Rattle after rear Hawk HPS Install

[NewDirection]

Hey guys,

I just installed new rotors and Hawk HPS pads in the rear of my 135i convertible. Now when I go over deeper or rougher bumps, like train tracks, I get a loud rattle from both sides in the back. If I apply even slight brake pressure as I go over, there is no rattle.

Any ideas?

Thanks,
NewDirection

[Thunderguts]

I would say something must be loose. The drag from the brakes snugs it up so it doesn't rattle when the brakes are applied, but I would say you need to pull the wheels off and double-check everything.

[crowtrobot]

Originally Posted by Thunderguts

I would say something must be loose. The drag from the brakes snugs it up so it doesn't rattle when the brakes are applied, but I would say you need to pull the wheels off and double-check everything.

Agree. Make sure your caliper bolts and lug bolts are torqued.

[NewDirection]

SOLVED

I had a closer look at the OEM pads and found that they had two shims, one that wraps around the sides and another on top of that one. The shims that came with the HPS do NOT wrap around so they were allowing for a lot of up and down movement in the caliper. I ended up transferring the OEM shims (two per pad so four per side) and discarding the HPS shim. Now the sound is gone.

Thanks for the input guys.

[ShocknAwe]

What did you use to adhere the shim to the new pads?

[NewDirection]

Originally Posted by ShocknAwe

What did you use to adhere the shim to the new pads?

Hmm...Nothing, the top shim snaps into place and sort of holds it. But good point, it was stuck pretty hard to the OEM pad. Any suggestions?

[ShocknAwe]

Originally Posted by NewDirection

Hmm...Nothing, the top shim snaps into place and sort of holds it. But good point, it was stuck pretty hard to the OEM pad. Any suggestions?

Yeah the original shims are glued on. No idea what kind of glue it is. I've tried the red brake quiet goop and that doesn't hold up.

My pads are shimless currently and it's fine. Just rattles over bad bumps or on initial transfer of direction. Though I've got all the shims sitting on my bench waiting to be installed, just never found an adequate answer.

[Thunderguts]

That's good to know because I'll be replacing my pads with Hawk HPS soon. I loved HPS pads on my Prelude. I liked Endless pads better, but the HPS offered nearly the same feel for 1/3 the price and they didn't wear down like soft butter.

[NewDirection]

Originally Posted by Thunderguts

That's good to know because I'll be replacing my pads with Hawk HPS soon. I loved HPS pads on my Prelude. I liked Endless pads better, but the HPS offered nearly the same feel for 1/3 the price and they didn't wear down like soft butter.

You can always test by trial fitting your new pads and comparing the up and down motion with stock.

Other than the fitment issue, I have no other complaints.

[NewDirection]

Originally Posted by ShocknAwe

Yeah the original shims are glued on. No idea what kind of glue it is. I've tried the red brake quiet goop and that doesn't hold up.

My pads are shimless currently and it's fine. Just rattles over bad bumps or on initial transfer of direction. Though I've got all the shims sitting on my bench waiting to be installed, just never found an adequate answer.

How important is it that it be glued on? I figure as the pads wear the pistons will push the whole assembly against the rotor anyway. And the pins will keep them from flying away.

Still, I might try some threadlock.

[Thunderguts]

They won't fly off, but they may be noisy which is what you're finding now. I've always used CRC disc brake quiet and never had a problem. It's a little messy, but seems to work for me.

[ShocknAwe]

Originally Posted by Thunderguts

They won't fly off, but they may be noisy which is what you're finding now. I've always used CRC disc brake quiet and never had a problem. It's a little messy, but seems to work for me.

Would you mind defining always? Just for clarity.

[Thunderguts]

Well it's not like I run a shop so this is limited anecdotal evidence. I've changed pads four times I think and I've used the aerosol disc brake quiet each time without any squealing or rattling afterwards.

[Happy Jose]

You don't have the pins seated that hold the pads in place. This is somewhat difficult to do due to limited space. Get a short fat nail and try again.

[Gangplank]

How about some high temp grease on the back side?

Liqui Moly Brake Anti-Squeal Paste 100g https://www.amazon.com/dp/B00295ERQ2..._dvksDbGMGJ3AB