Noise from Disk Brakes
Is it normal for disk brakes to be noisy?
Both front and rear brakes make a similar noise on my Vectrix, but the front seems much louder (judged from the riding position).
The noise starts as soon as I can feel the slightest deceleration due to gentle pulling of the brake lever and it only gets a little bit louder with stronger brake force applied.
It sounds like a high-frequency electrical buzzing. The frequency reduces with reducing speed and it practically disappears below about 20km/h.
Could this be due to the holes in the disk? Front and rear disks have different hole patterns, that might explain the noise difference.
Any explanation / advice would be much appreciated!
Boy, sight unseen, this is a tougher question than you realize. But then I'm not a real expert, I'm just a former smog mechanic who's gone through life working on my own brakes and my friend's after high school auto shop.
1) Many pads have what was called a "Sensor" long before there were electronics to do the job. It's a little lip at the edge of the pad that drags on the edge of the disc when the pads are wearing out to warn you you're running out of brakes.
2) When your disc gets a glossy smooth finish, it will squeak even when there's plenty of pad on the pads. I take a piece of coarse samdpaper and take that right out. This is one thing that "Turning" rotors is for, in addition to removing damaged/uneven spots. Keep in mind that some motorcycles (Which scooters are) sometimes have this "Etched" surface on the disc rotor that isn't supposed to be turned, so taking samdpaper to it probably isn't within spec either.
3) Let me explain a product called "Disc Brake Quiet" as part of this one. Bascially, most calipers don't have the pad bolted or pinned directiy in place, they might have some clips or springs that are supposed to align the pads to press evenly on the rotor, but the cheaper the caliper (A HEM) the less that works. One edge then drags on the brake first, the pads wear unevenly, you get noise.You look at the pads and one edge is visibly worn beyond the others, well there you go. That sound won't go away until you replace those pads. If you try using the Disc Brake Quiet to glue the old pads to the caliper, you're not using superglue and there's a lot of pressure pushing one side of the pad until it's worn down even again, so expect them to come loose again if the face is not flat.
4) Junk can get in there and even a piece of a tumbleweed can make noise.
5) If your calipers have come loose, if the clips or springs are dragging, if if if. If it's out of place and can drag on the rotor, it'll make noise. Anything that runbs there that's not supposed to will give that sound. All you've described is the high speed whine of metal being rubbed agsinst. If it was metal on metal it would go from high frequency to a grinding as you slow. When one material is softer it can fade away as it slows.
I tried oil once. Wasn't terribly successful.
My V does exactly the same as yours, in fact I liked your description of the sound! You'll find that the noise is somewhat proportional in volume to how hard you squeeze the lever and apply the brakes. The frequency of the sound is proportional to the speed, like you mentioned. It's nothing to worry about and is attributable to the pads wiping past each hole in the disc as the disc rotates. All bikes with vented discs do it, it's just that usually you have a rattly old engine masking the noise.
Thanks for your post on the CAPcur question, sadly, it would seem that I may have posed quite a difficult problem!
All bikes with vented discs do it,
I completely agree. Very common noise in Barcelona's streets. Nothing to worry about.
here in Austria, change is recomended after two years. I´ll change it this winter when the bike is in its hibernation.
I have the equipment as I did change the brakefluid of my Virago to.
Does the "less-use" affect the lifetime of the brakefluid? Intersting Question, but I can´t say.