Intermittent Zinging Rotor Sound

[Herder000]

Got the bleed kit today and “burped“ them. Still zinging
Aitrui, which rotors do you mean? Shimano XT RT86 Ice-Tech rotors? I think they’ll still hit the pads but if they don’t make the noise I’ll be v happy!

 

[Aitrui]

Yes, or you can use the RT-76 also, which is much cheaper, and still has the same alloy middle part.

 

[Supratad]

Today I removed pads from rear clopper to bend out the spring and whilst doing so, I noticed the little black post mount adapter/ spacer had a little triangle of shiny alu at the back upper corner. The “legs” of the disc must be jussssst clipping it.
But why only at a certain speed and above?
What’s causing a lateral movement?

 

[urastus]

Today I removed pads from rear clopper to bend out the spring and whilst doing so, I noticed the little black post mount adapter/ spacer had a little triangle of shiny alu at the back upper corner. The “legs” of the disc must be jussssst clipping it.
But why only at a certain speed and above?
What’s causing a lateral movement?

while you're riding the bike and leaning it down while you yourself stay relatively upright - imagine how the stresses affect the wheels. Where the wheel contacts the ground via the edge of the tyre - the force is pushing that section of the wheel up. The axle acts as a fulcrum, so that the top half of the wheel is being levered down. For example, if your brakes are on the right then I'd expect that the rotor / caliper would make contact on right hand turns. You could emulate this by leaning the bike over at an angle while static and pushing down driving that bottom edge of the rim into the dirt.

 

[Supratad]

I was thinking that but the noise occurs when riding straight, not just on corners.
Obviously, force vectors in real life are very complex and I cannot claim I am 100% vertical but yes, that must be something bending laterally to cause this.
I’ve reseated the clopper by the usual method and the gap looks bigger but no test ride as it’s “pashin’ doon rite enuff “

 

[Herder000]

I've slightly improved mine, it sounds like a steam train now rather than a cat with a bell...

 

[Akiwi]

Did a 65 Km ride with my wife yesterday.
Problem fixed, it was the spring clip!!!!!!

 

[Herder000]

I realised I’d overfilled my reservoirs when I burped my brakes the other day. The pistons wouldn’t retract fully. I removed the excess fluid last night and have just tested it, no more “zinging”! I still have a slightly wobbly disc but now have more clearance when the pads retract so it no longer hits the pads. I occasionally hear a zing or two when cornering hard left but other than that it’s silent (well, the brake is anyway). I am beyond happy

 

[Akelu]

I was having this problem on my BR-MT520 the intermittent rubbing, did all the usual, aligning caliper, resetting pistons, even tried new rotor and break pad nothing fixed it. It was the spring rubbing against the rotor. I bent the spring apart a bit and now it doesnt rub. Not sure why thats needed but it works.

 

[urastus]

It was the spring rubbing against the rotor

That's my experience too

 

[Akelu]

Also, I bent It at the very top by putting two flat head screwd drivers together flat to flat evenly and pushing it against a table in that small slot. So I didn't bent the legs unevenly or something. Just kept bending bit more bit more until it didn't rub. I didn't actually take the bike for test to see if it wasnt rubbing, I just slid the spring back and forward in the caliper listening for it rubbing there.

It's weird that it happens even with new brake pads/new spring. Id love to know why this is happening. But after stressing so long I'm just a bit over it all and happy to have a quiet bike.

 

[urastus]

Also, I bent It at the very top by putting two flat head screwd drivers together flat to flat evenly and pushing it against a table in that small slot. So I didn't bent the legs unevenly or something. Just kept bending bit more bit more until it didn't rub. I didn't actually take the bike for test to see if it wasnt rubbing, I just slid the spring back and forward in the caliper listening for it rubbing there.

It's weird that it happens even with new brake pads/new spring. Id love to know why this is happening. But after stressing so long I'm just a bit over it all and happy to have a quiet bike.

They are fairly maleable springs (easy to bend). They probably fatigue. Not like normal spring steel.

 

[Akelu]

They are fairly maleable springs (easy to bend). They probably fatigue. Not like normal spring steel.

I found it to be the opposite, i was quite surprised by the force necessary to bend them, maybe im just weak

 

[urastus]

I found it to be the opposite, i was quite surprised by the force necessary to bend them, maybe im just weak

How we view the force needed to bend these springs is subjective You were probably surprised given their light, delicate design. Saying that, I'm surprised that a better design has not been implemented.

 

[Akelu]

How we view the force needed to bend these springs is subjective You were probably surprised given their light, delicate design. Saying that, I'm surprised that a better design has not been implemented.

Its interesting how the new spring did the exact same thing, manufactured at a different plant and having a very slight difference in design. It must be the caliper itself? Perhaps it is sitting too low on the rotor so the rotor comes up higher inside the caliper? Thats the only thing i can think of. Could it maybe be a caliper mounting issue? As nice at is to have this quiet, it would be nice not having to bend springs to get them to work..

 

[urastus]

Its interesting how the new spring did the exact same thing, manufactured at a different plant and having a very slight difference in design. It must be the caliper itself? Perhaps it is sitting too low on the rotor so the rotor comes up higher inside the caliper? Thats the only thing i can think of. Could it maybe be a caliper mounting issue? As nice at is to have this quiet, it would be nice not having to bend springs to get them to work..

They're just not a good design. They really are fragile. For example, one side can sit totally flush if it is not symmetrical, this means that the other side is angling out toward the hinge of the spring (near the top of the pads).

I can also imagine that they get knocked about when something (little stones, gum nuts, sticks, bark, mud) gets caught in the caliper.