Brake Pads Swell?

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Brake Pads Swell?
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flag Aengis
Posted: Jul 9, 2016 at 16:24 Quote
This is going to be a strange question. Do brake pads swell when they get hot under heavy use?

I ask because I just bought a pair of Shimano Saint brakes with metallic pads. After I brake hard going into a corner, coming out of that corner (not using the brakes), the brakes will make a squeaking/rubbing sound. After about 4 or 5 rotations of the back wheel, the squeaking stops. The only thing I can think of that would cause that is maybe the pads are swelling when they get hot and rubbing the rotor. Then when they cool down, the pads contract and no longer rub the rotor.

Anyone else had a similar experience?
flag jazzawil
O+ FL
Posted: Jul 9, 2016 at 21:12 Quote
Aengis wrote:
This is going to be a strange question. Do brake pads swell when they get hot under heavy use?

I ask because I just bought a pair of Shimano Saint brakes with metallic pads. After I brake hard going into a corner, coming out of that corner (not using the brakes), the brakes will make a squeaking/rubbing sound. After about 4 or 5 rotations of the back wheel, the squeaking stops. The only thing I can think of that would cause that is maybe the pads are swelling when they get hot and rubbing the rotor. Then when they cool down, the pads contract and no longer rub the rotor.

Anyone else had a similar experience?

Using ice tech rotors?
flag Ploutre
Posted: Jul 10, 2016 at 2:44 Quote
They don't, but you have a few other options of what could happen:

- caliper not properly aligned, and "bends" the rotor slightly
- sticky pistons which takes longer to get back to their original position, not helping with the quick increase in temps inside the caliper

Probably some other reasons, like mineral oil needing some time to cool down a bit to allow the pistons to retract, but that's all I can think of.

Aligning the pistons on a Saint is a pain in the arse if you have the finned pads..
flag Aengis
Posted: Jul 10, 2016 at 6:40 Quote
Yes, I am using an ice tech rotor
flag jonbikes
Posted: Jul 10, 2016 at 9:03 Quote
Moat likely cause is dirty and sticky pistons in the caliper causing a delayed time in returning to their resting position.
flag jazzawil
O+ FL
Posted: Jul 11, 2016 at 22:31 Quote
Aengis wrote:
Yes, I am using an ice tech rotor

I recently got ice tech rotors for my zee brakes on my trail bike. Never rubed before with standard rotors. So, a bike mechanic friend told me that the icetechs have a habit of rubing for a few seconds after heavy braking because of the 2 dissimilar metals, aluminium/steel, expanding and contracting from temperature changes at different speeds causing them to warp temporarily

Seemed legit to me
flag RunsWithScissors
Posted: Jul 12, 2016 at 5:51 Quote
jazzawil wrote:
Aengis wrote:
Yes, I am using an ice tech rotor

I recently got ice tech rotors for my zee brakes on my trail bike. Never rubed before with standard rotors. So, a bike mechanic friend told me that the icetechs have a habit of rubing for a few seconds after heavy braking because of the 2 dissimilar metals, aluminium/steel, expanding and contracting from temperature changes at different speeds causing them to warp temporarily

Seemed legit to me

This sounds much more plausible than pads swelling under heat to me. Bimetallic springs in home heating thermostats work off of this very principle. Interesting problem. If you find the reason/solution please keep us posted...
flag Aengis
Posted: Jul 13, 2016 at 7:23 Quote
This sounds more logical to me. Everything is brand new on my set up. New Saint brakes, new Ice rotors. So in theory, there should not be any noise. But, what you described makes sense. Thanks for the insight.

RunsWithScissors wrote:
jazzawil wrote:
Aengis wrote:
Yes, I am using an ice tech rotor

I recently got ice tech rotors for my zee brakes on my trail bike. Never rubed before with standard rotors. So, a bike mechanic friend told me that the icetechs have a habit of rubing for a few seconds after heavy braking because of the 2 dissimilar metals, aluminium/steel, expanding and contracting from temperature changes at different speeds causing them to warp temporarily

Seemed legit to me

This sounds much more plausible than pads swelling under heat to me. Bimetallic springs in home heating thermostats work off of this very principle. Interesting problem. If you find the reason/solution please keep us posted...
flag Aengis
Posted: Jul 13, 2016 at 7:31 Quote
For what it's worth, I found a Shimano promo video that explains the dual layer technology on the Ice rotors. Explanation begins a 1:55

https://youtu.be/-7KfQInRNHs
flag audios89
Posted: Jul 21, 2021 at 11:25 Quote
I've experienced the swell of Ice-tech rotors (Dura Ace SM-RT900) - couldn't explain it from any other indicator. After releasing the brakes post med-hard braking the front would resonate to a loud howl for about 10 seconds until the rotor cooled off. Rotor was true and using shimano resin pads.

Replaced with a solid steel Centerline-X rotor and problem disappeared. I've not had consistent good luck with Ice-tech rotors, road or mtn variety. I'm 190 and come into corners pretty hard.
flag thekragle
Posted: Aug 22, 2021 at 9:48 Quote
LAZY PISTON. I had the exact same issue, and had tried everything i could with no results. Someone here suggested the lazy piston. Pull the pads off and attach a bleed funnel, advance the pistons by pulling the leaver a few times, but not too much to pop the pistons out. Clean around the base of the pistons with rubbing alcohol and push them back in with a plastic pry tool. Work them back and forth and you will probably see one not advancing as much. Keep working them individually and with them advanced lube them with a little mineral oil, just make sure to clean with alcohol before installing the pads. Worked great for me.
flag audios89
Posted: Aug 16, 2022 at 15:17 Quote
Could be in part due to a lazy piston, but it stopped happening once I switched to a simple 1-piece steel rotor...
flag Wishiwasbiking
Posted: Aug 20, 2022 at 7:14 Quote
thekragle wrote:
LAZY PISTON. I had the exact same issue, and had tried everything i could with no results. Someone here suggested the lazy piston. Pull the pads off and attach a bleed funnel, advance the pistons by pulling the leaver a few times, but not too much to pop the pistons out. Clean around the base of the pistons with rubbing alcohol and push them back in with a plastic pry tool. Work them back and forth and you will probably see one not advancing as much. Keep working them individually and with them advanced lube them with a little mineral oil, just make sure to clean with alcohol before installing the pads. Worked great for me.

+1 on the sticky/lazy piston. I get this every 3-4 months and do the same as above and it goes away.
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