screeching noise from rotors + brakepads after replacement?

[toyotafan113]

It has been 2 days since I replaced both rotors and the brakepads on my front axle.

Every time I press brake padals from 30mph to 5mph, the screeching noise embarasses me from the pedestrians and neighbors.

The noise is less louder on highway, say from 60mph to 35mph.

The noise seems less when I soft-press brake pedals while in normal drive from idle, say from 10mph to 2-5mph.

The brakepds and rotors - plus shoes and drums for the rear axle - were all installed by a Toyota mechanic at a local Toyota dealership. The price was reasonable, and I did it based on the reliable labor by its worker, or so I believed.

Q1:
How can I reduce this noise? WD-40 was tempting me to spray, but I did not do it. Shall I take it back to the mechanic to re-inspect it?

I have run 50 miles both highway and city with these rotors, attempted several hard brakes, say from 60mph to 15mph, 6 times. Although the pedal vibrates less after this exercise, the noise got louder.

Q2:
FYI: The new rotors have surface cuts that are sprial-crossed from its central circle. The brakepads are ceramic. All parts are brand new. Is it possible the new brakepads be fragmented to pieces?

Thanks for any input.

[DjiNN]

Usually new rotors and brakes does cause some "screeching" noise in the beginning i would say wait a week. Break them in for a week and see if there is any rotor damage ( deep groove in one spot).

[Keolaaina]

Do not spray anything on your rotors. If your brakes do not work then there is a problem. If the screech but work then that is normal, for new parts. Some pads even have a brake in process. Like go a certain speed then a complete stop, several times.
Also does anything feel wrong? Like maybe something installed improperly? If not then you should be good.

[Ziggyy]

Its not normal. Take it back & have it re-inspected. If your parts are of premium quality, then there should be no noise, no pedal vibration (pulsation) etc. Noisy brakes are a thing of the past, unless the parts used are dirt cheap. The tech that replaced them, could of done many things wrong, didn't clean corrosion from the wheel hub, thus causing your vibration as the rotor is not seated correctly, causing excess runout. Not lubricating caliper brackets, where brake pads contact. Bending hardware etc. I've been in the trade for over 22 years & have seen my fair share of hacks fixing brakes, especially dealer mechanics. (no offence)
No one in the trade likes putting on parts brought in by the customer. The install quality will usually suffer, & never ever, even think about putting anything remotely oily on brakes. I've seen my fair share of this too.

[toyotafan113]

Found the problem & solved the noise & more questions remain.

It was the shim on the brakepad on the right-front wheel that caused the squeaking noise. The Toyota mechanic said the shim was not glued well to the pad, and hence the noise was coming from the shim.

The mechanic told me not to worry about driving without a shim, and said the indicator is on the caliper and thus when the pad is worn, the noise from the rotor due to the contact with the indicator will tell when I should replace the brakepads.

Now, only my right-front wheel does not have a shim. My driver side, or left-front, is fine with a shim and makes zero noise.

Q: Is it safe to drive without a shim on the RF wheel? The noise is gone, the brake works, and the car runs well. But I wonder how safe my car will be, both on highway and city cruise, during operation.


The only solution is

1. either to purchase another set of brakepads with shims, OR
2. just buy a set of shims
   so I can restore a complete brake system on the front axle again.

FYI: The brakepads are ceramic and 6-days old, driven for 170 miles and did 60mph-to-20mph hard-brake test 8 times. No other aggressive driving applied. The rotors are new too.

Thanks for any input.

[Ziggyy]

Its fine to drive without the shim. They are there to help absorb vibration & thus reduce noise. If the pads are that new, then you can always return them for warranty, due to being defective. You will unfortunately need to tie up your time to do the repair over again, or, just drive it. It won't affect performance, safety, or stopping ability, just noise prevention. Who knows, it may never make any noise for the duration of the brake pad life the way it is.

[fishexpo101]

If the rotors still have the machining marks (crossing arcs on the rotor friction face), then you need to keep driving normally before the noise will start to lessen. There will always be some noise with brakes, especially brand new ones - but a very loud, harsh screeching noise is usually a sign of brake vibration.

You mentioned ceramic pads - where they Toyota OEM? or some compatible ceramic pad made by some other manufacturer. I'm not sure I quite understand the mechanic - the disc wear indicator is not on the caliper, but on the pad itself. Toyota OEM shims are not glued on, they are free floating. You are supposed to put some high temperature grease or pad quiet material to fix the shims to the pad.

