bought a second set of mavens because my bike fell off a bus, so another meticulous sram bleed. How do you prevent the bleeding edge port pulling...
bought a second set of mavens because my bike fell off a bus, so another meticulous sram bleed.
How do you prevent the bleeding edge port pulling air when doing a vacuum bleed on the caliper? Most of the time it works fine but sometimes it’s jacuzzi levels of bubbles coming out and they end up being pushed into the caliper when I release the syringe plunger.
I do 1.5 full rotations from closed on the screw.
Try opening it less, I usually aim for about half a turn at most. I think you might be pulling in air around the thread when you open 1.5 turns.
The instructions for code are one full turn. There is an oring on the fitting, but yeah, who knows how well it seals. Plus the interface from the syringe to the port.
Echoing what others have said, I only do 1 full turn of the Bleeding Edge fitting. Also always double check the fittings' connections to the hoses are snug and that no air is getting sucked in around loose fittings. One final trick is to degas the fluid in the lever syringe by clamping the hose off before you connect, and pulling on the syringe handle a few times to pull gas out of suspension.
When I bleed my Mavens with the vacuum technique, there are a LOT of bubbles that come up initially. I just keep repeating the process until eventually none come out. It takes a long time if you're really obsessive like me, like over 30-45min per brake, but you can be sure that you have a really good bleed at that point. I'd guess when I shortened my front hose the last time I probably did the cycle over 30 times.
I think I already said I basically only do vacuum bleeds on Codes lately, but I am wondering if it's not causing more problems than not by pulling air in past the master cylinder seals (they are usually one way seals.
One way to do it would be to have a vacuum machine set to something like 0,8 bar to not depressurise the system too much.
was the lever throw shorter on DRT/MAXIMA mix VS full Maxima? i guess on the 612 it has to be due to the calipers
Not sure, but I don't think there should be. The levers are slightly different (and the Maxima is longer), but just the position of both bearings at the lever shouldn't change the freestroke. Basically the Maxima lever vs DRT lever gives you a tiny bit more power in exchange for a slightly softer lever feel.
But yea, DRT with 612 calipers is the best of both worlds, quite firm lever feel from DRT, short free stroke because of the caliper, and power that is about the same as full on MXA but feels better to use. I was actually tempted buying another set of calipers to replace the MXA calipers on the ebike ...
Hey guys, are the lever/master cyclinder assemblies that came on the TRP G-spec DH brakes the same as the current TRP DH-R EVOS? They look the same but I can’t be certain.
bought a second set of mavens because my bike fell off a bus, so another meticulous sram bleed. How do you prevent the bleeding edge port pulling...
bought a second set of mavens because my bike fell off a bus, so another meticulous sram bleed.
How do you prevent the bleeding edge port pulling air when doing a vacuum bleed on the caliper? Most of the time it works fine but sometimes it’s jacuzzi levels of bubbles coming out and they end up being pushed into the caliper when I release the syringe plunger.
Try opening it less, I usually aim for about half a turn at most. I think you might be pulling in air around the thread when...
Try opening it less, I usually aim for about half a turn at most. I think you might be pulling in air around the thread when you open 1.5 turns.
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the tutorial after the first time.
My process (from fresh) was:
- degas fluid in the syringes
- do the standard procedure, pushing and pulling fluid through the system though I generally find that pulling a bit to create negative pressure then pushing on the other syringe to get the bubbles out with higher fluid speed nets the best results
- close caliper port but don’t disconnect syringe
- vacuum bleed the lever
- pressurize lever a tiny bit, unscrew syringe and close lever
- open caliper port, vacuum bleed caliper, pressurize caliper (not just equalize, put some juice into it), then close
- piston massage with two discs
- pull levers down over night with ski straps, then repeat bleed process
Got them feeling great right off the get go. Very time consuming but worth it. The previous set of mavens took 4-5 bleeds to get them feel right and I assume I’ll have to bleed these ones again after two days at the bikepark or so, but I feel like this is a better starting point than I had when i only followed the standard sram bleed procedure on my first set.
one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with.
Hey guys, are the lever/master cyclinder assemblies that came on the TRP G-spec DH brakes the same as the current TRP DH-R EVOS? They look the...
Hey guys, are the lever/master cyclinder assemblies that came on the TRP G-spec DH brakes the same as the current TRP DH-R EVOS? They look the same but I can’t be certain.
No. Different MC piston diameter, 10mm for the Quadiem/G-Spec DHR and 9mm for the DH-R EVO. The older models had slightly fatter lever blades with regressive leverage curve.
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the...
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the tutorial after the first time.
