Cobra Brake Problem

[Flghtmstr1]

Hi everyone, I've had Cobra brakes on my car for ~10k miles now, and since I bought the kit used and was using the existing rotors and pads, they wore out. I just bought OEM Brembo rotors and Hawk HPS pads, and put them on.

When I took my car out to bed the pads, I noticed a disconcerting knocking / clicking sound that varies in frequency with vehicle speed while the brakes are applied. If I brake lightly, there is no sound or anything, but if I increase pedal pressure, the sound will appear and continue to intensify the harder I push.

I ripped the brakes back off and checked the rotors, thinking they might be bad. The run-out was 1-2 thousandths depending on where I checked on the rotor surface. The rest of the system looked fine. The pedal firmness is great, the car stops great, but this knocking seems very wrong. I'm scared to drive the car, but it's the only one I own, so I don't have a choice. I drove it to work this morning, and the problem was still there. Is there anything I may have overlooked? I've been doing tons of searching on this forum, but haven't found anything that sounds like the problem I'm having.

Thanks!

 

[02nightmaregt]

I've had some crazy break problems too and hell yea they're scary. does it pull either way when you break?

 

[blacksheep-1]

I hope I can help here. I've run the Hawk pads on a race car and they seem to need a little "breaking in" plus it needs to be done correctly or you will have problems, especially with the race pads. The runout you mentioned might be part of the problem, but are you sure that you replaced all of the "anti rattle" brackets? (the little metal tabs and stuff). If you don't get those on, and straight, they can cause problems. This would explain the knocking sound.
1 more thing, maybe the new rotors aren't indexing properly on the spindle, recheck those and retorque the wheels and see what happens.

 

[waggs]

i'm having the exact same issue with my bullitt brakes that i installed this weekend. my guess right now is that the rotors are warped a little. i'm gonna get them turned this weekend so hopefully that fixes the problem

 

[Flghtmstr1]

I don't think it's the rotors. That's why I mentioned their run-out. One-thousandth of an inch is approximately .025 millimeters. Spec is .1 millimeters and under.

 

[Flghtmstr1]

Update: I bit the bullet, and bought Motorcraft (not OEM Ford) pads at the dealer, and put them on. The problem is gone, so the Hawks are going in the trash. Oh well; live and learn.

 

[waggs]

Update: I bit the bullet, and bought Motorcraft (not OEM Ford) pads at the dealer, and put them on. The problem is gone, so the Hawks are going in the trash. Oh well; live and learn.

just curious, what was wrong with the hawk pads? i bought some brembo replacement rotors and motorcraft pads and i had this problem. did you get new anti rattle clips?