It is OK to run without pads, but keep in mind that they do act as a heat shield for the brake system. Keeps the heat from the pads from directly transferring to the caliper and potentially "boil' the brake fluid. When this happens, you will have a completely loss of braking. Mechanic is only 1/2 fixing the problem, they installed it - they should fix it and fix it the right way.

[Ziggyy]

Shims are used to dampen vibrations, not as heat shields to keep brake fluid from boiling. Thats a little far fetched. Your probably scaring the guy now. Most dealers don't even use genuine Toyota brake pads, as they won't be competitive in pricing.

[fishexpo101]

I totally agree - shims primary purpose is to dampen vibrations between pads and the caliper. But they do serve as an intermediate interface for thermal control as well. For most people that look after their car, you could probably never get the temperature up high enough to transfer enough heat to boil the fluid in the caliper. But if someone never changed the brake fluid in the car and it is heavily contaminated with moisture, I'd be willing to bet that without shims, it will boil the fluid in the caliper.

As for Toyota dealerships not using OEM pads, that is a first I've heard, unless it is different from region to region. Every shop that I've gone to (Eastern states) - all they every used was OEM parts. Fluids were the only thing that I've seen that might change from visit to visit.

[Ziggyy]

I'm sorry but I still disagree. Shims would have virtually zero effect on brake fluid boiling. Thermal control is achieved through the transfer of heat to the cast iron or aluminium caliper & the vented or non vented brake rotor, then to the air. You can purchase inexpensive brake pads that don't even come with shims. Years ago brake pads never had shims. Personally after approximately 22 years & say over 5000 brake jobs I've done, never have I seen brake fluid boil on a passenger vehicle as a result of not having shims, & I've seen 30 to 50 year old brake fluid. Indy, Nascar, driving with two feet, maybe.

You should still do a copper content test every few years & flush your brake fluid.

[fishexpo101]

That's fine if you disagree, not trying to change anyone's mind on that matter of shims. Personally, I have cases of the brake fluid boiling over in braking system, and not necessarily in extreme braking events either. For extreme braking events, auto-x and road courses, circle and oval tracks, this definitely will be an issue to look into. But to state that shims have virtually zero effect on thermal transfer is incorrect.

As for how much this contributes to overall thermal management, that is still hotly contested - sort of like arguments between convention vs synthetic fluids and displacement vs forced induction.

Doesn't help that there are many ways to control heat in the braking system. Modern pads have started to use integrated shims or have "goo" to help with vibration, some recommend the reuse of OEM shims or to forgo them altogether, if the backing plate of the pad can take the heat loading. A few pads have a interface material between the friction material and the backing plate - which negates the thermal advantages of adding an additional shim. Older pads had differences in brake friction material - namely asbestos, that helped with heat transfer.

Caliper design, the piston itself more specifically, and the mass of the rotor also influence the amount of heat that could be transferred. For most single stop events, the rotor is the primary source for thermal control (heat sink). Anything that is not absorbed by the rotor will be passed through the pad to the caliper piston (shim or no shim) to be radiantly dissipated by that caliper assembly. Beyond that will be taken by the fluid itself. Brake fluid has a decent heat capacity, but introduce even a small quantity of moisture and it is not uncommon to see those dry boiling temps drop to a 1/3 of what they where out of the bottle.

Will you have catastrophic brake failure or excessive brake fade if you run without shims? In most cases, probably not, but do you really want to take that risk? Only takes the brakes fading one time ("spongy pedal" fade) to be a recipe for ruining someones day.

[Ziggyy]

Shims were designed for one thing only, noise prevention. Not much material there to dissipate any heat generated by braking. Its only a few thousands of an inch thick. Were not talking a race car here, he's driving a street car. I'm sure if he went racing with it he'd figure out the meaning of brake fade in the first multiple high speed stops with it, and then realize, hey gotta improve the brakes, like install some 4 times the size. Having brake fade without shims is not gonna happen, your just scaring the poor guy. Older pads never had shims & they used to squeal like crazy. Ask me, I've replaced them under warranty hundreds of times. In the 80's most pads never came with shims, but if you buy the same pads now, hey, what do they come with, you'll never guess, shims, to reduce noise (squealing) the #1 brake complaint in the industry. The "interface material" is a glorified noise dampner, & the goo, junk, wears off in a few months. Never even seen it on a new vehicle. Been to 20 or 30 manufacturer seminars about new products over the years, & thats the reason for their development.
He is some more reading material. hxxp://www.trelleborg.com/en/Automotive/Technology/Selling-silence---auditory-comfort-with-brake-shims-2/

Time to put this to bed.

