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Bedding Brakes

In an effort to educate our customers (current and prospective) we want to address a few braking specifics when it comes to installing, bedding-in and running/racing a big brake kit.  

The Main objective in bedding-in the brakes is to get the pad material to transfer onto the rotor surface evenly. Several things will disturb this process, I will try to cover all of them. Driving this kit like a grandma, (the way you drive when you are trying not to spill your coffee) will NOT help you or your brakes.  Honestly it is possibly the worst thing you can do if you did it for the first month or so, of occasional driving. The pad material will only transfer evenly if the rotor is at the proper, consistent, uniform temperature and the rotor "is true". The trueness of your rotors is integral to uniform pad material deposition (on to the rotor surface). First we will cover rotor trueness, because there are many things that can cause your rotor to run true/un-true.  What many don’t consider is that a .001 chunk of dirt or debris on the hub mounting surface can cause more than twice, sometimes 3 times that deviation at the rotor braking surface. Next I will cover the bedding-in process, as this is not a stock set of brakes and these require quite a bit more heat than a street set of pads. When this procedure is followed you will be rewarded with long consistent pad and rotor life.

Rotor trueness:
Several things will determine the trueness of your rotors.

1. The original rotor mounting surface (the hub face) has to be true. We have had more than one customer that had a bent hub and in one case we sent out a new set of rotor hats just because they were so angry and insisted the fault was with our kit.  This obviously did not solve their problems, and it cost both of us plenty of time and money. We still have yet to receive the undamaged rotor hats in return, even after this customer found and admitted that their hub was bent.

2. The hub face has to be clean. We recommend a wire brush or a Scotch-loc (on a die grinder, as shown in the instructions) and in many cases a small file to knock down any burrs or dings in the steel surface of the hub face will be required. Pay close attention to that face, and how clean and blemish free it is. I have seen several hubs that had a small piece of rust, dirt, even a crescent piece of aluminum or steel.  Sometimes this turned out to be from removing an aluminum wheel or old rotor hat "not carefully". Also from installing the AZP rotor assembly "not carefully". This crescent was stuck in the threads and when the rotor hat assembly was installed it was pinched between the rotor hat and the hub face. It left a depression in both the rotor hat and the hub face that had to be filed out using a small machinist file. If the rotor hat assembly goes on not true, do not force it, remove it and try again slowly, until it slides all the way on to the hub centric center diameter of the rotor hat, making sure both surfaces are clean and rust free. Also I have seen where someone removed the old cast iron stock rotor, using a hammer on the inside rotor surface. While entertaining and thoroughly satisfying as a removal method of your old failing brakes, they failed to notice that the rotor or the hammer left an upset edge on the hub that no matter how tight you made the lugnuts this still left the rotor assembly untrue. Only solution was, to use a file to make sure we removed this deformation completely.

3. The interface between the rotor hat and the rotor has to be clean and true. Since this is a two piece rotor, this interface introduces another possible place for error. During my assembly procedure I clean and inspect both surfaces thoroughly. I have had to remove casting burrs or small dings with a light filing. I am very careful not to disturb this interface while torquing the fasteners. There have been cases where I missed a piece of debris and of a small (very small) piece of paper towel being left in between these faces. I try to take as much care during assembly as possible, but it HAS happened. If you need to remove the rotor from the rotor hat. The 13.06" and 12.19" rotor torque spec is 24-27 ft/lbs on the 5/16-18 socket head cap screw with a 1/4 inch Allen Head Socket. The front 14.25" and rear 12.9" use 1/4-20 threads with a 3/16 inch socket head cap screw, and only require 15-18 ft/lbs. During re-installation install all fasteners all the way down to the locking washer, leaving them just loose enough to feel slight movement between the tolerances of the fasteners and the holes in the rotor. This might take 3 hands but its worth the hassle, place a paper towel on the work bench (so as not to scratch the shiny rotor hat face) hold the rotor hat down or fasten it to the bench if you can, and apply a rotation opposite the arrow to load and help center the rotor hat on the pattern of fasteners, torque two opposing fasteners and continue to tighten the rest in a star pattern as you would lug nuts, again torque to 24-27 ft/lbs (for 5/16-18) or 15-18 ft/lbs (for 1/4-20) depending on your fastener size.

Almost all the cases where customers experience an issue. One of the 3 items above solved all of their problems. By removing the rotor hat assembly and paying close attention to detail when performing these steps you will guarantee that you will not have a problem with trueness.