My process (from fresh) was:
- degas fluid in the syringes
- do the standard procedure, pushing and pulling fluid through the system though I generally find that pulling a bit to create negative pressure then pushing on the other syringe to get the bubbles out with higher fluid speed nets the best results
- close caliper port but don’t disconnect syringe
- vacuum bleed the lever
- pressurize lever a tiny bit, unscrew syringe and close lever
- open caliper port, vacuum bleed caliper, pressurize caliper (not just equalize, put some juice into it), then close
- piston massage with two discs
- pull levers down over night with ski straps, then repeat bleed process
Got them feeling great right off the get go. Very time consuming but worth it. The previous set of mavens took 4-5 bleeds to get them feel right and I assume I’ll have to bleed these ones again after two days at the bikepark or so, but I feel like this is a better starting point than I had when i only followed the standard sram bleed procedure on my first set.
one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with.
That is a seriously intensive bleed process, but I'm glad you found something that works, as it sounds like getting a good bleed on Mavens is a bit tricky.
I'm curious about this statement: "one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with."
Are you saying that, after bleeding the brake, you squirt the excess oil back into the bottle, and when you do so it foams? If so, are you putting the syringe tip/hose below the surface before pushing the plunger? If not, then I would expect the stream coming out of the syringe to pull some surrounding air with it when it breaks the surface of the oil in the bottle, which could make a foam/bubbles, but if you are putting it below the surface, then there isn't really an opportunity for air entrainment from the stream of oil.
I have heard some pretty wild claims about how much dissolved air is in brake fluid (this person was suggesting something like 10%), with the suggestion being that it comes out of solution over time leading to mysterious bubbles on what should have been near perfect bleeds. What you're describing with the oil in the bottle sounds almost like if there was such a huge amount of air that it's like carbonated water, where at rest it has few/no bubbles, but if you agitate it then bubbles appear out of nowhere. If your oil had that much gas in it, it really makes me wonder if pulling a quick vacuum in the syringe would be sufficient to de-gas it, or if you'd need to put the oil in some sort of vacuum bottle and let it sit for hours.
For the record, I don't know if the above stat on dissolved air/gas is accurate, and I would love it if anyone who really knows the ins and outs of hydraulic fluid specs could confirm the reality of the situation, because it would really help explain a lot of these mystery bleeds that go bad out of nowhere.
Hey guys, are the lever/master cyclinder assemblies that came on the TRP G-spec DH brakes the same as the current TRP DH-R EVOS? They look the...
Hey guys, are the lever/master cyclinder assemblies that came on the TRP G-spec DH brakes the same as the current TRP DH-R EVOS? They look the same but I can’t be certain.
No. Different MC piston diameter, 10mm for the Quadiem/G-Spec DHR and 9mm for the DH-R EVO. The older models had slightly fatter lever blades with...
No. Different MC piston diameter, 10mm for the Quadiem/G-Spec DHR and 9mm for the DH-R EVO. The older models had slightly fatter lever blades with regressive leverage curve.
Thought this group would get a laugh out of this. I was inspired by Troy Brosnan and all our brake nerd conversations in this thread, and did something weird on my gravel bike. It's an old entry level QR disk CX bike from 2014 that I picked up for $400, so it isn't the coolest gravel bike ever but it's fine and it was a great deal. Anyway it came with mechanical disks, and the power and modulation was underwhelming, especially from the rear brake. I upgraded to compressionless brake housing and bumped up the rear rotor to 160mm with metallic pads, but it wasn't quite what I was hoping for and everytime I pulled the brakes they felt a little vague and underwhelming. The rear brake especially would fade hard on long descents, which left me doing more braking on the front, which is super sketchy on questionable surfaces like gravel or wet asphalt.
Not anymore. I had a random 180mm HS2 rotor (2.0mm thick) sitting around and an old +40mm post mount adapter, so now I'm running the Troy Brosnan/Martin Maes big-rotor-in-the-back setup on my gravel bike. Feels great. The rear brake feels every bit as grabby as the front, and they feel balanced, plus the rear brake doesn't fade anymore (not yet anyway). Had to ditch the Avid CPS conical washers to get the caliper where it needed to be, but who cares. Bike rips now, and it's crazy how much firmer the rear lever feels now. It means the mechanical disks are feeling fine, and no leaky pistons or contaminated pads! Once again, borrowing MTB tech to make road bikes more fun.
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the...
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the tutorial after the first time.
