I've talked about my hand problems a lot, but brake setup plays a huge role. It's part of the reason I've tried so many different brakes. What...
I've talked about my hand problems a lot, but brake setup plays a huge role. It's part of the reason I've tried so many different brakes.
What I found is that brakes with a ton of power but super linear pulls (Maxima, MT7, Code mainly) don't help and/or make issues worse for me. This comes down to power delivery but also ergonomics and how that power delivery influences power delivery. Some brakes just can't be run close due to the lack of power early in the lever pull. If the lever has to be shot out into space to get power from it, it'll change where your hands engage with the bar and where the pressure points are. Further out and your hand rotates more inwards towards the stem, closer in and it rotates further outward. How this helps or hurts depends on your hands/bars/arms/etc. You can experiment with this somewhat by putting the lever out at extreme angles, pulling it, and noting where your hands feel tense against the bar, move it all the way in and repeat to note the difference.
This is where very grabby, very strong (Maven, Intend, T4V4, Radic) brakes make a big difference for me esp if they have contact adjust. You can tune the lever position based on where it feels best and make adjustments to mitigate or reduce arm pump. Everyone has different hands/arms/wrists/etc, but also bars have different sweep and riders use different roll on the bar (which influences sweep angles also). For the average rider without issues, it may seem pedantic or fiddly to mess with this, but for people who have problems or issues, it can be a remarkable change in how you feel riding. I wish I had an objective way to measure and map this out, but being sensitive to it - it's pretty easy to feel.
Point being, I find a direct correlation to brake lever position / braking power delivery and how bad my hand issues get aggravated. If you experiment with lever positioning and pull, you'll probably find that the pressure points on your hands move as the lever position is moved in/out.
I don’t know about all of that I just know that the more outstretched your index finger is, the more strain there will be on your forearm. Being able to ride with that index finger curled closer to the bar reduces that strain immensely.
Why change brakes if they're working great? From your post: "These work great and tend to not over heat too badly for me, I also really...
Why change brakes if they're working great? From your post: "These work great and tend to not over heat too badly for me, I also really like the lever feel." Seems like they're perfect for you.
That is a very fair question! I think I’m just aware that when I got the codes, they were about the most powerful brakes I could...
That is a very fair question! I think I’m just aware that when I got the codes, they were about the most powerful brakes I could easily find, but things have moved on, and being a larger guy I’m very curious to try something new. Also codes were originally on a sentinel, I’m now on a spire and riding a chunk faster
Being 175lbs riding weight myself I feel I can benefit from stronger brakes than the codes, so it’s definitely worth it to get something more powerful.A...
Being 175lbs riding weight myself I feel I can benefit from stronger brakes than the codes, so it’s definitely worth it to get something more powerful.
A colleague of mine always thought his guides ultimate were enough at 230lbs
Now on mavens he knows he was wrong
190 kitted out and my Guide RSCs are right at the limit. I just love the ergonomics, though.
That is a very fair question! I think I’m just aware that when I got the codes, they were about the most powerful brakes I could...
That is a very fair question! I think I’m just aware that when I got the codes, they were about the most powerful brakes I could easily find, but things have moved on, and being a larger guy I’m very curious to try something new. Also codes were originally on a sentinel, I’m now on a spire and riding a chunk faster
Being 175lbs riding weight myself I feel I can benefit from stronger brakes than the codes, so it’s definitely worth it to get something more powerful.A...
Being 175lbs riding weight myself I feel I can benefit from stronger brakes than the codes, so it’s definitely worth it to get something more powerful.
A colleague of mine always thought his guides ultimate were enough at 230lbs
One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling sharp and where I wanted it, after a couple rides the bite point kept pulling in towards the bars further and further to the point where the lever was pulling all the way into the bar. I did another lever bleed to get the air out of the system, which returned the bite point to perfect. Riding around the parking lot it felt mint. Again on the first ride the bite point completely disappeared. It seems like there is an air gap somewhere into the system, but no brake fluid is coming out of any of the ports or elsewhere. The system seems completely sealed so far as I can tell. Looking for advice - front brake lever pulling into the bar is scary! Thanks
Hayes Dominion A4 weirdness - looking for advice.One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling...
Hayes Dominion A4 weirdness - looking for advice.
One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling sharp and where I wanted it, after a couple rides the bite point kept pulling in towards the bars further and further to the point where the lever was pulling all the way into the bar. I did another lever bleed to get the air out of the system, which returned the bite point to perfect. Riding around the parking lot it felt mint. Again on the first ride the bite point completely disappeared. It seems like there is an air gap somewhere into the system, but no brake fluid is coming out of any of the ports or elsewhere. The system seems completely sealed so far as I can tell. Looking for advice - front brake lever pulling into the bar is scary! Thanks
Likely that there is air elsewhere trapped in the system. You may need to do a full bleed instead of just a lever bleed.
Being 175lbs riding weight myself I feel I can benefit from stronger brakes than the codes, so it’s definitely worth it to get something more powerful.A...
Being 175lbs riding weight myself I feel I can benefit from stronger brakes than the codes, so it’s definitely worth it to get something more powerful.
A colleague of mine always thought his guides ultimate were enough at 230lbs
Hayes Dominion A4 weirdness - looking for advice.One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling...
Hayes Dominion A4 weirdness - looking for advice.