After confirming there are no issues with the items above, this next step is very important, because you "can" cause irreversible damage to the rotor (this might only solved by aggressive turning of the rotors on a brake lathe, or possibly blanchard grinding, performed at a quality clutch re-builder or machine shop). Fortunately 99% of the time going back thru steps 1-3 has solved the problem.

Another factor in rotor trueness, is initially (the first time) raising the temperature to its maximum uniformly and slowly. Very much like a fresh motor you do not want to fire up a stone cold brand new motor and do some wide open throttle drag passes to max boost and speed, this will most surely result in permanent damage the first time. Likewise you do not want to hammer the brake pedal on stone cold rotors when performing the bedding process.  The objective is to raise the temperature slowly and uniformly. There are a few differences (with respect to heat cycling) between your new rotors and a new motor that do not follow. Elevating your new rotors up to "and above" the normal operating temperature of their optimal use is key, to their longevity. Hear me again UP TO and ABOVE their normal operating temps. Herein lies the difference, obviously you do not want to overheat a new motor. But there is all sorts of evidence that engine blocks (cast iron) seems to settle or move around during initial and extended heat cycles. It seems very counter intuitive to what you might want do to a brand new part but it must be done to maintain the longevity of your rotors. This over heating event performs a bit of stress-relieving, in its intended form/use, and surely all of my testing supports this.  Rest assured cast iron is one of the best materials for a heat sink, and a friction deposition medium.  It isn't until you have spent more than 10 times the dollar amount that you might decide on carbon fiber to perform the same task.

4. Elevating the rotor to the proper temperature slowly, is key to not warping (un-evenly depositing pad material on) the rotors. The proper temperature for this "stress relieving" is way above the operating temperature for the pads that I supply, so slightly over heating the rotors is what you will be doing. Fortunately I have NEVER seen rotors actually WARP!!! What I have seen is uneven pad deposition on untrue rotors or rotors that were heat cycled below the maximum operating temperature for quite a while. Fortunately in each case I have witnessed rotors suffering from both problems, decrease "warping" symptoms after performing a complete bed-in procedure, once trueness or the problem with steps 1 thru 3 had been eliminated as a possible source.

5. All of the suspension components have been replaced, and you have confirmed they have no play in them.  The first customer with this problem went back and forth with me for over 7 months.  He is a competent mechanic, and owns/runs a garage and specializes in performance vehicles.  He knows them well, and has/had installed several of our brake kits on his customers cars and his own personal car.  We had been through every possible scenario of what could be wrong.  We were both very frustrated, he was so fed up that he purchased new rotors and rotor hats.  Before shipping I had them checked for truness, something that is normally never necessary.  He installed them on the car and the problem persisted.  Obviously he called exasperated, again we spent quite a while on the phone covering every item in detail.  When I asked about the suspension he assured me all the pivots had been replaced.  I asked how many miles on the chassis, and he proudly stated 200K +.  Then I asked, if he had ever replaced the front upper control arms.  He immediately replied "We replaced the bushings with Urethane."  I repled "No, the entire control arm. Remember there is an outer ball joint that is integral to the upper control arm, and not serviceable or grease-able"  I knew from earlier conversations he had factory upper control arms. There was a bit of silence, he replied "You know, I don't think we have!?!?"  A few days later I received a 7 minute voice message, where he described in detail how the initial diagnosis felt exactly like a brake rotor out of true, and the pressure on the rotors under load exhibited every sign of the rotors being out of true. Then he followed with a sincere apology for being so convinced the problem was with our brakes.  I called him back and re-assured him no apology was necessary.  We truly feel to this day if you have a problem, we want to make it right.  Please don't worry about sparing our feelings.  If you are having problems we want to make it RIGHT.

Next we are covering the complete bed-in procedure and have performed this countless times and it has worked flawlessly on every set. Again raising the temperature "gradually" "consistently" is the most important thing. Shocking a new stone cold rotor and pad set is the worst thing you can do. First we will cover how you and I can know how much pedal pressure is enough. This method has been documented by another manufacturer, I do not claim to be the originator, but it works excellent for our purposes.

Bed-in procedure definitions.

