Berge20

Before I lug the bike into the LBS, wanted to check here and see if this is just par for the course.

I'm totally new to disc brake systems and am just starting out on a SRAM Red Hydraulic Flat Mounts w CLX-R 160mm centerlock rotors. When I am riding at speed, no sound. When I am riding and feather or only slowly depress the rear break shifter, no sound/good slowing. If I do a hard pull on the rear brake, it will make something between a gurgling and a grinding sound. Good stopping power. Pretty/very sure it is a metal sound, so don't confuse my gurgling with a liquid issue, but it's what it sounds like to me. Nothing high pitched or anything.

After releasing the rear brake from that type of hard stop, you will occasionally, and for a short period of time, hear something rubbing constantly. I assume that's the disc warping and now not quite setting right in the system. However, it goes away quickly (heat dissipation perhaps?) depending on how hard/long the brake was.

Long and short, just trying to figure out if this is just normal for this setup. Or if I have one or two separate issues within the system.

It is my understanding that these were "bedded in" by the LBS originally.

SurferRosa

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hokiefyd 

Disc brakes can sound like they're grinding, especially if you're used to a quiet rubber pad rim brake. That's because they sort of are (grinding). Even organic pads have a pretty hard/firm consistency and they're squeezing a metal brake rotor. I've found that disc brakes are generally noisier than rim brakes, especially before everything really breaks in. Some rotors have a simple machined finish to them and you'll see that this machined finish is "parallel" to the pads at two points around the rotor and "perpendicular" to the pads at two other points. This machined finish will eventually wear in (basically, it's polished up by the brake pads) and brake operation can be noisy until this happens. I've also found that different hole patterns in the rotors can create different noise patterns. You can also check to make sure the caliper is positioned correctly on the rotor, and that the pads are not scraping along the "spokes" of the rotor.

Unless you hear a sharp grinding noise accompanied by score marks or similar on the rotor surface, it's probably just a different noise than you're used to hearing.

Berge20

oooops!

Rolla

Yeah, the gurgling sound might just be the brake rotor holes passing between the pads. The front brake on one of my bikes does that when braking at higher speeds. In general, it sounds like everything's okay with yours -- no rubbing, no squealing -- but there's also no danger in pulling the pads out and inspecting them, or in repositioning the caliper if it gets out of alignment. There are lots of YouTube videos out there worth looking at, even if you don't actually perform any of the repairs or maintenance they depict. They might help to de-mystify some of the inner workings and help you prepare for potential issues that might pop up.

ClydeClydeson

I would not assume the LBS bedded in the pads before purchase. Take the bike on a ride where you hit the biggest hills in your area, and build up a good head of steam on the downhills and apply your brakes such that you come to a stop gradually so as to maximise the length of break-in cycles. You can alternate F and R brakes on each run.

Berge20

Thanks all. Is it typical for a brake to warp temporarily after heavy use and then rub slightly for a few minutes after? Just trying to get my head around all of this.

hokiefyd 

I would not say that it's typical for a rotor to truly "warp", no. Brake rotors are almost never perfectly laterally true. This is just due to the nature of the imprecision involved, including the rotor itself, the flatness (or not) of the hub surface to which it's mounted, the runout between that and the axle bearing on which the hub spins, etc. You very often need to true the rotor (by physically bending it) as it's installed to the wheel. Do that once and then don't remove that rotor again unless you must, because that rotor is now matched to that exact mounting spot on the hub. If you re-clock the rotor on the hub (as in, removing it and reinstalling in a different position than when you trued it), you will likely need to re-true the rotor. Watch videos online on how to do this -- it's not hard and just takes some time and patience.

Anyway, all that to say that the rotor is probably not perfectly laterally true and it sounds like it takes a half beat for your caliper pistons to retract into the calipers. The rhythmic light brushes of the rotor against the pads as the rotor spins are what you're hearing. Once the pads fully retract back into the caliper, there's enough clearance generated and the rotor no longer bushes against the pads as it spins.

You can eyeball the trueness of the rotor by slowly spinning the wheel on a bike stand. Look down at the rotor and caliper interface along the fork blade. You'll likely be able to see the small gap between the rotor and the pads. Hydraulic brakes should have an even gap on both sides. As you spin the wheel, your rotor may appear to shift left or right a little bit. This is an indicator that the rotor is not perfectly laterally true and may need some correction.

Iride01 

I was new to disc brakes last year. It took 300 miles of riding before the pads wore in to provide way more than adequate stopping power. And they did sometimes sound like they were grinding.

But if you need an excuse to browse the LBS, take it back and let them see it or reassure you. And don't forget to take your bike back for any free inspection and adjustment they might have mentioned when you bought it.

Rolla

I agree with hokiefyd -- probably just the pistons aren't uniformly retracting. They can/should be cleaned and lubricated occasionally, but FOLLOW THE INSTRUCTIONS regarding when, how, and what to use.

Bill Kapaun

Try getting out of the saddle and lean the bike to each side for a couple wheel revs and see if it goes away "quickly".

Berge20

Roger all. Thanks again and will keep at it. Minor issue at most it appears, but good thoughts on how to clear it up potentially.

prairiepedaler

Hi Berge, welcome aboard Bike Forums.

You may want to read this thread >

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cxwrench

Post #2 pretty much had this covered...

Berge20

The internet is great

Trevtassie

When bedding in disc brakes never come to a complete stop. It allows heat from the disc to cook the pads hard before they've had a chance to deposit material on the discs. Slow to a near stop, then release and roll away to start the next cycle. It's never a good idea to come to a complete stop and hold the brakes on after severe braking in any case, that'll cook the pads too.

sjanzeir

And you still missed a couple of "breaks" in your edit

Berge20

fooferdoggie 

they can my 203 ice tech order on our tandem often does. that after any braking, even the new one does it though not as bad.

Berge20

Initially I would have said this helped, but when I tried it today, it didn't really seem to. Curious as to what it would indicate (possibly) if so? Trying to learn from you all! Thanks

Bill Kapaun

Side play in the wheel bearings.
I'm not into disc brakes, but a "bit" of side play allows the rotor to "knock" the pads into a slightly "more retracted" position.