One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling sharp and where I wanted it, after a couple rides the bite point kept pulling in towards the bars further and further to the point where the lever was pulling all the way into the bar. I did another lever bleed to get the air out of the system, which returned the bite point to perfect. Riding around the parking lot it felt mint. Again on the first ride the bite point completely disappeared. It seems like there is an air gap somewhere into the system, but no brake fluid is coming out of any of the ports or elsewhere. The system seems completely sealed so far as I can tell. Looking for advice - front brake lever pulling into the bar is scary! Thanks
As Jaloypj said, do a full bleed. Also, double check that the hose nut at the lever is fully torqued. When I had them, at least once I thought I had it tightened up enough, but the bleed felt like crap. I put an actual torque wrench to bring it up to whatever value they say, and ended up turning the nut like at least 2 full rotations more, and the problem went away.
Hayes Dominion A4 weirdness - looking for advice.One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling...
Hayes Dominion A4 weirdness - looking for advice.
One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling sharp and where I wanted it, after a couple rides the bite point kept pulling in towards the bars further and further to the point where the lever was pulling all the way into the bar. I did another lever bleed to get the air out of the system, which returned the bite point to perfect. Riding around the parking lot it felt mint. Again on the first ride the bite point completely disappeared. It seems like there is an air gap somewhere into the system, but no brake fluid is coming out of any of the ports or elsewhere. The system seems completely sealed so far as I can tell. Looking for advice - front brake lever pulling into the bar is scary! Thanks
Clean the calipers really, really well and make sure they are completely dry. Go ride and inspect afterwords to verify that they are not leaking anywhere. I have both heard and seen that the newer Dominions have been prone to leak which can cause issues similar to a bad bleed even when there is no air in the system. But first make sure that there is no air in the system, full bleed and work the pistons out to make sure nothing is trapped behind them. Hayes has been quite good, from what I have heard with the warranty process if that is the issue, leaking.
https://youtu.be/yKDVB37AOic?si=UjivGrJdZkxmFB-Y Interesting video regarding brembo’s DFM methods for F1 brakes. I’ve heard some anecdotes about how F1 brake fluid is vastly superior to DOT fluid, but after looking at the composition details it’s still poly- glycol ether based fluid, same as DOT. Will try to get my hands on some as I have some connections to a LMP race team with a few Rolex wins.
I have a feeling that as I have theorized, system fluid pressure is key to management of the fluids boil point, and the idea that using phenolic or other thermoplastic inserts are more armchair theory vs having any practical application in high performance applications especially considering that F1 or LMP car brakes operate at temperatures that no mtb brake would ever hit, >800c. I have a few phd chem eng. at work and will have to pick their brains on the idea of localized boiling and if that’s an actual fluid phenomenon that could cause degradation but I have a feeling that the heat flux isn’t high enough to cause that to happen even if the thermodynamics support the idea. Pretty wild to see how little material is used regardless of the forced induction aero being used for brake cooling. Interesting stuff nonetheless.
I don't have any data right now to say one way or another but my gut is telling me no. What I do know is that...
I don't have any data right now to say one way or another but my gut is telling me no. What I do know is that boiling temp increases pretty significantly based on the pressure that the fluid is it. I have heard engineers in the industry stating that line pressures are over 1000psi for peak braking events, that's 68X more pressure than the atmospheric pressure of 14.7 psi that the boiling point it rated at, but that's all the data that I have to go off of, I don't have extra any inline wireless pressure transducers lying around at the moment to corroborate this
I do have an array of thermal stickers that I was planning on placing on my rotors and calipers this last weekend to see how hot they get doing some practice runs for a DH race coming up later this month, but I got lost in the weekend and forgot to stick them on. Will make sure to do it the Thursday before I pack up for the race.
The way I look at it, even if we took the pressure out of the equation, our brake fluids have thermal conductivities of around .13W/m·K which makes them very good insulators. It will take a lot of sustained heat to actually get the fluid up to the temp of the caliper, which is probably why Brembo has no issue using Al pistons, I would bet that they have not only run the CFD simulations but also performed a significant amount of lab testing to back up their decisions. If I have some time I'll try to setup something simple in comsol to simulate the amount of thermal energy needed to heat a mineral oil to its boiling point, and maybe try to add pressure into the equation, could be a fun thought experiment.
I like both your thought experiments and proposed real world experiments. I did not know that brake fluid was such a poor conductor of heat, that...
I like both your thought experiments and proposed real world experiments. I did not know that brake fluid was such a poor conductor of heat, that is really interesting.
Having said that, am I crazy to think that getting even a small layer of the fluid up to the boiling point could be problematic? In other words, these hypothetical hot pistons will transfer heat fairly readily to the fluid layer in direct contact with them, I would imagine. The fluid may then not as readily transfter the heat throughout the rest of the hydraulic system, but it doesn't seem like you'd need to boil the whole system for it to be a problem. It seems like just the immediate layer right around the pistons would be enough. I am thinking of when one is boiling a pot of water, and before it reaches a full rolling boil, you start seeing bubbles coming of the layer of water in direct contact with the heated surface at the bottom of the pot.
I haven't looked into aluminum piston properties myself, but the great thermal conductivity of aluminum (when compared to steel) is why Shimano sandwiches it in their Icetech rotors. On the other hand, while aluminum may conduct well internally, it also has fairly high reflectivity and low emittance, which is why aluminized materials are often used in radiant heat barriers in construction and HVAC systems, so if Brembo had a piston face that minimized surface contact between the piston and pad backing, that might work in their favor.