Pedal pressure:
Lets say rolling down the road "NO" foot on the brakes is 0% brake pedal force, and when applying the brakes the moment your tires lock, is 100% pedal force (for ABS cars continuous actuation of the ABS motors will be considered 100% pedal force) felt by a buzz or a grinding feeling at the brake pedal (I'm sure if you have ABS you have all felt it before) so half of this pedal pressure will be 50%. Obviously this will be different for different tire compounds so this will not be an equal scale for cars with lesser grip. A car with track tires (tread wear of 100 or less) will have much more grip than a car with street tires, so 50% on track tires will slow the same car much faster than 50% on street tires. I mention this so that all can be aware that if you have street tires you might need to apply a few percent less pressure than I have recommended if you don't have ABS. This is not exact science and probably has a margin of error greater than +/- 15% so don’t worry if you’re a little bit off. If you do most of what I recommend you will have successfully bedded in the brakes.

For the rest of this discussion we will assume you have better than (lower) than a 200 treadwear rating. Tires harder than 200 treadwear without abs will surely be able to lock the tires at-will over 100 mph with 75% less pedal pressure than it took with factory brakes (IF you could even lock the tires with the factory brakes).

Bedding-in the rotors:

Drive thru the neighborhood/industrial complex, (a place with little to NO traffic) use them like normal, make sure the pedal feel is as good or better than the original brakes and makes no noise.  If its not you have not properly bled the brakes, return to the shop (slowly) and find the problem.

You might (I say "might" because it doesn't happen all the time) notice a "whump whump whump...." during the first several pedal applications. This is the edge of the new pads going over the edge of the new rotor slots it will go away within the first half dozen or so pedal applications, this is normal.

Again use as normal, getting a feel for your new brakes, stay under 35-40 miles per hour for the first dozen or so applications, just to get the feel and to keep "slowly" increasing the temperature of the rotors. Go to a safe place where you can stop from 60+ without fear of causing an accident. Several customers have made new customers because their friends that followed on the maiden voyage of their new brakes very nearly rear ended them on just the 2nd or 3rd stop. Meaning the factory brakes weren’t as good at 100% capacity as the Wilwoods were at 60% while being bed-in. These brakes are more than twice as good as your factory, brakes and you will be shocked at how effortless and controllable they are. DON’T LET YOUR FRIENDS FOLLOW YOU IN THEIR CARS!!!

Bed-in procedure details:
First I need to cover a few DONT'S and WHYS!!!

Do not come to a complete stop with your foot on the brakes during the duration of this test (if you can help it). i.e. once you have put a considerable amount of heat into them if you have to stop at a light/sign, stop a few cars short and roll/move slowly during the duration of the red light until it turns green or you can proceed.

Coming to a complete stop with very hot pads does 2 things, it leaves a pad imprint on the rotor, transferring an abnormally high amount of pad material. This increased material leaves a raised area, a crystalline and pad composite growth that you will be able to feel (at the brake pedal) if not see on the rotor. Also if the heat is high enough and the pressure high enough and left long enough you will in-effect "surface heat-treat" the rotor in one area. As time goes on this harder spot wont wear near as much as the rest of the rotor surface and as a result this high spot will get hotter and hotter transferring more and more pad material. This is often mistaken as WARPED rotors when in effect it is a true and straight rotor, but the rotor develops a high spot on both sides of the rotor. Turning the rotors seems to be the only solution. In rare cases even turning that won't solve the problem as the crystalline growth happens in both directions (above and below the cast iron surface of the rotor) if drastic enough and if the lathe cut isn’t deep enough, the high spot will reappear. Usually this is only in the most drastic of scenarios when in extreme race conditions, street driven rotors will usually be completely repaired by a conventional brake lathe turning.

If you were ever to attend a high performance driving school where they rent you a car, you would surely experience this problem with a majority of the cars they supply.  I have a few close friends that are/were mechanics and instructors at Bondurant, and I know for a fact that Bondurant, Skip Barber, (and I'm confident all the others) consider this to be one of the most common problems with all of their rental race cars, and since they have so many new students the instructors just preach all they can and the mechanics just replace the parts when they are so bad they are not safe.

Overview of  the bed-in procedure:
In short, the objective is to gradually bring the rotor/pads up to and slightly above operating temps. Then drive around a while using little, to no brakes, letting the rotors completely cool to ambient temps.  Then your done.

Now on to the detailed bed-in procedure:
Put a small amount of heat in the rotors from a stroll around the neighborhood (or a warm up lap at the track) follow these instructions and you should have completely bedded rotors.

