Hawk HPS pads Bad knock
07-07-2009, 11:23 PM
#1
Hawk HPS pads Bad knock I just swapped in some Hawk HPS pads and have 80 miles on them right now, under hard braking they knock pretty bad. I have everything torqued down correctly and lubed up, nothing is loose nor am I leaking fluid, the lines were vacuum bled and look good. The rotors are the stockers with a fresh turn, I miced them when I got them back from the shop and they are ok.
Any ideas?
*** EDIT ***The knock is consistent, like I had a bump in my rotor and can only be heard under hard braking ***EDIT***
Any ideas?
*** EDIT ***The knock is consistent, like I had a bump in my rotor and can only be heard under hard braking ***EDIT***
Last edited by Cthulu; 07-07-2009 at 11:29 PM.
07-08-2009, 07:48 AM
#3
07-08-2009, 08:03 AM
#4
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A micrometer is the wrong tool to measure rotor warp, or run-out as it's technically known as. The micrometer will check rotor thickness, which can be in spec on a warped rotor. Instead you should use a dial indicator and a stable base and check how much the rotor moves "in and out" when it's rotated. This will also take into account the runout of the whole system which includes rotor and hub.
Or you can take the rotor off and lay it on a granite surface plate and use a height gauge and check for variation in height from the surface of the plate.
The interface between the rotor and the hub can also affect runout. If either are very rusty then it's possible that the rotor is not sitting flat against the hub.
Or you can take the rotor off and lay it on a granite surface plate and use a height gauge and check for variation in height from the surface of the plate.
The interface between the rotor and the hub can also affect runout. If either are very rusty then it's possible that the rotor is not sitting flat against the hub.
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07-08-2009, 12:14 PM
#10
Hmm, looks like a get to buy a new tool, the rotors are freshly turned but a poor job could have been performed. :-) Autozone here I come. Thanks for the advice guys, I'll measure the runout and see if it is within spec.
07-08-2009, 03:40 PM
#11
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I had the same problem after installing, the HPS pads.
The noise was loud, so I did not want to try going through the bedding in process.
Thinking that I had left something loose, I removed the tires to see what I did wrong and found nothing. I inspected the the discs, they were parallel and flat.
After cleaning the pads and rotors (in case there was any contamination) then reassembling, I still had the same problem.
In the process of driving around the block and trying to figure out what the issue was, the knocking got less and then finally disappeared.
It really did seem as if there were some sort of contamination on the disc surface causing the friction coefficient to be high for part of the disc and then low for the rest of it.
I have replaced many brakes in my life and am very good about making sure that there is no grease, oil or coatings on the rotor prior to installing the pads. Maybe this time the machine shop used something while machinining the rotors that the brake cleaning fluid did not remove. I have never used the Hawk pads before, perhaps it is something peculiar to them.
Regardless, after the pads bedded to the discs, they have performed fine for the past 6000 miles or so.
The noise was loud, so I did not want to try going through the bedding in process.
Thinking that I had left something loose, I removed the tires to see what I did wrong and found nothing. I inspected the the discs, they were parallel and flat.
After cleaning the pads and rotors (in case there was any contamination) then reassembling, I still had the same problem.
In the process of driving around the block and trying to figure out what the issue was, the knocking got less and then finally disappeared.
It really did seem as if there were some sort of contamination on the disc surface causing the friction coefficient to be high for part of the disc and then low for the rest of it.
I have replaced many brakes in my life and am very good about making sure that there is no grease, oil or coatings on the rotor prior to installing the pads. Maybe this time the machine shop used something while machinining the rotors that the brake cleaning fluid did not remove. I have never used the Hawk pads before, perhaps it is something peculiar to them.
Regardless, after the pads bedded to the discs, they have performed fine for the past 6000 miles or so.
07-08-2009, 11:20 PM
#13