Would be pretty cool to build a thermal test system to subject heat to pistons and measure the fluid pressure loss based on various line pressures. Based on the fact that most fluids exhibit similar characteristics where as heat increases the inverse of the bulk modulus of the fluid decreases, thus compressibility increases, giving you some sort of predictability in the system response. It wouldn’t be that hard to measure the thermal effect in a system once you a lookup table to account for the density change.
Hayes Dominion A4 weirdness - looking for advice.One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling...
Hayes Dominion A4 weirdness - looking for advice.
One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling sharp and where I wanted it, after a couple rides the bite point kept pulling in towards the bars further and further to the point where the lever was pulling all the way into the bar. I did another lever bleed to get the air out of the system, which returned the bite point to perfect. Riding around the parking lot it felt mint. Again on the first ride the bite point completely disappeared. It seems like there is an air gap somewhere into the system, but no brake fluid is coming out of any of the ports or elsewhere. The system seems completely sealed so far as I can tell. Looking for advice - front brake lever pulling into the bar is scary! Thanks
As others have said, redo a fresh bleed and check all the fittings.
It sounds like you have a leak somewhere since as you add pressure during use the levers creep closer to the bar.
Hayes Dominion A4 weirdness - looking for advice.One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling...
Hayes Dominion A4 weirdness - looking for advice.
One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling sharp and where I wanted it, after a couple rides the bite point kept pulling in towards the bars further and further to the point where the lever was pulling all the way into the bar. I did another lever bleed to get the air out of the system, which returned the bite point to perfect. Riding around the parking lot it felt mint. Again on the first ride the bite point completely disappeared. It seems like there is an air gap somewhere into the system, but no brake fluid is coming out of any of the ports or elsewhere. The system seems completely sealed so far as I can tell. Looking for advice - front brake lever pulling into the bar is scary! Thanks
Which brake and which bike do you have? A loss like that points to a leak in the system. Possibly the reservoir bladder, possibly the hose. As others have said, check torque on the hose fittings, but there's a quick diagnostic you can do to determine if it's an internal rupture on your hose. Pull the wheel out of the drops and insert a pad spacer. Set the lever up into the bleed position and attach your syringe to the lever without the plunger in it. you'll need to keep that syringe vertical, so you'll need to figure that out. With the syringe vertical, add a bit of fluid to it, maybe a cm or so. Slowly and lightly pull the lever. This is key. If the lever goes to the bar, watch the fluid level in the syringe. and pull it the same way a few more times. If you notice the fluid level is dropping but not returning to the same height, stop pulling the lever. This is indicating you have an internal rupture in your brake line and it needs to be replaced. This is generally not a warrantable condition as it's related to damage, be it form a crash or poor hose routing. Most bikes have routing down pat these days, but I wouldn't say all do, so if it's the rear brake I'd look where you could make the hose arc smoother.
If the lever is going to the bar but the fluid level is maintaining volume, that indicates a MC piston seal failure. Warranty that bugger.
If the lever firms up, I would inspect the bladder. I've seen brands develop slight tears at the seal surface that would not allow fluid to leak but in use would allow the res to ingest a smidge of air or overzealous syringe use causing the diaphragm to pop out of its sealing surface resulting in the same slow air ingestion.
Super curious about today's BOTD brake set up. Maven calipers matched to Lewis levers. Say what you will about Lewis, but their levers feel really good. Very light and smooth. I'd definitely be interested to see how much of a faff it was pairing them, or if it went pretty smoothly.
When cleaning contaminated rotors I boil a pan of water and dish soap on the hob (use an old pan, or feel the wrath of your partner) and leave the rotor in there a few mins bubbling away. Got the tip from the yeti race team mechanic years ago.
Hayes Dominion A4 weirdness - looking for advice.One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling...
Hayes Dominion A4 weirdness - looking for advice.
One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling sharp and where I wanted it, after a couple rides the bite point kept pulling in towards the bars further and further to the point where the lever was pulling all the way into the bar. I did another lever bleed to get the air out of the system, which returned the bite point to perfect. Riding around the parking lot it felt mint. Again on the first ride the bite point completely disappeared. It seems like there is an air gap somewhere into the system, but no brake fluid is coming out of any of the ports or elsewhere. The system seems completely sealed so far as I can tell. Looking for advice - front brake lever pulling into the bar is scary! Thanks
When you say another bleed to get air out of the system, did you actually pull air out? Or was it just a general term?
If you are sure sure sure there is no more air while doing a bleed and then you have air in the system the next time you bleed, you have a leak somewhere. I'd do the things others have mentioned.
Regarding the nut, thanks for that one, I have code rscs that seem to be pulling some air slowly (also have a wandering bite point a while after a bleed) and is for sure a very easy thing to check. The old set I had (that GF uses) still functions flawlessly and it's been in use since 2019, had two bleeds and then a full rebuild in 2024.
https://youtu.be/yKDVB37AOic?si=UjivGrJdZkxmFB-Y Interesting video regarding brembo’s DFM methods for F1 brakes. I’ve heard some anecdotes about how F1 brake fluid is vastly superior to DOT fluid, but...
https://youtu.be/yKDVB37AOic?si=UjivGrJdZkxmFB-Y Interesting video regarding brembo’s DFM methods for F1 brakes. I’ve heard some anecdotes about how F1 brake fluid is vastly superior to DOT fluid, but after looking at the composition details it’s still poly- glycol ether based fluid, same as DOT. Will try to get my hands on some as I have some connections to a LMP race team with a few Rolex wins.
