This always seemed very odd to me that one could degas the fluid using a simple syringe as a vaccum chamber. The following link explains the problem in details: but in short air from the room, outside of the syringe chambers enters the syringe chamber every time when pulling hard on the shaft, and allowing the opposite process to happen: aerating the fluid with turbulence of outside air getting mixed with the fluid. So while you might have some tiny and just a few bubbles effectively getting out of the fluid as a desired effect, this is marginal and most of what you see in this video is the unwanted opposite effect happening. loads of wet air from outside getting nicely mixed with the fluid in the process. Which is why SRAM never recommended this very syringe based procedure, and this is why the MTBN videos show you to gently knock the syringe with you thumb and shake it a bit too. Like we say back home " the devil is hidding into the fine details". Last but not least i did a quick research which shows the following: moisture, i.e water is absorbed by the brake fluid from the air, but the air does not get dissolved in brake fluid, this is no water, and even water needs high pressure in order to dissolve a gas i.e. CO2 using your sodastream and its what 6bars+ of pressure to dissolve CO2 in water. So the direct consequence is : if there are bubbles of air not dissolved into, but trapped into the fluid, you will see most of them, and the microscopic ones, invisible to the eye, will surely not be removed with a makeshift system D improvised vaccum chamber using an ordinary syringe. Bottom line, everyone does what they want but honestly, I believe this does more harm than not. And the desired effect will only be, by luck, achieved if doing this process multiple times and at the end the last few times very gently, which will reduce to negligible the aerating undesired effect, and the allows the bubble untrapping wanted effect. Only if doing this very gently, which more or less is equivalent to tapping and knocking the syringe gently with your thumb, just like MTBN shows in their vids and SRAM and multiple other people recommend over the web. www.mtbr.com/threads/degassing-just-dont.1009602/
1. SRAM do recommend doing this, you just pull the vacuum when connected to the calipers. 2. The bubbles aren't coming out of the fluid, its the was of the container/tube/caliper. If you've ever welded an aluminium engine sump you'd see how porous aluminium can be, oil seeps deep into it
There is something to be said about vacuuming the fluid, but the reality is that most of the bubbles he's seeing is from air getting by the seal at the bottom. If you want to vacuum fluid, you need a vacuum chamber. Throw an open container of brake fluid in the camber, use a compressor to pull a vacuum, come back later and you'll have any bubbles removed. Alternatively, just bleed the brakes normally then ride and come back afterwards and do a maintenance bleed where you essentially just top it off. Any bubbles in the fluid will have made their way to the top and you can remove them instantly.
Amazing. By clamping the hose and pulling on the plunger, you're drawing air past the seals on the plunger (note to others: the bubbles aren't magically appearing down at the plunger due to air being drawn through the hose end). Congratulations--you're introducing *more* air bubbles into your oil, not removing them. This kind of incredibly misguided information is what gives RU-vid a bad rap. Oh, and by the way, that's why none of the videos from SRAM, Park Tools or any of the MTB channels do it.
Air is dissolved in the fluid. When you create a vacuum the air can no longer stay in solution, and thus creates bubbles and rises to the top. So why bother pulling the air out of solution? Because gasses will also come out of solution when heated. This is bad to have in your brake system. You ever boil water and see a bunch of tiny bubbles rising before the boil? That’s the dissolved gasses escaping the water before the water reaches boiling temperature. Someone didn’t pay attention in chemistry class.
@@monkeypainter808 I work in a car factory, and we use vacuum filling for the brake fluid, clutch system, and coolant, but not for this reason. With vacuum, you remove all the air from the system, and you don't need additional bleeding. Also, it's way faster this way, we don't have a minute to completely fill up this system's.
@@bardocz they’re not mutually exclusive. One of the reasons they vacuum bleed rather than pressure bleed is the benefit of pulling dissolved gasses rather than promoting dissolved gasses.
syringes are not made for hard vacuum.. YOU are creating those bubbles, when you're pull back on the plunger creating that liquid vacuum, the fluid is pushing open the gasket and letting air in. This is not only unnecessary it's creating more of a problem. This step isn't in any bleed videos for a reason..
