Nerding out on Brakes shall we? Not another tech deraliment

The disposable nature of Shimano brake components is a real head-scratcher and a bit of an anachronism in today's world.  Is there anyone doing good quality rebuild kits that can be trusted?

As for the colour of the fluid, I once bled a set of lower end Shimanos only because they hadn't been done for three years and a few thousand kilometres – they still worked fine otherwise.  The fluid came out black but after the bleed they didn't feel noticeably different.  It's possible the performance of the entire system was degraded, but they still felt fine and the visual condition of the fluid didn't seem to have much of an effect on the outcome.

On rebuilds, Magura is the same way. I don't get it either, but it's not something I'm a fan of with them. For an industry so heavily invested in the environment, it seems silly to me brands like Shimano (and there are others) are so content to just tell people to throw stuff out if it fails and replace it. Maybe there is a technical or liability reason, but I'm not a fan of this when brands like SRAM, Hope, Hayes, etc all provide rebuild kits for levers and calipers. In the grand scheme of things we throw out, it's minor, I get it, but it just seems wrong to me when there are alternatives.  

On the fluid, I'm not sure if the coloring matters or not. I probably wouldn't have made a comment about it except I had a Shimano rep directly tell me it wasn't normal. They told me to warranty them and throw them out. I didn't and they worked fine, so who knows what the right answer is. I've seen it go black after 1-2 rides and most sets I've seen had the same thing happen. I can't make sense of whatever it is and agree it's probably a non-issue, but Shimano says otherwise. 

I've used the phenolic caliper piston kits from Exnavi (found on Amazon/ALi) without issues, and indeed they improved brake feel. Less retraction than the ceramic pistons, leading to a sharper bite point, and importantly, no wandering bite point. I did try the Ti MC pistons but those were bad. Undersized which allowed the piston to rock and lose seal, generally at times when you didn't want em to. Gave em a go after one unit swelled up and began locking in the MC bore (Ala Sram) and the other nipped a P cup. After all the issues I walked away from Shimano brakes. When they work they work really well, but when they crap the bed they leave a big ol stain. The new gen seems to have acquiesced to phenolics on all models, but the plastic MC pistons remain. That keeps em off my bike parts diet.

FWIW, regarding the oil colouring, Sram's R and RS brakes, where the parts are painted on the outside, have a gray oil when you do a bleed after a while, while RSC and above brakes (not sure how that relates to the new bronze and silve rmonikers) are anodized, which means the master bore is also anodized and thus doesn't wear as much as the raw one in the case of painted outsides. The gray colouring of the oil are aluminium wear particles.

@lucacometti did a Maven vs. Motive comparison for us! Maybe a bit of obvious results, but still interesting nonetheless. #theforumknowsfirst 

Video says Maven Bronze have 4x18mm, while https://www.sram.com/en/sram/models/db-mvn-brz-a1 says it's 2x18 and 2x19.5.

Who's correct on this one?

Also Sram spare parts catalog says:

2 11.5018.058.001 DISC BRAKE CALIPER PISTON KIT - (INCLUDES 2-19.5MM, 2-18MM CALIPER PISTONS, SEALS, O-RINGS) - MAVEN ULT/SLV/BRZ (A1)

2 11.5018.058.002 DISC BRAKE CALIPER PISTON KIT - (INCLUDES 4-18MM CALIPER PISTONS, SEALS, O-RINGS) - MAVEN BASE (A1)\

(I know, SRAM naming is also confusing for me)

I believe the bronze was the same as ultimate and silver with 2x18 and 2x19.5 and the base is 4x18. But I think they stopped making the bronze and replaced it with the base. 

On the topic of Shimano brakes- I have found a setup that I feel is worth sharing.  Match a TRP DHR EVO caliper, a Shimano brake line and a Shimano lever of your choice.  Clean fluid, more firm bite point, shorter lever throw, consistency through the life of the pads, and more power.  I have done this twice now, one with XT and the other with Deore lever bodies and they feel the same.

The part about the calipers/pistons is correct.  Maven bronze has the same caliper as silver/ult/expert and based is 2x18.  This would be the first I'm hearing about maven bronze being discontinued, last I checked (2 days ago) you could still order up a set of bronze brakes, but maybe that's just existing stock.  Fwiw, this move would make sense, the bronze/base cost is very close and the base lever action does feel pretty damn good (smooth/light).  