My process (from fresh) was:
- degas fluid in the syringes
- do the standard procedure, pushing and pulling fluid through the system though I generally find that pulling a bit to create negative pressure then pushing on the other syringe to get the bubbles out with higher fluid speed nets the best results
- close caliper port but don’t disconnect syringe
- vacuum bleed the lever
- pressurize lever a tiny bit, unscrew syringe and close lever
- open caliper port, vacuum bleed caliper, pressurize caliper (not just equalize, put some juice into it), then close
- piston massage with two discs
- pull levers down over night with ski straps, then repeat bleed process
Got them feeling great right off the get go. Very time consuming but worth it. The previous set of mavens took 4-5 bleeds to get them feel right and I assume I’ll have to bleed these ones again after two days at the bikepark or so, but I feel like this is a better starting point than I had when i only followed the standard sram bleed procedure on my first set.
one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with.
That is a seriously intensive bleed process, but I'm glad you found something that works, as it sounds like getting a good bleed on Mavens is...
That is a seriously intensive bleed process, but I'm glad you found something that works, as it sounds like getting a good bleed on Mavens is a bit tricky.
I'm curious about this statement: "one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with."
Are you saying that, after bleeding the brake, you squirt the excess oil back into the bottle, and when you do so it foams? If so, are you putting the syringe tip/hose below the surface before pushing the plunger? If not, then I would expect the stream coming out of the syringe to pull some surrounding air with it when it breaks the surface of the oil in the bottle, which could make a foam/bubbles, but if you are putting it below the surface, then there isn't really an opportunity for air entrainment from the stream of oil.
I have heard some pretty wild claims about how much dissolved air is in brake fluid (this person was suggesting something like 10%), with the suggestion being that it comes out of solution over time leading to mysterious bubbles on what should have been near perfect bleeds. What you're describing with the oil in the bottle sounds almost like if there was such a huge amount of air that it's like carbonated water, where at rest it has few/no bubbles, but if you agitate it then bubbles appear out of nowhere. If your oil had that much gas in it, it really makes me wonder if pulling a quick vacuum in the syringe would be sufficient to de-gas it, or if you'd need to put the oil in some sort of vacuum bottle and let it sit for hours.
For the record, I don't know if the above stat on dissolved air/gas is accurate, and I would love it if anyone who really knows the ins and outs of hydraulic fluid specs could confirm the reality of the situation, because it would really help explain a lot of these mystery bleeds that go bad out of nowhere.
There's definitely more air dissolved in mineral oil than you'd think. I can take a container of mineral oil that's been sitting (not shaken up), draw 2/3 a syringe, clamp off the hose, then pull the syringe handle and get a pretty significant amount of bubbles appearing from the oil in the syringe body.
I basically just follow SRAM's Maven bleed process exactly and have had good results. It just takes a long time (lots of cycles) to vacuum out all the air. I didn't bother with the lever strapped to the bar thing because whenever I tried that on my Dominions, it only firmed up the lever feel for the first run.
I don't have a strong preference for mineral oil vs. DOT, but it does seem to me (anecdotally) that air dissolves in the mineral oil more readily. On the other hand, if your seals are good it's not too difficult to vacuum it out, whereas there's no good way to remove water moisture that gets into DOT. I'll probably replace my second set of Dominions with Mavens, but it's not because I'm super passionate about the mineral oil vs. DOT debate, just that I prefer the feel/consistency of them.
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the...
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the tutorial after the first time.
My process (from fresh) was:
- degas fluid in the syringes
- do the standard procedure, pushing and pulling fluid through the system though I generally find that pulling a bit to create negative pressure then pushing on the other syringe to get the bubbles out with higher fluid speed nets the best results
- close caliper port but don’t disconnect syringe
- vacuum bleed the lever
- pressurize lever a tiny bit, unscrew syringe and close lever
- open caliper port, vacuum bleed caliper, pressurize caliper (not just equalize, put some juice into it), then close
- piston massage with two discs
- pull levers down over night with ski straps, then repeat bleed process
Got them feeling great right off the get go. Very time consuming but worth it. The previous set of mavens took 4-5 bleeds to get them feel right and I assume I’ll have to bleed these ones again after two days at the bikepark or so, but I feel like this is a better starting point than I had when i only followed the standard sram bleed procedure on my first set.
one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with.
That is a seriously intensive bleed process, but I'm glad you found something that works, as it sounds like getting a good bleed on Mavens is...
That is a seriously intensive bleed process, but I'm glad you found something that works, as it sounds like getting a good bleed on Mavens is a bit tricky.
I'm curious about this statement: "one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with."
