Has anyone thought (in theory atleast) about modifying a motorcycle brake master cylinder, like a Brembo or equivalent, for use on a downhill bike? What issues...
Has anyone thought (in theory atleast) about modifying a motorcycle brake master cylinder, like a Brembo or equivalent, for use on a downhill bike? What issues, aside from handlebar radius and the large brake fluid reservoir, might arise?
Main issue would be your friends making motorbike noises at you on every group ride
Any (real) idea why one side of the Saint master piston looks like it has been scratching itself to the point that the surface looks matte...
Any (real) idea why one side of the Saint master piston looks like it has been scratching itself to the point that the surface looks matte? The other side looks more glossy and normal.
As Primoz just said, clearly its being sideloaded. In addition to that, it might have to do with the surface finish on the inside of the...
As Primoz just said, clearly its being sideloaded. In addition to that, it might have to do with the surface finish on the inside of the master cylinder body. In the huge volume of discussion of the Shimano wandering bite point phenomenon, I saw it pointed out that Shimano master cylinder bodies are bare aluminum, while the claim was made that other more boutique brakes like Hopes are hard anodized after the master cylinder is bored, so they have a smoother internal surface. I could imagine that after a lot of cycles, especially if there is any oxidation that has formed, the Shimano may offer a significantly more abrasive surface.
FWIW, in the pre silver/bronze Code days RSC was anodized while everything under it was not. Doing a bleed rsc has clear fluid even after two years while lesser models have a very dirty fluid due to wear of the aluminum bore and suspending the particles in the fluid because of it.
Any (real) idea why one side of the Saint master piston looks like it has been scratching itself to the point that the surface looks matte...
Any (real) idea why one side of the Saint master piston looks like it has been scratching itself to the point that the surface looks matte? The other side looks more glossy and normal.
As Primoz just said, clearly its being sideloaded. In addition to that, it might have to do with the surface finish on the inside of the...
As Primoz just said, clearly its being sideloaded. In addition to that, it might have to do with the surface finish on the inside of the master cylinder body. In the huge volume of discussion of the Shimano wandering bite point phenomenon, I saw it pointed out that Shimano master cylinder bodies are bare aluminum, while the claim was made that other more boutique brakes like Hopes are hard anodized after the master cylinder is bored, so they have a smoother internal surface. I could imagine that after a lot of cycles, especially if there is any oxidation that has formed, the Shimano may offer a significantly more abrasive surface.
FWIW, in the pre silver/bronze Code days RSC was anodized while everything under it was not. Doing a bleed rsc has clear fluid even after two...
FWIW, in the pre silver/bronze Code days RSC was anodized while everything under it was not. Doing a bleed rsc has clear fluid even after two years while lesser models have a very dirty fluid due to wear of the aluminum bore and suspending the particles in the fluid because of it.
Thanks for that tidbit @Primoz, that's quite interesting!
FWIW, I don't know how it's handled in the current Bronze & co days, haven't had my hands on any of the newer brakes. The situation I described (RSC anodized, R(S) and lower not) applies to Guide and G2 brakes too. And the reason for the difference is that with RSC (and Ultimate) brakes both the master and the caliper are anodized after all the machining, so anodized inside and out. Lower tiers are painted on the other hand and are obviously painted only on the outside.
FWIW, in the pre silver/bronze Code days RSC was anodized while everything under it was not. Doing a bleed rsc has clear fluid even after two...
FWIW, in the pre silver/bronze Code days RSC was anodized while everything under it was not. Doing a bleed rsc has clear fluid even after two years while lesser models have a very dirty fluid due to wear of the aluminum bore and suspending the particles in the fluid because of it.
Could this be one part of the equation that makes green Shimano brake fluid go dark together with dirt from slave pistons? I cleaned and checked the actual bore and there's no sign of wear. If the piston would be metallic instead of plastic I guess there could be signs of wear. This could be case with aftermarket titanium etc. pistons.
I'd say yes. DOT fluid is translucent amber and with painted brakes becomes opaque (non-transparent) grey-ish if they are used. If the brakes sit unused for a long period of time this does not happen, ergo it looks like it comes from bore and piston wear.
Yeah, aftermarket titanium/alloy pistons from AliExpress are obviously a great idea when you take all this info into account There's a reason Lewis for example does PEEK pistons - hard, stable, chemically stable. Maybe a bit hard (PEEK is often used as a counterpart material to steel when it comes to gears to make them quieter). Trickstuff does POM (Delrin) and Igus has an article Piccola uses (used?) one of their bearing grade (plastic) materials.
FWIW, in the pre silver/bronze Code days RSC was anodized while everything under it was not. Doing a bleed rsc has clear fluid even after two...
