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Looking for smooth rotors

Old 06-15-22, 05:02 PM
  #1  
rosefarts
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Looking for smooth rotors

Like smooth as a babyís butt.

Iíve had several bikes with disc brakes. It seems that with little exceptions, the brakes make an annoying chatter. ThThThThTh you get the idea. This is not a squeal and the brakes work great.

Its clearly caused by the multiple cutouts for weight savings or cooling or whatever marketing reason they come up with.

So Iím hoping to find a smooth braking surface. Does this exist? Is there a disadvantage other than 20-30gm in weight? Why does every rotor have this?

Maybe for cooling but is it really?

Do I have options? Earbuds maybe?
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Old 06-15-22, 05:11 PM
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Those cutouts are to eliminate or reduce brake fade when the rotors get hot enough to outgas organic material from the pads. Without the cutouts, the vapors from outgassing would create a low friction barrier between the pad and the rotor, reducing braking ability. I doubt these are the source of your problem, as the brake pads are chamfered at the edges to avoid this. More likely, your rotors are glazed and they are chattering. Try to roughen the surface with some steel wool (without soap).
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Old 06-15-22, 06:56 PM
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Originally Posted by hayden52 View Post
Those cutouts are to eliminate or reduce brake fade when the rotors get hot enough to outgas organic material from the pads. Without the cutouts, the vapors from outgassing would create a low friction barrier between the pad and the rotor, reducing braking ability. I doubt these are the source of your problem, as the brake pads are chamfered at the edges to avoid this. More likely, your rotors are glazed and they are chattering. Try to roughen the surface with some steel wool (without soap).
Seems like quite the claim considering that automobile disc brakes are smooth unless itís a Porsche or something. Motorcycles seem to have them, but even then, not on every one.

My mountain bike plus me and a pack still comes in way under 200lbs.

I can try some steel wool but it sure feels like a design problem. The chattering brake I had made the entire bike vibrate once it warmed up, this is totally different.
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Old 06-15-22, 08:00 PM
  #4  
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Originally Posted by rosefarts View Post
Like smooth as a baby’s butt.

I’ve had several bikes with disc brakes. It seems that with little exceptions, the brakes make an annoying chatter. ThThThThTh you get the idea. This is not a squeal and the brakes work great.

Its clearly caused by the multiple cutouts for weight savings or cooling or whatever marketing reason they come up with.

So I’m hoping to find a smooth braking surface. Does this exist? Is there a disadvantage other than 20-30gm in weight? Why does every rotor have this?

Maybe for cooling but is it really?

Do I have options? Earbuds maybe?
could be due to the pads or rotor - low-to medium quality pads and/or low quality rotors (stamped / not heat treated) ?

could be due to incorrect pad break-in ? pads not bed in correctly

rotors overheated and warped ?

could be pad / rotor mismatch ? sintered (metal) pad used on stamped / non heat treated rotors ?

if pad is contacting area outside of the rotor track could lead to issues ?

example: Shimano has rotors with two different 'tracks' where the pad meets - if the larger / deeper pad is used on a rotor for the smaller / shallow pads the pad could contact the cut outs or 'arms'

???

Last edited by t2p; 06-15-22 at 08:21 PM.
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Old 06-15-22, 08:06 PM
  #5  
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Is the "ThThThThTh" noise happening when you apply the brakes, or after when you release the levers?

If the latter, clean your pistons and/or realign your calipers.

If the former, true your rotors or replace them.
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Old 06-15-22, 08:10 PM
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Originally Posted by rosefarts View Post
Like smooth as a baby’s butt.

So I’m hoping to find a smooth braking surface. Does this exist? Is there a disadvantage other than 20-30gm in weight? Why does every rotor have this?
recently upgraded a bike to / with better brake system including better pads and rotors

the pads and rotors are Shimano Ice-Tech; the Ice-Tech 3 layer rotor features an aluminum core sandwiched between stainless steel outer plates

I went with the finned resin pads (instead of sintered)

I smile almost every time I pull a brake lever - smooth

Last edited by t2p; 06-15-22 at 08:43 PM.
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Old 06-15-22, 08:13 PM
  #7  
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I have a Trek Marlin 6 29r with Tektro hyd. disc brakes. These brakes have never been noisy and they work great. I pulled the pads this year and no sign of wear and I'm thinking I got it new in 1995. I hope you find the problem
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Old 06-15-22, 08:30 PM
  #8  
rosefarts
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The bike was new in March. Not cheap.

The front is Magura 4 piston while the rear is their 2 piston. 180mm. I actually have no idea whose rotors.