I have a feeling that as I have theorized, system fluid pressure is key to management of the fluids boil point, and the idea that using phenolic or other thermoplastic inserts are more armchair theory vs having any practical application in high performance applications especially considering that F1 or LMP car brakes operate at temperatures that no mtb brake would ever hit, >800c. I have a few phd chem eng. at work and will have to pick their brains on the idea of localized boiling and if that’s an actual fluid phenomenon that could cause degradation but I have a feeling that the heat flux isn’t high enough to cause that to happen even if the thermodynamics support the idea. Pretty wild to see how little material is used regardless of the forced induction aero being used for brake cooling. Interesting stuff nonetheless.
The 800degC temp is the rotor to pad contact. They make sure to both keep them warm enough but at the same time have enough cooling. As you can see in the video, they take away everything from the caliper they can. This is for weight savings (unsprung mass and all) bu to also bring the fluid as close as possible to the cooling air. So much so they have cooling fins, ribs and barbs to ensure the caliper itself is cooled. So caliper and by extension oil is cooled, pad and rotor cooled, but kept warm enough.
As for System pressures and boiling prevention, all is fine and well as long as you have said pressure. QED PWR nuclear reactors where water is under 150 bar to prevent boiling at 350°C. But as soon as you take away the pressure, the fluid will boil. With brakes that happens every time you let off them.
Super curious about today's BOTD brake set up. Maven calipers matched to Lewis levers. Say what you will about Lewis, but their levers feel really good...
Super curious about today's BOTD brake set up. Maven calipers matched to Lewis levers. Say what you will about Lewis, but their levers feel really good. Very light and smooth. I'd definitely be interested to see how much of a faff it was pairing them, or if it went pretty smoothly.
Not Mavens, but I'm using Lewis masters paired with Magura calipers. I'd been intrigued about eeking more power out of the stock LH4 I was initially using. The LH4 caliper uses 17 & 14 mm pistons, so I gained quite a bit with the quad 17 mm pistons in the Magura
I was thinking about pairing them with a Cura 4 caliper or a Maven base caliper, but was unsure if the 18 mm pistons would mean I'd have too much lever throw before the pads would contact and didn't want to risk it. Plus I found the Magura calipers for cheap
My Lewgura set up has more throw than stock, but the power bump more than makes up for it, they have immense power and a really nice light lever feel
Getting some pretty horrendous pad rattle coming from my shigura brakes - have been running the same setup for ~18 months now but it’s only been over the last 3 months or so that I’ve been getting it since buying a fresh set for a new bike.
Using Galfer pro pads (which I’ve always used) - wonder if I’ve got a bad batch in terms of tolerances or the backing material isn’t working well with the magnetic piston?
Either way it’s driving me mental, brand new bikes with new brakes sounding like a filing cabinet being pushed off a cliff through any sort of rough corner. In a straight line it’s not quite as bad.
Getting some pretty horrendous pad rattle coming from my shigura brakes - have been running the same setup for ~18 months now but it’s only been...
Getting some pretty horrendous pad rattle coming from my shigura brakes - have been running the same setup for ~18 months now but it’s only been over the last 3 months or so that I’ve been getting it since buying a fresh set for a new bike.
Using Galfer pro pads (which I’ve always used) - wonder if I’ve got a bad batch in terms of tolerances or the backing material isn’t working well with the magnetic piston?
Either way it’s driving me mental, brand new bikes with new brakes sounding like a filing cabinet being pushed off a cliff through any sort of rough corner. In a straight line it’s not quite as bad.
Anything I can try before just buying mavens?
trickstuff power or sinter pads, one piece per side rather than 4, never had any issue or noise with either
Getting some pretty horrendous pad rattle coming from my shigura brakes - have been running the same setup for ~18 months now but it’s only been...
Getting some pretty horrendous pad rattle coming from my shigura brakes - have been running the same setup for ~18 months now but it’s only been over the last 3 months or so that I’ve been getting it since buying a fresh set for a new bike.
Using Galfer pro pads (which I’ve always used) - wonder if I’ve got a bad batch in terms of tolerances or the backing material isn’t working well with the magnetic piston?
Either way it’s driving me mental, brand new bikes with new brakes sounding like a filing cabinet being pushed off a cliff through any sort of rough corner. In a straight line it’s not quite as bad.
Anything I can try before just buying mavens?
This seems to be a galfer thing with their springs. Try bending the tangs of the pad spring into the sides of the pads so that they're held more tightly in place I.e. "preloading" the pad spring. Just be careful to keep the tangs flat with the pad backing and stop them sticking out into the rotors when the pads wear down.
I usually do this before fitting new pads as the rattle drives me nuts if I don't.
The galfer pads are often a little bit short in the length department, They rattle Bad in shimano's and gets worse as it wears the caliper. Opening the spring helps alot.
