Are these rotors cooked?

**sierraskier** · 11-25-2016, 12:17 PM

Let me start this off by saying this ain't my first rodeo - I've successfully decontaminated rotors/pads before ...but I've tried decontaminating/cleaning these rotors with alcohol and brake cleaner twice and sanded a layer off the pads each time. It actually works and they feel/sound/perform good until they really heat up, then they honk, fade and loose significant stopping power. The whole bike/brakes probably only have ~30ish rides on them and pads have plenty of life. Starting to think rotors might be cooked but don't know what to look for in that scenario

**stuckathuntermtn** · 11-25-2016, 12:37 PM

I heard blued equals cooked, but then again, my rotors look a lot like that and work fine.
Hard to tell from the pic.
I only use alcohol. I haven't needed sandpaper much with metal pads.
You try those? It really helps. I get the yellow Trucker ones off Amazon. The hotter they get, the better they work. They don't fade till after about 2,000 kinda technical feet. And no squeal.

**kidwoo** · 11-25-2016, 01:40 PM

The rotors are fine, you've probably got messed up pads. Overheated rotors still work. Those aren't the aluminum core ones that you can really screw up.

Mine look like that too but it's more from constantly having to burn off the brake fluid that leaks onto my pads from the pistons.

**cmcrawfo** · 11-25-2016, 10:28 PM

Did you change the pad compound recently? What kind of brakes are they?

**stuckathuntermtn** · 11-26-2016, 07:42 PM

They don't do the 3 layers with Aluminum in the middle anymore? Since when?

How big are your rotors, OP? Maybe time to go up a size? I run 8" front and 7" rear. Not because I'm so rad or anything, it just works for me. I'm a bigger guy. Bigger rotors heat up slower and cool down quicker. And, oh yeah, you can stop quicker.

**kidwoo** · 11-26-2016, 08:51 PM

Originally Posted by stuckathuntermtn

They don't do the 3 layers with Aluminum in the middle anymore? Since when?

I'm wrong, I thought just the ones with the fins were aluminum. I've just never run the ones I have (like this) down that far. I was thinking these were just like the old centerlock ones.

**sierraskier** · 11-26-2016, 11:02 PM

Thanks guys. So they are whatever Ice Tech rotor that comes with XTM8000 kit (left it at my parents house where there's no snow). The rear is a 180, and yes on my other bike I upgraded the rear rotor to a 203 for better stopping power, so will probably get to that on this bike eventually. I swapped the OEM finned shimano pads (which I believe are metallic) with some kool stop organic finned pads. Cleaned rotors again as well...I've done one ride and no honking so far but it was more of a cross country ride so did not really have enough long descents to really heat them up. Over all much smoother feel but they are still breaking in. So the verdict is gonna be out for awhile until I can get on a bigger descent.

**XXX-er** · 11-26-2016, 11:13 PM

Ime the only time a rotor was truly phucked was when the area between the holes in the rotor wore so much that when I replaced the pads they got eaten real quick by the un even rotor surfaces

so it had to be real wear on the disc ... not just heat blued

**Crampedon** · 11-26-2016, 11:42 PM

I had a good talk with a tech at Sram a few weeks ago, a customer very begrudgingly bought a new complete bike that came with new Sram guides, after I warrantied his last avid's on another bike and replaced with Shimano…. these howled after a few weeks. The bike manufacturer would happily credit my account and let me put Xt's on his bike but I called Sram first. Got a long rap about proper break in 20 ALMOST stops, 12 ALMOST stops at a faster speed, he stressed NEVER coming to a complete stop during bed in and went on to say you are putting pad material onto the rotor, and THAT becomes the braking surface. In their testing they have never found a product or technique to adequetly clean rotors. He sent me new pads and rotors for this guys bike and we followed his protocol exactly, and it worked perfectly. He said to consider rotors a wear part and disposable as much as pads…. Another guy with the same brakes was crying and we just put on XT's and he's super happy. Just passing along some new spewing from Sram warranty, but it's interesting.

**cmcrawfo** · 11-27-2016, 12:44 AM

Originally Posted by sierraskier

Thanks guys. So they are whatever Ice Tech rotor that comes with XTM8000 kit (left it at my parents house where there's no snow). The rear is a 180, and yes on my other bike I upgraded the rear rotor to a 203 for better stopping power, so will probably get to that on this bike eventually. I swapped the OEM finned shimano pads (which I believe are metallic) with some kool stop organic finned pads. Cleaned rotors again as well...I've done one ride and no honking so far but it was more of a cross country ride so did not really have enough long descents to really heat them up. Over all much smoother feel but they are still breaking in. So the verdict is gonna be out for awhile until I can get on a bigger descent.

^^This is your problem.

If you switch from a sintered to an organic pad, it recommended that you replace the rotor....or ghetto fix it by sanding the shit out of them. The sintered material is embed into your rotor now, and that what's causing the sounds.

Some organic pads do not respond well to brake cleaners either So that could also be part of your problem.

Either sand / replace the rotor. Or switch back to sintered pads.