Are you saying that, after bleeding the brake, you squirt the excess oil back into the bottle, and when you do so it foams? If so, are you putting the syringe tip/hose below the surface before pushing the plunger? If not, then I would expect the stream coming out of the syringe to pull some surrounding air with it when it breaks the surface of the oil in the bottle, which could make a foam/bubbles, but if you are putting it below the surface, then there isn't really an opportunity for air entrainment from the stream of oil.
I have heard some pretty wild claims about how much dissolved air is in brake fluid (this person was suggesting something like 10%), with the suggestion being that it comes out of solution over time leading to mysterious bubbles on what should have been near perfect bleeds. What you're describing with the oil in the bottle sounds almost like if there was such a huge amount of air that it's like carbonated water, where at rest it has few/no bubbles, but if you agitate it then bubbles appear out of nowhere. If your oil had that much gas in it, it really makes me wonder if pulling a quick vacuum in the syringe would be sufficient to de-gas it, or if you'd need to put the oil in some sort of vacuum bottle and let it sit for hours.
For the record, I don't know if the above stat on dissolved air/gas is accurate, and I would love it if anyone who really knows the ins and outs of hydraulic fluid specs could confirm the reality of the situation, because it would really help explain a lot of these mystery bleeds that go bad out of nowhere.
There's definitely more air dissolved in mineral oil than you'd think. I can take a container of mineral oil that's been sitting (not shaken up), draw...
There's definitely more air dissolved in mineral oil than you'd think. I can take a container of mineral oil that's been sitting (not shaken up), draw 2/3 a syringe, clamp off the hose, then pull the syringe handle and get a pretty significant amount of bubbles appearing from the oil in the syringe body.
I basically just follow SRAM's Maven bleed process exactly and have had good results. It just takes a long time (lots of cycles) to vacuum out all the air. I didn't bother with the lever strapped to the bar thing because whenever I tried that on my Dominions, it only firmed up the lever feel for the first run.
I don't have a strong preference for mineral oil vs. DOT, but it does seem to me (anecdotally) that air dissolves in the mineral oil more readily. On the other hand, if your seals are good it's not too difficult to vacuum it out, whereas there's no good way to remove water moisture that gets into DOT. I'll probably replace my second set of Dominions with Mavens, but it's not because I'm super passionate about the mineral oil vs. DOT debate, just that I prefer the feel/consistency of them.
From my experience, clamping the levers to the bar is only useful if you lever bleed after. Just does a solid job of bringing all the bubbles to the top of the system
The bubbles when creating a vacuum, is it air trapped in the Oil, or the oil boiling due to lower pressure/vacuum?I know water boils at lower...
The bubbles when creating a vacuum, is it air trapped in the Oil, or the oil boiling due to lower pressure/vacuum?
I know water boils at lower temperatures in lower pressures, and assume the same thing happens with other liquids.
Shimano specifies a boiling point of >200°C @ 1 atm. Unfortunately, the vapour pressure is listed as "data not available", but I'd be surprised if you could boil it under whatever vacuum you can produce in a plastic syringe without an external source of heat. The last time I did that to Shimano mineral oil nothing happened, anyway.
Okay, serious question since y'all are discussing syringes, vacuums, and de-gasing brake fluid: do you have any tips or tricks for smoothly drawing fluid into a syringe without introducing a bunch of air bubbles?
I might just have a really old syringe with an old/bad/sticky seal, but it doesn't draw smoothly and it sticks, then skips and sucks in a bunch of air whenever I pull fluid. Very turbulent, not laminar flow. Any advice appreciated, even if it's just "throw your syringe away."
Plunger out, finger over the end and pour the fluid in, plunger back in a bit, flip it over and push the air out. Or do it you’re usual way and leave it for half an hour and let it all settle.
Okay, serious question since y'all are discussing syringes, vacuums, and de-gasing brake fluid: do you have any tips or tricks for smoothly drawing fluid into a...
Okay, serious question since y'all are discussing syringes, vacuums, and de-gasing brake fluid: do you have any tips or tricks for smoothly drawing fluid into a syringe without introducing a bunch of air bubbles?
I might just have a really old syringe with an old/bad/sticky seal, but it doesn't draw smoothly and it sticks, then skips and sucks in a bunch of air whenever I pull fluid. Very turbulent, not laminar flow. Any advice appreciated, even if it's just "throw your syringe away."
From my experience, the bleed kits with the hard syringes like the ones in the Sram Pro kit are a huge improvement.
I believe Park and Jagwire use them in their kits as well.
Okay, serious question since y'all are discussing syringes, vacuums, and de-gasing brake fluid: do you have any tips or tricks for smoothly drawing fluid into a...
