# Disc Brake Pulsating / Vibration



## tnetz798 (Jun 4, 2013)

Hey guys, 
I'm new to the disc brakes and mine has the hydraulic setup. This is a new bike and when I went out the first time, the brakes felt really smooth and stopped well. After a little bit of "breakin" I notice some clicking or catching coming from the rear brake. I was already near the shop so I stopped in and he said there was some gunk (barely visible) on the rotor and he cleaned it up.

This fixed the problem for a while but now its back, and I think its front and rear now. Is this normal? Everything works fine and stops great but the brakes aren't smooth like they were. I'm guessing this is just the nature of these things but figured I'd ask to be sure. 

Thanks!


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## tnetz798 (Jun 4, 2013)

This is more of a pulsating / vibration, I should say. Started on the second ride out, maybe 10 miles on it.


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## Shibby (Jan 13, 2004)

tnetz798 said:


> This is more of a pulsating / vibration, I should say. Started on the second ride out, maybe 10 miles on it.


What brand/model brakes?

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## wschruba (Apr 13, 2012)

Probably chalk it up to a bad bedding process. You need to clean the rotors again (use isopropyl alcohol and a lint free rag). Apply the brakes lightly 10-20 times each from about 15 mph to walking speed, without stopping completely. Repeat stopping a bit harder the second go around.

If that doesn't solve the issue, you may have an out of true rotor.


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## tnetz798 (Jun 4, 2013)

The brakes are Cannondale Helix 6 Hydraulic Disc, 180/160 mm...just looked that up 

I didn't do any type of break in so that's a good possibility. I will say after searching around on the forum, this seems to be a real common problem with no real fix, at least none that I've read about. I don't want to make this bigger than it is, so I'll just clean them up for now and see where that takes me. Otherwise its back up to the LBS.


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## coopdad (Nov 6, 2010)

This brings up another question. My brakes work good from the LBS, does one need to still be-in the brakes?

Also, is bedding-in some sort of chemical process activated by heat or is it a process of changing the shape of the pads (or both)?


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## bikeabuser (Aug 12, 2012)

The wife's car did this, and the fix was having the rotor turned because it had warped just enough to cause a chatter/pulsation.

Bedding in is the process that occurs as the brake pads take a proper seating within their carriers, and become squared up with the disc during the first X number of light braking applications.


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## eb1888 (Jan 27, 2012)

Bedding in is depositing(embedding) microscopic amounts of brake material onto the rotor.


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## tnetz798 (Jun 4, 2013)

I took it into the shop and explained what it was doing. They heated the pads, cooled the rotors with water and all kinds of other stuff to bed them in. It was great for about 10 mins and then the vibration, pulsating, catching....whatever you want to call it,, came back. Now I have 2 options...takes it back up to the lbs and be "that guy" or replace/upgrade the brakes on a brand new bike.


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## DennisF (Nov 4, 2011)

coopdad said:


> Also, is bedding-in some sort of chemical process activated by heat or is it a process of changing the shape of the pads (or both)?


Here is my understanding of the brake pad bedding process learned from automotive sites and bedding the rotors on my cars. I'll try to summarize:

Brakes work by two processes -- friction and adhesion. Friction is self-explanatory. Adhesion is like dipping your fingers in honey and touching the rotor while it is turning. The material in brake pads works by friction of course, but it is also sticky. Adhesion is not a designed-in feature of brake pads -- it is just an unavoidable property.

So you buy new pads and rotors for your car or bike, and use the brakes to slow to a standstill without proper bedding. There will be a glob of brake pad goo left on the rotors where it came to a stop. Due to the glob on the rotors, they now wear unevenly. The brake pedal on a car pulsates. Most people think the rotors are warped, but actually the thickness varies.

But if you bed your new pads properly, you can avoid this. Do hard braking, but not to a complete stop. Speed up and do it again. This distributes goo evenly around the rotor. It also hardens the pads, making them less gooey and less likely to deposit gobs of goo on the rotors.

When bedding in a car it takes maybe 10-20 cycles. You will smell the brakes, and if you look at the rotors at night, they will be a dull red.

When you have completed all the speed up/hard braking cycles, drive for a few minutes to cool the rotors or drift to a stop without using your brakes.