Cross-post from RideMonkey:  I finally got around to trying LikeWater with one of my Mavens that needed a bleed. The viscosity difference from Maxima mineral oil is massive. Very easy to degas and dislodge bubbles. I did a cup (Pinner) & syringe fluid replacement pulling down from the cup, pausing after 1 syringe full to empty the old oil out and refilling the cup. Piston advancement and retraction (piston massage) seemed smoother and easier. Actual lever feel is about the same, maybe a *hair* smoother. No obvious leaks or change in feel after a couple rides. I'll probably swap over to this for the rest of my quiver as my brakes feel like they need a bleed.

The hope love has really started to come out here. I'm probably going to get them next, messed with some tech 4 v4s braided hose the other day and really liked the way they feel, super smooth but positive enough on the bite. 

Can I come into this thread with a question? I would like to attempt my first brake bleed (ever) on a Shimano Saint, since it seems a little inconsistent. The rear brake gets weird sometimes, where I have to throw the lever in quick succession a few times because the contact point is suddenly right in the beginning of the stroke and it feels wooden (that means air in the system, right?).

Bought that AliExpress bleed kit after it received some high praise in the Tech Rumours thread. But now I'm trying to figure out which oil to get. Standard choice seems to be Shimano SM-DB-OIL, but I randomly found a reddit thread where they recommend lower viscosity oil, Redline Likewater in particular.

So, which one should I get (and why) and how much of it? Assuming the standard Shimano stuff is in there, do I need to flush everything out if I want to try a different option?

Also, do I go lever bleed or gravity bleed?

Bonus question: my brand new XT brakes (the now older model, but came on a new bike and were ridden like 10 times by now) had a wandering bite point in the rear pretty much from the beginning. Do I even bother trying to fix it? Seems to be a hopeless endeavor from what I've read.

Bonus question 2: I just remembered that some bike shop person in Whistler claimed to have broken brakes while trying to bleed them?! If that's an actual risk, is it more like 0,5 % or 50 %?

Do it. I've just upgraded my old T3 V4 braided line pair on the DH rig to T4 levers and oh boy, what a neat and relatively inexpensive upgrade.

My recommedation is to go for LikeWater or Putolines HPX R 2.5 fork oil. Both help massively with the wandering bite point issue and are better if you ride at colder temps.

Gravity bleed and lever bleed after it is good, I’ve always used a shimano cup at the lever and a syringe at the caliper. 

Yeah you need to flush the all of the old brake fluid out if you change fluids.

I guess its possible to somehow break your brakes while bleeding but highly unlikely, its an really easy process, especially with Shimano. 

Since I saw this one 7 years ago this is how I've bled all my shimano and it has always worked well. I use putoline 2.5W but used to use the normal shimano.

Breaking Shimano brakes during a bleed is easy. You just have to apply pressure to the system, this pushes on the membrane which is then pushed against a pin in the cover of the membrane on the lever. Same issue if you have air in the system and go on a plane.

Its very easy to damage it if you don't know what to look for. 

I've had alot of trouble with my Shimano xt brakes- the first set of brakes I've worked on myself. But after a while I've now got them working reasonably well. I'll probably buy the new hope brakes in the next year. A few tips anyway-

- The syndicate bleed guide above is good but I've also always had to do a lever bleed on top of that, with the pads and rotors installed, in order to get acceptable levels of free stroke.

- There are 2 ways in which you can fairly easily break them. The first is by over pressurising the system, IE pushing the pistons back in without a bleed funnel. This can unseat or even puncture a rubber diaphragm inside the lever assembly. This will present as oil leaking out of the end of the lever, and can be fixed quite easily by either repairing the puncture or reseating the diaphragm. The second way they can break is the pistons can crack as they're made of ceramics. You can minimise the chances of this by buying the correct bleed block, but I think they can still crack if you're unlucky.

- I've had to lube and exercise the pistons to get them moving properly. Walk them out (not all the way out), lube with mineral oil and get them moving in unison before cleaning.

What Ali express bleed kit are you using that you've seen recommended?

Thanks everyone, the replies have already been super helpful! Although I'll admit the task seems as daunting as ever.

This is the AliEx kit (gotta switch to your country), bought the 2022 STD variant (box with 10 different connector pieces or whatever they're called). Someone in the Tech Rumors thread even claimed to have seen it used in the DH World Cup pits.

The point with the lever bleed for free throw is interesting! Would that also apply to other brakes? Derailing my own question here, but I've parking lot tested my friends Dominions. Based on reviews alone, I thought they are exactly what I want (super light lever, lots of modulation, strong power), but they feel terrible to me: extremely strong but bite to almost full power within the first 3 mm of lever pull. 