Again find a place where you can complete these stops (intense deceleration events) safely. Between each stop (deceleration events) wait about 3/4 to 1-1/2 miles to let the temps stabilize but not cool off. More than 2 miles is too long between stops. I say "Deceleration event" because you wont be coming to a complete stop on any of these events.

Get the car up to 60 mph and apply the brakes with a 40%~50% effort down to 5~10 MPH. This will take a while make sure there is no one behind you.
Get the car right back up to 60 and repeat once again.
Get the car back up to 60+ mph
(no more than 3 times total)

With the car at 80 or so: 
Apply the brakes at a 60%~70% effort from 80 mph down to 5~10 mph.
Repeat once again.
Again get the car up to speed again, (80 mph) and apply the brakes at 80% effort down to 5~10 mph.
Repeat once and you should be finished, if you didn’t smell brakes or see smoke then your not done. Repeat until you know you have put too much heat into them. This will be evident by a slight feeling of "Oh man I think I did something wrong, the whole car feels different."  This is just the rotor at its hottest, and outside the proper temperature range for the BP-10 pads supplied.  If you are installing more aggressive pads, at the track, just install the new pads, and (warm the rotors/pads up gradually) perform an abbreviated version of the bed-in process, not decelerating to such a slow speed, and this should be fine. 

The on un-coated rotors, most of the smoke is from all the oils that the rotors are shipped in burning off of the inside of the cooling veins of the rotor.  We currently supply all standard rotors with Wilwood's E-coating, so the brake smoke will be slightly less.  Don’t be alarmed, if you will find 2 rings of brake dust on the inside of your clean rims, look closely and you will notice the slots doing their job as witnessed by several pairs of more dense brake dust trails on the inside of the rim corresponding with where the slots routed the dust. On un-coated rotors you will see this also, and the oils that you couldn't remove with brake cleaner, will be flung out of the cooling veins when they were super heated.

After you have smelled, or witness the brake smoke, do one more stop to make sure all is consistent, then, chances are you are done. If you have ABS, on your last few stops, (deceleration events) try STANDING on the pedal to get full ABS actuation (100%) to see just how good the brakes work. Again a decrease in performance means you over did it, ("got them over heated" and this is what we want) let the brakes cool and try it again later, but you will be SHOCKED at how good they work and how much you can abuse them. As with any brake system, you can do damage getting them too hot for too long, as in "riding the brakes for the hell of it or doing "brake stands" on the freeway or rolling races". But rest assured, you WILL have to try to find that point. Your better judgment will tell you to stop long before you have damaged anything.

If you don’t have ABS gradually work your way to more and more pressure to find where the limit is so that you don’t "flat-spot" your tires. Trust me its very easy to under estimate these brakes. Also if your going to continue to run them or your track session isn’t finished, don’t be alarmed when you feel pedal movement (what feels like a slightly warped rotor), this is the hot rotor moving around and will return to true once you let it cool off, just don't come to a complete stop while they are very hot. Also try not to do this in the rain as it might prematurely cool the rotors, or take longer to get them up to temp.

I realize some might have a track ONLY car. This can be done at the track with no problem. Announce at the drivers meeting or, at your session meeting that you have new brakes and you are bedding them in and that you will stay off line if you see traffic coming. Line up at the end of the group and go out and perform your bed-in process as close to what has been described as possible. If you have not completed the process and the leaders are catching you, go ahead and roll through pits slowly and wait for the pack to pass and continue until finished. Inform the stewards and the leaders in the group, and announcing it in the group meeting will make all aware and keep everyone from wondering what you are doing. Don't worry, everyone will understand, especially when later in the day the only cars able to out brake you are the open wheel race cars. Honestly several customers have called back (from the track) and stated that they can out-brake every other car on the course except the open wheel variety. When your 3000 lbs+ car can out stop cars that weigh 1/3rd less you know you are doing something right.

Do an extra cool down lap or roll around the neighborhood/industrial complex before you come to a complete stop, make sure to let it cool quite a bit before you come to a complete stop.  Try to use no brakes, or your parking brakes to decelerate into your shop/garage or the pits.  Let cool to ambient or until your next race session and you should be good.

We love to hear your track experiences, (good or bad) if your driving home from the track and you just gotta tell somebody, (because you know your wife or girlfriend wont care) give us a call, we know exactly how you feel. 

Thanks for purchasing our products, and feel free to contact us if you have any questions.