No. The Ice Tech rotors shouldn't feel inferior.
I'm not sure where the problem lies, but the two new Ice-Techs rotor isn't likely the problem source.
It sounds like you're doing all the right things, maybe the pads/rotors need more time to bed in.

 

No. The Ice Tech rotors shouldn't feel inferior.
I'm not sure where the problem lies, but the two new Ice-Techs rotor isn't likely isn't the problem source.
It sounds like you're doing all the right things, maybe the pads/rotors need more time to bed in.

I just spent a week riding in Park City and Moab. I would think/hope that type of riding would just about bed in any rotors.

I'm a little baffled with this as well. I'm now curious if Shimano changed something on the rotors or pads. Not sure what else to think.

 

Did you bed in the rotors? They won't work well otherwise. If not, the second time you use them they should work well.

 

Yes, I bed in the new rotors.

 

If they're the made in China rotors, they take a lot longer to bed in than the made in Japan version, or so I've read on here.

 

Are the RT86 rotors made in China or Japan (should say on one of the arms)? My experience is the China made ones are terrible. They were difficult to bed in, lack of power, and super noisy. Comparing the Japan to China ones there's a distinct difference in finish quality. I've since moved on to using Sram HS2 rotors with Saint brakes and way better. Never had an issue with Japan made ones, not sure if Shimano moved all RT86 to China production but last 3 I bought were all China.

 

I'd make sure the rotor and pistions are properly aligned and that the pistons are moving evenly. Probably not a contamination issue if you didn't already have contamination issues.

 

Great feedback. Thank you, everyone. I bought the rotors on Universal Cycles. They were on sale compared to some of the other online stores. The side of the rotors is stamped with Japan, so it looks like they are not made in China. At least as far as I know.

When I put in the new pads, I pushed back on the caliper pistons so that the new rotors could slide back in. This may be the culprit. Maybe it's a good bleed and checking that the pistons are all in alignment.

Thanks again. I'll circle back once I confirm if this takes me back to the brakes I loved.

 

When I put in the new pads, I pushed back on the caliper pistons so that the new rotors could slide back in. This may be the culprit. Maybe it's a good bleed and checking that the pistons are all in alignment.

Check that you don't have a lever leak. From the round cap at the end of the lever reservoir. It has vent holes, there should not be oil coming through them. You can use a paper towel to see if it gets oil residue.

 

Shimano brakes are known to weep at the pistons, especially if they sit for an extended period of time. That gets mineral oil all over the pads.

 

This was my first thought, especially when the OP said they pushed the pistons back in (which you're supposed to do obviously). I cracked a piston pushing it back while using the Park Tool piston tool (it's metal). From then on, I only used plastic tire levers. OP should pull the pads and inspect the backsides to see if there is any trace of fluid (even a ring stain). That's a sure sign you have a leak, typically.

 

I am confused how you were using RT56 rotors with metal pads. They are not compatible. Those are resin only rotors. It seems you might have been getting "extra" bite by literally destroying your rotors.

The RT86 rotors are metal pad compatible. But metal takes more time to bed in because it is so much harder.

 

I am confused how you were using RT56 rotors with metal pads. They are not compatible. Those are resin only rotors. It seems you might have been getting "extra" bite by literally destroying your rotors.

The RT86 rotors are metal pad compatible. But metal takes more time to bed in because it is so much harder.

Wow! I never knew that. The rotors and pads combo mentioned above came with my then-new bike. I just looked at my old wheelset and the RT56 rotors and yes they're worn a little but not a crazy amount. Especially after 1.5 years of riding year-round. I'll reach out to Pivot and ask about this, although I am guessing they'll just tell me those are the standard pads that come with that brake set

 

Sounds like the new rotor might have contaminated the old pads while bedding in. Best scenario would be to clean the rotor and pads with rubbing alcohol & possibly sand down the pads and rebed.

You can also try and clean the rotors with rubbing alcohol and spray the pads as well, do a few rebedding runs and spray the pads with water before each time.... could help remove the contaminants.

If previous braking power hasn't returned, torch the pads with a propane torch for 45 seconds each.

If you don't want to torch the pads, replace.

The rotor shouldn't be the root of the problem, but it likely caused it. Pads are contaminated with a little oil or fresh rotor material...

 

Did you bleed the brakes when you installed the new pads? I would also give the pistons a good clean with some IPA and a toothbrush, lube with mineral oil, cycle each piston a few times and wipe clean. Just cleans any crap off the seals. Sticky seals/pistons are more likely to present as brake rub where the pistons don’t fully retract, but it could also be that they’re extending unevenly, resulting in a loss of power. Always worth doing anyway.

 

Start over incase there is a contamination by cleaning the discs with brake cleaner or rubbing alcohol, burn the pads and sandpaper them with a fine grit after wards, then bed-in till you can easily lock the wheels with one finger.