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I picked up my set last August and had run them without complaint until the other week when my front lever started pulling much farther into the bar about 2 minutes into a mild descent. I inspected the brakes and couldn't find any sign of fluid leaks or anything of the sort. I subsequently performed a gravity bleed and had the brakes feeling new again. Next ride, exact same issue! At this point, I was sure there had to be a leak somewhere, so, rebled them and strapped the lever to the bar to pressure test overnight and sure enough, they held perfect pressure. I did notice that when I opened the reservoir to bleed them after the rides, they did seem to be down a small amount of fluid and I was also able to "pump" them back up to a normal feeling (similar to Shimano's wandering bite problem). My conclusion is that there must be a leak somewhere in the system, just not exactly sure how to deduce that problem yet. I think it must be up at the lever as the pads and rotors are not being contaminated, but I can't see any signs of leakage. Let me know what you guys think.
FYI: I have checked the torque and fitting of all the barbs/olives and brake hose fittings, definitely not the issue
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I...
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I picked up my set last August and had run them without complaint until the other week when my front lever started pulling much farther into the bar about 2 minutes into a mild descent. I inspected the brakes and couldn't find any sign of fluid leaks or anything of the sort. I subsequently performed a gravity bleed and had the brakes feeling new again. Next ride, exact same issue! At this point, I was sure there had to be a leak somewhere, so, rebled them and strapped the lever to the bar to pressure test overnight and sure enough, they held perfect pressure. I did notice that when I opened the reservoir to bleed them after the rides, they did seem to be down a small amount of fluid and I was also able to "pump" them back up to a normal feeling (similar to Shimano's wandering bite problem). My conclusion is that there must be a leak somewhere in the system, just not exactly sure how to deduce that problem yet. I think it must be up at the lever as the pads and rotors are not being contaminated, but I can't see any signs of leakage. Let me know what you guys think.
FYI: I have checked the torque and fitting of all the barbs/olives and brake hose fittings, definitely not the issue
Not claiming to have any sort of magic solution, but if the increase in lever throw followed a sustained pull (for example, on the steepest part of the trail) then it could be a cracked inner liner in the hose. That can lead to fluid leaking into the braided reinforcement layer, without any visual indicator, other than perhaps a slight bulge in the outer polymer layer. Even weirder, the elasticity of the outer polymer can gradually squeeze most of the fluid back through the crack, into the inner liner, leaving no evidence if you don't catch it in the heat of the moment.
Normally, the easy test for this is, while the bike is at rest, simply to squeeze the lever so the pads engage the rotor for an extended period, and see if the lever engagement point gradually creeps inward toward the bar. You have already essentially done this though, by strapping the lever to the bar overnight, and it doesn't sound like it crept in (unless you had it close to bottoming under the strap pressure and therefore couldn't notice the slight additional movement to a fully bottomed position when you checked it the next day). One possibility that occurred to me is that strapping the levers down is totally static, whereas, since it is the front brake, that hose is flexing quite a bit as the fork cycles on the descent. If you had a hairline crack, it might only open when the hose is in a flexed condition, so you may want to push on the fork repeatedly while squeezing the lever, in case hose flex opens up the crack allowing you to replicate the problem.
If that's not it, I think you're right on with the thought of looking to the lever as the likely culprit. If you had fluid blowing past the M/C seal, then that could cause the problem, but why that would only happen after 2min of descending is non-obvious to me.
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I...
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I picked up my set last August and had run them without complaint until the other week when my front lever started pulling much farther into the bar about 2 minutes into a mild descent. I inspected the brakes and couldn't find any sign of fluid leaks or anything of the sort. I subsequently performed a gravity bleed and had the brakes feeling new again. Next ride, exact same issue! At this point, I was sure there had to be a leak somewhere, so, rebled them and strapped the lever to the bar to pressure test overnight and sure enough, they held perfect pressure. I did notice that when I opened the reservoir to bleed them after the rides, they did seem to be down a small amount of fluid and I was also able to "pump" them back up to a normal feeling (similar to Shimano's wandering bite problem). My conclusion is that there must be a leak somewhere in the system, just not exactly sure how to deduce that problem yet. I think it must be up at the lever as the pads and rotors are not being contaminated, but I can't see any signs of leakage. Let me know what you guys think.
FYI: I have checked the torque and fitting of all the barbs/olives and brake hose fittings, definitely not the issue
While bleeding, have you also pushed pistons in and out trying to free any possible trapped air behind them?
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I...
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I picked up my set last August and had run them without complaint until the other week when my front lever started pulling much farther into the bar about 2 minutes into a mild descent. I inspected the brakes and couldn't find any sign of fluid leaks or anything of the sort. I subsequently performed a gravity bleed and had the brakes feeling new again. Next ride, exact same issue! At this point, I was sure there had to be a leak somewhere, so, rebled them and strapped the lever to the bar to pressure test overnight and sure enough, they held perfect pressure. I did notice that when I opened the reservoir to bleed them after the rides, they did seem to be down a small amount of fluid and I was also able to "pump" them back up to a normal feeling (similar to Shimano's wandering bite problem). My conclusion is that there must be a leak somewhere in the system, just not exactly sure how to deduce that problem yet. I think it must be up at the lever as the pads and rotors are not being contaminated, but I can't see any signs of leakage. Let me know what you guys think.
FYI: I have checked the torque and fitting of all the barbs/olives and brake hose fittings, definitely not the issue
I had the same symptoms on my rear one, after many bleeds still was getting the lever to the bar on long descents, also some crashes. Then I read somewhere that some batches of T4V4 had some tolerance issues at the master cylinder, probably a seal or something like that, sent the brakes back to hope and they fixed them and sent them back, no problem since
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I...
