I purchased a set of cross-drilled brake rotors and carbon-metallic pads from KVR through Corksport for my '99 ES. It took 5 weeks to get them and I know they weren't ordered for ten days after I placed the order... but that and other Corksport woes are a different story. I installed them myself.

Now, I have a loud metallic "clunk" from both front wheels every time I apply the brakes. I didn't think they were the brakes, but perhaps a suspension problem. After a couple of weeks of driving and the noise persisting (in fact, getting worse), I raised the car, removed the front wheels, and inspected. I spent two hours inspecting everything I could think of that could cause the clunking... mounts, bushings, CV joints, struts, pads, calipers, etc. I couldn't find anything wrong. While I was putting the wheels back on, I accidently brushed the rotor and heard the same metallic clunk. I took a close look at the rotor and noticed how much play or slop there was in the rotors' wheel stud holes. Rotating them in either direction caused the clunks. It sounds and looks like the rotors are rotating and hitting the wheel studs when the brakes are applied.

I e-mailed KVR (and copied Corksport) about the problem. A week later, after getting no reply from either, I called KVR directly. They verified that I had the correct part number and then instructed me to take the wheel stud and rotor stud hole measurements. The wheel studs measured 12mm at the hub and the rotor stud holes measured 13mm. I relayed the measurements back to KVR and they checked them against their specs.

According to them, the measurements are correct and the 1mm difference "can't possibly be causing the noise." They believe it is a problem with the caliper and pads not returning after the brakes are released, and that they return suddenly when a bump is hit and that's the noise I am hearing. However, as I emphasized to them, the clunk occurs when brake pressure is applied, not after it is released. They stand by their reason and say I should take it to a brake shop if the noise bothers me. Yeah... it definitely bothers me... it's about as loud as hitting the rotors with a hammer, not to mention I can feel the clunk in the steering.

I already reinspected the brakes. The caliper bolts are correctly torqued. The caliper moves freely on the slide pins. The piston moves freely. The pads move freely.

So... does anyone agree with their story? I guess I don't have a choice but to take it in to a brake shop... I know the dealer won't touch it because of the aftermarket parts.

At first, I was thinking the problem was suspension-related. I was thinking the front struts were making the noise, being caused by the car diving. However, the clunks are heard seperately when the wheels are turned. The first clunk comes from the side the wheels are turned to, immediately followed by the other side. If the struts were making the noise, the clunks would be heard first from the side opposite the turn, since the vehicle will dive first on that side.

Sorry for the long post... any ideas? Or is my theory on the rotors rotating and hitting the wheel studs sound like the culprit? Thanks!

 

I'm guessing that it's the pads moving within the calipers. The friction between the wheel, hub and rotor with the lugs nuts torqued down is so great that the rotor will NEVER move relative to the studs. Trust me, it just won't happen. Also, the rotor should have screws that hold it in place when the wheels aren't installed (unless the KVR rotors don't have screw holes like the stock rotors). Also, keep in mind that the metallic sound made by the rotors will be very different when it's got a 40-lb wheel and tire assembly bolted to it.

Did you install the new pads using the stock pad hardware and shims? Also, did you re-lube the caliper slide pins when you put everything back together?

 

There are no screws that hold the rotor in place. There's no holes for that in the hub, OEM rotors, or KVR rotors. I don't know if that changed with the '01+ models. Another wierd thing is that the rotors (OEM and KVR) are "semi-vented." In other words, you have alternating sections (approx. 30 degrees) of solid and vented sections of the rotor. Of course, the cross-drilling only occurs in the vented sections...

I used the stock hardware and shims. The caliper slide pins were removed, cleaned, regreased, and reinstalled. Twice. As was any other friction surfaces to ensure proper movement. Except for the pad material and color, the KVR pads look identical to the stock pads.

And one other thing I forgot to point out. The clunks are nonexistant while the brakes are cold. Of course, you get the wonderful squealing from the cold carbon metallic pads until they warm up... Combine the cold-brake squeals, warm-brake clunks, and CAI, and I kind of miss a quiet car...

 

A few other things I should mention...

If I apply the brakes very lightly, the clunk doesn't occur until the vehicle comes to a complete stop.

There is a very slight clunk at the onset of hard acceleration after braking.

I would have never thought the rotors would rotate with the lug nuts tightened properly. Hence my initial suspicion of the suspension. However, KVR was not surprised by my description. In fact, their second step was to have me measure the studs and rotor stud holes to ensure there wasn't too much slop between the studs and rotors. Their first step was checking their database to ensure the same rotor isn't used on another vehicle with different stud sizes.

 

I had a clunk in the brake in my old subaru 2.5rs w/ stock brakes in similiar stopping conditions as you. The sube tech told me that it was the brake pad sliding in the caliper since they was some freeplay between them. They greased the pads with some bronze grease the the clunk sound went away but after a rainstorm; it came back. I believe that they should have been a clunk sound in the first place.

P

 

I think I have solved the problem... I removed and disassembled the caliper and brackets. I was shocked to find that the lower caliper slide pins had no grease on them. When I put them together last time, I know I cleaned and greased both slide pins.

The lower slide pin slides in a rubber sleeve. I made sure to thoroughly clean the sleeves and pins before greasing them. No matter how much grease I applied or how much I worked the pins around, they just wouldn't slide nearly as easily as the upper slide pins, which do not slide in a rubber sleeve. I spent a lot of time really working the grease into the sleeve. I don't know if the rubber absorbs any of the grease, but I apparently didn't get enough in there last time.

The rubber sleeves are also grooved just like the upper slide pin itself (the lower slide pin is not grooved). It appears to me that the grease would just go into the grooves rather than stay between the rubber and pin. You put a lot of grease in, but it just slides into the grooves and out the exposed end of the pin. There is a plastic cap that fits onto the end, but I doubt it does anything for holding the grease in... it barely stays on itself.

For now, the clunk is gone from both sides. We'll see how long this lasts... it didn't clunk for the first couple of weeks after I put the new rotors and pads on.

Here's a pic of the "semi-vented" cross-drilled rotors. I call them semi-vented because it has sections of solid rotor and sections of vented rotor. I thought this was wrong, but the OEM rotors I removed are the same way (minus the cross drilling, of course). Are there many vehicles out there with this type of rotor? Do the '01+ have fully vented?

 

OK... so I spoke too soon. The clunking is back after one day of silence. Now, it is less metallic sounding, but even louder! I AM SO SICK OF THIS!!!

I guess I'll take it into a reputable brake shop... if there is such a thing. I'm sure I'll have to replace the KVR parts and buy the parts that the brake shop has. Whatever... I hate this car.