It's late at night, my bike is sleeping soundly in its shed, and for the first time, I understand what really retracts the brake pistons - and the brake pads. Thanks for sharing!
i actually 100% wanted to know about how the pads reset themselves. I just installed new brake pads last week and was wondering about that and thinking it couldn't be the little tension spring thingy that comes with the pads. I seriously appreciate you guys explaining this because I had no idea.
Yes, self adjusting pads is the main reason I switched to hydraulics! Really take for granted these pieces of technology that make riding nowadays more convenient. Less time adjusting equals more time riding!
@@erikdg "Brute" force or not; that's just semantics. A measuring tool should only be used for measuring. Applying any force to it that it wasn't designed for can make it lose its accuracy. Chain wear is measured in fractions of a percentage point, so I wouldn't risk it.
dunno I've been using the spacers that came with my brakes... worked fine; and I guess any tool that has an edge and blade that is not gonna bend / break would work as well to separate the pistons enough to fit through the rotor again
What about if the pads won’t move to grip the rotor and brake? I adjusted the cable and it still won’t grip the rotor. It happened after I loosened the outside screw on the side
Spot on as always! Also important: Bleed your breaks only with bleed blocks. 'cause otherwise you might run into a problem once you change your rotor or pads. And when you then start to push back the calipers you might kill the membrane in your brake lever by accident. Reason: Without bleed block there is a chance you put to much hydraulic fluid into the system.
Hello. Thanks for your video but I still cannot fully insert both pistons into caliper. I have new brake pads but after installing them there is too little space for brake rotor to fit. I tried to push back pistons using screwdriver and old pads but it didnt work. Then I cleaned the pistons and tried to push pistons back separately but pushing one caused the other to come back out. How do I reset their position? Do I need to unseal system and then set them to position?
One thing I do wish was that disc breaks had a slightly larger gap,because it can be very annoying fine tuning the very small gap between the pads and rotor
The PS-1 is fine and dandy if you are at home or in a shop, however, what do you do if you accidentally actuate a brake in the field while changing a flat, or cannot justify buying a tool you hope you never need?
You use the flathead screwdriver on the multi tool that everyone should be carrying. Just don't dig the point of the screwdriver into the soft-ish parts of the piston and it'll be fine.
I learned the hard/expen$ive way NOT to use the Park Tool PP-1.2 Hydraulic Brake Piston Press without the brake pads installed... cracked the ceramic cup/piston in the Shimano Ultegra R8020 disc brake caliper - love the new PS-1 Pad Spreader - and do not even think about using a tire lever
when you bleed your brakes, use a bleed block to ensure the brakes are bled with the pistons fully retracted. Post bleed; when you set the pistons/pads to touch the rotors after you've closed the system, the fluid level will fall. This fall in fluid will mean you do not need to open the bleed port when adjusting, since there's enough "vacuum" volume for you to fiddle with piston travel.
@@MTMXBLIsn't it going to slowly suck air from the atmosphere? I always bleed with the pistons in adjusted position so I leave no room for air to get into the system.
It *shouldn't* be necessary, for the reason MTMXBL explained in his reply. However, if the system is overfull of fluid, usually from doing shortcut "lever bleeds" with the pads in place instead of a bleed block, and therefore the pistons advanced a little during the process, the fluid pressure from pushing them back can potentially damage the diaphragms in the lever body causing leaks.
Both great tools. PS-1 does get between pads that are compressed together easier. The PP-1.2 does better pushing directly on the pistons. The PS-1 is able to simulate the brake feel at the lever without installing the wheel. Both are great for similar but different reasons.
There are brands that offer rebuild kits and have service intervals. There are other brands that offer no serviceability when it comes to these seals. For those they recommend replacing the caliper.
So the pads aren’t permanently fused together? 😂 I need to stop listening to people who don’t know what tf they’re talking about. Thank you for the simple, clear video.
One of the pistons will typically advance quicker than the other/ others. Its not important to have them advance at the exact same time. Once one of the pads meets the rotor it stops advancing and the other piston/'s start advancing more.
Very timely video I am in currently replacing my brake pads on my bicycle. I would be interested in seeing a video of how to clean that O-ring when dirt gets in there.