I used to vacuum the fluid as in the video back around 2011 when I had a bike with Avids. I always got lousy bleed jobs. I'd forgotten about this tactic until seeing this video because I've been on Shimano for years. However, my wife's bike has Sram TLs and I don't vacuum, I just follow Park's video and I get rock solid pressure in the system. So no going back to vacuuming for me.
You can also just do this as well right before you pull off the top syringe when it's attached to your brakes and it also pulls any air remaining in the fluid in the brake line as well. I do believe that is mentioned in the how-to video and is a crucial step.
This video really helped me understand how to get my sram brakes dialled. It’s felt like pot luck in the past as to how well bled the brakes felt after bleed process. I was about ready to give up and get some Xt’s, as they are so much easier to get right. In the past to cover up a bad bleed I’ve just pushed extra fluid in the Caliper post bleed, thus pushing the pistons out and firming up the lever. I can’t say I’d advise this as it’s very difficult to align the pads correctly and generally leads to a slight rub over the rotor face. Over time this just ends up cooking your pads and rotor face. I’ve seen a lot of comments over the internet suggesting this method. I’ve tried it, but ultimately it’s a bad idea. Even if you skip this initial step, the biggest factor in getting the brakes bled correctly has to be vacuuming as much air as possible from the lever. Really take your time and carefully push and pull the syringe. Just thought I’d put this out there in case it further helps anyone. Thanks for these videos bud, really useful content 👍
It’s really not difficult. Even if you don’t get it absolutely bang on all you need to do is go on a few rides and then do a leaver bleed / top up as any air that might have been still in the system will make it’s way to the highest point after it’s had some heat and vibration have gone through the system and simply pulling the brake through use will pull the air out.
there is absolutely no way you have syringes of high enough quality where air won't get past the seals - especially the SRAM bleed kit, this won't achieve anything. you pull a vacuum during the final bleed process anyway with both syringes upright, this way the quality of the seals do not matter.
great vid and yes there seems to be so many vids on this and Everyone seems to do it a lil diff. i believe its called De gasing by sram as well as air bubble release they say to clip off syringe then de gas. thanx for doing vids....
Many say it makes no difference, as you’ll forever keep pulling air pockets in as you create a vacuum. But I believe getting the initial bubbles out absolutely makes a difference, even it it doesn’t completely illiminate all air bubbles. I’ve felt the difference enough times to feel that it helps
Thank you! I was ready to replace the rear brake on my brand new bike after bleeding didn't fix the squishy lever that hit the bars with one finger. Sram Guide fyi. I bet your method will fix my issue!
Sorry mate, I tried this and realized it is not bubbles emerging out of the fluid the bubbles are from sucking in air around the plunger. You can see this in the video. There is a vacuum step on the lever syringe to pressurize the system at the end of bleeding.
Almost everyone already gave the correct explanation: these are bubbles from the syringe. I tried it myself, exactly with the same syringes to be sure of it, several times, before your video. But the real question is: why only these crappy brakes would need such a thing? With other brakes you just pour the fluid in a tank. The reason is that when using this sram crap you try to think of everything to keep a consistent bleed status. When i bleed the R I have a rock solid lever, super consistent for like 1 bike park day, maybe half. And then they are spongy again. If it were air in the fluid, they would be spongy always, even right after the bleed. You can try any kind of magic with code R, even degassing the dot 5.1, but you will get the same result. Once I realized it and I put the R where they belong (the trash bin) everything became perfect.
I did the remedy 8 not long ago and didn’t realise how bad they were! And yep sram video didn’t say to do this, but they do say to do it once you’ve put the new fluid through the system. It took forever vacuuming it out of the top syringe on the bike. I found there was still microscopic bubbles no matter how long I tried for.
Yep, the more you get out of the fluid you’re introducing, the better finish you’ll get. If you want the full slice you pump all your vaccumed fluid into the system and then start again with the process. Minimising how much air will be left in the system. Brakes will be rock solid
This literally pulls air into the syringe. If you do it according to the official procedure this will never be a problem. So basically don't do what he does in this video, you will just get more air into your brakes.
@@monkeypainter808 no, the seals on these syringes are not that strong at all. All you're doing is introducing a bunch of air by defeating the seal lol! I tried this with water and soapy water and it was the same. "Degassing" water? Pure water and still got bubbles coming up and they never stopped??? Come on now! The only reason the bubbles might stop coming up as much is only because the DOT fluid is also a lubricant and creates a liquid film seal on top of the measly rubber seal while water does not lol! That's the only reason you see less bubbles the more you do it, but you literary introduced more air into the system for no reason lol!