So far, my favorites from lever pull have been Hopes, but the lever shape was terrible for my taste. New version seems to mitigate this though, so if I'm ever in the market for new brakes, it's gonne be those (or Maven Base if I find them for super cheap). Anyway, I've been surprisingly happy with the Saints. It was a bit disappointing to get something this "old" on my latest purchase, but so far they do everything I want quite well.

if you want light lever pull, get the intend

I was about to sass you about them never being in stock, but they actually have some available at this moment in time!

Trinity 2.0 black & silver - Intend

Finally got hold of a set of GR4s after years on the Tech 4 V4. As with all things Hope the build quality is a work of art. First impressions:

I bled the ‘old’ way without using the bleed port because I didn’t have the adapter for the funnel yet .Hopes new bleed video gives a few new steps which seem to work good.

Lever is a touch heavier throw than the v4 but much shorter throw before bite due to the new cam design. It’s still very light. 

Extra hook on the lever is really nice, way more secure 

Bigger piston is noticeable in the power increase, not huge on the v4. 

Still a lot of feel at the lever which is my favourite thing about the hopes compared to the mavens or Shimano that have that on/off. Just preference.

Love they share the same pads and some hardware so all my T4 spares are not useless!

This guy always does interesting combos. I dig it

I noticed yesterday that I've managed to kink my rear brake hose on my DHR Evos in 2 places - one at the junction into the head tube (from swapping forks out..) and the other at the entrance to the levers (from my light pushing it in that place).

Never had hoses kink before, could it be that the TRP hoses are softer than anything else (ie Formula and SRAM)? Could I be losing power from the flex?

I'm a little late for this to be news, but I'll post anyway.

After 2.5 years of use I had an issue with the Code RSC brakes. It's going to need a new lever body, I'll replace it and throw them on my spare bike. 

I installed the set of Hayes Dominion A4s that I had been planning to install on the spare bike, but hadn't gotten around to. 

A few quick observations.

The Hayes are easy to get a good bleed on but the process is messy. It's almost the opposite of the bleeding edge system, which is a little more difficult to get a perfect bleed but is very clean. It's a mild pain that Hayes only includes one barb and olive, I originally left my front hose a bit too long and had to wait until more arrived to shorten the hose. Aligning the calipers was easy with the grub screws. 

The brakes feel good, and are quick to get used to. The initial bite is similar to Codes but power ramps up faster more like Shimano.

Can’t answer the question about the hose softness, but wanted to chime in and say it’s unlikely that the kinked lines are causing any power issues. I’ve ridden with some pretty severe kinks with no problems…

Does anyone run smaller rotors in the cold (freezing plus or minus 10-15F) weather to try to keep them working better? Specifically for all-mountain, enduro or whatever we call it these days type of riding. 

I do a lot of enduro fat biking in those temps and run 200/180 rotors. Runs are between 300-500M of elevation drop. Anything smaller wasn't cutting it and anything bigger was too much. On my summer bike and same trails I run 220/200. I also run Sinter green pads so the initial bite is not too dependent on how much heat you have in the system. So to your question, yes downsize. 

No I haven't, thought about it, but just didn't bother, no issues using 203's in freezing temperatures.

I have had this happen on my SRAM setup where the kink was bad enough to cause brake loss. The plastic tube in the brake hose kinked at the sharp head tube routing exit and starting leaking fluid in the housing. Kinda like a pinch flat within the hose. No external fluid loss but enough to cause pressure loss in the system. Some frames like speciazlied have a sharp exit port which I now sand a little bit to make it smoother. Kevlar lined hoses are more resilient because when the same happened to my Intend hose it kept working just fine. YMMV but the general rule of thumb is to replace it.

Funny enough, I trimmed and bled a pal's Elixir for brake issues this weekend (yes, we talked about how updating the brakes would be a good idea). Anyway, the brake with the kinked hose was working-ish. The kink was bad enough to cause a fluid restriction, so the pistons wouldn't return the way they're supposed to. This of course meant a real short lever stroke and pad rubbing.  Nipped the hose down a smidge, new comp bushing and bled and the brake feels fine. Power wasn't an issue, just brake functionality. His was bad enough that I didn't feel 'rounding" the hose back into shape was a valid repair option. If yours isn't terrible, you can give that a go with a set of needle nose pliers. Easy does it, don't go ham fisting the job. I've done it numerous times back in my industry days. When companies were still figuring out how best to run hydro lines there were numerous kinked brake line issues we addressed in the field. Some just needed to be rounded out again and rerouted, but sometimes they were bad enough to cause internal failures. Those were a hoot for everyone involved.