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I picked up my set last August and had run them without complaint until the other week when my front lever started pulling much farther into the bar about 2 minutes into a mild descent. I inspected the brakes and couldn't find any sign of fluid leaks or anything of the sort. I subsequently performed a gravity bleed and had the brakes feeling new again. Next ride, exact same issue! At this point, I was sure there had to be a leak somewhere, so, rebled them and strapped the lever to the bar to pressure test overnight and sure enough, they held perfect pressure. I did notice that when I opened the reservoir to bleed them after the rides, they did seem to be down a small amount of fluid and I was also able to "pump" them back up to a normal feeling (similar to Shimano's wandering bite problem). My conclusion is that there must be a leak somewhere in the system, just not exactly sure how to deduce that problem yet. I think it must be up at the lever as the pads and rotors are not being contaminated, but I can't see any signs of leakage. Let me know what you guys think.
FYI: I have checked the torque and fitting of all the barbs/olives and brake hose fittings, definitely not the issue
I had a set that did that on one side - would feel great and then spongy, pump it back up to be great, then spongy.
Would definitely hit up Hope and see what they have to say, they were very responsive when I contacted them including being willing to hop on a call and check through various things that might be causing the issue if the diaphragm didn't cure the issue.
When I interviewed SRAM's Chris Mandell for the DB8 review he told me to be pretty hands off with pistons, to not even clean the pistons unless I absolutely had to, because it's easy to dry out or contaminate the pistons and seals if you're poking around too much. The official line is to do the piston massage as a way to evenly lubricate pistons and reset seal friction, and otherwise don't touch them.
Not cleaning them seems odd to me, because I feel like every bleed I've ever seen starts and ends with hosing the caliper off with Isopropyl alcohol, but maybe SRAM knows something I don't? The cynical take would be that SRAM doesn't trust home mechanics to not contaminate their brake pads by failing to clean the excess mineral oil off caliper surfaces after a q-tip job.
Question for the panel: what's the consensus on cleaning and lubing SRAM pistons with mineral oil and a q-tip? Inspired by this SRAM "Sticky Pistons...
When I interviewed SRAM's Chris Mandell for the DB8 review he told me to be pretty hands off with pistons, to not even clean the pistons unless I absolutely had to, because it's easy to dry out or contaminate the pistons and seals if you're poking around too much. The official line is to do the piston massage as a way to evenly lubricate pistons and reset seal friction, and otherwise don't touch them.
Not cleaning them seems odd to me, because I feel like every bleed I've ever seen starts and ends with hosing the caliper off with Isopropyl alcohol, but maybe SRAM knows something I don't? The cynical take would be that SRAM doesn't trust home mechanics to not contaminate their brake pads by failing to clean the excess mineral oil off caliper surfaces after a q-tip job.
I've always cleaned SRAM pistons and massaged them as regular service. A simple wipe with q-tips and some iso alcohol. I can see the issue of using fluid on the extended piston intorducing dirt into the system and the massage would seem to accomplish the same thing.
I don’t know about all of that I just know that the more outstretched your index finger is, the more strain there will be on your forearm. Being able to ride with that index finger curled closer to the bar reduces that strain immensely.
190 kitted out and my Guide RSCs are right at the limit. I just love the ergonomics, though.
Yeah that's brake setup 101 IMO, people who run their brakes half a mile away from their bars are cooked.
I wouldn’t put my 45kg beginner rider wife on those things
Hayes Dominion A4 weirdness - looking for advice.
One of my dominions keeps losing bite point. I bled the brake it an the bite point was feeling sharp and where I wanted it, after a couple rides the bite point kept pulling in towards the bars further and further to the point where the lever was pulling all the way into the bar. I did another lever bleed to get the air out of the system, which returned the bite point to perfect. Riding around the parking lot it felt mint. Again on the first ride the bite point completely disappeared. It seems like there is an air gap somewhere into the system, but no brake fluid is coming out of any of the ports or elsewhere. The system seems completely sealed so far as I can tell. Looking for advice - front brake lever pulling into the bar is scary! Thanks
Likely that there is air elsewhere trapped in the system. You may need to do a full bleed instead of just a lever bleed.
Dislikes very pinkbike, it’s a brake nerds thread not a crap brakes, let’s be honest with ourselves
As Jaloypj said, do a full bleed. Also, double check that the hose nut at the lever is fully torqued. When I had them, at least once I thought I had it tightened up enough, but the bleed felt like crap. I put an actual torque wrench to bring it up to whatever value they say, and ended up turning the nut like at least 2 full rotations more, and the problem went away.
Clean the calipers really, really well and make sure they are completely dry. Go ride and inspect afterwords to verify that they are not leaking anywhere. I have both heard and seen that the newer Dominions have been prone to leak which can cause issues similar to a bad bleed even when there is no air in the system. But first make sure that there is no air in the system, full bleed and work the pistons out to make sure nothing is trapped behind them. Hayes has been quite good, from what I have heard with the warranty process if that is the issue, leaking.
https://youtu.be/yKDVB37AOic?si=UjivGrJdZkxmFB-Y Interesting video regarding brembo’s DFM methods for F1 brakes. I’ve heard some anecdotes about how F1 brake fluid is vastly superior to DOT fluid, but after looking at the composition details it’s still poly- glycol ether based fluid, same as DOT. Will try to get my hands on some as I have some connections to a LMP race team with a few Rolex wins.
