Brake Pad and Rotor Bedding Procedure

[anglin]

There are some things you should know before you replace the brake pads and rotors on the front of your car.

One of the biggest concerns that folks seem to have when replacing their front brake components is the "warping" of the rotors. The XR seems to be sensitive to variations in the surface of the brake rotor and feeds these variations right up the steering column and into the driver's hands. In most cases it seems, the problem is not the actual warping of the brake rotors as much as is it the uneven deposit of brake pad material on the brake rotor. The uneven deposit comes from poor/lack of bedding the pads and rotors in.

Never replace pads and rotors at the same time. They should be bedded separately. Bed new pads on previously bedded rotors and bed new rotors on previously bedded pads.

A local Merkur owner was frustrated with the new brake components on his car. He had purchased the good, stock replacements from BAT and he thought the rotors were warped in less than 500 miles. I tried optimizing the setup (detailed below) and didn't change anything. I put on different rotors (some old, janky ones) and the judder went away, not surprisingly. So, I put the original rotors back on and decided to try bedding in the already improperly bedded pads. After three repeated bedding sessions over the course of three days, the judder was almost completely indistinguishable.

I don't want to pretend that I understand all of it and claim to be an expert, so here is a link to the StopTech web page and their info on bedding in brake components.

http://www.stoptech.com/tech_info/tech_ ... pers.shtml - the link called The "Warped" Brake Disc and Other Myths of the Braking System is the one you want (written by none other than Carroll Smith), but the other articles in there are very good. Look at the "Prevention" section of the myths article.

There are a few extra things you can to do optimize the braking system. I always clean the rust off of the hub and put a dial indicator on it to check for warping. Additionally, you can bolt the rotor onto the hub and measure runout of the rotor and index the rotor with the hub in one of its four possible positions (for 4 lug hubs) to minimize the total runout. This can help fine tune the brakes and minimize the pad/piston knock-back and reduce drag.

Edit: subject line changed

[Ray]

Good post. Rotors almost never warp, and that article is something that i've seen stickied on several enthusiast boards. I'd say throw it to the faq.

I bed my pads / rotors like this:

20-5mph, cool quickly, 20-5, cool quickly (hitting the brakes hard but not pending lock up)

then i'll do
2x 30-5mph, cool

2x 40-20, cool

2 x 60-20, cool

2x 40-20, cool,

2x 20-5, cool

then for a while i just wont "stop" with my foot on the brake. i'll use the ebrake and / or clutch.

[DPDISXR4Ti]

Never replace pads and rotors at the same time. They should be bedded separately. Bed new pads on previously bedded rotors and bed new rotors on previously bedded pads.

I'll highlight this point, as it is something which probably is NOT done 99% of the time. Realize too, that a re-surfaced rotor is essentially a new rotor as far as this conversation is concerned.

[flylear45]

One footnote to this, I had a set of front rotors on the XR for a Cougar (PBR conversion) that I purchased from NAPA that would not keep a good surface. In less than 1000 miles I would get a pulsation, and I could SEE the difference in transfer of pad material. I understand that a lot of rotors are made with powdered metall and pressed together with a heat and epoxy? bonding process I don't pretend to understand. Whatever, I believe I had a set of rotors with differing characteristics around the rotor, and they were causing my problems. I replaced the rotors, using the same pads, and all has been well since.

I DO bed my pads and rotors religiously, and this was a very unique situation. NAPA replaced my rotors for free. Either they believed they were bad or were just pacifying me, but I was happy in the end.

[Khmer75]

The stoptech article is very interesting. I have never heard the contamination theory before and I have had a lot of "warped" rotors in my life. I've been mulling this over and reviewing the symptoms. My car "judders" very badly under light or moderate brake applications, but it stops straight and without vibration or "judder" if I hit the brakes hard. Does this indicate to you guys that maybe the rotors are okay?
Eric

[85merwhat?]

If the judder is not in your steering wheel, then I would adjust the rear brakes. If a drum is out of round, under light braking the shoes are just catching the out of round part, but under heavy braking the shoes make full contact with the drum and the problem goes away. This would be the first thing I checked.

I am a full time mechanic and do about 2-3 brake jobs a day. We almost always replace both the pads and rotors, and normally turn drums and replace shoes. We really only turn rotors for warranty work, or if there is a pulsation. I have never come across a pulsation that was not solved by turning/replacing rotors and/or seized hardware and lines. Rotors do become warped, and they can quite easily. Lincoln continentals have a bad problem with it. Most of the time it is due to driver error, as in thinking a lincoln can stop as fast as a miata. Taurus and sables are the same way. An easy way to warp a rotor is to brake fast before entering a puddle.

My method for the break in period is to drive the vehicle down a street with speed bumps, gradually braking. This 5 minute test drive has never let me down and my customers are satisfied.

[85merwhat?]

And just to clarify my thoughts about a warped rotor, figure 2 in the article is what I would consider a warped rotor (the "Distortion or 'Coning' due to stress from Thermal Expansion"). This is also the most common that I come across in the field. If a rotor has hot spots (similar to figure 4) then the rotor would be replaced and depending on how well the pads are, they get scuffed or replaced.