Okay, serious question since y'all are discussing syringes, vacuums, and de-gasing brake fluid: do you have any tips or tricks for smoothly drawing fluid into a syringe without introducing a bunch of air bubbles?
I might just have a really old syringe with an old/bad/sticky seal, but it doesn't draw smoothly and it sticks, then skips and sucks in a bunch of air whenever I pull fluid. Very turbulent, not laminar flow. Any advice appreciated, even if it's just "throw your syringe away."
Yeah, as someone else already said, high quality syringes like in the Sram kit make a huge difference for a few reasons. One is that the bore of the syringe will start, and stay, more round than the more flexible plastic on your garden variety medical style ones. Another big thing, particularly when pulling a vacuum, is that the pieces of the plunger are all firmly affixed, usually screwed together, with an o-ring (or similar) seal, whereas on the medical style ones, the whole rubber tip (which forms the seal) of the plunger is just pressed on to the plastic part, and if you try to apply too much force in a pulling direction, to create a vacuum, the rubber tip will pull right off of the plastic portion.
To combat the stick slip, move it around dry first. Or pull oil in, flush it back out and then pull it back in. That way the seals will be lubricated a bit.
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the...
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the tutorial after the first time.
My process (from fresh) was:
- degas fluid in the syringes
- do the standard procedure, pushing and pulling fluid through the system though I generally find that pulling a bit to create negative pressure then pushing on the other syringe to get the bubbles out with higher fluid speed nets the best results
- close caliper port but don’t disconnect syringe
- vacuum bleed the lever
- pressurize lever a tiny bit, unscrew syringe and close lever
- open caliper port, vacuum bleed caliper, pressurize caliper (not just equalize, put some juice into it), then close
- piston massage with two discs
- pull levers down over night with ski straps, then repeat bleed process
Got them feeling great right off the get go. Very time consuming but worth it. The previous set of mavens took 4-5 bleeds to get them feel right and I assume I’ll have to bleed these ones again after two days at the bikepark or so, but I feel like this is a better starting point than I had when i only followed the standard sram bleed procedure on my first set.
one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with.
That is a seriously intensive bleed process, but I'm glad you found something that works, as it sounds like getting a good bleed on Mavens is...
That is a seriously intensive bleed process, but I'm glad you found something that works, as it sounds like getting a good bleed on Mavens is a bit tricky.
I'm curious about this statement: "one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with."
Are you saying that, after bleeding the brake, you squirt the excess oil back into the bottle, and when you do so it foams? If so, are you putting the syringe tip/hose below the surface before pushing the plunger? If not, then I would expect the stream coming out of the syringe to pull some surrounding air with it when it breaks the surface of the oil in the bottle, which could make a foam/bubbles, but if you are putting it below the surface, then there isn't really an opportunity for air entrainment from the stream of oil.
I have heard some pretty wild claims about how much dissolved air is in brake fluid (this person was suggesting something like 10%), with the suggestion being that it comes out of solution over time leading to mysterious bubbles on what should have been near perfect bleeds. What you're describing with the oil in the bottle sounds almost like if there was such a huge amount of air that it's like carbonated water, where at rest it has few/no bubbles, but if you agitate it then bubbles appear out of nowhere. If your oil had that much gas in it, it really makes me wonder if pulling a quick vacuum in the syringe would be sufficient to de-gas it, or if you'd need to put the oil in some sort of vacuum bottle and let it sit for hours.
For the record, I don't know if the above stat on dissolved air/gas is accurate, and I would love it if anyone who really knows the ins and outs of hydraulic fluid specs could confirm the reality of the situation, because it would really help explain a lot of these mystery bleeds that go bad out of nowhere.
You can find the amount of dissolved gas in any fluid by looking up a table of the Ostwald coefficient for that particular fluid.
Mineral fluid has 10% from my memory. Most liquids have about 10% dissolved atmosphere in them at STP. Mixing fluids, almost like that of bleeding brakes can increase the dissolved gas in a system until the liquid has had time to reach atmospheric equilibration.
Degassing is critical in many industries even those that deal with fluid pressures well over 200ksi, Chromatography for instance. Dissolved air is not in-compressible, oil isn’t either but it’s isothermal compressibility coefficient is much, much lower than air. Removing the air will increase the bulk modulus of the fluid within the system.
Okay, serious question since y'all are discussing syringes, vacuums, and de-gasing brake fluid: do you have any tips or tricks for smoothly drawing fluid into a...
Okay, serious question since y'all are discussing syringes, vacuums, and de-gasing brake fluid: do you have any tips or tricks for smoothly drawing fluid into a syringe without introducing a bunch of air bubbles?