I have a feeling that as I have theorized, system fluid pressure is key to management of the fluids boil point, and the idea that using phenolic or other thermoplastic inserts are more armchair theory vs having any practical application in high performance applications especially considering that F1 or LMP car brakes operate at temperatures that no mtb brake would ever hit, >800c. I have a few phd chem eng. at work and will have to pick their brains on the idea of localized boiling and if that’s an actual fluid phenomenon that could cause degradation but I have a feeling that the heat flux isn’t high enough to cause that to happen even if the thermodynamics support the idea. Pretty wild to see how little material is used regardless of the forced induction aero being used for brake cooling. Interesting stuff nonetheless.
Would be pretty cool to build a thermal test system to subject heat to pistons and measure the fluid pressure loss based on various line pressures. Based on the fact that most fluids exhibit similar characteristics where as heat increases the inverse of the bulk modulus of the fluid decreases, thus compressibility increases, giving you some sort of predictability in the system response. It wouldn’t be that hard to measure the thermal effect in a system once you a lookup table to account for the density change.
As others have said, redo a fresh bleed and check all the fittings.
It sounds like you have a leak somewhere since as you add pressure during use the levers creep closer to the bar.
Which brake and which bike do you have? A loss like that points to a leak in the system. Possibly the reservoir bladder, possibly the hose. As others have said, check torque on the hose fittings, but there's a quick diagnostic you can do to determine if it's an internal rupture on your hose. Pull the wheel out of the drops and insert a pad spacer. Set the lever up into the bleed position and attach your syringe to the lever without the plunger in it. you'll need to keep that syringe vertical, so you'll need to figure that out. With the syringe vertical, add a bit of fluid to it, maybe a cm or so. Slowly and lightly pull the lever. This is key. If the lever goes to the bar, watch the fluid level in the syringe. and pull it the same way a few more times. If you notice the fluid level is dropping but not returning to the same height, stop pulling the lever. This is indicating you have an internal rupture in your brake line and it needs to be replaced. This is generally not a warrantable condition as it's related to damage, be it form a crash or poor hose routing. Most bikes have routing down pat these days, but I wouldn't say all do, so if it's the rear brake I'd look where you could make the hose arc smoother.
If the lever is going to the bar but the fluid level is maintaining volume, that indicates a MC piston seal failure. Warranty that bugger.
If the lever firms up, I would inspect the bladder. I've seen brands develop slight tears at the seal surface that would not allow fluid to leak but in use would allow the res to ingest a smidge of air or overzealous syringe use causing the diaphragm to pop out of its sealing surface resulting in the same slow air ingestion.
Super curious about today's BOTD brake set up. Maven calipers matched to Lewis levers. Say what you will about Lewis, but their levers feel really good. Very light and smooth. I'd definitely be interested to see how much of a faff it was pairing them, or if it went pretty smoothly.
When cleaning contaminated rotors I boil a pan of water and dish soap on the hob (use an old pan, or feel the wrath of your partner) and leave the rotor in there a few mins bubbling away. Got the tip from the yeti race team mechanic years ago.
When you say another bleed to get air out of the system, did you actually pull air out? Or was it just a general term?
If you are sure sure sure there is no more air while doing a bleed and then you have air in the system the next time you bleed, you have a leak somewhere. I'd do the things others have mentioned.
Regarding the nut, thanks for that one, I have code rscs that seem to be pulling some air slowly (also have a wandering bite point a while after a bleed) and is for sure a very easy thing to check. The old set I had (that GF uses) still functions flawlessly and it's been in use since 2019, had two bleeds and then a full rebuild in 2024.
The 800degC temp is the rotor to pad contact. They make sure to both keep them warm enough but at the same time have enough cooling. As you can see in the video, they take away everything from the caliper they can. This is for weight savings (unsprung mass and all) bu to also bring the fluid as close as possible to the cooling air. So much so they have cooling fins, ribs and barbs to ensure the caliper itself is cooled. So caliper and by extension oil is cooled, pad and rotor cooled, but kept warm enough.
As for System pressures and boiling prevention, all is fine and well as long as you have said pressure. QED PWR nuclear reactors where water is under 150 bar to prevent boiling at 350°C. But as soon as you take away the pressure, the fluid will boil. With brakes that happens every time you let off them.
Not Mavens, but I'm using Lewis masters paired with Magura calipers. I'd been intrigued about eeking more power out of the stock LH4 I was initially using. The LH4 caliper uses 17 & 14 mm pistons, so I gained quite a bit with the quad 17 mm pistons in the Magura
I was thinking about pairing them with a Cura 4 caliper or a Maven base caliper, but was unsure if the 18 mm pistons would mean I'd have too much lever throw before the pads would contact and didn't want to risk it. Plus I found the Magura calipers for cheap
My Lewgura set up has more throw than stock, but the power bump more than makes up for it, they have immense power and a really nice light lever feel
Getting some pretty horrendous pad rattle coming from my shigura brakes - have been running the same setup for ~18 months now but it’s only been over the last 3 months or so that I’ve been getting it since buying a fresh set for a new bike.
Using Galfer pro pads (which I’ve always used) - wonder if I’ve got a bad batch in terms of tolerances or the backing material isn’t working well with the magnetic piston?
