AP Racing Brake Kit - Loose Pads Rattling Inside Calipers

[MINOCIN]

After installing my brake kit I was surprised to find that the brake pads were loose and rattling around inside the caliper. According to the instruction manual this brake kit does not require any shims to help hold the pads in place, but don't you think that these pads are just too loose?

Here's a link to a video showing how much the brake pad rattles (sorry, I don't know how to embed vids).

Jump to 20 seconds in. It took me a while to get my camera phone situated.

I thought that after pumping and bleeding the brakes that there would be some pressure against the rotor to hold them in place, but that doesn't appear to be the case. The brake pedal feel is still better than stock. It doesn't feel spongy like before and the brakes don't squeal, they just rattle when going over some of the bumpy stuff. Any ideas?

[Dave-ROR]

That is normal actually but it does vary by pad choice. Which pads are those?

Since the are racing calipers they don't have anti rattle provisions.

[JRitt]

Originally Posted by MINOCIN

After installing my brake kit I was surprised to find that the brake pads were loose and rattling around inside the caliper. According to the instruction manual this brake kit does not require any shims to help hold the pads in place, but don't you think that these pads are just too loose?

Here's a link to a video showing how much the brake pad rattles (sorry, I don't know how to embed vids).

Jump to 20 seconds in. It took me a while to get my camera phone situated.

I thought that after pumping and bleeding the brakes that there would be some pressure against the rotor to hold them in place, but that doesn't appear to be the case. The brake pedal feel is still better than stock. It doesn't feel spongy like before and the brakes don't squeal, they just rattle when going over some of the bumpy stuff. Any ideas?

Which pads are they? Every pad from every manufacturer is different. Even the pads from the same manufacturer will be different sizes depending on the batch, since there is a tolerance range that is acceptable for each manufacturer. In other words, one pad at the small end of the tolerance range may be .5mm shorter than one at the large end of the tolerance range. The calipers also have an acceptable tolerance range of size. Therefore, if you get tolerance stack-up (the pad is towards the minimum size, and the caliper is towards the maximum size), you can get some looseness. The true would be the same if the pads were on the large end of the scale, and the caliper were on the small end...then the pads would be very snug going into the caliper. You can think of this sort of like the panel gaps on cars, or expansion joints in a highway...there has to be a little space for everything to line up properly while still having some room to flex and move as usage conditions change.

Pad size also varies by manufacturer because of the pad material composition. CL Brakes Sintered pads are made of different materials than something like Ferodo, and they tend to grow/expand more when heated. Therefore, the 'cold' size of a CL Brakes pad tend to be smaller than those of other manufacturers. You can see this in their technical drawings.

The calipers are also designed to allow for a little bit of expansion of the pads under high heat conditions. This is particularly true of a racing caliper like the AP Racing CP8350. If it wasn't designed that way, you'd be limited on pad choice, and they wouldn't work well when heated to many hundreds of degrees on the track.

If the calipers were exerting too much constant pressure against the pads, the pads would be dragging on the discs at all times, generating heat, and wearing down your pads and discs.

If the noise bothers you too much, I'd recommend trying a different pad set, or a different pad manufacturer. Again though, it's a bit of a 'crap-shoot.' Pads vary in size by batch. Shoot me an email and let me know which pads you have.
Finally, thanks for purchasing a kit...hope you enjoy it!

[mines13]

100% agree with Jeff. I have had 3 different sets of pads in my 8350 calipers. The current set of HPS had to literally be grind-ed down about 1 to 1.5mm to clear the rotors with the pistons fully retracted. This didn't apply to the other two sets. The pads can be over/undersized on either axis.

[CSG Mike]

Which pads do you have? Are they still that loose after driving around the block a few times?

[MINOCIN]

Thanks everyone for your quick and informative replies. This forum and its members are awesome.

The brake pads in question are, "AP S100 Street Brake Pads - Model: 03 CP0929T16.8 S100".

The kit was installed 5 days ago, last Saturday. I have so far driven on both the freeway and city with the new kit (about 100 miles total so far). On the freeway the brakes are great, no rattles or squealing. I haven't really done any real hard braking and because of the weather I didn't get around to bedding them in.

The calipers are also designed to allow for a little bit of expansion of the pads under high heat conditions.

This makes sense. One time after a drive I checked the brake pads again after they had warmed up a bit to see if they were still loose. Yes, they were; however, not as much. I could still move them with my finger but I could feel that they were a little more wedged in there. In the above video the breaks are completely cold.

If the calipers were exerting too much constant pressure against the pads, the pads would be dragging on the discs at all times, generating heat, and wearing down your pads and discs.

Yeah, I would also imagine that the pads would probably squeal all the time too.

This is my first time using a brake kit and I understand that I purchased a track focused system. I was actually expecting heinous amounts of brake squeal. I just wanted to double check with people on this forum and get their help and opinions.

Overall, I'm very pleased with my purchase and I plan to do a write-up of the kit install on my build thread and post a few pics. I'm really looking forward to taking my FRS back to the track after this upgrade. The amount of wiggle the brakes have and the rattling noises were just really surprising.

