Which brake pads to use?

[Beav]

We were always told the noise came from hi-speed vibration - the faster the vibes, the higher the frequency of the sound. Similar to a damp fingertip rounding the rim of a piece of stemware. Supposedly the more abused the pad, the harder it became and more susceptible to the vibration.

When it was a daily problem for me I didn't really care what the reason was, it was obvious that the aftermarket pads were dealing with lifetime warranties and the OEMs weren't. Hence the softer OE pads were less prone to make noise.... My observation anyway...

[kuoh]

No no, I'm not talking about the edges that are supposed to be bent. I'm talking about the parts of the edges that are supposed to be flat, but became bent because the tech didn't get it seated on the pads right before lowering the caliper over them. When that happens, part of the shim touches the top instead of just the front and back of the caliper. It may or may not have contributed the noise, but it certainly gave all the signs of a rushed install.

KuoH

Originally posted by oab_au
The shims are suppose to have bent edges, or a raised center. This to form a compressible medium between the pad and piston, to allow the air to leak out from between the pad and disk before the full clamping pressure is applied.
It's the trapped air escaping that produces the squeal.
This is why things like roughing the pads, cutting grooves across the pad, grooving the disk, will stop the noise for a while.
OEM pads with new shims are the best way to prevent squeal.

[kuoh]

The trapped air may produce a squeal initially, but when you can generate the noise over a period of ten seconds during slow stops from 60 to 0, I would tend to discount that as the primary cause, at least in my case. At any rate, the new pads and freshly lubed calipers have completely eliminated the noise and the need for any fancy foot work to avoid embarassment.

KuoH

Originally posted by deadeye95
It's the trapped air escaping that produces the squeal.

I've always wondered about that. Thanks for the theory lesson.

[kuoh]

That was also what I've heard, though not being a mechanic or engineer, I didn't have the means to prove or disprove it. I'm guessing that in my case, the binding in the front calipers probably put the pads in contact with the rotors when I stepped on the brakes, but not hard enough so they had room to vibrate and generate the noise. It also accounted for the more frequent engagement of ABS on dry pavement, and the fact that the rear pads were worn down to 25% or less while the fronts still looked like they had 50% left.

KuoH

Originally posted by Beav
We were always told the noise came from hi-speed vibration - the faster the vibes, the higher the frequency of the sound. Similar to a damp fingertip rounding the rim of a piece of stemware. Supposedly the more abused the pad, the harder it became and more susceptible to the vibration.

[MoreIBNR]

If I go with ceramin pads, do I have to replace all 4 wheels at the same time? Or can I leave semi-metallic on the rear and just switch the fronts?

Originally posted by Beav
Yes, they are supposed to use shims, but even when present they aren't the end all to brake squeal.

When I have a customer complaining about brake noise I explain that there's a lot of things I can do but nothing that I can guarantee. Too many variables, from pad quality to people that drive in downtown traffic to how some people drive. I used to live in Colorado and would have people that drove down from a visit to the mountains with their foot on the brake the entire way. On some cars we would have to smash the plastic wheel covers to bits as they were melted into the holes in the wheels. Funny, Randy and I were just talking about this at lunch yesterday.

I was going to leave this thread alone originally because I can't recommend any brand(s) in particular for the above reasons. I can say that the products I normally have my best luck with are the OEM pads, a line of pads from Wagner that have a silver backing with raised sections that replace the shims and the ceramic pads.

In Colorado it seemed that most every day I would have a noise complaint but where I am at in Kentucky nobody complains. I don't know whether it's because more people are acclimated to the fact that all pads will make noise from time to time (and I don't mean loud squealing on every stop is normal) or because the pads don't squeal here, either because of humidity or quality. I'm just happy I don't have to deal with it anymore, it really could eat into my paycheck...

[Beav]

You can mix and match at will, it's just important to change the friction material in axle sets. No being lazy and only doing one wheel at a time, Andy and Aunt Bea will be back tomorrow...

Originally posted by oab_au


The shims are suppose to have bent edges, or a raised center. This to form a compressible medium between the pad and piston, to allow the air to leak out from between the pad and disk before the full clamping pressure is applied.
It's the trapped air escaping that produces the squeal.
This is why things like roughing the pads, cutting grooves across the pad, grooving the disk, will stop the noise for a while.
OEM pads with new shims are the best way to prevent squeal.

Harvey.

You may have answered these kind of rather "dumb" questions, but here I go again: do I still need new shims even with cross-drilled rotors if the barke pads are harder than OEM? I unde-rstand rotor was drilled to let the trapped air escape, thus extending its life. If cross-drilled rotors let the trapped air escape, shouldn't there be anymore squeal?