[toyotafan113]

Thanks everyone for a reply.

[fishexpo101]

Ziggyy - yeah, we've dragged this a little off topic - if we want to continue this, then we can take it to PM or start a separate topic. In this case - experience will vary, as our backgrounds are inevitably completely different.

I'm speaking from an R&D standpoint (computer simulation and modeling) and personal experience, both on and off track. I'll just toss a questions out there for anyone interesting in looking it up - What causes brake squeal, namely the mechanism behind it? A complimentary question would be - How do we address that brake squeal?

Lots of SAE whitepapers and some physics journals out there. Just Google them up, usually abstracts are free to download, but the main text are tied to a pay service, but many universities and some libraries have access to those articles. You can find that info is available in both theoretical computations (modeling) and lab/real world testing.

Viewers can make up their own minds on what to believe or not - not trying to scare anyone here.

To the OP toyotafan113 - did you get this brake issue sorted out with the dealership?

[toyotafan113]

To all participating in this thread:

1. Thanks for replies with much thought and issue I never knew before. That boiling brake fluid theory sounds plausible, but I wonder about its credibility. If the worst happens, I will carry my teapot and tea bags whenever I hear sizzles and boiling bubble of liquid. No, I do not belong to the TEA party.
   
2. Both the rotors and the brakepads are new - new rotors with “precision surface grinding” and ceramic brakepads. The rotors have no holes on its disk. The crossing arcs are still there, since the brake system is about 10 days old.

==========================


Hard topic1:

1. The ceramic brakepads were compatible units and not OEM. I believe the rotor wear indicator, or the needle that will scratch the rotor, is the little hook near the edge of the shim. What my mechanic showed me was a <3mm black, arc-shaped thin plate with splotch of black glue on it. The Toyota mechanic said this plate fell off and was not attached firm to the pad, and this was where the screeching noise originated. (It resembles the red part from the photo below, except mine was black. That is the shim, correct? I thought the shim is glued behind the brakepad and thus becomes one set to get inserted into the caliper. But since I have a shimless brakepad-caliper system, I may not hear the screeching noise, correct?)

http://img263.imageshack.us/img263/8...cbrake7vk2.jpg


==========================


Hard topic2:

1. I am still new to the auto world, and it has been 2 days since I flushed and refilled the engine oil – first time in my life and this car's life. Oh yes, the black coffee tastes great.
2. My next goals are: flush and refill transmission fluid, coolant fluid, and now I may need to add “brake fluid flush and refill” in this to-do list. Is the drain hole for this brake fluid near the front bottom of the car, like the engine oil plug?
3. DOT3 is the brake fluid, correct? How much oz or quart do I need to completely drain and refill the brake fluid system? Or this complete flushing and refilling the brake fluid necessary or recommended at all?

==========================

1. Yes, my Toyota mechanic took off the shim, and I hear no noise. The brake system works. I expect to replace the brakepads every 5 years or 50K miles, regardless of the condition of the brakepads whenever I reach that mileage. I do not heavily use the brake system, and tend to drive slow. I plan to install a new set of shim next time I install a new brakepad set.
   
2. As requested, I did not spray extra virgin olive oil, or WD-40, on the rotors in hope to reduce the noise. I am glad greasing the rotor was not the issue. I wanted to spray copper grease or that fresh throttle body cleaner on the rotors and the entire brake system behind my wheels near the axle to prevent rust-formation, but I won't do it – the experts on this forum will scream at me (!?). When I saw my mechanic replacing the rear shoes and drums, he did spray some brake cleaner, and black liquids dropped. Other than that, I do not see any need to spray anything on my brake system, and this has been the recommendation from the forum users.
   
3. If this absence of shim is not catastrophic for my safety and the front axle brake system, I would rather leave it as it is. However, I will install a new set of brakepads plus shims at next interval I mentioned above.
   
4. Again, thanks for all of your input.