Mountain Bike Reviews Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
21 Posts
Discussion Starter · #1 ·
So my SRAM Guide calipers have kinda chronically sticky pistons. I do the usual 'exercising' procedure: Extend them, put some fluid on the exposed portion, reset them, repeat ect. It never really seems to solve the problem more than temporarily.

I've got some of the SRAM DOT compatible grease. Would that be ok/helpful to try instead of the DOT fluid?

Thanks in advance
 

·
Registered
Joined
·
9,754 Posts
Personally, I don't lube the piston. I figure it'll only accumulate dust and dirt exacerbating the problem. I remove the pads, extend one piston as far as I feel comfortable, and blast around it with isopropanol in a spray bottle set to stream to clean out any accumulated dirt in the bores. If I'm motivated or having issues, I'll push it back in and repeat. This has worked for me.

No matter what you do, brand new brakes or old, one piston will always advance first at the expense of the other.
 

·
Registered
Joined
·
6,613 Posts
I also never lube the pistons for the same reason. ^^
I remove the wheel, pads and extend the pistons a bit and spray with a water/dish soap combo, rinse thoroughly and let dry. It has worked well for me.
 

·
.
Joined
·
823 Posts
Yeah, cleanliness and lubrication are your friends. I push the pistons out, use brake cleaner or a similar product on a q-tip, and clean off the pistons. Then I put some McKays Assembly Lube (suitable for rubber and brakes) on another q-tip, and apply it around the piston. Then I use another q-tip to wipe off the excess.

The rubber seals will become less resilient over time. Lubrication can help, but will not eliminate your problem.
 

·
Registered
Joined
·
1,729 Posts
Adding to the great ideas that have already been posted re: cleaning the pistons. The best way that I've seen to do it is in this ParkTool video

https://www.pinkbike.com/video/478889/
THIS has great info like using a 5-6mm spacer in between the pistons so that can't extent too far, but can be extended far enough to ensure that they're far enough extened to be properly cleaned....then cleaned using a cotton string (vs using a cotton bud)

This Park video is also great

What's interesting is that in one video they use alcohol/acetone to clean, and in the other video they use brake fluid.
 

·
Registered
Joined
·
3,413 Posts
I have read some conflicting info regarding lubing the pistons.

This park tool video recommends using either dot or mineral oil based on the system.

While this pinkbike article says not to lube them at all.

https://m.pinkbike.com/news/te...essment-2014.html#comment_wrap

Some coments suggest using a high temperature silicone grease.

"Neither mineral oil or dot are lubricants but corrosive brake fluids, and both actually cause the piston seals to slightly swell (this is designed into systems and prevent fluid leaks under high pressure)

Initially, using DOT or Mineral Oil makes it easy to reseat the pistons as they press back easily into the caliper bay.*

However, it then causes more drag on the piston / seal interface. It seems like a quick fix but often make piston imbalance worse. *The correct lubricant to use is high-temp silicon grease, Avid have their "Pit Stop" variant and Hope use "Hunter" for example. This does require a caliper rebuild to install properly, but ensures a long working life and good piston balance."

Sent from my moto x4 using Tapatalk
 

·
Registered
Joined
·
9,754 Posts
^^^ Sounds weird to me. The caliper pistons seals are wet by pressurized brake fluid from behind, either mineral or DOT, neither of which are corrosive, but either can cause incompatible seal material to swell. Lubing the pistons is simply putting lube between the piston and bore outside of the seal. Whatever you use, it should be compatible with the seal material so that it doesn't cause it to deteriorate. The seals need to grip the piston because it's the seals that pull the pistons and pads back from the rotor. As pads wear, the pistons move further and will slip forward in the seals establishing a new retracted position.
 

·
Registered
Joined
·
3,413 Posts
^^^ Sounds weird to me. The caliper pistons seals are wet by pressurized brake fluid from behind, either mineral or DOT, neither of which are corrosive, but either can cause incompatible seal material to swell. Lubing the pistons is simply putting lube between the piston and bore outside of the seal. Whatever you use, it should be compatible with the seal material so that it doesn't cause it to deteriorate. The seals need to grip the piston because it's the seals that pull the pistons and pads back from the rotor. As pads wear, the pistons move further and will slip forward in the seals establishing a new retracted position.
I got a response regarding this from Hayes:
"We lubricate the piston with DOT 4 because it has better lubricant additives than DOT 5.1.* The silicone greases that we have tested have shown good compatibility with the square seals, but we can't recommend "silicone grease" in general because there could be one with additives that harm the seal.* Also, some of our testing of silicone grease resulted in a significant retraction reduction resulting in difficult setup and/or rotor rub.

With any piston lubrication the user has to be careful to apply only a small amount.* Otherwise the lubricant can contaminate the pad by getting onto the pad backing plate and wicking into the pad material through the adhesion holes in the backing plate.

So I would recommend lubricating the piston with a small amount of DOT 4."

Sent from my moto x4 using Tapatalk
 

·
Registered
Joined
·
4,865 Posts
My routine whenever I change pads...

Pull wheel/pads

Put two quarters/nickels between pistons and pull brake lever until they’re held in place and tie the lever off to keep pressure on them. You can use something else but any less wide and your pistons can fall out (on multiple generations of XT/XTR anyway). Any wider and you won’t get as much piston exposed to clean.

Dip an old shoelace in rubbing alcohol and thread it through the caliper and floss it around the piston. Do the same for the other side

Push the pistons back in and put the wheel back in
 

·
Registered
Joined
·
306 Posts
My routine whenever I change pads...

Pull wheel/pads

Put two quarters/nickels between pistons and pull brake lever until they're held in place and tie the lever off to keep pressure on them. You can use something else but any less wide and your pistons can fall out (on multiple generations of XT/XTR anyway). Any wider and you won't get as much piston exposed to clean.

Dip an old shoelace in rubbing alcohol and thread it through the caliper and floss it around the piston. Do the same for the other side

Push the pistons back in and put the wheel back in
I like this idea. Brake cleaner is just too harsh.
 
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top