I know it doesn't happen too often, I mean when you know pretty much everything already, questions don't come up too often.

OK seriously, as some of you know, a couple of weeks ago I replaced my brake pads front and rear, and then flushed out the brake fluid with new DOT 5 fluid. Everything is working perfectly except one thing.

When I slightly push on the rear brake and as I come to a stop, probably the last 5 feet, the rear brake makes this awful sound. Not a squeal, no clunking, its kind of hard to describe, but more of a low growl. If I push down on the pedal a little harder it goes away, but that's not safe to use the rear that much. Anyone got any ideas? Is it just the new pads trying to seat to the surface? Should I pull the disc off and give it a good sanding? All thoughts considered. Thanks.

Wow! That was almost a normal conversation..... (he said to himself)

 

Yeah I'd imagine its just natural noise from the pad roughing up with the rotor. Remembver the rotors have 10K miles (don't you have like 10K miles on the bike?) and the pads are brand new, so they don't have the grooves in them that the rotors do. I'd imagine it would go away. I've always been taught with brakes, that you should jab on them several times, do some hard stops, to get the pads scuffed in. I'd bet that the sound you are hearing is a vibration from mixing old rotors / new pads.

Someone may say different, though, that's just my .01

 

Deej my 07 has been doing that since the day I bought it. Currently about 6500 miles. As your coming to a stop just before you stop it has a god awful grindy growly metal screechy sound. I actually thought it was the trackmaster skidding a little bit at first but it must just set up a harmonics just at the right speed and pedal pressure.

The pads and the disc look to be in top notch shape so, I got used to it and could give a rats *** if it growls now or not.

 

I just realized that I referenced it as disk and not disc.....Dee Dee Dee Ok now I have to edit it.....I know I'm sick. Ok well I think I might take the "disc" off and see if I can sand it, it can't hurt it right?

 

Actually I just looked at the rear disc again here at work, and I think I know what it is. Right at the very outside of the disc there is a high ridge like the kind you get in a piston cylinder. We used to use ridge cutters on them. It's about the thickness of a credit card and I think what is happening is the brake shoes are coming into contact with that first, then the lower part of the disk hast to twist slightly to hit the bottom part, so I'm gonna see if I can get the ridge out and see if that takes care of it. I'll follow up, no time this week, lots of company and other projects, but this will be interesting to see if that is what it is.

 

Hmmmmmm interesting.

When replacing your pads, you could lightly sand your discs with an electric drill and a 220 grit sanding disc, putting a light cross hatch pattern on them. This helps break the glaze on the disc and aides in bedding the new pads quickly. Install your new pads and go for your bedding run. Before making the first stop after changing pads pump the brake lever carefully before you really need to stop. The pistons are fully retracted into the caliper when you change the pads and the lever will feel long at the first brake application.
When bedding in the pads, be very careful as the brakes will not work at their optimum until fully bedded in...
Harder, high temperature pads usually have an overall lower coefficient of friction even when they are in their ideal operating temperature. Because of this you can expect having to pull on the brake lever much harder with them installed unless you go to a bigger brake system with more pad area. Softer, lower temperature pads generally have more initial bite and require less lever effort but they will fade much more quickly.
Through proper selection of brake pad material and careful bedding in you should be able to reduce pad fade to a manageable level except in the most extreme racing conditions.

 

Interesting, yeah I didn't think about turnin' the rotors... good eye, Deej.