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## tnetz798 (Jun 4, 2013)

Mine is definately a goo problem as the issue goes away after a good cleaning of the rotor. That said, the shop did everything they could to bed in the pads last time I was there. So in my mind its a pad problem. At this point I'll probably end up upgrading the brakes on my own. I'll ride it out until I get sick of clicking down the trails haha.


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## eb1888 (Jan 27, 2012)

tnetz798 said:


> At this point I'll probably end up upgrading the brakes on my own. I'll ride it out until I get sick of clicking down the trails haha.


SLX are 79 a wheel at Bluesky.
Warranty the brakes and sell them as new/unused.


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## DennisF (Nov 4, 2011)

tnetz798 said:


> Mine is definately a goo problem as the issue goes away after a good cleaning of the rotor. That said, the shop did everything they could to bed in the pads last time I was there. So in my mind its a pad problem. At this point I'll probably end up upgrading the brakes on my own. I'll ride it out until I get sick of clicking down the trails haha.


Well, I'm not convinced that heating the rotor artificially to bed them in, or whatever they did, is going to work. It think would be hard to duplicate the effects of several hard brakings on a stand.

The good news here is that your rotors aren't worn unevenly, because cleaning the rotors "fixes" it.

It wouldn't hurt to clean the rotors up, then go try to bed them in the usual way.

I have SLX brakes. They feel silky smooth, and everyone that rides it comments on how good the brakes are.


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## rangeriderdave (Aug 29, 2008)

You could replace the pads ,I had to do that once ,to fix the same problem.


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## tnetz798 (Jun 4, 2013)

Today i went out and lost a few of the rear rotor bolts as apparently they were loose. To me this is unrelated to my problem but what it did do is cause me to be really hard on my front brake for a good stretch of remaining downhill. I never rode the brake for long, just short bursts. This might have finally bed in the front brakes at least because they feel great. 

Now to locate my rear rotor bolts and do the same back there.


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## tnetz798 (Jun 4, 2013)

Just an update....The brakes are terrible in just about every way. I talked to the LBS and they're trying to warranty them through cannondale but its looking like the best I'm going to get is a new set of pads....IF they can even get pads since its pretty well known that pads don't exist for these calipers. We'll see. As far as the bedding in process, I've been riding a lot more and understand that process completely as I probably bed these pads in 3-4 times a ride. There are a few 5 min intervals where they're silky smooth, then right back to the crap. I'm most likely going to take advantage of the deal at Blue Sky.


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## cobba (Apr 5, 2007)

> IF they can even get pads since its pretty well known that pads don't exist for these calipers.


Brake pads are very easy to find and they are readily available, the Helix 6 brake uses the same pads as the Hayes Sole, the Hayes MX-2, the Hayes MX-4 and the Hayes MX-5 brake calipers.



> They heated the pads, cooled the rotors with water and all kinds of other stuff to bed them in.





> As far as the bedding in process, I've been riding a lot more and understand that process completely as I probably bed these pads in 3-4 times a ride.


Burnish - Brake power is generated by the friction material on the pads embedding into the surface of the rotor, re-bonding to the friction material still on the pads and then breaking apart or shearing. In order for this bonding/shearing to occur, the friction material must first be displaced onto the surface of the rotor. This typically happens during the first 10 - 50 stops of a brake system and is referred to as "burnishing" the rotor and pads. When a rotor is cleaned, it will need to be re-burnished again to re-deposit the friction material onto the surface.


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## theraggyone (Jun 3, 2013)

I had a set of helix 6s on the 2012 cannondale sl4 I used to own I put up with them for 4 weeks with a few trips back to the shop I brought the bike from before they got warrentied , I had pistons sticking, loss of power and huge amounts of vibration definatly the worst hydros I have used. Luckily cannondale agreed with my LBS that they sucked and swapped them for SLXs which were amazing. Hope you get it sorted

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## tnetz798 (Jun 4, 2013)

Thanks guys, it'll get sorted one way or the other here soon. I keep reading a lot about people having issues with these brakes. Some find pads that will work, as mentioned by the semantics authority in the post above yours, but they report that they had to grind down a part of the pad, etc, to get them to fit properly.

From what I've found is its a two part problem: the pads are too soft to bed in properly and they also seat really loose in the caliper. 

I talked to the LBS and he said cannondale was willing to warranty the pads but now he's trying to track down a set. I'm just going to buy the SLX's since I keep hearing great stuff about them and see if the LBS can throw me a bone with the install or something.


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