FWIW, in the pre silver/bronze Code days RSC was anodized while everything under it was not. Doing a bleed rsc has clear fluid even after two years while lesser models have a very dirty fluid due to wear of the aluminum bore and suspending the particles in the fluid because of it.
Could this be one part of the equation that makes green Shimano brake fluid go dark together with dirt from slave pistons? I cleaned and checked...
Could this be one part of the equation that makes green Shimano brake fluid go dark together with dirt from slave pistons? I cleaned and checked the actual bore and there's no sign of wear. If the piston would be metallic instead of plastic I guess there could be signs of wear. This could be case with aftermarket titanium etc. pistons.
Tried those Ti MC pistons when the ones on an old set of SLX brakes went and crapped out. No good. They were undersized and rocked enough in the bore during use to allow the primary seal to lose seal, I.E. lever go straight to the bar. Unfun to learn to say the least. Had high hopes since the alloy ones I used to replace the plastic Sram jobbers in his Levels worked a peach.
I'd say yes. DOT fluid is translucent amber and with painted brakes becomes opaque (non-transparent) grey-ish if they are used. If the brakes sit unused for...
I'd say yes. DOT fluid is translucent amber and with painted brakes becomes opaque (non-transparent) grey-ish if they are used. If the brakes sit unused for a long period of time this does not happen, ergo it looks like it comes from bore and piston wear.
Yeah, aftermarket titanium/alloy pistons from AliExpress are obviously a great idea when you take all this info into account There's a reason Lewis for example does PEEK pistons - hard, stable, chemically stable. Maybe a bit hard (PEEK is often used as a counterpart material to steel when it comes to gears to make them quieter). Trickstuff does POM (Delrin) and Igus has an article Piccola uses (used?) one of their bearing grade (plastic) materials.
Careful there, PEEK, PAEK, and PEKK are not replacements for any alloy steel or SS. Compressive strength of any of the PEEK materials in the family is between 13-18KSI in a neat form, no glass or carbon fill and generally will not ever be over 25KSI without significant carbon fiber loading. PEEK is one of the most expensive thermoplastics, and while it does have very good chemical resistance to solvents and heated solvent vapors it by no means is it a mechanical replacement for Aluminum or steel. Its also a PITA to machine, and sucks to mold as tool temps under 300°C will result in an amorphous material with severely reduced mechanical properties, on the flip side molding clear PEEK is pretty cool... All these plastics will suffer in the sense of CTE. Just doing some quick math a 60° increase in piston temp with PEEK would result in diametrical growth of about 55µm or .002". That might seem like nothing, but I have a hard time believing that it wouldn't have some effect on brake feel due to the extra compression on the piston seal.
I never said it's a replacement. I said PEEK is used as a counterpart material to steel in gears. Meaning one gear is steel, the other is PEEK. I'm not an expert in geartrain design and obviously you don't see PEEK gears in car transmissions and the like, but I did hear a steel/PEEK combo has been used in an eBike drive unit to quite things down, which is the role PEEK plays - use it where you need a quiet geartrain but also need more strength in gear the usual plastic materials give you. COnsidering you don't see aluminium gears, there must be something on PEEK that gives it an advantage, I'd bet it would be surface hardness or something along those lines.
Considering this (PEEK being used to pair to steel gears) while aluminium is neve used for gears, I said PEEK might be a bit hard, i.e. used as a brake master piston it might scratch up the bore too, just like a steel, titannium or probably even aluminium piston would. But I don't have any experience with it and it might be empty worries...
As for CTE, if that is an issue that arises with a master cylinder in the brake, there are bigger issues than CTE itself... With the way seals are done on a master piston, there should be quite a bit of clearance radially between the bore and the piston, shown by pistons being scratched on only one side. One exception here is Sram's piston selling and jamming, but year... In either case, POM is also used as a master piston material from what I've seen and the CTE of it is about twice as big as PEEK's. If CTE was an issue, everybody would be using aluminium pistons anyway...
I never said it's a replacement. I said PEEK is used as a counterpart material to steel in gears. Meaning one gear is steel, the other...
I never said it's a replacement. I said PEEK is used as a counterpart material to steel in gears. Meaning one gear is steel, the other is PEEK. I'm not an expert in geartrain design and obviously you don't see PEEK gears in car transmissions and the like, but I did hear a steel/PEEK combo has been used in an eBike drive unit to quite things down, which is the role PEEK plays - use it where you need a quiet geartrain but also need more strength in gear the usual plastic materials give you. COnsidering you don't see aluminium gears, there must be something on PEEK that gives it an advantage, I'd bet it would be surface hardness or something along those lines.