 

Alcohol is for cleaning off sealant. If you want to clean off oils, use acetone or brake parts cleaner. I've never had to sand a contaminated rotor. Swap pads and rub down rotor with acetone. One advantage of Shimano is you can buy a stack of pads for a reasonable price so this process isn't a time waster.

 

Naptha (lighter fluid) can also be added to the list of excellent oil removers.

 

Shimano brakes are known to weep at the pistons, especially if they sit for an extended period of time. That gets mineral oil all over the pads.

Because they weep even when they are not damaged.

I must be doing something wrong, because I never had these problems.

 

What can I say? It's a known problem. Doesn't mean every single person will suffer from it, but it's a real problem and I've verified it with shimano themselves. Their response was "yeah, we recommend removing the brake pads if you are going to let them sit for any period of time".

 

I have experienced these pad symptoms and never been able to validate any seepage. Several of us decided to take the theory to test by removing pads and incorporating a Dye Penetrant (NDT) and using only the developer to determine if any brake fluid is present at pistons. We performed test on four calipers with no positive indications of fluid presence. Note that all four of these brakes (calipers/pads) experienced the same phenomena repeatedly described in many threads. YMMV

 

well done.
I've had shimano OEM metallic pads seemingly lose power, after not being used for a longish period.
I never saw leaks or fluid stains on the pads or pistons. I've long wondered if the pad compound oxidizes or otherwise came into contact with something ambient causing the pad to go bad. Heating and sanding the pad solved the problem each time.

I've never experienced this problem with MTX ceramic pads.

 

I feel like a lot of these piston leaks could have been avoided by doing things right.

When you change the brake pads, you usually have to push the pistons in to fit the new thicker pads.
If you do it without opening the brake lever bleeding screw, you always run the risk of breaking either the piston seals or the master cylinder.

Why this? Because then there is a risk of over pressuring.

 

This is the source of many problems that people report, especially caliper and lever leaks. Was not an issue with old shimanos, people assume they can keep pushing pistons like in the past.

From my experience shimano caliper pistons do not leak. When there is oil on them it is a results of the above, or cracking pistons, both are user errors.

 

Just the data:

1. BR-M7120 + D02S + SM-RT68 203mm: a stock setup that worked great aside from the fact that I would regularly warp it, but can also induce pad fade in the course of high-energy-dump tests. Therefore it sits on the rear wheels of my eMTBs.
2. BR-M7120 + N04C-MF + RT-M800 203mm: could never get to work right despite lots of cleaning, rotor/pad sanding, baking, etc. It seems like I can never get these to the necessary operating temperature.
3. BR-M7120 + MTX GL131 + RT-M800 203mm: worked great on regular days, but on colder days (this is California Coastal "cold", not inland cold), it would take a couple moments of application to warm up to stop the mild squeal and produce the right bite... but it would cool off (and exit the squeal-free + right-bite envelope) almost immediately. Had it on the front wheels of my eMTBs until I got tired of the squeal.
4. BR-M7120 + MTX GL131 + SM-RT68 203mm: produces marginally better bite and warpage resistance than setup #1, and can't get to pad fade. This is what currently sits on the front wheels of my eMTBs.
5. Bonus (gravel)? RX820 + K05S-RX + RT-CL800 180mm & 160mm: works fine from day one, but have not had the opportunity to put through high-energy-dump tests.

In other words, I gave up on getting N04C-MFs to work on Ice-Techs. I can otherwise get Ice-Techs to work right, kinda. I'm going to try the BR-M7120 + D02S + RT-M800 203mm combination soon.

I have had my share of problems with Shimano brakes, but none of this "piston weeping" business was observed by me, esp. with the SO's eMTB (which I have claimed in the above as "mine" since I speak for her on this forum) that gets to sit for very long periods without getting ridden.

 

Yes, it actually happens.

I believe you, I’ve had it with M8100 and M6100. Bike sits unused for a few weeks and there’s no power. Not only ceramic piston models, plus both resin and sintered pads. Since switching Codes problems has gone.

well done.
I've had shimano OEM metallic pads seemingly lose power, after not being used for a longish period.
I never saw leaks or fluid stains on the pads or pistons. I've long wondered if the pad compound oxidizes or otherwise came into contact with something ambient causing the pad to go bad. Heating and sanding the pad solved the problem each time.

I've never experienced this problem with MTX ceramic pads.

As above M8100 and M6100 both have done it for me. OEM metal and resin pads, same symptoms.

I thought it was environmental contamination with the bikes being in the house. Aerosols, steam/oil from cooking in the air etc. Covered rotors and calipers with plastic bags. Issue was still happening. Problem has gone away with Codes.

I have experienced these pad symptoms and never been able to validate any seepage. Several of us decided to take the theory to test by removing pads and incorporating a Dye Penetrant (NDT) and using only the developer to determine if any brake fluid is present at pistons. We performed test on four calipers with no positive indications of fluid presence. Note that all four of these brakes (calipers/pads) experienced the same phenomena repeatedly described in many threads. YMMV

I thought you’ve never experienced this?