@@erod6468 you obviously didn’t pay attention in science class. “Pure water”? Where on this planet are you getting pure water with no dissolved gasses?? The seals are plenty strong to pull dissolved gasses out of solution. If you take just a syringe with a seal at the end, and you repeatedly pull the gasses out of solution and push them out of the syringe, you will eventually have a really hard time getting bubbles to form. That’s because you reached a point where you won’t be able to create sufficient vacuum to pull any more gasses out of solution.
@@monkeypainter808 idk where you're comment went, maybe you deleted it, but I don't think you read and understood my comment. Anyway, no need to get agro. Have a great day and have fun riding. 🤙🏽
No, the seals on these syringes are not that strong at all. All you're doing is introducing a bunch of air by defeating the seal lol! I tried this with water and soapy water and it was the same. "Degassing" water? Pure water and still got bubbles coming up and they never stopped??? Come on now! The only reason the bubbles might stop coming up as much is only because the DOT fluid is also a lubricant and creates a liquid film seal on top of the measly rubber seal while water does not lol! That's the only reason you see less bubbles the more you do it, but you literary introduced more air into the system for no reason to begin with lol!
Yes I understand that the majority of the bubbles are coming from the seal. But the process for me does consistently yield a stronger brake bleed compared to not doing it. The first pull gets a lot of bubbles, then as you repeat it you get just heaps of little bubbles coming up past the seal. I’d ignore this step completely if I wasn’t getting a result from it. It may be minimal but the difference is there absolutely
@@mtbtelly5522 cool bro. I will definitely give it a try. Have never had and issue bleeding sram brakes and my brakes always feel super firm since I don't like any sponginess. Have fun, stay safe. 🤙🏽
@@mtbtelly5522 Perhaps, both theories are correct. It doesn't have to be 100% bubbles from the seal, or 100% bubbles from dissolved in fluid. Perhaps, overall, it does draw microbubbles out of the fluid as well as introduce some air from the failed seal. Maybe the overall effect is as the author describes.
I had an argument withe the guy from park tool over this exact problem their video shows the wrong way also. the only way to remove the bubbles is with vacuum pre bleed as shown in this video or using the pressure method as used by motorcycle mechanics otherwise microscopic bubbles remain in suspension in the fluid..dot 5 seems to be worse than the older stuff.
I work in refrigeration and we can not contaminate the systems even with the smallest amount of air. But when we pump oil into the compressors there must be loads of air in that oil! nothing you can do...
The air is coming from the syringe seal. How the heck would there be over 20ml of air in about 40ml of brake fluid? Also, if the air was somehow in the fluid, the volume of the fluid would reduce as you did it.
Hey man, have you seen the bleed process Troy's mechanic? Recommend it, made my codes far sharper than the SRAM process. Also worth mentioning that the pistons get sticky very easily, where I live they need a clean every few months
When do the hydraulic fluid become under vacuum in a disc break system? I know it's fascinating to see all that air being released out of the fluid but it will never happen unless you suck oil out of one ends.
You can still do it with the crap syringes. Just cant be too aggressive or you will suck a gulp of air past the seal and have to redo it. But you get the feel for it for how hard you can pull.
Thank you for this instructional video. You can call me crazy, but when I bleed out my Elixir brakes on my Kona Honzo, I almost fill the rear brake syringe at the disc brake side, and then flush out the whole line into the syringe on the brake lever side. I then take off the syringe from the disc brake, put the screw back in, and then do all of the airing out of the bubbles at the brake3 lever syringe, flipping the brake lever. Works like a charm, and my brakes are super solid. I use to go nuts trying to air out the bubbles at both syringes, and it always had some air bubbles left in the line. Hope this helps someone. Cheers.
Hey brother, when I bleed my Code R’s I always have very little clearance between my pads and my rotor. They drag and are hard as hell to get set up. I have about four years on these brakes so I rebuilt the caliber, but this did not help. Any advice. I followed your advice and SRAMs. I always feel like when I do my final push to pressurize the system that’s way over services it and pushes out the pistons too close to the rotor.