Considering this (PEEK being used to pair to steel gears) while aluminium is neve used for gears, I said PEEK might be a bit hard, i.e. used as a brake master piston it might scratch up the bore too, just like a steel, titannium or probably even aluminium piston would. But I don't have any experience with it and it might be empty worries...
As for CTE, if that is an issue that arises with a master cylinder in the brake, there are bigger issues than CTE itself... With the way seals are done on a master piston, there should be quite a bit of clearance radially between the bore and the piston, shown by pistons being scratched on only one side. One exception here is Sram's piston selling and jamming, but year... In either case, POM is also used as a master piston material from what I've seen and the CTE of it is about twice as big as PEEK's. If CTE was an issue, everybody would be using aluminium pistons anyway...
PEEK is indeed quite hard, and yes can (and indeed does) scratch up materials that would be perceived to be harder. One example in my line of work is desalination plant HP pumps that use PEEK for the casing wear rings. These definitely do scratch up the corresponding impeller wear rings that are made from super duplex.
I finally got around to bleeding my brakes using the Canyon / Aaron method that was linked a while back. The rear brake on one of my sets of my Mavens always felt a bit soft to me, and when I used this method it seemed to firm it up quite a bit. It was pretty shocking at how many bubbles I was able to draw out using this method of isolating the caliper then the lever (so much that I wondered whether I had a leaky connection but I'm pretty sure that wasn't the case given that I never saw any leaks when pressurizing, and that the amount of bubbles steadily decreased). I'll definitely be switching to this method from now on.
I never said it's a replacement. I said PEEK is used as a counterpart material to steel in gears. Meaning one gear is steel, the other...
I never said it's a replacement. I said PEEK is used as a counterpart material to steel in gears. Meaning one gear is steel, the other is PEEK. I'm not an expert in geartrain design and obviously you don't see PEEK gears in car transmissions and the like, but I did hear a steel/PEEK combo has been used in an eBike drive unit to quite things down, which is the role PEEK plays - use it where you need a quiet geartrain but also need more strength in gear the usual plastic materials give you. COnsidering you don't see aluminium gears, there must be something on PEEK that gives it an advantage, I'd bet it would be surface hardness or something along those lines.
Considering this (PEEK being used to pair to steel gears) while aluminium is neve used for gears, I said PEEK might be a bit hard, i.e. used as a brake master piston it might scratch up the bore too, just like a steel, titannium or probably even aluminium piston would. But I don't have any experience with it and it might be empty worries...
As for CTE, if that is an issue that arises with a master cylinder in the brake, there are bigger issues than CTE itself... With the way seals are done on a master piston, there should be quite a bit of clearance radially between the bore and the piston, shown by pistons being scratched on only one side. One exception here is Sram's piston selling and jamming, but year... In either case, POM is also used as a master piston material from what I've seen and the CTE of it is about twice as big as PEEK's. If CTE was an issue, everybody would be using aluminium pistons anyway...
You are correct, you did say counterpart. In the example that you gave the reason why is correct for certain applications, but I can guarantee that it's not neat PEEK, i.e. unfilled virgin PEEK. Most likely its carbon or glass filled with ETFE or PTFE added as a lubricant, but I would bet that more often than not its PPS, without carbon black added both materials look nearly identical in color, have very similar mechanical and chemical resistance characteristic, but PPS costs 1/2 that of PEEK.
PEEK is not harder than aluminum. Pulling from my material DB here at work, we have a hardness tested calibrated for Rockwell A and B, 6061-T6 ranges from 56-62B. PEEK doesn't even move the needle on the Rockwell B scale, at all, It's not even close. LOL.
CTE is something that any competent seal designer should take into consideration, especially when designing a seal gland where the seal is being used as a rollback spring, let alone one that can see as aggressive temp swings as I would presume that a disc brake piston would be subjected to. Having to design anything around a moving target is tricky and ends up being an exercise in compromise.
Curiosity, has anyone experimented with different dots? I was googling the differences between some 5.1 and some 4 and it seems for racing application on motors and cars the 4 series is the one that is most used,
Would a bike brake feel better with a dot with a higher boiling point or a low viscosity one? Anyone tried something?
Isn't the general consensus that a lower viscosity for mineral oil brakes makes them feel better?
Interesting though, for the racing fluid it says not to mix it with polyglycol fluids, if I understand it correctly that's off the shelf DOT4 and DOT5.1?
Isn't the general consensus that a lower viscosity for mineral oil brakes makes them feel better?Interesting though, for the racing fluid it says not to mix...
Isn't the general consensus that a lower viscosity for mineral oil brakes makes them feel better?