I might just have a really old syringe with an old/bad/sticky seal, but it doesn't draw smoothly and it sticks, then skips and sucks in a bunch of air whenever I pull fluid. Very turbulent, not laminar flow. Any advice appreciated, even if it's just "throw your syringe away."
I usually pour some fluid into a small dish, take the plunger out and wet it in the fluid before pulling fluid into it. When you're pulling fluid in, as long as you get the fitting below the surface you shouldn't be introducing any additional air.
Degassing thoroughly after is still the bane of my existence but I'm certain it makes a difference to the bleed.
Short note on my latest experience with the HS2 rotors. Run them on a pair of hayes dominion, brilliant never had to think about it.
Eventually bent and scratched my front disc. Swapped front an rear with my favourite discs, that I always believed had the most bite so far, galfer wave discs.
All good and such until I realized, the HS2 could potentially have even more bite than the galfer. Definately surpised me, because the wave discs always were a safe bet on aggressive braking and bite. props to sram then!
One thing that I thought about after watching the video, they started off copying Trickstuff "because that was the best idea" (or something like that).
I would probably put solid money that if they started copying SRAM or Shimano, they would have had lawyers or authorities banging on the door real fast telling them to stop screwing around, while there was probably close to no risk copying a very small brand from Germany. Not just "because TS are the best so let's copy them".
I understand they want to "hide" their past of copying TS (and the blatant DRT copy with the logo etched on it was just bad taste and bad manners), to avoid any confrontation, but at the same time you can't blame people from commenting all those "looks like a session" comments.
I do hope Trickstuff is going to improve upon the DRT or MXA, quite a lot to do that would be pretty easy (improve rollback, improve the top cap and membrane, ..), and I also hope Lewis will sort their QC (brakes are good, finish and sometimes quality control not so much, bit of hit and miss)
Try opening it less, I usually aim for about half a turn at most. I think you might be pulling in air around the thread when you open 1.5 turns.
The instructions for code are one full turn. There is an oring on the fitting, but yeah, who knows how well it seals. Plus the interface from the syringe to the port.
Echoing what others have said, I only do 1 full turn of the Bleeding Edge fitting. Also always double check the fittings' connections to the hoses are snug and that no air is getting sucked in around loose fittings. One final trick is to degas the fluid in the lever syringe by clamping the hose off before you connect, and pulling on the syringe handle a few times to pull gas out of suspension.
When I bleed my Mavens with the vacuum technique, there are a LOT of bubbles that come up initially. I just keep repeating the process until eventually none come out. It takes a long time if you're really obsessive like me, like over 30-45min per brake, but you can be sure that you have a really good bleed at that point. I'd guess when I shortened my front hose the last time I probably did the cycle over 30 times.
I think I already said I basically only do vacuum bleeds on Codes lately, but I am wondering if it's not causing more problems than not by pulling air in past the master cylinder seals (they are usually one way seals.
One way to do it would be to have a vacuum machine set to something like 0,8 bar to not depressurise the system too much.
Not sure, but I don't think there should be. The levers are slightly different (and the Maxima is longer), but just the position of both bearings at the lever shouldn't change the freestroke. Basically the Maxima lever vs DRT lever gives you a tiny bit more power in exchange for a slightly softer lever feel.
But yea, DRT with 612 calipers is the best of both worlds, quite firm lever feel from DRT, short free stroke because of the caliper, and power that is about the same as full on MXA but feels better to use. I was actually tempted buying another set of calipers to replace the MXA calipers on the ebike ...
Hey guys, are the lever/master cyclinder assemblies that came on the TRP G-spec DH brakes the same as the current TRP DH-R EVOS? They look the same but I can’t be certain.
Thanks I’ll give that a shot. I think I remember it being two full turns on the maven but might be completely wrong, haven’t watched the tutorial after the first time.
My process (from fresh) was:
- degas fluid in the syringes
- do the standard procedure, pushing and pulling fluid through the system though I generally find that pulling a bit to create negative pressure then pushing on the other syringe to get the bubbles out with higher fluid speed nets the best results
- close caliper port but don’t disconnect syringe
- vacuum bleed the lever
- pressurize lever a tiny bit, unscrew syringe and close lever
- open caliper port, vacuum bleed caliper, pressurize caliper (not just equalize, put some juice into it), then close
- piston massage with two discs
- pull levers down over night with ski straps, then repeat bleed process
Got them feeling great right off the get go. Very time consuming but worth it. The previous set of mavens took 4-5 bleeds to get them feel right and I assume I’ll have to bleed these ones again after two days at the bikepark or so, but I feel like this is a better starting point than I had when i only followed the standard sram bleed procedure on my first set.
one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with.
