Front Brake Grinding Sound By DrRocco (Read 8,603 times)

[DrRocco]

For the first 75 Km or so I put on my scoot, I used the rear brake much more than the front.  I didn't really think about it for a while.  Even the very minimal time I had spent on a motorcycle had me grabbing the "clutch" lever on the scoot before hitting the front brake.  Obviously, the clutch lever being the rear brake on the scoot was slowing me down pretty good and then I didn't leave much work for the front brake to do.  Eventually, I thought about what I was doing and started making an effort to grab the front brake first and then supplement with the rear.  Once I started actually using the front brake as intended, as most of the braking force, I started to notice a terrible grinding sound.  At first, I chocked it up to the pad needing to wear down to seat properly on the disc.  I started using the front brake a little harder than normal to help with the wear in.  Now, with right at 200 Km on the scoot, the grinding sound isn't getting better.  It might even be getting worse.

 There isn't any shimmy or other weirdness.  It's doing its job: stopping the bike.  It just sounds bad.  I've looked at the disc and it doesn't seem warped.  For about 7/8 of the tire rotation, the disc clears the pads by less than 1/16" and then it does rub the pad for a bit.  It still turns very easily by hand.  Even if I rest my forehead on the bike to ensure my head doesn't move and then watch as I turn the wheel by hand, I can't see any irregularities in the rotor.  There are no uneven grooves or pad deposits.  The grinding sound doesn't pulsate when I brake, so I don't think it's a warped rotor.  I've got one on my truck right now I need to replace and it's NOTHING like that.  It's just a loud grinding sound.

Normal? Not normal?

[kz1000st]

Not normal. Did you look at the brake pads? If they're not inexplicably worn out the surface might have picked up something that's grinding into the disc. I would check the rotor for signs of something carving into it, take out the pads and lightly sand any glaze off. Also, believe it or not, checking the routing of the speedometer cable. It might be binding under front end compression. Been there, fixed that.

[cyborg]

Pads metal side in? I've seen that one,,,,

[DrRocco]

I'll tear into it today when I get back from class and let you guys know what I find.

[cyborg]

I've also seen the caliper not tightened and the caliper " tipping" so check the outer edge of the disk itself to see if the caliper is touching because it's moving and loose

[DrRocco]

I'd be able to check that with my hand, right? When I first started looking into this, I grabbed the caliper and tried to move it around. It's either tight or I'm not strong enough to move it.

[mxmatt]

Grinding usually means metal on metal. I had a caliper bolt work it's way loose on me last month and it created all kinds of havoc. I'd take the caliper off and take a real good look at things. May be that the pads were installed backwards. Keep usposted. Nice looking scoot you have there.

[jvino]

All the advice I've seen so far seems right on. Possibly use a power washer on the front caliper it might get the particle unstuck and work better. Other than that I would take kz advice and just take of the two bolts and look at it.

Good luck and keep us posted.

[DrRocco]

I took the caliper off and removed the pads. The only thing out of the ordinary I found was that one of the socket head brass bolts that hold the pads in place was not tight. It was still flush with the caliper, it just wasn't tight. I sanded the glaze off the pads, used a C-clamp to push the caliper back in, put a little silicone lube on the back side of the pads and re-assembled everything. Nothing has changed. After really paying attention to the sound and feel, it does have a little bit of a pulse in the brake feel. More than anything though, it just sounds like grinding. Check this out. The audio is terrible, but right at the very end of the stop I make at 1:27, you can hear a little bit of the trouble. When I hit that front brake, it sounds like I'm dragging a cinder block on concrete. Any other ideas?

[cyborg]

i watched the video,,you definitely have a metal to metal contact somewhere,,,,i hate to be a drag but i would take the caliper off again,,look everything over again something metal is touching the disk when you apply the brakes,,,

[DrRocco]

I'll take it apart again tomorrow Pete. This time, I'll document the whole process and post another video. Maybe one of you guys will see something I'm missing. If anyone has any specific shots I need to include in the video, please let me know and I'll do my best to include them.

[cyborg]

well the noise happens when you pull on the lever as i could tell from the video,,so either there's a anti squeal shim turned around so the retention tabs are scraping the disk face,,,you may have semi metallic pads with a bigger chunk of metal imbedded in one of the pads thats making the noise,,,mine make a whirring sound but thats because of the holes drilled in the disk,,this sound of yours truely does sound like metal to metal to me

[DrRocco]

I agree about the sound. I just don't know where it could be coming from. It's such a simple system. There aren't any shims or wear indicators. Again, I'll crack it open again tomorrow and give everyone a better look. Just so you can be thinking of possible causes in the mean time, here's what I'm working with...

Pads

Disc

[cyborg]

i know this is your first bike but i can tell by your posts you're no dope,,the system is very simple and direct,,but there may have been a machining error on the caliper or when they stamped the backing plate for the pad it may have a tab or something erroneous thats contacting the disk,,,the grinding noise is loud and strong enough it must be leaving marks that you can sleuth out ,,,take it out again before you take it apart again and run the brake a few more times so it leaves a nice mark you an see easily

[jvino]

I agree I would take of that caliper again and check the pads up close. The only time I noticed it was when the bike was at a stand still. Keep us posted I think it might not be anything to worry about might just be breaking in. But with that said seems like the rotor is bent a slight amount.
Mabey call how you bought it from and ask them?