Not an O-ring, it's a square ring. There was a Tech tuesday a few months ago that detailed how to clean the piston and to fix a lazy piston. Since that cleans the piston-seal interface partly, that's the only thing that's reasonable for a home mechanic to do. Otherwise it's disassembly which is not advisable. In short, iirc: remove the wheel and pads. carefully squeeze the lever to reveal more piston, but not so much it pops out. Clean the outer edge, where it interfaces with the seal, with a q-tip dipped in your correct braking fluid. Push the pistons back in. Repeat until pistons both move freely and equal.
@@RenAigu one thing YOU MUST DO after you're done with the "brake fluid cleaning" treatment, you MUST clean your pistons and callipers with isopropyl before you insert the pads back in. And be very thorough about it. Otherwise you will wreak havoc on the pads and discs.
You could say they have the lever and caliper all in one unit. You pull the lever and subsequently the cable which at the caliper pulls on an another lever that pushes a pushrod and so on. The piston and seal are exactly the same as in full hydraulics.
@@8BitZ0mbieI think they're talking setups like TRP HYRD's which are hydraulic at the caliper instead of full cable actuated. Both pistons move, not just one like Avid BB7's. In the case of HYRD's, treat them just like any other hydraulic pistons.
Some brakes have a "pad contact adjust" which allows you to adjust when that happens in your lever pull. Most brakes do not have that and there is no adjustment for it.
I didnt get it. What do you mean “unless the lever is pulled”? In both cases (wheel on/ wheel off) the lever is pulled but the seal in one case adjusts the pads back but in the other doest. According to video when the wheel is in the seal adjusts the pads back in to position but when the wheel is off the seal doesnt adjust the pads back in to position. Why so?
I've accidentally popped my pistons out, no big deal. Just make sure they aren't contaminated when you put them back in. But I'd advise not to pop them out unless they're sticking for some reason.
You must have a high stress tolerance, accidentally popping out a brake piston is among the worst thing I can imagine happening when working on a bike. A huge mess and pain in the ass for mineral oil systems, for DOT systems you can add health hazard and potentially ruining painted surfaces.
I'm surprised you didn't talk about resetting pistons during a pad replacement, and opening up the system at the lever to give the fluid somewhere to go. I also like to teach people to use the right tool to spread pistons during brake service. Cracked ceramic pistons on Shimano brakes make for a very bad day at the shop.
Yeah man. I open up the system each time I put in new pads to push back the pistons. One time I didn’t open up the system and pushed back the pistons, I blew my bladder.
No need to open the system when you always use a bleed block when bleeding. If you bleeded without a bleed block you might habe to much oil in your system. And yes, then you have to either open it or see what breaks first (usually the membrane in the brake lever).
with a flat brake disk the pads can float quite close to the disk, ready to make contact w/ little travel at the lever... a little trick to reposition the pads as close to the disk as possible on a regular basis: use rubber bands to keep the brake lever pulled in overnight. you need just enough pressure for the pads to touch the disk and w/ time the caliper piston will slightly slide thru the square seal closing the gap between the pads and the disk. in the morning the brakes will feel firm -given there's no air in the system.
Not only pointless, I read somewhere it's even detrimental. You want a bit of friction between the square seal and piston whereas with lubrication, the advancing piston doesn't flex the seal. It just slides out and does not retract.
The tool itself is a clue that you can also use an old rotor. While I don't have this one, many of the times I have purchased Park Tool tools they were chosen over cheaper options to support the production of high quality repair help videos that have been of great help to me.
I struggled to get past the first two minutes of this, never use dot fluid in mineral brakes, it will destroy them. Mineral oil also has a higher boiling point than dot fluid And don't do the bleed nipple or sealing screw tight. They will shear or strip the thread.
Good information but except for the diagrams the explanation with the cut away parts was completely wasted because you couldn’t actually see anything except for his fingers sometimes. If you’re going to use something like the cut away parts for gods sake please position the camera above where we can actually see what you’re doing!