Boiling your organic pads in a pot of water will remove any potential contaminants left from the cleaner... although this step is probably less important.

and Run the larger rotor in the front. It will give you better stopping power.

LC · 11-27-2016, 06:40 AM

Just ride them if they feel fine but keep feeling the braking surface for it wearing thinner. If you have RT86s (Ice Tech) then replace them when you start seeing the inner material. It's a trickier decision with the RT76s but replace it if the slight wear freaks you out. I buy RT86 if I see them cheap but normally RT76 and get about a summer and a half from them riding mostly big alpine singletrack descents.

**sierraskier** · 11-27-2016, 11:11 AM

Originally Posted by cmcrawfo

^^This is your problem.

If you switch from a sintered to an organic pad, it recommended that you replace the rotor....or ghetto fix it by sanding the shit out of them. The sintered material is embed into your rotor now, and that what's causing the sounds.

Some organic pads do not respond well to brake cleaners either So that could also be part of your problem.

Either sand / replace the rotor. Or switch back to sintered pads.

Boiling your organic pads in a pot of water will remove any potential contaminants left from the cleaner... although this step is probably less important.

and Run the larger rotor in the front. It will give you better stopping power.

So just to clarify, I just did the Kool Stop pad swap right after I started this thread, before my last ride. The OEM pad/rotor combo is what was honking/sucking this whole time, on basically new brakes/bike. It didn't start right away but probably 10-15 rides in after I super-heated the brakes a couple times. The build kit came with a 203 on the front and a 180 on the rear. The new pads actually feel pretty good so far on the 1 ride I did, and have not been honking, but as I said I haven't really heated the brakes yet so will need a few more rides. If all else fails I will eventually replace the rotor (and upgrade to 203 in the process) but not going to do that unless absolutely necessary.

After Crampedon's experience tho, I will certainly try to warranty these first as there is no possible way new brakes purchased in June with ~30ish rides on them should be done yet.

Crampedon, interesting info and new detail on the bedding process. I did try to re-bed them each time I cleaned the rotor and pad, same with the new pad, but definitely not to the extent you describe above.

**jm2e** · 11-28-2016, 10:48 AM

- I feel like SRAM loves to spell out a super complicated process for maintaining their shit, so that when the customer says it's broken they can just respond by telling you you're stupid for doing it wrong. Same thing goes with their elaborate bleed process and suctioning all the invisible air out of the brake fluid. I wonder if they explained what was happening differently between an almost stop and a complete stop.

- clarification: The RT-86 rotors have the alloy sandwich. The RT-76 rotors are all stainless. They otherwise look the same.

- Ironically, I'm going through this same issue with my wife's new bike. Less than 30 rides. After a couple weeks the brakes suddenly just had zero bite. The rotor had a funky glaze on it and they would squeal with a pulsating/vibrating sound that seemed to be keeping any kind of lock up from happening. Kind of like how ABS feels on your car. In a bad way. I sanded the shit out of them, Wiped with brake fluid and changed out the pads. Seemed alright for a couple rides but then after a couple long descents the front started acting up again. Only option now seems to be trying brand new rotors and brand new pads and see if it goes away. Otherwise I'm worried there's something wrong at the caliper level.

**kidwoo** · 11-28-2016, 12:21 PM

Originally Posted by jm2e

- I feel like SRAM loves to spell out a super complicated process for maintaining their shit, so that when the customer says it's broken they can just respond by telling you you're stupid for doing it wrong. Same thing goes with their elaborate bleed process and suctioning all the invisible air out of the brake fluid. I wonder if they explained what was happening differently between an almost stop and a complete stop..

Seriously. That break procedure is silly. But it at least describes almost every braking scenario of descending a trail for 10 minutes with a turn or 20.

Originally Posted by jm2e

-
- clarification: The RT-86 rotors have the alloy sandwich. The RT-76 rotors are all stainless. They otherwise look the same...

Ah. Thank you. I mangled a rotor badly enough to split it this summer and it was definitely stainless all the way through. Makes sense. I buy cheap.

Originally Posted by jm2e

-
- Ironically, I'm going through this same issue with my wife's new bike. Less than 30 rides. After a couple weeks the brakes suddenly just had zero bite. The rotor had a funky glaze on it and they would squeal with a pulsating/vibrating sound that seemed to be keeping any kind of lock up from happening. Kind of like how ABS feels on your car. In a bad way. I sanded the shit out of them, Wiped with brake fluid and changed out the pads. Seemed alright for a couple rides but then after a couple long descents the front started acting up again. Only option now seems to be trying brand new rotors and brand new pads and see if it goes away. Otherwise I'm worried there's something wrong at the caliper level.

I assume you mean brake cleaner? Regardless, that sounds like the brake pads are getting oily...which is why new ones would have fixed it for a while. Every single pair of shimano brakes I've had eventually starts leaking around the pistons, thereby contaminating the pads. You might have a bad one out of the gate. You can usually burn it off with some really heavy long, brake dragging.

