Sound during heavy braking

[TomekSZ]

Hi,

riding my lemans pretty sharply around town noticed a strange thing. When the brakes are warm up and with sharp crashes they make strange sounds. Something like blowing into an empty bottle. I checked the pads and they still in stock. In addition to the sound, they also give a slight vibration to the steering wheel. Do you have an idea what this could be? Maybe something with a brake pump?

[MartyNZ]

Some suggestions:

The sound could be could be a pad vibrating, caused when one piston is not moving as much as it's paired piston. If so, then the answer is to take the wheel off, remove the pads, and clean around the pistons in the calipers, and clean/degreased the pads and pins. Free the movement of all 8 pistons by exercising them until they all move the same.

Little blocks of wood 18mm X 40mm pushed into the caliper between the pistons you are not working on will help you avoid popping a piston out of the caliper accidentally as you work the brake lever.

 

Also make sure that the disks are clean and grease free.

 

The handlebar vibrations could be caused by a warped disk. Just spin the wheel, and check for wobble. I couldn't see any runout limit in the workshop manual, but I'd expect that anything like 1mm runout would need replacement.

 

Also check that the disk and caliper attachment bolts are all tight.

 

Then I'd finish with bleeding fresh fluid through the system.

 

Also worth checking are wheel bearings. See Lucky Phil's observation here:http://www.v11lemans.com/forums/index.php?showtopic=18641&page=2&do=findComment&comment=210595

Another thread on this is here: http://www.v11lemans.com/forums/index.php?showtopic=13947

Edited August 9, 2017 by MartyNZ

[coreytrevor]

One thing I've seen more than once is brake pads that got soaked with fork oil from leaking seals that never got replaced. They can make a sound like you describe and kind of a vibration too at lower speeds. After a while the pads don't really look like anything is wrong with them, so it can be hard to tell visually. Sometimes there will be junk packed into the pad grooves from the oil and brake dust etc. That's a giveaway.

 

I would try new pads and cleaning the rotors really well. Make sure the holes in the rotors don't have oil and junk stuck in them. The rotors need to be clean enough that a cloth with brake cleaner rubbed on the rotor comes away clean.

[TomekSZ]

hello,

 

I checked the fork and oil spills - none of them flowed, although in fact they were never exchanged sealants - unless at 2 thousand kilometers because now it has invaded 18 thousand. Anyway, it's not that though looking at the brakes rather they are clean. I will try to clean it even more precisely.

[TomekSZ]

Ok as simply as this - MOTUL P2 Brake Clean and even i do not open the calipers just sprawy into the caliper and on the brake wheels.  

[Chuck]

Thanks for the update..