Is this also relevant when using a fresh, sealed DOT fluid container? I usually break open a new one of those small ones from SRAM every time I bleed, and bleed all my bikes at once to get the most out of it.
Your right. Even Park Tool’s SRAM bleed video does not include this step. I found it in a bleed video by Clint Gibbs on his channel. It’s known as “degassing” the fluid. The air bubbles are not originating from around the seal, rather they appear out of no where suspended in the fluid. All I know is that I did this step and followed the bleed direction exactly. My SRAM brakes feel amazing.
DOT fluid does not hold any microbubbles, the bubbles he showed were pulled past the syringe, into the vacuum. This process isnt shown in the official videos because it does literally nothing. You pull air into the syringe, then you push it out. If you dont do this step, and your brakes feel bad, its for some mistake in the bleeding process, not this
People i draw bak once lighty flik the the syrunge couple times with finger key is draw bak lightly!!! Push the air out lock ur collar on the hise goid to go
You can boil water at way less than 100degrees by reducing the pressure around it. Water boils at about 68degrees C on Mount Everest. Could it be you are seeing a similar phenomenon here with the dot fluid now under a reduced atmospheric pressure hence the vacuum? The oil is starting to boil? I can’t find any data on what pressure dot fluid boils at so can’t confirm this, just my thoughts.
also what I done with the squishiness was before you take the last syringe off the brake caliper (after putting the bleed screw back into the lever side), I forced more fluid into the system, and at the same time holding that pressure I then twisted/closed off the port. If that makes sense?
@@James-dn1hu I know that. My question was does it have to be sram brake fluid. There are lots of better brands of brake fluid than Sram brake fluid on the market. There is a whole host of high end motorcycle brake fluids out there. But there may be issues with seal compatibility. Brake fluid should not contain air or foam like he showed in the demonstration. That is really shit fluid.
@@cunning-stunt oh fair enough. Would be hard to say as the fluid used in motorbikes may be stronger and could effect the seals like you said. Sorry I’m not sure
Any dot 3 or 4 brake fluid will work. I use nulon. Problem with auto stuff is once the container seal breaks the fluid is hydroscopic and starts absorbing water. Smaller containers are therefore better. Dont use dot 5 as it is silicone. However dot 5.1 is standard with better abs compatibility... just stick with dot 4...
Don't use Automotive Dot fluid, it is different, just use Dot5.1, any brand of Dot 5.1 is fine, but it's makeup is suited to the seal in your MTB brake system.
Plastic pistons (will lose shape) of different sizes (why?) for the same brakes: makes no sense. Exept selling the 30$ rebuild kit every year. SRAM can not be trusted.
I have a remedy 8 and just gave up on the brakes and went with a set of 4 piston SLX's. Would have tried this if I had known about it a few months ago! Oh well, I'm really liking the shimanos anyway
I put hope brakes on my remedy 8. Frigging love them. But my rear is now starting to feel a bit spongy. Might try this method. I have only done MtB brakes a few times. But done car brakes many times. When I bleed car brakes, I always use an air-conditioning vacuum pump to bleed them. It makes it very easy to bleed with only yourself. And probs has this added benefit built in
Sean it doesn't matter much. I did exactly what he's doing and it didn't help my Code R brakes at all on my Remedy 8. I found the best thing to do is after your all done bleeding your sram brakes is to take the bleeding edge tool and put it in the brake caliper, open the bleeder and put pressure in the system, then close the bleeder before removing the tool. My levers feel great now.
@RollinRat Good info here. Thanks! I'm a massive fan of Shimano and the Japanese in general (except for whale hunting). SRAM is a soulless company to me. Just a bottom line for investers.
Great video, but honestly.. why worrying about bleeding Sram brakes, I'd you can just throw them in the trash and get Shimano, like I did! Way more reliable and literally a complete peace of mind!
Exactly. Keep the sram brakes for as long as they work (2 weeks in a friend of mine's case...) and then just get a 4pot SLX, replace the fake bite point screw with an actual screw, and that's all you need.
Idk man, I've had my code rscs for 2 years and they're still perfect. I much prefer the feel of the RSC sram brakes with the swing link system to shimano brakes. Just personal preference I guess. And yes, I have used shimano, I run xt brakes on a different bike