Interesting though, for the racing fluid it says not to mix it with polyglycol fluids, if I understand it correctly that's off the shelf DOT4 and DOT5.1?
The only ingredient listed in the MSDS for RBF 700 is "diamines", so that wasn't much help.
But it is polyglycol based. Presumably it shouldn't be mixed because that would degrade its performance.
Isn't the general consensus that a lower viscosity for mineral oil brakes makes them feel better?Interesting though, for the racing fluid it says not to mix...
Isn't the general consensus that a lower viscosity for mineral oil brakes makes them feel better?
Interesting though, for the racing fluid it says not to mix it with polyglycol fluids, if I understand it correctly that's off the shelf DOT4 and DOT5.1?
they're all Motul racing dots, so should be high quality but yeah they do have different viscosity in colder temperatures and different dry/wet boiling points
I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after the initial piston engagement. On top of that, I had the impression that air kept getting into the system, so I ended up bleeding them multiple times each season. I’m done with Shimano.
Now, faced with the dilemma of choosing a single brake set for an enduro bike, if price wasn’t an issue, which would you go for?
They don’t need to have insane power (like Maven). What matters to me:
- Minimal dead zone and smooth lever action.
- Mineral oil compatibility.
- High-quality craftsmanship—no sketchy screws (like MT7) or poor assembly tolerances (e.g., what I’ve heard about Dominion from Dale).
I’m fine with maintenance, as long as it’s not something I have to do every few rides.
Awesome threadPlenty of valuable tips and tricks.I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after...
Awesome thread
Plenty of valuable tips and tricks.
I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after the initial piston engagement. On top of that, I had the impression that air kept getting into the system, so I ended up bleeding them multiple times each season. I’m done with Shimano.
Now, faced with the dilemma of choosing a single brake set for an enduro bike, if price wasn’t an issue, which would you go for?
They don’t need to have insane power (like Maven). What matters to me:
- Minimal dead zone and smooth lever action.
- Mineral oil compatibility.
- High-quality craftsmanship—no sketchy screws (like MT7) or poor assembly tolerances (e.g., what I’ve heard about Dominion from Dale).
I’m fine with maintenance, as long as it’s not something I have to do every few rides.
Dominions are out due to them being dot fluid by your requirements anyways. The construction and tolerances are totally fine on them, it's the finish that dale had an issue with. I would probably do the Formula Cura 4s since you seem to not want Shimano. I absolutely loved the set I tried, very similar to the Dominions in feel IMO, just not quite as powerful.
Awesome threadPlenty of valuable tips and tricks.I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after...
Awesome thread
Plenty of valuable tips and tricks.
I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after the initial piston engagement. On top of that, I had the impression that air kept getting into the system, so I ended up bleeding them multiple times each season. I’m done with Shimano.
Now, faced with the dilemma of choosing a single brake set for an enduro bike, if price wasn’t an issue, which would you go for?
They don’t need to have insane power (like Maven). What matters to me:
- Minimal dead zone and smooth lever action.
- Mineral oil compatibility.
- High-quality craftsmanship—no sketchy screws (like MT7) or poor assembly tolerances (e.g., what I’ve heard about Dominion from Dale).
I’m fine with maintenance, as long as it’s not something I have to do every few rides.
Dominions are out due to them being dot fluid by your requirements anyways. The construction and tolerances are totally fine on them, it's the finish that...
Dominions are out due to them being dot fluid by your requirements anyways. The construction and tolerances are totally fine on them, it's the finish that dale had an issue with. I would probably do the Formula Cura 4s since you seem to not want Shimano. I absolutely loved the set I tried, very similar to the Dominions in feel IMO, just not quite as powerful.
Seconded for the Cura 4s. Also the FCS upgrade is noticeable improvement in overall performance. I prefer the lever shape and it allows a lot of tweak to the power delivery. My biggest issue with them is that I can't run as close to the bar as I prefer. I like my full pull to be ~1cm to the bar and these are closer to 1.5-1.75cm (I can go measure if needed) so they are a bit further out than I like. Without FCS I could run them closer, but I like the feel and delivery I get more with the FCS.
If you don't run your levers really close to the bar, I'd say those are an excellent option.
Awesome threadPlenty of valuable tips and tricks.I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after...
Awesome thread
Plenty of valuable tips and tricks.
I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after the initial piston engagement. On top of that, I had the impression that air kept getting into the system, so I ended up bleeding them multiple times each season. I’m done with Shimano.
Now, faced with the dilemma of choosing a single brake set for an enduro bike, if price wasn’t an issue, which would you go for?
They don’t need to have insane power (like Maven). What matters to me:
- Minimal dead zone and smooth lever action.
- Mineral oil compatibility.