![[Sub Thai] APT. - ROSÉ & Bruno Mars](http://i.ytimg.com/vi/bYjhzP8x_uc/mqdefault.jpg)
Very good! ..I love understanding these things fully. One of the best brake caliper vids ever. Much appreciated !
Can't believe the mechanism is so simple and smart. Great video. Great topic.
It's late at night, my bike is sleeping soundly in its shed, and for the first time, I understand what really retracts the brake pistons - and the brake pads. Thanks for sharing!
i actually 100% wanted to know about how the pads reset themselves. I just installed new brake pads last week and was wondering about that and thinking it couldn't be the little tension spring thingy that comes with the pads. I seriously appreciate you guys explaining this because I had no idea.
Really enjoy these, please continue making them
I love my PS-1. Thank you, Park Tool.
Excellent explanation 👍
Allways imagined it would be more complicated but never thought I'd know. Appreciate the explanation 👍 thanks
Yes, self adjusting pads is the main reason I switched to hydraulics!
Really take for granted these pieces of technology that make riding nowadays more convenient. Less time adjusting equals more time riding!
Wolf Tooth's 8-bit Tire Levers are perfect for this job.
If you don't have that tool on hand. A chain wear measuring tool will do the job too. At least the one I have does.
I wouldn't use a measuring tool for any brute force task. A plastic tire lever would be a better, cheaper choice.
@@mattgies it's not exactly brute force. Just a little pressure is enough. If I had to use brute force on the pistons something would be very wrong.
@@erikdg "Brute" force or not; that's just semantics. A measuring tool should only be used for measuring. Applying any force to it that it wasn't designed for can make it lose its accuracy. Chain wear is measured in fractions of a percentage point, so I wouldn't risk it.
dunno I've been using the spacers that came with my brakes... worked fine; and I guess any tool that has an edge and blade that is not gonna bend / break would work as well to separate the pistons enough to fit through the rotor again
I love knowing more than I wanted to.
Great vid, very informative. thanks for the upload.
enjoyed your video 📹 very informative 👍
When do you use the PS-1 as opposed to the PP-1.2? They seem to do similar things but are shaped differently.
What about if the pads won’t move to grip the rotor and brake? I adjusted the cable and it still won’t grip the rotor. It happened after I loosened the outside screw on the side
Spot on as always!
Also important: Bleed your breaks only with bleed blocks. 'cause otherwise you might run into a problem once you change your rotor or pads. And when you then start to push back the calipers you might kill the membrane in your brake lever by accident. Reason: Without bleed block there is a chance you put to much hydraulic fluid into the system.
Right?! The bleed block also needs to be the correct thickness for the system, to set that fluid volume as well.
Hello. Thanks for your video but I still cannot fully insert both pistons into caliper. I have new brake pads but after installing them there is too little space for brake rotor to fit. I tried to push back pistons using screwdriver and old pads but it didnt work. Then I cleaned the pistons and tried to push pistons back separately but pushing one caused the other to come back out. How do I reset their position? Do I need to unseal system and then set them to position?
This is good to know on any hydraulic disc brake, as the same pressure happens no matter the size.
One thing I do wish was that disc breaks had a slightly larger gap,because it can be very annoying fine tuning the very small gap between the pads and rotor
The PS-1 is fine and dandy if you are at home or in a shop, however, what do you do if you accidentally actuate a brake in the field while changing a flat, or cannot justify buying a tool you hope you never need?
You use the flathead screwdriver on the multi tool that everyone should be carrying. Just don't dig the point of the screwdriver into the soft-ish parts of the piston and it'll be fine.
put plastic piston plugs
What are those handlebars? I love them..
Whiskey Milhouse bars.
I learned the hard/expen$ive way NOT to use the Park Tool PP-1.2 Hydraulic Brake Piston Press without the brake pads installed... cracked the ceramic cup/piston in the Shimano Ultegra R8020 disc brake caliper - love the new PS-1 Pad Spreader - and do not even think about using a tire lever
Great video!
Great video! Question is it necessary to open the bleed port on the lever when resetting the pistons?
i never did that, so i dont think it is needed
Hi everyone , Thank you Merci ❤😊
when you bleed your brakes, use a bleed block to ensure the brakes are bled with the pistons fully retracted. Post bleed; when you set the pistons/pads to touch the rotors after you've closed the system, the fluid level will fall. This fall in fluid will mean you do not need to open the bleed port when adjusting, since there's enough "vacuum" volume for you to fiddle with piston travel.