Originally Posted by sierraskier

It didn't start right away but probably 10-15 rides in after I super-heated the brakes a couple times.

You might have just glazed your pads. That happens sometimes with the metal ones. The solution is usually just to keep riding them till you wear past the cauterized layer.

**gramboh** · 11-28-2016, 01:07 PM

Related question:

I have a pair of Zee brakes with Shimano metallic finned pads that I was using with some old rotors on my old DH bike. I put in new pads during Crankworx and was a lazy turd and didn't break them in properly which resulted in horrible howling and even shuddering on the front brake the last time I used them. Previous set of metallic finned pads were silent so I know it was a bed-in fail.

On my new bike, I now have those same brakes but bought new RT86 rotors (203mm f/r). Same caliper/lever/hose/pads (metallic finned) but new rotors. Front brake works perfectly. Rear brake is howling like a bitch especially when wet, but power is fine.

I used brake cleaner and sanded the pads before I swapped brakes to the new bike. I did a bed-in on the hill in the alley behind my house on the cleaned pads/new rotors with about 7-10 gradual stops for each brake.

Guessing I should hit the rear pads with cleaner and sand them again?

**jm2e** · 11-28-2016, 02:03 PM

Brake fluid gets the rotors nice an shiny. Just like baby oil on a lady.
Both applications make me faster!

**jono** · 11-28-2016, 10:58 PM

Avoiding full stops when bedding pads (or when they're extremely hot, if possible) is a good practice. I also do that with Shimanos. In auto racing, warped rotors from holding hot pads in one spot was a well known issue twenty plus years ago. I expect the chance of transferring a little extra pad material into just one spot on the rotor while stopped hot is different but similar (warping being less of an issue with thin/solid rotors). If the friction coefficient changes a little in a couple of spots it will set up a resonance, aka squeal.

It's worth noting that SRAM's choice of brake fluid allows for higher temps than mineral oil and as a result they are probably expecting more from their pads. Not that anyone is melting the aluminum cores on Shimanos, but if the SRAM system can take higher temps it can be designed with less material.

**kidwoo** · 11-29-2016, 09:24 AM

I do know someone who flew halfway around the world just to boil his guides on his race run last year. Not your average race course but still.......... I don't know anyone who's boiled mineral oil, at least that they were aware of.

I thought the claim shimano always made was that their oil mix transferred less heat than dot 5, like more of an insulator. Makes sense why their caliper pistons have so many problems it it makes the heat stay even more localized.

**jono** · 11-29-2016, 11:38 AM

Please don't take my post as an endorsement of DOT 5.1 systems, it's not that. There's plenty of evidence that Shimano has this better sorted, even if not by a huge margin. And note that I refer only to the complete systems: if SRAM does indeed cut down on the mass of the first-line heat sink, the rotor, then they can easily design a system that is as prone to boiling (or moreso) even with a higher temp fluid (and if that fluid isn't brand-new 'dry' it probably isn't a higher temp fluid anyway). Every other component in the system matters, too. I was just pointing out that their choice of fluid lends credence to the idea that their pads might run hotter and thus be more sensitive to bed-in procedures.

**kidwoo** · 11-29-2016, 12:17 PM

I think the shimano setup is just better insulated. I've only done it once or twice and on some unusual riding on my dh bike but people glaze those metal pads on shimanos all the time it seems. I think that's the idea with the heat sink fins and the ceramic pistons too. Like you said......a system. I'd probably guess that generally speaking the shimano pads run hotter, it just stays right there at the pad, where as sram can let that heat run a little bit since they've got the dot 5.

Mostly I just think sierraskier drags his brakes too much and rides like a sissy.

**SLCMunchie** · 11-29-2016, 12:21 PM

I THINK i've got a similar setup. shimano XTR brakes with metallic finned shimano pads, and a sram rotor. bike shop said that sram rotor sucked and sram admits it and they thought the shimano works better. Brakes still work well, but squeel after prolonged use on a downhill. i'll get around to switching out the rotor some day, but for the meantime i've just had to live with it. so, rotor isn't cooked, is just the design sucks for some reason. seems to be particularly bad after doing a lot of braking in dusty conditions.

**sierraskier** · 11-29-2016, 12:22 PM

Originally Posted by kidwoo

Mostly I just think sierraskier drags his brakes too much and rides like a sissy.

That is likely most of the issue

**jm2e** · 11-29-2016, 12:32 PM

Two questions I'm curious about in this thread:
1. What is this "known" problem with the Shimano pistons/calipers? I always thought they were pretty reliable. Hence the fact that Shimano has been dominating the brake wars for about a decade and regardless whether Guides are a step in the right direction, there are a ton of people who are very reluctant to find out.

2. Other than the alloy sandwich in Shimano XT/XTR rotors, is there any difference between any rotor? They're all just stamped pieces of stainless steel, right? Shimano, SRAM, Ebay special, it's all just a flat piece of metal with little holes cut out. Am I wrong here? (edit; I'm talking about the braking surface. Debates about two piece rotors and 6-bolt vs center lock are a different issue)