- High-quality craftsmanship—no sketchy screws (like MT7) or poor assembly tolerances (e.g., what I’ve heard about Dominion from Dale).
I’m fine with maintenance, as long as it’s not something I have to do every few rides.
Thirded for Cura 4s.
Had multiple sets on several bikes over several years and the only thing they needed was pads when it was time and a bleed if I moved them to/from a frame with internal routing.
Hope Tech 4 is like a Cura 4 for maintenance, can find spares and exploded view drawings of parts. Hope use DOT where Formula is mineral oil (used Formula and Pentosin CHF), even more modulation in feel vs Cura, longer levers than Formula (may or may not be a pro/con).
Hope has more adjustable levers than Formula which may or may not be a pro/con depending on what you like (one of my beefs with Magura is I don't like the feel of some of the levers as I'm a 1.5-2 finger braking person).
I liked the Hope enough to rotate out my Cura fleet over the past year or two.
Awesome threadPlenty of valuable tips and tricks.I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after...
Awesome thread
Plenty of valuable tips and tricks.
I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after the initial piston engagement. On top of that, I had the impression that air kept getting into the system, so I ended up bleeding them multiple times each season. I’m done with Shimano.
Now, faced with the dilemma of choosing a single brake set for an enduro bike, if price wasn’t an issue, which would you go for?
They don’t need to have insane power (like Maven). What matters to me:
- Minimal dead zone and smooth lever action.
- Mineral oil compatibility.
- High-quality craftsmanship—no sketchy screws (like MT7) or poor assembly tolerances (e.g., what I’ve heard about Dominion from Dale).
I’m fine with maintenance, as long as it’s not something I have to do every few rides.
if money is not a problem then of course, Intend Trinity and Trickstuff Maxima must be at the top of the list, although the latter might nor have the shortest stroke, look at the Radic Kaha for that, all more powerful and of course higher quality than shimano, not sure about the 612 die bremse but they have the same size pistons and master as the maxima
Gentlemen, I didn’t expect so much consensus on Formula. I admit that this setup wasn’t on my radar due to its relatively low popularity, actually very little popularity - wondering why?. I prefer the brake lever to sit relatively far from the handlebars, so that shouldn’t be an issue here. However, I’m curious about the braking power you’ve mentioned as being moderate—will they be weaker than Shimano? Additionally, how would you rate their performance in terms of lever smoothness, ease of operation, and maintenance?
It is better in all regards for me? I had two bikes last year. One with an XT 4 pot and another with the Cura4s. Curas have more power, better modulation. I think the tests typically show 20% more power than XTs. Lever feel is hard for me to describe but I like it and only rode Shimano prior. Power comes on earlier and more linear than Shimano but delivery can be adjusted quite a bit with the fcs. Only had to bleed once after 2 years. Bleed is easy, similar to sram. A top bleed is easier on Shimano, but full bleed better on formula.
I and many others swapped the organic pads that come with them out. I use MTX red. I never used the originals but I hear the power isn’t stellar.
NSMB and Enduro mag have a good write up on them that can explain the feel more descriptively than me.
Gentlemen, I didn’t expect so much consensus on Formula. I admit that this setup wasn’t on my radar due to its relatively low popularity, actually very little popularity - wondering why?. I prefer the brake lever to sit relatively far from the handlebars, so that shouldn’t be an issue here. However, I’m curious about the braking power you’ve mentioned as being moderate—will they be weaker than Shimano? Additionally, how would you rate their performance in terms of lever smoothness, ease of operation, and maintenance?
I have not a wide experience in different brakes (only shimano and few srams) but I for sure would recommend the cura 4s. I have them for a couple of years now and they are really great ! I love the feel, the power and the robustness of the set. they helped me greatly with arm pumps on long and steep downhills and are basically maintenance free. I would love to try the FCS lever though to see the fine tuning they offer. On the power side, it's enough for me but I can't tell how precisely they compare to the competition
P.S: I use them with the formula mineral oil (I'd like to test the bionol one though) and I run currently Galfer advanced pads that I think provide a bit more bite than the standard ones (planning on testing the standard trickstuff also)
Awesome threadPlenty of valuable tips and tricks.I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after...
Awesome thread
Plenty of valuable tips and tricks.
I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after the initial piston engagement. On top of that, I had the impression that air kept getting into the system, so I ended up bleeding them multiple times each season. I’m done with Shimano.
Now, faced with the dilemma of choosing a single brake set for an enduro bike, if price wasn’t an issue, which would you go for?
They don’t need to have insane power (like Maven). What matters to me:
- Minimal dead zone and smooth lever action.
- Mineral oil compatibility.