[DSPXR4ti]

Well Ray, you have a way of bedding your rotors & pads that was a write up in all of the brake MFG going back 15 years, it was then with all of the floating rotors that they were putting on the cars and then the cheap White box rotors that most brake shops at the time to help keep cost down but if you don't your brake job right, which is adjusting your rear brake to that help with not warpping the front rotors and of course not over torqueing your wheels and then doing a test drive a retorque will help immensely.

Ben DSP XR4ti

[Rocky Leitch]

All right. So you bedd these brakes, and rotors. what about
tire ware? Karmann has a thinner tire ware, she feeds all the road mishaps
through her body to my foot. I assume that she does not have ABS in her systems,
so it's up to me to mash hard or pulse on the brake if need be.
Am I right?


Rocky

[anglin]

I have never come across a pulsation that was not solved by turning/replacing rotors and/or seized hardware and lines.

This is the point of the article on the StopTech web page. Of course turning or replacement will cure (most of) the judder/pulsation problems because the problem is uneven deposits of friction material on the rotor. So if there is a new surface for the pads to contact (whether you turned the rotors to get it or replaced them) then the judder/pulsation will stop. However, if you don't bed the rotors and pads in properly, it is just going to return again later, especially with the front suspension set up in the Merkur because it seems SO sensitive to this sort of problem.

My method for the break in period is to drive the vehicle down a street with speed bumps, gradually braking. This 5 minute test drive has never let me down and my customers are satisfied.

The problem with this method is that the transfer of pad material to the new rotors probably never takes place because the temperatures never get warm enough. The StopTech method gets the pads warm enough that you smell them. Hell, I was bedding some of the race-oriented pad compounds and started to reach for my fire extinguisher because of the smoke coming from the pads.

Just a quick check/guess here (and no, this is not some sort of challenge), but I get the feeling that you didn't read the article linked above.

Of course, the bottom line is that the people who drive Tauruses probably don't give a dizz-amn about braking performance. They may never drive hard enough to get the brakes hot enough to transfer pad material.

So you bedd these brakes, and rotors. what about
tire ware?

Let's stay on topic for this FAQ Peer Review if we can.

[Maurice S]

Well HEY!...It works!...I had the soft brake judder (mild but annoying) and also a firm kick back to the left and right ONCE when applying heavy brake...did the full series of 10 (60-10mph) almost stops cooled it by hiway driving 40 miles, did a second set and then a third...the brakes are much more progressive now...you have to mean it if you really want to stop, or maybe it's just the hotter tires from driving? The first set was done on relatively cool tires as theres an industrial area near by....The hardest thing I would think is finding a place to do it without being harrassed by cops...I also had the luxury of a cloverleaf interchange nearby so that getting cool on the freeway was easy...Smooth as butter now...I'm hoping they feel good tomorrow morning. 1st set of stops there was smoke and smell everywhere, by the third much less so, so alot of junk does burn off, my rotors look like theyve been turned. I highly recommend the procedure. Also bedded in the rears I guess?? by having to use the hand brake till I got to the highway. And it's not about performance...it's about are cars being particularly sensitive to brake shudder...they stop about the same now...just smooth as butter...and the little 20-30 mph steering wheel twitch (that happen regadless of braking or not) is GONE!

My rotors are Brembos I dont know if cheapie white box rotors would stand up to it...but anyway if you've tried everything what have you got to lose?


PS on my last cool down run I got into a 3 lane absolutely perfect roll on after juking traffic then wide open for like 5 miles...me a Neon ST-4 and a convertible pimped out side piped SN95 GT...I didnt even down shift and I got a length on both...I think they both down shifted cause they made it up to my rear quarter but then started faded slowly at about 100mph two about three car lengths...the Mustang guy's tupee must have blown off cuz he quit at about 115...the ST-4 quit at 140 still fading...I'd never done a windows down hammer down top speed run....man the turbos just a whistling away even when I came off it...Talk about a great night...He's probably thinking what the HELL was that? LOL!

One last thing....think about the wear and tear saved on everything from bushings to inner and outer tierod ends and steering rack etc....

[anglin]

Well HEY!...It works!... I had the soft brake judder (mild but annoying)... did the full series of 10 (60-10mph) almost stops cooled it by hiway driving 40 miles, did a second set and then a third...

Word. People don't believe it until they try it. Brake bedding is important.

also a firm kick back to the left and right ONCE when applying heavy brake...

That's a totally different problem. That one giant twitch is from the bushings in the TCA (or alignment).

the brakes are much more progressive now...you have to mean it if you really want to stop, or maybe it's just the hotter tires from driving?

If you feel like they are weak now, you will probably feel more confident the next time you drive the car. They don't feel super powerful right after the bedding.

... then wide open for like 5 miles...me a Neon ST-4 and a convertible pimped out side piped SN95 GT... the Mustang guy's tupee must have blown off cuz he quit at about 115...the ST-4 quit at 140 still fading...

Save that for the street racing thread. I know we don't actually talk about street racing much, but whatever... does that really count for anything?

http://forum.merkurclub.com/forum/viewtopic.php?t=6391

[Freejack]

Chris already touched on it a bit, but I would add that bad TCA bushings will amplify any existing brake problems.

Jake