@@MTMXBLIsn't it going to slowly suck air from the atmosphere? I always bleed with the pistons in adjusted position so I leave no room for air to get into the system.
It *shouldn't* be necessary, for the reason MTMXBL explained in his reply. However, if the system is overfull of fluid, usually from doing shortcut "lever bleeds" with the pads in place instead of a bleed block, and therefore the pistons advanced a little during the process, the fluid pressure from pushing them back can potentially damage the diaphragms in the lever body causing leaks.
Great explanation. I kind of prefer the PP1.2 rather than the PS-1. Any particular reason to choose one over the other?
Both great tools. PS-1 does get between pads that are compressed together easier. The PP-1.2 does better pushing directly on the pistons. The PS-1 is able to simulate the brake feel at the lever without installing the wheel. Both are great for similar but different reasons.
@@parktool thanks
Are these seals considered a maintenance item that should be replaced at recommended intervals?
There are brands that offer rebuild kits and have service intervals. There are other brands that offer no serviceability when it comes to these seals. For those they recommend replacing the caliper.
Not gonna lie, I _absolutely_ thought it was the clip doing all the work here. Consider me informed!
So the pads aren’t permanently fused together? 😂
I need to stop listening to people who don’t know what tf they’re talking about.
Thank you for the simple, clear video.
What do you do when one or more pistons advance further than the others.
One of the pistons will typically advance quicker than the other/ others. Its not important to have them advance at the exact same time. Once one of the pads meets the rotor it stops advancing and the other piston/'s start advancing more.
@@parktooldang, this is an important sub comment!❤thanks for clarifying that they balance themselves out
Dominion brakes r good!!👍
Very timely video I am in currently replacing my brake pads on my bicycle. I would be interested in seeing a video of how to clean that O-ring when dirt gets in there.
Not an O-ring, it's a square ring. There was a Tech tuesday a few months ago that detailed how to clean the piston and to fix a lazy piston. Since that cleans the piston-seal interface partly, that's the only thing that's reasonable for a home mechanic to do. Otherwise it's disassembly which is not advisable. In short, iirc: remove the wheel and pads. carefully squeeze the lever to reveal more piston, but not so much it pops out. Clean the outer edge, where it interfaces with the seal, with a q-tip dipped in your correct braking fluid. Push the pistons back in. Repeat until pistons both move freely and equal.
th-cam.com/video/vQXFFgRButo/w-d-xo.html
@@RenAigu one thing YOU MUST DO after you're done with the "brake fluid cleaning" treatment, you MUST clean your pistons and callipers with isopropyl before you insert the pads back in. And be very thorough about it. Otherwise you will wreak havoc on the pads and discs.
@@parktool thank you for the link. I just watched it and that’s what I’m gonna do.
@@channul4887 thank you for your comment and that’s what I’m gonna do use a little alcohol
Is that I was looking for 😊
Mtb: disc brakes are so simple and easy to adjust
Roadies: I can’t tech.
What about cable actuated hydraulic brakes? How do they work?
Usually only one pad moves with cable. And there is a spring that returns it when you let go of the brake
@@8BitZ0mbieBB7 uses 2 pads
You could say they have the lever and caliper all in one unit. You pull the lever and subsequently the cable which at the caliper pulls on an another lever that pushes a pushrod and so on. The piston and seal are exactly the same as in full hydraulics.
@@8BitZ0mbieI think they're talking setups like TRP HYRD's which are hydraulic at the caliper instead of full cable actuated. Both pistons move, not just one like Avid BB7's.
In the case of HYRD's, treat them just like any other hydraulic pistons.
That's what he is explaining
How to cut or reduce lever travel, i like the least travel posible but mine only 'starts' breaking middle lever...thnks
Some brakes have a "pad contact adjust" which allows you to adjust when that happens in your lever pull. Most brakes do not have that and there is no adjustment for it.
You can overfill the system, don't use a bleed block or use a thinner bleed block. This will only last a while until the pad wears away though.