Funny you mentioned bedding in, I drove through a snow and slush storm, basically caking the bike in ice when it had zero miles. I wonder if the road grime affected it.
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Old 06-15-22, 08:41 PM
  #9  
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Originally Posted by rosefarts View Post
The bike was new in March. Not cheap.

The front is Magura 4 piston while the rear is their 2 piston. 180mm. I actually have no idea whose rotors.

Funny you mentioned bedding in, I drove through a snow and slush storm, basically caking the bike in ice when it had zero miles. I wonder if the road grime affected it.
I'm old fat and slow - so slow break in and proper bedding now comes naturally lol
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Old 06-16-22, 03:53 AM
  #10  
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The old Avid G3 Solid Sweep can still be found if you look.
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Old 06-16-22, 05:29 AM
  #11  
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You can also get SRAM Centerline rotors (note: Centerline, not Centerlock). https://www.jensonusa.com/SRAM-Centerline-Rotor They're not solid, but their cutouts are shaped to rotate "in line" through the caliper rather than having a bunch of hole punctures in the rotor.

I, too, have experienced the "ThThThThThThTH" sound coming from my disc brakes. It seems to happen more with hydraulics than with cables for some reason. I've done a lot of swapping around on my bikes, of brake systems, pads, and rotors. Note: I have bikes with Tektro Aries (cheap cable calipers) and with inexpensive Shimano hydraulics, and both take the same brake pad, and I've swapped pads around as well as trying different configurations of brakes and rotors. I consistently get the ThThTh noise with light application of the hydraulic brakes. The exact same set of pads (like, the same physical pads) on the same physical rotors don't seem to make the same noise if squeezed by the cable calipers. I'm thinking there may be something where the steel cables in the cable brakes transmit more general noise from the brake, which drowns out the little "burble" noises you get (ThThTh) as the pads close and expose the little rotor holes. The hydraulic hoses and fluid doesn't transmit the same general noise from the brake, so you can hear that pad interface more. I don't know...just a theory.
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Old 06-16-22, 07:11 AM
  #12  
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I just got my first set of disc brakes when I got my new bike a few years ago. They don't make noise or squeal. Not even in wet conditions.

I really doubt the holes are the reason for your noise. They might contribute to it's unique sound, but they aren't the reason for it, IMO.

I've had plenty of rim brakes that squealed annoyingly too. Some even when dry. Many when slightly wet from damp roads.
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Old 06-16-22, 08:04 AM
  #13  
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Iíve pretty much only ridden this bike in wet conditions. The only time I can elicit a squeal is that very first grab after a while of not braking in wet conditions. After that theyíre dry and quiet. That isnít what Iím asking about at all.

FWIW, a couple years ago I got some ultralight cutout and cheap rotor for my old bike. It made that sound so badly that I was worried it would chew through my pads in a single descent. I replaced it with a Centerline and it stopped. I totally forgot about that until now. Maybe Iíll try that again.

Pretty sure SRAM and Magura are both 1.8, unlike shimano at 2.0. So thatís also something to think about.
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Old 06-16-22, 12:59 PM
  #14  
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I've had a number of bikes that had chatter or pulsing in the disc setups. In all the cases it was one of a few things. First and most common was that the caliper was not pressing the pads to the rotor evenly. Mostly due to the caliper being something other than dead on parallel to the rotor. If the pads aren't pressed evenly they will scuff a little harder at each edge of each opening and make that chuffing sound you seem to be trying to describe. Some setups are reasonably tolerant. But I've had a couple which were hellishly sensitive to this issue. I had all these variations despite only dealing with half a dozen brands and models over the years.

The couple of times I had actual chatter which wasn't RPM related, just a wild operatic screech, it was some sort of contamination on the pads and thus on the rotor as well. Mostly from oily/greasy fingers in the shop but on one instance due to some oil I picked up off the road since the chatter started at mid ride after going through a small puddle on the road. Cleaning both rotor and pads fixed these in most cases. One time the pad had soaked the oil in so badly and cleaning was doing so little that I gave up and had to toss them.

The bottom line though is that vented rotors CAN run smoothly and quietly. But in some setups finding that setup can be a challenge to our fine tuning abilities.
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Old 06-17-22, 07:31 AM
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if the rotor is warped, it will cause that irregular noise/feel.
I would try the Centerline's as mentioned.
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Old 06-17-22, 11:19 AM
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Before spending any cash, why not try cleaning the rotor, pads and calipers, straighten the rotors, and align the calipers followed by a decent bedding in?
This eliminated 99% of squealing on my trp spires (type c, 160mm discs).
When they get wet there's a little squeal at the start of the pads engaging but it quickly disappears. Nowhere near as loud as before.
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