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[Richard230]

The brake pads on my 2012 Zero S have a couple of visible holes in the rear of the pad assembly.  My BMW has the same type of holes in the back of its rear pad and the owner's manual says that these holes are used for determining when the brake pads have worn out.  The manual says that the brake pads must be replaced when their thickness drops to 1mm and the disc surface must not visible when looking through the inspection holes.

However, I note that the rear brake caliper on my Zero has a couple of metal nail-like devices on each side of the pad that look like they would contact the disc (and no doubt make some sort of noise) before the pad backing rubs against the disc. 

I can't verify if these are wear indicators or how they work as I typically inspect my brake pads by looking at their ends and replacing them before they get less than 2mm thick.

While I was looking at my rear caliper today I noticed that the rubber cap that seals the bleeder valve to keep dirt out of it was missing.  I found a suitable rubber cap in my collection of rubber "vacuum" hose caps that are sold for a few dollars at automobile accessory stores.

[Larry295]

Well I haven't checked the pads wear, but it's funny because I was just checking them out on my Ducati too a few hours ago!! Not sure how to check them on the Zero though...

But anyway what's interesting is that you mentioned the metal sound that the rear brake makes. I have 350 miles on my bike and thought it was just the fact that the pads were not broken in, since I try not to use the brakes much.

But what is that sound, is it normal, and does anybody else experiences it?

[CliC]

What kind of noise? Mine developed a high-pitched squeal shortly after I got it (though really it's purer in tone than most squeals). Richard230 suggested it might be something on the disc (and consequently the pad), so I have cleaned the disc several times with a solvent. This did help, but did not eliminate the noise completely. (I was too lazy to remove the caliper and pad and clean it, too; figured I'd just wear it off the pad and clean it off the disc periodically.) I've also mashed the rear brake from 50 mph or so a few times, to try and get the pad to "seat" or "break in" a little, and that seemed to help a bit as well.

Something else tells me it's a resonating part issue, because there are times when I'm rolling to a stop, with no rear brake at all (regen, for example) and I start to hear the same noise. I've jacked the bike up and run it and confirmed it is coming from the caliper, but apparently other things besides braking can excite the resonance (like taking off slowly, or regen braking, both of which also excite other thin-metal buzzes that I have yet to pinpoint).

[Lipo423]

The entire braking system in our bikes is pretty "symple" (let's be diplomatic), as it is essentially build-up around a light Dirt-bike concept...I do have the same "noises", the front brake has "some movement" and does a kind of "clock" whenever you brake (which i thought it was due to the floating disk, but it is because of the calliper-pads design).

I got tired of it and I'm going to change my front braking system; will have to build a new brake support for avoiding having to change the fork (which will also be modified -spring change, oil & tuning, etc...).

I'm using a Bembo 16x18 radial pump, Axial 4 pistons calliper and Supermotard 320mm disk (it is not clear if I will need an build-specific disk because of the Zero rim), we'll see.

Stay tuned, I'm starting the project the next week...

[Richard230]

My brakes are completely quiet when operated.  Lots of car and motorcycle brakes squeal and that is usually claimed to be due to some foreign material imbedded into the pads, or due to vibration caused by a loose pad, or just due to the design of the caliper or the pad material.  

There are compounds that can be applied to the back of brake pads that reduce these vibrations and they seem to work for automobile calipers. But the backs of our brake pads seem to be exposed and I don't think that compound would work.  

Most brake calipers use an "anti-rattle" spring located at the top of the pads to keep them from vibrating.  Perhaps this spring is missing or was installed incorrectly at the factory  when the pads were installed.    

[Larry295]

mine is not a squeal. It's a metal rubbing type of noise. Doesn't sound right. Just like metal is rubbing against the disc...

[Lipo423]

Larry295,

For motorcycles there are basically three kind of brake pads:
- Organic (they are made of a combination of different fibers + resin) -they wear faster, but are no good for water-
- Semi-metal (low quality steel + other components) -half way
- Sintered (copper alloy) -best performer, but needs high quality stainless steel rotors-

The ones in our bikes are sintered, which have the best performance for all conditions (dry, wet, hard use, etc...), if they come together with suitable caliper, disk, and pump 

[Larry295]

Lipo: so is the metal rubbing noise normal ? I mean I don't get that on my Triumph, or Ducati, even even my Tmax before...

[Richard230]

Metal rubbing noise is not normal, although sintered brake pads do make a slight "metallic" noise when slightly scraping against the disc when the brake is not being used.  However, you shouldn't hear the noise when riding more than a few mph and it is not very loud.

Of course, you can always do what I do and wear earplugs. Then most noises won't bother you so much.   

[Larry295]

oh when I ride it's fine. And it's not being bothered that is the problem.  It's just that it feels wrong when you hear this metal rubbing thing...

[manlytom]

Hi Larry,

are u certain is metal rubbing or just the brake pads at work. As there is no other noises just wind and brake pads you might mistake the normal braking noise with metal rubbing. On other bikes you just dont hear it as the motor drowns out everything.
What is the milage on the bike ? In case very low mileage they tend to be a bit harsher as well until "broken in."

[Lipo423]

Hello Larry,

There is some metal rubbing (especially with sintered pads as there is close to 100% metal-to-metal contact). From my opinion what makes the noise more noticiable -as Tom pointed out- is the fact that this is not an IC bike...the other reason could be the disk metal quality level (sintered pads are able to "eat" a soft disk easily).

Maybe you did not hear the noise in the other bikes because of different pads compouds/braking design... As far as I remember the original Tmax did not come with sintered pads -probably Triumph either.

I believe we all will end up with Richard's earplugs...that maybe the solution

[Larry295]

I have 350 miles on the bike. So that may be it. I'll ride some more and we'll see what happens.
As long as I don't see grooves on the discs, I guess everything is normal
thx for the info guys.