No. Different MC piston diameter, 10mm for the Quadiem/G-Spec DHR and 9mm for the DH-R EVO. The older models had slightly fatter lever blades with regressive leverage curve.
That is a seriously intensive bleed process, but I'm glad you found something that works, as it sounds like getting a good bleed on Mavens is a bit tricky.
I'm curious about this statement: "one problem I noticed is that with the tiny ports on the sram syringes the oil foams a lot when I put it back into the bottle so it seems there’s a lot of dissolved air in the fluid to begin with."
Are you saying that, after bleeding the brake, you squirt the excess oil back into the bottle, and when you do so it foams? If so, are you putting the syringe tip/hose below the surface before pushing the plunger? If not, then I would expect the stream coming out of the syringe to pull some surrounding air with it when it breaks the surface of the oil in the bottle, which could make a foam/bubbles, but if you are putting it below the surface, then there isn't really an opportunity for air entrainment from the stream of oil.
I have heard some pretty wild claims about how much dissolved air is in brake fluid (this person was suggesting something like 10%), with the suggestion being that it comes out of solution over time leading to mysterious bubbles on what should have been near perfect bleeds. What you're describing with the oil in the bottle sounds almost like if there was such a huge amount of air that it's like carbonated water, where at rest it has few/no bubbles, but if you agitate it then bubbles appear out of nowhere. If your oil had that much gas in it, it really makes me wonder if pulling a quick vacuum in the syringe would be sufficient to de-gas it, or if you'd need to put the oil in some sort of vacuum bottle and let it sit for hours.
For the record, I don't know if the above stat on dissolved air/gas is accurate, and I would love it if anyone who really knows the ins and outs of hydraulic fluid specs could confirm the reality of the situation, because it would really help explain a lot of these mystery bleeds that go bad out of nowhere.
For those of you who've run XT but then ran Saints, is there much power difference?
Thank you for this!
Thought this group would get a laugh out of this. I was inspired by Troy Brosnan and all our brake nerd conversations in this thread, and did something weird on my gravel bike. It's an old entry level QR disk CX bike from 2014 that I picked up for $400, so it isn't the coolest gravel bike ever but it's fine and it was a great deal. Anyway it came with mechanical disks, and the power and modulation was underwhelming, especially from the rear brake. I upgraded to compressionless brake housing and bumped up the rear rotor to 160mm with metallic pads, but it wasn't quite what I was hoping for and everytime I pulled the brakes they felt a little vague and underwhelming. The rear brake especially would fade hard on long descents, which left me doing more braking on the front, which is super sketchy on questionable surfaces like gravel or wet asphalt.
Not anymore. I had a random 180mm HS2 rotor (2.0mm thick) sitting around and an old +40mm post mount adapter, so now I'm running the Troy Brosnan/Martin Maes big-rotor-in-the-back setup on my gravel bike. Feels great. The rear brake feels every bit as grabby as the front, and they feel balanced, plus the rear brake doesn't fade anymore (not yet anyway). Had to ditch the Avid CPS conical washers to get the caliper where it needed to be, but who cares. Bike rips now, and it's crazy how much firmer the rear lever feels now. It means the mechanical disks are feeling fine, and no leaky pistons or contaminated pads! Once again, borrowing MTB tech to make road bikes more fun.
There's definitely more air dissolved in mineral oil than you'd think. I can take a container of mineral oil that's been sitting (not shaken up), draw 2/3 a syringe, clamp off the hose, then pull the syringe handle and get a pretty significant amount of bubbles appearing from the oil in the syringe body.
I basically just follow SRAM's Maven bleed process exactly and have had good results. It just takes a long time (lots of cycles) to vacuum out all the air. I didn't bother with the lever strapped to the bar thing because whenever I tried that on my Dominions, it only firmed up the lever feel for the first run.
I don't have a strong preference for mineral oil vs. DOT, but it does seem to me (anecdotally) that air dissolves in the mineral oil more readily. On the other hand, if your seals are good it's not too difficult to vacuum it out, whereas there's no good way to remove water moisture that gets into DOT. I'll probably replace my second set of Dominions with Mavens, but it's not because I'm super passionate about the mineral oil vs. DOT debate, just that I prefer the feel/consistency of them.
The bubbles when creating a vacuum, is it air trapped in the Oil, or the oil boiling due to lower pressure/vacuum?
I know water boils at lower temperatures in lower pressures, and assume the same thing happens with other liquids.
I'm thinking degassing brake fluid is placebo especially due the fact that fluid is always under positive pressure.