…. until they start weeping fluid out the piston seals. Then you buy a new set because they’re disposable.

Don’t ride them for a month and they’ve got no power.

Many years and miles on Shimano's and I have never experienced this.

 

How would an oil leak at the pistons get to the pads? I'd think that it would drip from gravity down and away. At least it would be quite visible.

 

Through the holes in the back of the pad that are "holding" the sintered material on.

Because of how brake pads are made (the sintering process), they're full of tiny capillaries. Capillaries transmit fluid excellently, even if thick [your circulatory system says, "hi!"]. You can see it in action if you spray the pads with brake cleaner: they wick and get "wet".

Even if pistons aren't leaking--they do, when damaged or out of spec, which is largely a warranty concern--your brakes collect tons of crap riding. When you are riding constantly, it's being scrubbed off. If you pull your pads, and see no evidence of oil on the backside (which you can use tissue paper for if it's not obvious), you can be relatively sure that the issue came from outside the brake.

Fwiw, we see environmental contamination from road bikes frequently. It's a whole thing, that happens in two ways: something gets on the bike, and it works fine for the rest of the ride, but soaks in and begins causing problems; causes issues immediately (such as riding through a rainbow-slick puddle).

Final thought: all seals weep. If they don't, they aren't sealed, or they certainly won't slide. My mountain bike sat for 8 months post injury. I just assumed it would need work to...work right.

 

The RT56 rotors are designed to only be used with resin pads. By using the metal N94C-MF pads you probably had amazing power and were absolutely annihilating them. Let the RT86 rotors properly break in and the performance will be great!

 

The RT56 rotors are designed to only be used with resin pads. It is stamped on the rotor itself. By using the N04c-MF pads you probably had amazing, albeit noisy possibly grindy sounding braking but were absolutely annihilating the rotors with the metal pads.

Properly bed in the RT86 rotors and break them in and you will have great performance.

 

I thought you’ve never experienced this?

Hey bonehead,
Some reason you wish to take this statement out of context? Why not add your reply that lead to this statement?

I said that I have never experienced weeping pistons.

…. until they start weeping fluid out the piston seals. Then you buy a new set because they’re disposable.

Many years and miles on Shimano's and I have never experienced this.

 

Blah-blah-balh, derp-derp-derp...six years, zero issues

 

I've had zero issues in five years with two sets of SLX 7000 brakes. This set of 9000 failed from the box.

2025 edit - actually the 7000 are leaking, on inspection. I let these bikes sit over the winter without riding them and I think the oil built up to a point where it became a problem.

 

I've had brake pad contamination twice in 4 years of running Shimano XTs, between various bikes. I still have the OG 4 yr old set, on its 3 bike/frame now.

The first instance was shortly after installing a set of MTX red pads... they just never really felt all that powerful. The second was with the stock Shimano finned pads on another bike. I tried the quick cleaning of the pad and rotor with solvent, and a light scuff of the pads to break the glaze. Didn't really work and I tried it twice.

In a final attempt, I tried it all. Cleaned with solvent AND scuffed the rotor really good. Cleaned with solvent, torched the pads till the smoke stopped, scuffed them and cleaned a final time with solvent. In both cases the brakes bedded in well and power returned to normal.

I've never noticed any signs of oil on the caliper, around the pistons, and I've had bikes sit for periods of time. I did have 2 master cylinders (both right/rear) start leaking in those 4 years. Their cheap enough, but it would be nice if they were serviceable and/or had a better finish/coating in the piston bore to extend their life.

My biggest complaint is they need regular cleaning, re-lubing, re-centering and piston advancement to keep the bite point somewhat in a preferred spot. Otherwise they start grabbing closer to the grip and often the pistons will start to advance unequally.. leading to pad rub and extended lever throw.

 

Hi. I can confirm same problem here. Yesterday I installed brand new slx m7120 brakes. Rotor in the front is RT86 (brand new) and brakes came with N04C pads. I cleaned calipers and rotors prior installation and bleed the brakes properly. I went to bed in but stopping power I had the next didn't get any improve. I even put my bike upside down over the night to check if there will be air inside. In the past when there was air inside with my br m447 (cheaper brakes) and keeping my bike on a wall the next day I had to pump the lever to get the braking power back. I had no issues with lever next morning. Maybe it needs time to bed in but my old brakes. When I replaced resin brake pads, oil and bleed them I had amazing stopping power with only 2 pistons. These are 4 pistons brakes that supposed to be much more powerful and maybe 4 or 2 times more expensive. I'm 100% sure the pads weren't contaminated. So I have no idea if I need to change pads for resin ones. I will wait some more time to bed in because tr86 was made in China. If you think I should go with resin pads please let me know

 

I will wait some more time to bed in because tr86 was made in China.

Those rotors are known to take forever to break in.