This weekend I headed home from school to work on my car. I was changing rotors and pads on the front, which should have been a pretty easy process. Unfortunately after reassembling everything and going out for a drive the car makes a clunking sound from the front end under braking. The sound is variable with wheel speed i.e. it slows down as the car slows down. I disassembled and reassembled everything on both sides and the problem still persists.

The rotors are the drilled rotors from Vertex with Hawk HPS pads.

Any ideas as to what this might be?

All help greatly appreciated.

 

Chris,
Boy are you in luck...kind of. I have the answer to your question unfortunately, you aint gonna' like it. Your brand new rotors are warped or there may be a small gouge in the surface of the rotor somewhere. I had the same problem with the EXACT type of rotors you have described. I got them from another source but they did the same thing. I currenctly have Zimmerman drilled rotors on the rear and factory rotors on the front. I bought mine from the Race Store in Akron, Ohio. I waited for over a month for them to be delivered from Germany and when they got here they did exactly what yours did. I too went through the assembly/reassembly self doubt that you did. It was the rotors.

The noise you describe WILL NOT get any better. Take off the rotors and send them back.

I hope this helps.

Regards,
Max

 

In trying to track this problem down I was reading in the factory manuals that there is some sort of adhesive between the brake damper and the pads. It also says that it should be changed every time the pads are changed.

Is the damper change necessary? If not, what type of adhesive should I use. If I do need them, what can I expect to pay for them?

 

[quote]Originally posted by rihaa:
<strong>In trying to track this problem down I was reading in the factory manuals that there is some sort of adhesive between the brake damper and the pads. It also says that it should be changed every time the pads are changed.</strong><hr></blockquote>

I think they're referring to anti-squeal shims. If the brakes don't squeak, you don't need them, and unless you have full-metallic pads or some exotic racing pads, they probably won't.

My favorite way of fending off brake squeal (I have a Volvo - for the rear brakes, you can ONLY get/use metallics) is to thoroughly clean off any surface that touches the pad backing and smear the pads with a tiny bit of PTFE, copper, or moly high-temp brake grease wherever they touch something besides the rotor. This includes the pins, springs, pistons, and caliper. Use the old pad as a guide to where to smear.

If they still squeal, breaking up the glaze on the rotors with emery paper always works. Notice how<a href="http://www.smartcart.com/Paragon/cgi/display.cgi?item_num=944Rotors" target="_blank"> new rotors </a>have a crosshatch surface? New rotors don't squeal because the roughness breaks up harmonics.

If you have to have shims, or dampers I guess, you can go to your FLAPS and get self-adhesive metal stickers that you cut to fit your pads. I would stay away from the red Permatex goop, because it makes a mess and it can funnel heat into your brake fluid, or so I've heard.

<img src="graemlins/yltype.gif" border="0" alt="[typing]" /> Gee, I really went off on a tangent there. Bricksters know their brake squeal, I guess.

 

Its not that the brakes are squeeking. If that was it it wouldn't bother me at all. It is a clunk/knock type sound that is wheel speed variable.

 

Maybe the wheel bearings are loose?

 

This sound has only started since changing the brakes. Would the bearings all of a sudden just start to cause noises like that?

 

bearings would if not repacked properly and tightend properly. basic check of a clunk is jack up front. grab tire and try and move back and forth. side to side and top to bottom. You also stated that you changed the rotors. You should have attended to the bearings at that time. HTH

 

[quote]Originally posted by rihaa:
<strong>Its not that the brakes are squeeking.</strong><hr></blockquote>
I was just addressing the "dampers" question. I thought Max had your answer for the clunking.

&lt;shrug&gt;

 

Chris,
Yeah, you might want to read my post. I am not over simplifying things. From what you describe your situation is the same as mine was. Rotors can be warped or gouged right out of the box. It happens. You do what you want but I think you find that your "clunk" goes away as soon as you replace those front rotors.

Good luck,
Max

 

Hey Max, where did you buy those warped rotors? What brand? Perhaps, I'll make a list of places and parts to stay away from...

 

I'm shying away from them being warped because I am not getting any pulsation in the pedal. It is merely a sound. I was under the impression that if the rotors were wapred there would be pedal feedback.

Please correct me if I am wrong.

Also when changing the pads do you need to put in new dampers and adhesive as perscribed by the factory manuals? I'm just trying to investigate every possibility while I am here at school so I can get this straightened out whenever I get a chance to work on it. Hopefully it will be this weekend.

Thanks for the replies and keep 'em coming.

 

Maybe I can eliminate a little possible confusion about the bearing issue? Up to 86, Porsche used a front hub similar to Bmw, in that you had to dissasemble the bearings to remove the rotor. On my 87, the rotors just pop off after removing the two little screws (that you better have the right size f---ing phillips for).

 

Ah... yes the simpler rotor design.... Ok, that leaves us with.... EARTHQUAKES! that coincidentally hits right only when you use your brakes ??? <img src="confused.gif" border="0">

 

Thanks for the clarification SpecialTool. Mine are the ones where the rotors just slip off.

Nobody has answered my question about the dampers and the adhesive strip that goes along with them. Is this something that is necessary to do? and might this be the cause of the problem?