From my experience, clamping the levers to the bar is only useful if you lever bleed after. Just does a solid job of bringing all the bubbles to the top of the system
Shimano specifies a boiling point of >200°C @ 1 atm. Unfortunately, the vapour pressure is listed as "data not available", but I'd be surprised if you could boil it under whatever vacuum you can produce in a plastic syringe without an external source of heat. The last time I did that to Shimano mineral oil nothing happened, anyway.
You are no way boiling oil by depressurising it with a plastic syringe with a square seal.
Okay, serious question since y'all are discussing syringes, vacuums, and de-gasing brake fluid: do you have any tips or tricks for smoothly drawing fluid into a syringe without introducing a bunch of air bubbles?
I might just have a really old syringe with an old/bad/sticky seal, but it doesn't draw smoothly and it sticks, then skips and sucks in a bunch of air whenever I pull fluid. Very turbulent, not laminar flow. Any advice appreciated, even if it's just "throw your syringe away."
Plunger out, finger over the end and pour the fluid in, plunger back in a bit, flip it over and push the air out. Or do it you’re usual way and leave it for half an hour and let it all settle.
From my experience, the bleed kits with the hard syringes like the ones in the Sram Pro kit are a huge improvement.
I believe Park and Jagwire use them in their kits as well.
Yeah, as someone else already said, high quality syringes like in the Sram kit make a huge difference for a few reasons. One is that the bore of the syringe will start, and stay, more round than the more flexible plastic on your garden variety medical style ones. Another big thing, particularly when pulling a vacuum, is that the pieces of the plunger are all firmly affixed, usually screwed together, with an o-ring (or similar) seal, whereas on the medical style ones, the whole rubber tip (which forms the seal) of the plunger is just pressed on to the plastic part, and if you try to apply too much force in a pulling direction, to create a vacuum, the rubber tip will pull right off of the plastic portion.
They do cost more obviously but they last so much longer and are such better quality. Got a homie you could go halfsies on a nice kit with?
To combat the stick slip, move it around dry first. Or pull oil in, flush it back out and then pull it back in. That way the seals will be lubricated a bit.
You can find the amount of dissolved gas in any fluid by looking up a table of the Ostwald coefficient for that particular fluid.
Mineral fluid has 10% from my memory. Most liquids have about 10% dissolved atmosphere in them at STP. Mixing fluids, almost like that of bleeding brakes can increase the dissolved gas in a system until the liquid has had time to reach atmospheric equilibration.
Degassing is critical in many industries even those that deal with fluid pressures well over 200ksi, Chromatography for instance. Dissolved air is not in-compressible, oil isn’t either but it’s isothermal compressibility coefficient is much, much lower than air. Removing the air will increase the bulk modulus of the fluid within the system.
I usually pour some fluid into a small dish, take the plunger out and wet it in the fluid before pulling fluid into it. When you're pulling fluid in, as long as you get the fitting below the surface you shouldn't be introducing any additional air.
Degassing thoroughly after is still the bane of my existence but I'm certain it makes a difference to the bleed.
Short note on my latest experience with the HS2 rotors.
Run them on a pair of hayes dominion, brilliant never had to think about it.
Eventually bent and scratched my front disc. Swapped front an rear with my favourite discs, that I always believed had the most bite so far, galfer wave discs.
All good and such until I realized, the HS2 could potentially have even more bite than the galfer. Definately surpised me, because the wave discs always were a safe bet on aggressive braking and bite. props to sram then!
Dale just posted a comprehensive deep dive into Lewis brakes. The "Counterfeit Origins" chapter is super interesting. Solid investigative work!
https://youtu.be/59xC6Q51po8?si=iWQy3wxS_URGbXqT
That's a pretty sweet paint job on those Lewis brakes.
One thing that I thought about after watching the video, they started off copying Trickstuff "because that was the best idea" (or something like that).
I would probably put solid money that if they started copying SRAM or Shimano, they would have had lawyers or authorities banging on the door real fast telling them to stop screwing around, while there was probably close to no risk copying a very small brand from Germany. Not just "because TS are the best so let's copy them".
I understand they want to "hide" their past of copying TS (and the blatant DRT copy with the logo etched on it was just bad taste and bad manners), to avoid any confrontation, but at the same time you can't blame people from commenting all those "looks like a session" comments.
I do hope Trickstuff is going to improve upon the DRT or MXA, quite a lot to do that would be pretty easy (improve rollback, improve the top cap and membrane, ..), and I also hope Lewis will sort their QC (brakes are good, finish and sometimes quality control not so much, bit of hit and miss)
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