Why are my Kopis binding on the brake pads?

[m20e34]

I found the car on e30tech, but I would imagine the previous owner was on r3v too. Condition-wise, the car has come a long way since I bought it. Here is a picture I saved from the e30tech ad:



I changed up the front up a bit you can see. The interior was trashed when I bought it, now it's almost mint. The exterior will be a 9/10 once I get the new rear bumper trim and euro bumper trim parts installed. Also have a spoilerless trunklid to go on that needs painted. The lid on it has a huge ass dent in the back.

[MR 325]

Spoilerless 318iS, you shall be the first to do it my man

Those wheels used to belong to fuzz, hehe. The wheels on his car now used to be on your car!

Love the car btw.

[Jordan]

I've heard of this problem before, typically only on wheels with very tight caliper clearance.

I think you have realized by now the caliper expands to fit the pad in, and it will get smaller as the pads do.

You have 3 options.

A thin custom spacer.
Remove the brake pads, and have a machine shop take a couple mm off of them.
Grind on the caliper until clearance is made


Swapping calipers might also work.

Do you have ATE or Girling calipers? The girling front calipers are superior in design to the ATE.

[Bavarian3]

The Kopis do not have a tight fitment around the calipers.... there is plenty of room in there...

The caliper doesn't expand (it doesn't get any bigger)... I don't know what you mean Jordan...

Are all the bolts on there tight and straight? Did you install them or did a shop do the work? Can you take a photo of it?

I just installed new fresh HPS and Balo rotors on my 86 ETA, there is no rubbing issues at all nor should there be.

[MrK]

Calipers do expand. Think of them as 'claws' that hold the brake pads onto the discs. thicker pads will make the calipers wider (front to back, that is)

[Bavarian3]

Do you mean the piston inside the caliper?

[Jordan]

No.. the caliper is 2 parts. The slide on rails within each other, thus expanding and contracting with pad thickness.

[Dave]

aardvarc racing sells 3mm spacers - I think I paid 70 plus ship for the set.

[m20e34]

The caliper is not touching the wheel in any way, only the pad.

"Binding" is a bad word. Since the pads can be pushed up into the caliper, the wheel was pushing the pad up ever so slightly, maybe a mm. The springs on the top of the pads that push back down to prevent squealing, were pushing the pad down onto the hub of the wheel right at the part where the wheel hub and brake disc hub meet. The wheel hub is bigger, so it makes contact.

I dremeled the backing plate so that at the bottom of the pad, the backing plate matches up with the friction material instead of having overlap. This fixed the problem.

Jordan: Not sure which calipers I have, if I had to guess, I'd say ATE.

[m20e34]

Spoilerless 318iS, you shall be the first to do it my man

Those wheels used to belong to fuzz, hehe. The wheels on his car now used to be on your car!

Love the car btw.

I don't know who fuzz is, but the previous owner said he traded some Borbet Ts for the Kopis if I remember correctly.

[Jordan]

So wait.. I was under the assumption the caliper was binding on the back of the spokes... but you are saying the brake pad itself is binding on the inside hub surface of the wheel.... Thats a new one.

Are you sure you've installed everything properly? With this new information I believe something is VERY wrong.

[m20e34]

So wait.. I was under the assumption the caliper was binding on the back of the spokes... but you are saying the brake pad itself is binding on the inside hub surface of the wheel.... Thats a new one.

Are you sure you've installed everything properly? With this new information I believe something is VERY wrong.

The brake pad backing plate is grazing on the inside hub surface of the wheel right at the very edge of where the wheel hub and brake disc hub meet - because the disc & wheel hubs are not flush, the wheel hub is bigger.

Something very wrong is exactly what I thought, but everything is correct, trust me. The wheel hub should have a smaller diameter, but since no one else has this problem, it can't be the root cause.

The only explanation is that is that the pad backing plates are 1-2mm oversize.

edit: The backing plate is touching on the corner (bottom/outside) to the wheel hub corner (top/inside) so the backing plate could be oversize in height or thickness or both.

[Jordan]

Compare your old pads to the new ones, see if that is the difference.

Clearance the backing plate of the new pad as needed to prevent rubbing.

or just buy pads that fit.

[m20e34]

Compare your old pads to the new ones, see if that is the difference.

Clearance the backing plate of the new pad as needed to prevent rubbing.

or just buy pads that fit.

In my original post I stated that when I changed pads, I installed the stock basketweaves. Now I go to put the Kopis back on and I have this. The old pads have been gone for 4 months.

The car sees plenty of track time, I'm not going to order a bunch of track pads to go through and see if they fit. Modifying the Hawk pads took 15 minutes including removal and installation of both wheels and it was free.

[MR 325]

I don't know who fuzz is, but the previous owner said he traded some Borbet Ts for the Kopis if I remember correctly.

This guy http://www.r3vlimited.com/board/showthread.php?t=64966 :)