[Dave-ROR]

Interestingly my S100s fit pretty tight.. if these new green painted pads I bought from CSG are as awesome as I suspect I can send you the S100s I have.

[MINOCIN]

Thank you, that is a very gracious offer, but if the same pads are pretty tight on your brake kit then why are they so loose on mine?

Even the pads from the same manufacturer will be different sizes depending on the batch, since there is a tolerance range that is acceptable for each manufacturer. In other words, one pad at the small end of the tolerance range may be .5mm shorter than one at the large end of the tolerance range.

Is that really all there is to it or are there possibly other things that I should be looking into? Although I can't imagine what. Everything in the kit fit fine and the install went really smoothly. Perhaps this weekend I'll remove the pads and measure them to see if they fall within the product dimensions.

The noise itself doesn't really bother me. I guess I'm just looking for some peace of mind. The roads in my area are really old and bumpy. The pads aren't going to crack, shatter or brake apart after a while from rattling around so much are they? Does anyone else with this brake kit or any other brake kit for that matter have pads that are this loose?

[CSG Mike]

We haven't had any issues, you don't want a "dead on" fitment inside the caliper; you'll never be able to remove the pads after severe heat cycles if that were the case.

The tolerance for "looseness" in a fixed caliper like this is different from a floating caliper that uses shims to "push" the pads together into a tight fit.

[MINOCIN]

Well, the brake pads are no longer rattling around inside the brake calipers. They are now firmly pressed against the rotor and I can't move them with my finger anymore, even when everything is cold. So no more rattling noises when driving around town on bumpy streets.

What changed? Well, I finally got around to trying to bed the brakes.

Last night in the middle of the night I found a long and empty highway and I drove for almost 3 hours trying to bed the brakes. I say try because I'm not quite convinced that I was able to pull it off. I tried to follow the instructions provided by essex in there videos:
http://www.ft86club.com/forums/showp...5&postcount=14

Here are some pics of the rotors.




(In the above pic you can barely see how the brakes must've bled a bit during the bedding process. It's easier to see in person)



(If you look at the pad in the pic above it looks as though I've hardly used them)




The reason why I don't think that I bedded them correctly is because the brakes now squeal once they have warmed up a bit. They only squeal though around the last 8 feet of stopping. If I stop short then the brakes barely get a chance to let out a squeak. Also, the initial pad bite when cold is pretty bad and unless the brakes are completely warmed up then the pads will feel a bit mushy, like stock. Overall though, I can definitely feel the car slowing down more quickly than before and with less effort. When the brakes are completely warmed up they grab like glue and they feel nice (^_^). If the brakes are too hot, to the point where they are fading, then they will squeal on any and all brake input until they have cooled down some.

When attempting to bed the brakes I never triggered the ABS, but I definitely feel like my tires were not quite up to the challenge. My RS3s are almost a year old now and are bit worn. I think I'll try bedding the brakes again with my track wheels & tires, 235/40ZR17 NT01s on 17x8 RPF1s.

Sorry for getting off topic. Almost hijacked my own thread lol.
Anyway, I guess the problem with the loose pads was mainly due to my sissy driving style after the install. The reason why I was driving like a pansy though was because I thought something was wrong, but after a week of careful, delicate and restrained driving I finally couldn't take it anymore. Letting loose and bashing on the car fixed the problem

So I guess the lesson here is, "beat on your brakes kids."

(metaphorically speaking of course)

[dradernh]

Originally Posted by MINOCIN

If the brakes are too hot, to the point where they are fading, then they will squeal on any and all brake input until they have cooled down some.

When attempting to bed the brakes I never triggered the ABS, but I definitely feel like my tires were not quite up to the challenge.

So I guess the lesson here is, "beat on your brakes kids."

Rotors look fine, and most of what you're saying is spot-on.

I do wonder, however, what it is you did to get the brakes to fade. Can you share? Edit: Oops, saw Mike's post - forgot you were on the S100s, thought you were on the C300s.

Yes, you have more brake than tire.

No, the lesson is: bed your brakes in properly.

Congratulations on succeeding!

[OrbitalEllipses]

Depending on the aggressiveness of the pad compound, you may find it necessary to bed them in again after a certain time. Just be aware of that.

[CSG Mike]

It looks like you're actually overheating the S100.

This is a street pad; they'll fade quickly, even with the BBK.

[MINOCIN]

True that. Slowing down from around 60 mph to 15 mph back to back it only took about 4 tries before the pads started to fade. Which is understandable for a street pad. According to the essexs instructions, I thought I was supposed to overheat the pads in order to get them to rub/transfer a layer of compound onto the rotor?

It actually took quite a few tries to get the pads to finally start smoking. 60 mph wasn't cutting it so I increased the speed a bit in order to get them cooking. However my brakes don't look cooked along the edges like they do in the essex pics.
http://www.essexparts.com/learning-c...ds/post/Bed-in
Hopefully that burnt smell really was the brakes and not something else; like my engine, clutch or transmission

As I was doing the bedding procedure I kept thinking how nice it would be to have that corvette in the essex video ^^
Getting the little FRS to accelerate within the sections of straight road available became a challenge onto itself lol