Chamfering brake pads

[Guest ratchethack]

Gents!

 

Yesterday I went for the usual amount of front brake approaching a stoplight. Instead of the expected response from the big Brembo's, I got a chatter and vibration that startled me enough to back off the brake immediately. I tried it again carefully, and it was back to the normal routine for the rest of the day.

 

Inspecting the brake afterward, there was no sign of road debris or scoring of the disks. The pads have a good 3 mm left on them, and the calipers are relatively clean and free of built-up brake dust and road crap between pistons and calipers, having been well cleaned at last tire change.

 

This has happened several times over the years with these brakes with different, but same mfgr. pads. I've never had any other brake do this. It ain't a big thing, but I'd hate to have it happen at the wrong time.

 

My pads of choice are Ferodo Premium. I like these very much. They generally have superb, linear, fade-free performance under all conditions with the Brembo's, I get good life out of them, and they're easy on rotors. No desire to try other kinds of pads (been there, done that). I'm also not interested in using "anti-squeak" compound on the backs of the pads. I've used this stuff many times before and IMHO it doesn't work, just makes a mess, and the Brembo's don't squeak anyway.

 

I read somewhere that putting a 45 degree chamfer or bevel on the leading edge of brake pads can alleviate a tendency to chatter. It'd be easy enough to do, but I've never tried it.

 

Any experience with this out there?

 

Many TIA.

[mike wilson]

Aren't there anti-chatter/squeal shims/clips for this sort of problem? One man's squeal is another's chatter. 8-) It's just a matter of frequency.

[Dan M]

 

Any experience with this out there?

 

Many TIA.

 

Hey Ratch,

 

We've chamfered pads to eliminate chatter / squeak many times. Usually it's only needed on specific situations where the rotor is worn and shows a lip on the edges. Then the chamfering is not so much required on leading and trailing edges, but the sides, as the pad gets "trapped' between the inside and outside lips of the rotor causing it to vibrate. If your rotors are flat and the pads do not overhang the edges, I doubt that chamfering wil have much effect. I'd start by cleaning with brake clean and roughing the face of the pads with 80 grit sandpaper. Then when installing, tweak the clips that apply pressure to the pads. Their function is to eliminate chatter or squeal.

 

Hope this helps.

 

edit: I'm with you on the anti-squeak pastes and sprays. They are just a bandaid for brakes that are not right, be it faulty parts, installation or both.

[dlaing]

What sort of frequency vibration?

I have had the sensation of warped rotors with a vibration apparently equal to the rpm of the rotor.

But it was not accompanied by any particular noise, atleast that I noticed.

Solution was to clean the semi-floaters.

[Guest ratchethack]

Hey Dan -- thanks for the response. This is wot I was hoping for -- the perspective of a Pro. I took a gander at the Imperial Automotive site. I reckon you oughta know y'er business.

 

The Brembo rotors are as flat and smooth as they can be with no scoring inside or out, and pads don't overhang the edges. I never heard of tweaking the clips, will give this a shot. Looks like this might be about all that can be done. Hopefully it'll have some effect.

 

I'd be interested in your take on this:

 

I b'lieve I might've dreamed this one up. Not that I'd do this on the Guzzi, but on offroad bikes, on occasion over the years I've removed significant scoring of rotors by setting the wheel up on a bench with the spindle well clamped, and hit the rotor with an angle grinder, spinning the rotors as I "brighten 'em up" and restore them to something much closer to "smooth & flat". Since no one I've spoken with about this seems willing to resurface rotors on bikes like they do on car rotors designed for resurfacing (the only alternative for bikes being new rotors) I've found this to be a viable technique that has extended rotor service life many years. The word "precision" certainly doesn't apply here. Installing the rotor "backwards" on the wheel allows access to angle grind the other side. I don't even bother following up with emery cloth, just use 'em "as is" right off the grinder. I reckon I can get away with this several times before I have to get new rotors. A new set o' pads and Bob's yer's Uncle. How bad could this be?

 

Any comment?