Originally posted by KUL RIDE


You may have answered these kind of rather "dumb" questions, but here I go again: do I still need new shims even with cross-drilled rotors if the barke pads are harder than OEM? I unde-rstand rotor was drilled to let the trapped air escape, thus extending its life. If cross-drilled rotors let the trapped air escape, shouldn't there be anymore squeal?

The squeek that is produced by the trapped air is made by the air being forced out of a very small hole. Since the holes in the crossdrilled rotters are some what larger and there are many of them, there's no reason for a squeek. You can think of it like whistleing, you need to make a small hole in your mouth inorder for a pitch to be made, if you open your mouth too much a whistle will not be produced. At least that's how I think of it

[wawazat??]

Mine do every stop. I do not have the shims on the pads as the originals were to far gone for re-use. I'm going to order more this evening.

Todd

[Beav]

Normally I don't come straight out and say BS!, but it's time to bring this to an end. This stuff about out-gassing creating brake squeal holds as much water as a gnat's butt. Think for just a moment.... if the friction material produced enough gas to create a squeal every single time you stepped on your brake how long would the freakin' pads last?? Think about how fast a teapot of water dissipates when the water boils hard enough to create a whistle.

The only thing those holes create is sales for the manufacturer and a reduced swept area for the pads to work against.

[wawazat??]

Originally posted by Beav
Normally I don't come straight out and say BS!, but it's time to bring this to an end. This stuff about out-gassing creating brake squeal holds as much water as a gnat's butt. Think for just a moment.... if the friction material produced enough gas to create a squeal every single time you stepped on your brake how long would the freakin' pads last?? Think about how fast a teapot of water dissipates when the water boils hard enough to create a whistle.

The only thing those holes create is sales for the manufacturer and a reduced swept area for the pads to work against.

Beav,
I didn't mean to get you bent out of shape, I was just reporting my observations with the particular combination of pads and cross-drilled rotors. I don't race my car or worry about reduction in swept area. I purchased the rotors for the looks and the pads for the longevity, as you mentioned in one of your previous posts. I just wanted to give those who are offering their conjecture without experience an actual example of a combination that still produces a squeal when stopping.

Todd

[Trevor]

Here here Beav,

The sqeel is caused by simple mechanical reciprocal vibration (high frequency chattering) as you have previously pointed out. Violin bow, finger on wine glass, scraping metal, how could it be more simple.

Whistling, farting gasses what a lot of hot air and bull****. That is what the shims are for, ie to assist in reducing clearance and not allow room for vibration and they are arranged to provide spring tension to maintain a constant pressure. However it must be accepted that vibration can still occur resulting in noise in some circumstances. Exactly the same problem was present with drum brakes and was assisted by chamfering the leading edge of the lining.

However the snake oil accessory trade will always attract suckers particularly if they offer something different with eye appeal ( see what I have and you haven't stuff). My car goes faster than yours because my exhaust oatlets are chrome and pretty, etc. etc. etc. They should " Get real " as they say, lets leave them to it!

Trevor.

[Beav]

My apologies to you Todd and anyone else that thinks this upsets me. It doesn't. I just thought there was too much energy being spent on a subject that holds no more merit than placing magnets around one's fuel lines.

The rotors that are cross drilled, etc. may be better due to their casting process, amount and/or type of steel used, etc. but definitely not by the holes drilled into them. Race cars might benefit from them but then we're referring to vehicles that have larger swept areas and a typical weight one-third less (minimal)than the SVX. I believe that most people's true desire to own these rotors is driven by wanting to correct recurring warpage, not noise reduction. These rotors may provide that, but it won't be because of the holes.

One last tidbit on disc brake noise. There is one vehicle that I know of that absolutely never has a brake squeal, no matter what type/quality of pad is installed. The rotors can be warped, rusted, grooved, or smooth as a baby's butt. The older style Toyota pick-ups and Four Runners had a four piston caliper that was unique in the respect that the leading pistons were a smaller diameter than the trailing pistons. Look at it this way, if you hold a fresh piece of chalk perpendicular to the chalkboard it squalls like a banshee when you move it sideways. Take the same piece of chalk and tip it slightly to one side and it is silent when moved. By using the smaller piston at the leading edge of the pad, less pressure is exerted on the pad and a kind of 'tipping' is induced and the pad won't set up a vibration. I've seen the newer versions are four pistons of equal diameter and they do make noise from time to time. How unfortunate they decide to change them. Apparently another mediocre engineer was trying to justify his existence (read: his position on the payroll.)