- High-quality craftsmanship—no sketchy screws (like MT7) or poor assembly tolerances (e.g., what I’ve heard about Dominion from Dale).
I’m fine with maintenance, as long as it’s not something I have to do every few rides.
How about the new Magura Gustav?
They look very promising. Maybe not got the absolute power, but it will have basically all the power aviable whatever you throw at it.
I have not a wide experience in different brakes (only shimano and few srams) but I for sure would recommend the cura 4s. I have them...
I have not a wide experience in different brakes (only shimano and few srams) but I for sure would recommend the cura 4s. I have them for a couple of years now and they are really great ! I love the feel, the power and the robustness of the set. they helped me greatly with arm pumps on long and steep downhills and are basically maintenance free. I would love to try the FCS lever though to see the fine tuning they offer. On the power side, it's enough for me but I can't tell how precisely they compare to the competition
P.S: I use them with the formula mineral oil (I'd like to test the bionol one though) and I run currently Galfer advanced pads that I think provide a bit more bite than the standard ones (planning on testing the standard trickstuff also)
Awesome threadPlenty of valuable tips and tricks.I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after...
Awesome thread
Plenty of valuable tips and tricks.
I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after the initial piston engagement. On top of that, I had the impression that air kept getting into the system, so I ended up bleeding them multiple times each season. I’m done with Shimano.
Now, faced with the dilemma of choosing a single brake set for an enduro bike, if price wasn’t an issue, which would you go for?
They don’t need to have insane power (like Maven). What matters to me:
- Minimal dead zone and smooth lever action.
- Mineral oil compatibility.
- High-quality craftsmanship—no sketchy screws (like MT7) or poor assembly tolerances (e.g., what I’ve heard about Dominion from Dale).
I’m fine with maintenance, as long as it’s not something I have to do every few rides.
How about the new Magura Gustav?They look very promising. Maybe not got the absolute power, but it will have basically all the power aviable whatever you...
How about the new Magura Gustav?
They look very promising. Maybe not got the absolute power, but it will have basically all the power aviable whatever you throw at it.
Well, there is not much info about them, tests neither.
First impressions suggests they fit better eMTB which is not my story yet.
Main issue would be your friends making motorbike noises at you on every group ride
FWIW, in the pre silver/bronze Code days RSC was anodized while everything under it was not. Doing a bleed rsc has clear fluid even after two years while lesser models have a very dirty fluid due to wear of the aluminum bore and suspending the particles in the fluid because of it.
Thanks for that tidbit @Primoz, that's quite interesting!
No probs, happy to share.
FWIW, I don't know how it's handled in the current Bronze & co days, haven't had my hands on any of the newer brakes. The situation I described (RSC anodized, R(S) and lower not) applies to Guide and G2 brakes too. And the reason for the difference is that with RSC (and Ultimate) brakes both the master and the caliper are anodized after all the machining, so anodized inside and out. Lower tiers are painted on the other hand and are obviously painted only on the outside.
Could this be one part of the equation that makes green Shimano brake fluid go dark together with dirt from slave pistons? I cleaned and checked the actual bore and there's no sign of wear. If the piston would be metallic instead of plastic I guess there could be signs of wear. This could be case with aftermarket titanium etc. pistons.
I'd say yes. DOT fluid is translucent amber and with painted brakes becomes opaque (non-transparent) grey-ish if they are used. If the brakes sit unused for a long period of time this does not happen, ergo it looks like it comes from bore and piston wear.
Yeah, aftermarket titanium/alloy pistons from AliExpress are obviously a great idea when you take all this info into account
There's a reason Lewis for example does PEEK pistons - hard, stable, chemically stable. Maybe a bit hard (PEEK is often used as a counterpart material to steel when it comes to gears to make them quieter). Trickstuff does POM (Delrin) and Igus has an article Piccola uses (used?) one of their bearing grade (plastic) materials.
Tried those Ti MC pistons when the ones on an old set of SLX brakes went and crapped out. No good. They were undersized and rocked enough in the bore during use to allow the primary seal to lose seal, I.E. lever go straight to the bar. Unfun to learn to say the least. Had high hopes since the alloy ones I used to replace the plastic Sram jobbers in his Levels worked a peach.
Careful there, PEEK, PAEK, and PEKK are not replacements for any alloy steel or SS. Compressive strength of any of the PEEK materials in the family is between 13-18KSI in a neat form, no glass or carbon fill and generally will not ever be over 25KSI without significant carbon fiber loading. PEEK is one of the most expensive thermoplastics, and while it does have very good chemical resistance to solvents and heated solvent vapors it by no means is it a mechanical replacement for Aluminum or steel. Its also a PITA to machine, and sucks to mold as tool temps under 300°C will result in an amorphous material with severely reduced mechanical properties, on the flip side molding clear PEEK is pretty cool... All these plastics will suffer in the sense of CTE. Just doing some quick math a 60° increase in piston temp with PEEK would result in diametrical growth of about 55µm or .002". That might seem like nothing, but I have a hard time believing that it wouldn't have some effect on brake feel due to the extra compression on the piston seal.
