MT7 caliper will work with a M8000 XT lever? Thanks!
Just built up MT5 calipers with M988 levers.
Feel great.

Used the magura barb and Shimano olives in hooking them up.
Brakes bled easily.

Cheers

Edit- not in love with stock performance pads. Going to try some koolstop organics as well.
 
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slyfink

Turbo Monkey
Sep 16, 2008
5,809
1,600
Ottawa, Canada
Not trying to be a d!ck, and I'm only saying this because I just went through it earlier this week looking for similar information, but the spreadsheet on page 1 has a tab for fluids. I guess something called Redline Likewater is the best fluid, followed by Trickstuff's, and then Shimano. The "Royal Blood" doesn't even warrant a ranking...
 

slyfink

Turbo Monkey
Sep 16, 2008
5,809
1,600
Ottawa, Canada
Question for y'all about automotive brake cleaner... does that stuff also remove the bit of brake pad that gets transferred to the rotor?

I remembered I have a spare bike with Shimano brakes on it, so I swapped out the front brake to my current bike, while I decide whether to get Magura calipers or the whole MT5 system. I acquired some brake cleaner and soaked the rotors with it and wiped it down. I'm wondering if I need to re-condition the rotor now.

And on that note, is a Shigura system better than an all-Magura system?
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,718
798
Anybody got a defensible model for the cause of fluid leaks in contemporary Shimano calipers/
There's almost no doubt this is caused by the ceramic pistons as slim says, Shimano calipers never suffered widespread slave-piston leakage issues (in fact rarely had any caliper/slave issues) before they switched.

I don't think the cause is exclusively the micro-cracking slimshady mentions, I'm also not sure that is actually the primary cause of failure - however they are brittle and what he describes is certainly plausible. In my experience they leak after being left unridden for some time, and I suspect the cause is the rougher surface of the ceramic piston wearing the bore and/or seal. The lack of riding may cause a temporary reduction in boundary lubrication which accelerates the issue.

For whatever it's worth, my friend got some brand new (latest generation) XTR brakes about 6-months ago and it didn't take long before the calipers leaked all over his rotors and ruined the near-new and expensive icetech pads. I'm against supporting a company that leaves known-issues unaddressed over an entire decade, but to each their own.

If I still ran Shimano brakes and had this issue, my first point of attack would be replacing the ceramic pistons with alloy ones - either aftermarket (alixpress/ebay) - or preferably genuine Shimano alloy pistons if accessible. I kept a pair of M800 and M810 calipers around in case I needed to update the more modern calipers, but moved on.

If you run Shimano brakes and have no issues, that's great - because they do stop very well when they're running trouble free. Problems can occur at both ends, so depending on what exactly is happening, the solution is replacing the entire MC/lever assemblies, or the caliper pistons/seals, or both.

Question for y'all about automotive brake cleaner... does that stuff also remove the bit of brake pad that gets transferred to the rotor?
My take is to stick to 100% pure acetone (if addressing oil contamination) or 100% isopropyl for general cleaning. Auto brake cleaners can have additives which have little impact on auto brakes (with large surface areas and vacuum boosters) but may contaminate MTB brakes.

Likely fine though, just give them a few runs. I don't think the transfer thing matters much, we ride in rain/mud etc too right?
 

vinny4130

Monkey
Jun 11, 2007
304
98
albuquerque
https://www.bikemag.com/gear/components/brakes/beatdown-hayes-dominion-brakes/

These things are honestly sounding really promising. Any monkeys running them?
Yes I have two bike with them and have sold a handful to others that ride more often than myself. Bleeding is different the caliper loves to hide bubbles but with two bleed ports it’s easy to get them out, but a unique method after doing it a few times now. Lever is also different to bleed. But the brakes feel great and have the biggest pads so wear is fantastic. I pulled pads today that had been on a customers bike for a few months now and raced the BME last weekend which was 8300’ of descending and looked almost new. Still highly recommended the lever feel is really good.
 

William42

fork ways
Jul 31, 2007
3,676
289
If you run Shimano brakes and have no issues, that's great - because they do stop very well when they're running trouble free. Problems can occur at both ends, so depending on what exactly is happening, the solution is replacing the entire MC/lever assemblies, or the caliper pistons/seals, or both.
I've been trying to explain to a buddy that he doesn't want Shimano Brakes - he's lived in a relatively flat area all his life, and he's going to mountains. My own somewhat frequent near death experiences have made me pretty avid anti shimano, but he really really wants them. He's gonna do him, which means he'll get whatever he wants. He's liked the power some maguras have to offer, you said there are issues at both ends for shimano, he particularly likes the lever feel of shimano though. Are there any shimano levers that don't eventually deal with getting fucked that can be mated to a magura caliper for a somewhat reliable brake? I've looked at the spreadsheet for power listings, but I don't see much about reliability. I know you're in an area that's pretty hard on brakes though.

As an aside, some anecdotal evidence is this; I never really figured out why my shimano brakes kept sucking until I read this thread, but they definitely blew real fucking hard, and I will never run their brakes again if I can possibly avoid it. I'd experienced the "oh shit pull the lever to the bar" experience several times, but rode it out and laughed and thought I'd escaped injury to ride again. It wasn't until I was off the bike for about a month due to injuries from turning what was supposed to be a small creek gap into a huge OTB drop because of no brakes that I realized how fucking dangerous they are.
 

jonKranked

Press Button, Receive Stupid
Nov 10, 2005
54,756
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media blackout
Are the 2019 models still problematic?
i don't think the new xtr stuff has been out long enough for long term durability. i'm curious about this too, but unfortunately not terribly optimistic. i'll likely be looking elsewhere for my next set of brakes. and i've been using shimano exclusively since saint first came out in 2003.
 

Happymtb.fr

Monkey
Feb 9, 2016
830
217
SWE
i don't think the new xtr stuff has been out long enough for long term durability. i'm curious about this too, but unfortunately not terribly optimistic. i'll likely be looking elsewhere for my next set of brakes. and i've been using shimano exclusively since saint first came out in 2003.
According to this review the new xtr brakes still have an inconsistent bite point ...
https://m.pinkbike.com/news/review-whyte-s-120c-works.html