[Dan M]

 

I b'lieve I might've dreamed this one up. Not that I'd do this on the Guzzi, but on offroad bikes, on occasion over the years I've removed significant scoring of rotors by setting the wheel up on a bench with the spindle well clamped, and hit the rotor with an angle grinder, spinning the rotors as I "brighten 'em up" and restore them to something much closer to "smooth & flat". The word "precision" certainly doesn't apply here. Installing the rotor "backwards" on the wheel allows access to angle grind the other side. I don't even bother following up with emery cloth, just use 'em "as is" right off the grinder. Since no one I've spoken with about this seems willing to resurface rotors on bikes like they do on car rotors designed for resurfacing (the only alternative for bikes being new rotors) I've found this to be a viable technique that has extended rotor service life many years. I reckon I can get away with this several times before I have to get new rotors. A new set o' pads and Bob's yer's Uncle. How bad could this be?

 

Any comment?

 

 

Wow. How much material are you removing? I would be worried about the two surfaces not being parallel. We often remove the glaze from the surface of the rotors with a "scotch-lock" pad by 3M on a die grinder while the rotor is turning on the lathe. We also "finish" rotors this way after cutting. The surface is better for bedding-in new pads. It does not remove any significant material, just cleans up the surface. The only way I would remove more than a few thousands material is on a lathe. Most rotors will have a minimun thickness stamped on them or specified in a manual. You can go that thin safely. If your grinding has not produced any pulsation in the braking then what the hell, go for it.

[Guest ratchethack]

Wow. How much material are you removing? I would be worried about the two surfaces not being parallel.

Like I said, this isn't precision work here. I guess the right question might be, "How PRECISION does it need to be -- as long as it works like new??" I reckon I've taken as much as two or three thousandths off either side every time I've done this, maybe less. Seems to me it can take some inaccuracy and non-parallel here, 'cause the pads will "bed in" to accomodate -- within reasonable ranges of course.

The only way I would remove more than a few thousands material is on a lathe. Most rotors will have a minimun thickness stamped on them or specified in a manual. You can go that thin safely. If your grinding has not produced any pulsation in the braking then what the hell, go for it.

Well, that's wot I figure. Again, the alternative has been new rotors, and this is quick and easy enough. At the rate I've been going, I'm probably able to get as much as 20K, even 30K miles extended use out of rotors this way without any detectable adverse effects.

 

Thanks f'er the feedback.

[Dan M]

I'm probably able to get as much as 20K, even 30K miles extended use out of rotors this way without any detectable adverse effects.

 

Thanks f'er the feedback.

 

If you can not detect a problem then there is no problem

I would continue doing it if I were you. If the rotor faces are out of parallel to each other the effect is the caliper piston gets shoved in when on the thick part of the rotor and is allowed to come back out in the thin part. What that would mean to you is a pulsating brake lever, and a grab & release sensation when slowing. Doesn't sound like you have any of that so continue on man!

Besides on a dirt bike you are not generating near the braking force or the heat that you are on your V11.

[Guest ratchethack]

If you can not detect a problem then there is no problem I would continue doing it if I were you.

Thanks f'er the vote o' confidence. That's wot I was kinda fishin' for. Good to have the Pro feedback!

If the rotor faces are out of parallel to each other the effect is the caliper piston gets shoved in when on the thick part of the rotor and is allowed to come back out in the thin part. What that would mean to you is a pulsating brake lever, and a grab & release sensation when slowing.

I'd been more concerned about radial measurements for parallel (that is, variance in rotor thickness within pad contact area from ID to OD), not angular parallell (that is, lack of consistent rotor thickness though 360 degrees at a given radius pad contact point). Any variation here will likely continue to be negligible. If it ever starts to pulsate, I reckon it's time for a new rotor. I can easily enough verify wots' going on with a caliper measurement. So far, I've never had one be off perceptibly enough to give any pulsation, but yes, I imagine this would be more'n possible eventually.

 

Good stuff.

 

Thanks again, Dan.

[quazi-moto]

I've chamfered linings for drum brakes and I suppose it could be done on disc brake pads as well, but I've never done it before.