I never said it's a replacement. I said PEEK is used as a counterpart material to steel in gears. Meaning one gear is steel, the other is PEEK. I'm not an expert in geartrain design and obviously you don't see PEEK gears in car transmissions and the like, but I did hear a steel/PEEK combo has been used in an eBike drive unit to quite things down, which is the role PEEK plays - use it where you need a quiet geartrain but also need more strength in gear the usual plastic materials give you. COnsidering you don't see aluminium gears, there must be something on PEEK that gives it an advantage, I'd bet it would be surface hardness or something along those lines.
Considering this (PEEK being used to pair to steel gears) while aluminium is neve used for gears, I said PEEK might be a bit hard, i.e. used as a brake master piston it might scratch up the bore too, just like a steel, titannium or probably even aluminium piston would. But I don't have any experience with it and it might be empty worries...
As for CTE, if that is an issue that arises with a master cylinder in the brake, there are bigger issues than CTE itself... With the way seals are done on a master piston, there should be quite a bit of clearance radially between the bore and the piston, shown by pistons being scratched on only one side. One exception here is Sram's piston selling and jamming, but year... In either case, POM is also used as a master piston material from what I've seen and the CTE of it is about twice as big as PEEK's. If CTE was an issue, everybody would be using aluminium pistons anyway...
PEEK is indeed quite hard, and yes can (and indeed does) scratch up materials that would be perceived to be harder. One example in my line of work is desalination plant HP pumps that use PEEK for the casing wear rings. These definitely do scratch up the corresponding impeller wear rings that are made from super duplex.
I finally got around to bleeding my brakes using the Canyon / Aaron method that was linked a while back. The rear brake on one of my sets of my Mavens always felt a bit soft to me, and when I used this method it seemed to firm it up quite a bit. It was pretty shocking at how many bubbles I was able to draw out using this method of isolating the caliper then the lever (so much that I wondered whether I had a leaky connection but I'm pretty sure that wasn't the case given that I never saw any leaks when pressurizing, and that the amount of bubbles steadily decreased). I'll definitely be switching to this method from now on.
You are correct, you did say counterpart. In the example that you gave the reason why is correct for certain applications, but I can guarantee that it's not neat PEEK, i.e. unfilled virgin PEEK. Most likely its carbon or glass filled with ETFE or PTFE added as a lubricant, but I would bet that more often than not its PPS, without carbon black added both materials look nearly identical in color, have very similar mechanical and chemical resistance characteristic, but PPS costs 1/2 that of PEEK.
PEEK is not harder than aluminum. Pulling from my material DB here at work, we have a hardness tested calibrated for Rockwell A and B, 6061-T6 ranges from 56-62B. PEEK doesn't even move the needle on the Rockwell B scale, at all, It's not even close. LOL.
CTE is something that any competent seal designer should take into consideration, especially when designing a seal gland where the seal is being used as a rollback spring, let alone one that can see as aggressive temp swings as I would presume that a disc brake piston would be subjected to. Having to design anything around a moving target is tricky and ends up being an exercise in compromise.
Curiosity, has anyone experimented with different dots?
I was googling the differences between some 5.1 and some 4 and it seems for racing application on motors and cars the 4 series is the one that is most used,
Would a bike brake feel better with a dot with a higher boiling point or a low viscosity one?
Anyone tried something?
Isn't the general consensus that a lower viscosity for mineral oil brakes makes them feel better?
Interesting though, for the racing fluid it says not to mix it with polyglycol fluids, if I understand it correctly that's off the shelf DOT4 and DOT5.1?
The only ingredient listed in the MSDS for RBF 700 is "diamines", so that wasn't much help.
But it is polyglycol based. Presumably it shouldn't be mixed because that would degrade its performance.
they're all Motul racing dots, so should be high quality but yeah they do have different viscosity in colder temperatures and different dry/wet boiling points
Awesome thread
Plenty of valuable tips and tricks.
I’ve battled with my Shimano XTR Trail brakes many times, but I’ve never managed to eliminate that spongy feel after the initial piston engagement.
On top of that, I had the impression that air kept getting into the system, so I ended up bleeding them multiple times each season.
I’m done with Shimano.