There is a plastic spacer to put inside your brake caliper when tire os off.
I got these with my, very cheap, bike. I had no idea what they were at first.
he said square seal but what i saw was a circle shaped one, or anything i misunderstood?
The cross section of the seal is square. It needs to be round to go around the piston of course.
@parktool ok, thanks for clarifying
Just make sure whatever tool you use to spread the pads apart is clean.
And if you don't have a PS-1 you can always just use a tire lever.
So why doesnt the seal adjust the calipers when the wheel is off?
They will not adjust unless the lever is pulled. The reason you need to separate the pads after you pull the brake is because it adjusted to nothing.
I didnt get it. What do you mean “unless the lever is pulled”? In both cases (wheel on/ wheel off) the lever is pulled but the seal in one case adjusts the pads back but in the other doest. According to video when the wheel is in the seal adjusts the pads back in to position but when the wheel is off the seal doesnt adjust the pads back in to position. Why so?
@@andriskadaga 2:58 overexcursion, seal is in new position relative to the plane of the brake, piston is now at rest at seal's maximum range
Thats why I run Sram Guide calipers - they retract themselves! Lol
I have lost count of how many piston seals I have replaced when they get deformed .
It's even worse when you have the pads removed, then the piston pops out entirely, and it floods the floor with fluid, lol.
I've accidentally popped my pistons out, no big deal. Just make sure they aren't contaminated when you put them back in.
But I'd advise not to pop them out unless they're sticking for some reason.
You must have a high stress tolerance, accidentally popping out a brake piston is among the worst thing I can imagine happening when working on a bike. A huge mess and pain in the ass for mineral oil systems, for DOT systems you can add health hazard and potentially ruining painted surfaces.
I'm surprised you didn't talk about resetting pistons during a pad replacement, and opening up the system at the lever to give the fluid somewhere to go.
I also like to teach people to use the right tool to spread pistons during brake service. Cracked ceramic pistons on Shimano brakes make for a very bad day at the shop.
Yeah man. I open up the system each time I put in new pads to push back the pistons. One time I didn’t open up the system and pushed back the pistons, I blew my bladder.
No need to open the system when you always use a bleed block when bleeding. If you bleeded without a bleed block you might habe to much oil in your system. And yes, then you have to either open it or see what breaks first (usually the membrane in the brake lever).
@@GokkunGuru You did not use a bleed block.
As long as you don't fully open/seat the pistons back in to the caliper, no need to open the system. Inviting trouble with potential air in the system
with a flat brake disk the pads can float quite close to the disk, ready to make contact w/ little travel at the lever...
a little trick to reposition the pads as close to the disk as possible on a regular basis: use rubber bands to keep the brake lever pulled in overnight. you need just enough pressure for the pads to touch the disk and w/ time the caliper piston will slightly slide thru the square seal closing the gap between the pads and the disk. in the morning the brakes will feel firm -given there's no air in the system.
So... to lubricate the pistons is pointless.
Not only pointless, I read somewhere it's even detrimental. You want a bit of friction between the square seal and piston whereas with lubrication, the advancing piston doesn't flex the seal. It just slides out and does not retract.
Any thin tough metal would do, why buy the tool unless you're a repair shop
The tool itself is a clue that you can also use an old rotor. While I don't have this one, many of the times I have purchased Park Tool tools they were chosen over cheaper options to support the production of high quality repair help videos that have been of great help to me.
I struggled to get past the first two minutes of this, never use dot fluid in mineral brakes, it will destroy them.
Mineral oil also has a higher boiling point than dot fluid
And don't do the bleed nipple or sealing screw tight. They will shear or strip the thread.
I think you commented on the wrong video... he didn't bleed the brakes here... what video were you watchjng?
Good information but except for the diagrams the explanation with the cut away parts was completely wasted because you couldn’t actually see anything except for his fingers sometimes. If you’re going to use something like the cut away parts for gods sake please position the camera above where we can actually see what you’re doing!
I've never understood why people get so worked up ab this...spread the pads and move on!
You talk to people like they are school children. And, your explanation as to why the pads retract isn’t even correct.