Either way it’s driving me mental, brand new bikes with new brakes sounding like a filing cabinet being pushed off a cliff through any sort of rough corner. In a straight line it’s not quite as bad.
Anything I can try before just buying mavens?
trickstuff power or sinter pads, one piece per side rather than 4, never had any issue or noise with either
This seems to be a galfer thing with their springs. Try bending the tangs of the pad spring into the sides of the pads so that they're held more tightly in place I.e. "preloading" the pad spring. Just be careful to keep the tangs flat with the pad backing and stop them sticking out into the rotors when the pads wear down.
I usually do this before fitting new pads as the rattle drives me nuts if I don't.
The galfer pads are often a little bit short in the length department, They rattle Bad in shimano's and gets worse as it wears the caliper.
Opening the spring helps alot.
It's for a magura brake unfortunately so there's no spring involved, just magnets!
Will try the one piece trickstuff pads
Hey hey folks, having an interesting conundrum with my Hope T4 V4's and am interested to see if any of you have had similar issues. I picked up my set last August and had run them without complaint until the other week when my front lever started pulling much farther into the bar about 2 minutes into a mild descent. I inspected the brakes and couldn't find any sign of fluid leaks or anything of the sort. I subsequently performed a gravity bleed and had the brakes feeling new again. Next ride, exact same issue! At this point, I was sure there had to be a leak somewhere, so, rebled them and strapped the lever to the bar to pressure test overnight and sure enough, they held perfect pressure. I did notice that when I opened the reservoir to bleed them after the rides, they did seem to be down a small amount of fluid and I was also able to "pump" them back up to a normal feeling (similar to Shimano's wandering bite problem). My conclusion is that there must be a leak somewhere in the system, just not exactly sure how to deduce that problem yet. I think it must be up at the lever as the pads and rotors are not being contaminated, but I can't see any signs of leakage. Let me know what you guys think.
FYI: I have checked the torque and fitting of all the barbs/olives and brake hose fittings, definitely not the issue
Not claiming to have any sort of magic solution, but if the increase in lever throw followed a sustained pull (for example, on the steepest part of the trail) then it could be a cracked inner liner in the hose. That can lead to fluid leaking into the braided reinforcement layer, without any visual indicator, other than perhaps a slight bulge in the outer polymer layer. Even weirder, the elasticity of the outer polymer can gradually squeeze most of the fluid back through the crack, into the inner liner, leaving no evidence if you don't catch it in the heat of the moment.
Normally, the easy test for this is, while the bike is at rest, simply to squeeze the lever so the pads engage the rotor for an extended period, and see if the lever engagement point gradually creeps inward toward the bar. You have already essentially done this though, by strapping the lever to the bar overnight, and it doesn't sound like it crept in (unless you had it close to bottoming under the strap pressure and therefore couldn't notice the slight additional movement to a fully bottomed position when you checked it the next day). One possibility that occurred to me is that strapping the levers down is totally static, whereas, since it is the front brake, that hose is flexing quite a bit as the fork cycles on the descent. If you had a hairline crack, it might only open when the hose is in a flexed condition, so you may want to push on the fork repeatedly while squeezing the lever, in case hose flex opens up the crack allowing you to replicate the problem.
If that's not it, I think you're right on with the thought of looking to the lever as the likely culprit. If you had fluid blowing past the M/C seal, then that could cause the problem, but why that would only happen after 2min of descending is non-obvious to me.
While bleeding, have you also pushed pistons in and out trying to free any possible trapped air behind them?
I had the same symptoms on my rear one, after many bleeds still was getting the lever to the bar on long descents, also some crashes. Then I read somewhere that some batches of T4V4 had some tolerance issues at the master cylinder, probably a seal or something like that, sent the brakes back to hope and they fixed them and sent them back, no problem since
I had a set that did that on one side - would feel great and then spongy, pump it back up to be great, then spongy.
Contacted Hope and they recommended changing out the diaphragm (https://www.hopetech.com/_repository/1/documents/Hope_TECH_4_Assembly.pdf HPSP405) which was pretty inexpensive and that cleared the issue.
Would definitely hit up Hope and see what they have to say, they were very responsive when I contacted them including being willing to hop on a call and check through various things that might be causing the issue if the diaphragm didn't cure the issue.
Question for the panel: what's the consensus on cleaning and lubing SRAM pistons with mineral oil and a q-tip? Inspired by this SRAM "Sticky Pistons" thread on here, and this video: https://www.youtube.com/watch?v=AY80Zt47M3A
When I interviewed SRAM's Chris Mandell for the DB8 review he told me to be pretty hands off with pistons, to not even clean the pistons unless I absolutely had to, because it's easy to dry out or contaminate the pistons and seals if you're poking around too much. The official line is to do the piston massage as a way to evenly lubricate pistons and reset seal friction, and otherwise don't touch them.
Not cleaning them seems odd to me, because I feel like every bleed I've ever seen starts and ends with hosing the caliper off with Isopropyl alcohol, but maybe SRAM knows something I don't? The cynical take would be that SRAM doesn't trust home mechanics to not contaminate their brake pads by failing to clean the excess mineral oil off caliper surfaces after a q-tip job.
I've always cleaned SRAM pistons and massaged them as regular service. A simple wipe with q-tips and some iso alcohol. I can see the issue of using fluid on the extended piston intorducing dirt into the system and the massage would seem to accomplish the same thing.
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