Now, faced with the dilemma of choosing a single brake set for an enduro bike, if price wasn’t an issue, which would you go for?
They don’t need to have insane power (like Maven).
What matters to me:
- Minimal dead zone and smooth lever action.
- Mineral oil compatibility.
- High-quality craftsmanship—no sketchy screws (like MT7) or poor assembly tolerances (e.g., what I’ve heard about Dominion from Dale).
I’m fine with maintenance, as long as it’s not something I have to do every few rides.
Dominions are out due to them being dot fluid by your requirements anyways. The construction and tolerances are totally fine on them, it's the finish that dale had an issue with. I would probably do the Formula Cura 4s since you seem to not want Shimano. I absolutely loved the set I tried, very similar to the Dominions in feel IMO, just not quite as powerful.
Seconded for the Cura 4s. Also the FCS upgrade is noticeable improvement in overall performance. I prefer the lever shape and it allows a lot of tweak to the power delivery. My biggest issue with them is that I can't run as close to the bar as I prefer. I like my full pull to be ~1cm to the bar and these are closer to 1.5-1.75cm (I can go measure if needed) so they are a bit further out than I like. Without FCS I could run them closer, but I like the feel and delivery I get more with the FCS.
If you don't run your levers really close to the bar, I'd say those are an excellent option.
Thirded for Cura 4s.
Had multiple sets on several bikes over several years and the only thing they needed was pads when it was time and a bleed if I moved them to/from a frame with internal routing.
Hope Tech 4 is like a Cura 4 for maintenance, can find spares and exploded view drawings of parts. Hope use DOT where Formula is mineral oil (used Formula and Pentosin CHF), even more modulation in feel vs Cura, longer levers than Formula (may or may not be a pro/con).
Hope has more adjustable levers than Formula which may or may not be a pro/con depending on what you like (one of my beefs with Magura is I don't like the feel of some of the levers as I'm a 1.5-2 finger braking person).
I liked the Hope enough to rotate out my Cura fleet over the past year or two.
if money is not a problem then of course, Intend Trinity and Trickstuff Maxima must be at the top of the list, although the latter might nor have the shortest stroke, look at the Radic Kaha for that, all more powerful and of course higher quality than shimano, not sure about the 612 die bremse but they have the same size pistons and master as the maxima
Maybe this helps:
About 13mm-14mm of lever throw on the 612 to the bitepoint.
Eae903 jasbushey SilentG
Gentlemen,
I didn’t expect so much consensus on Formula. I admit that this setup wasn’t on my radar due to its relatively low popularity, actually very little popularity - wondering why?.
I prefer the brake lever to sit relatively far from the handlebars, so that shouldn’t be an issue here. However, I’m curious about the braking power you’ve mentioned as being moderate—will they be weaker than Shimano?
Additionally, how would you rate their performance in terms of lever smoothness, ease of operation, and maintenance?
It is better in all regards for me? I had two bikes last year. One with an XT 4 pot and another with the Cura4s. Curas have more power, better modulation. I think the tests typically show 20% more power than XTs. Lever feel is hard for me to describe but I like it and only rode Shimano prior. Power comes on earlier and more linear than Shimano but delivery can be adjusted quite a bit with the fcs. Only had to bleed once after 2 years. Bleed is easy, similar to sram. A top bleed is easier on Shimano, but full bleed better on formula.
I and many others swapped the organic pads that come with them out. I use MTX red. I never used the originals but I hear the power isn’t stellar.
NSMB and Enduro mag have a good write up on them that can explain the feel more descriptively than me.
I have not a wide experience in different brakes (only shimano and few srams) but I for sure would recommend the cura 4s. I have them for a couple of years now and they are really great ! I love the feel, the power and the robustness of the set. they helped me greatly with arm pumps on long and steep downhills and are basically maintenance free. I would love to try the FCS lever though to see the fine tuning they offer. On the power side, it's enough for me but I can't tell how precisely they compare to the competition
P.S: I use them with the formula mineral oil (I'd like to test the bionol one though) and I run currently Galfer advanced pads that I think provide a bit more bite than the standard ones (planning on testing the standard trickstuff also)
How about the new Magura Gustav?
They look very promising. Maybe not got the absolute power, but it will have basically all the power aviable whatever you throw at it.
Try the Trickstuff Power pads, I’d say.
Well, there is not much info about them, tests neither.
First impressions suggests they fit better eMTB which is not my story yet.
i'll delete if already posted, but sram non-circular brake piston patent? is this new?
https://patents.google.com/patent/DE102024102985A1/en?assignee=Sram%2c+Llc&before=priority:20250101&after=priority:20230101&sort=new
New or not, it shouldn't be granted. Formula did oval pistons years ago.
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