Hi Guys,

This is a little something I typed up for one of the Subaru boards, but since I didn't see anything like it here I thought I would share.

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First and foremost – brakes are a no joke thing on your car. If you are new to brakes have someone teach you how to work on them. Despite all the reading in the world on this subject this is something you should be taught to do instead of trying to figure it out yourself.

Second – If you are new to brakes get someone to teach you. Yes, it had to be said twice. It’s that important.

Now, this is by no means an all inclusive document on brakes. Instead it is a few tips and tricks I have learned over the years.

Some background on my brake experience: I started helping Dad work on the brakes on the family cars and trucks when I was seven by handing him tools. By 12 I was doing the disk brakes myself with his supervision. By 15 I had the arm strength to do the drum brakes on my own. By 16 I was doing brakes unsupervised by him. Now, this does not mean I am immune to learning new things. Far from it. Quite often I see someone with lots of experience post up a new tip or trick to working on brakes, and if it makes sense I try it out. Most of the time it works nicely.

On to the tips and tricks. I will try and keep this brand generic as we can cover that later.

Pads –
Run the proper pad for what you are going to be doing with the car!!! Do not run street pads on the track. They can’t take the heat.
Do not run high end track pads on the street. They need time to warm up to operating temp.
Do not run track pads and expect to get low dust and no noise. In a race environment dust and noise fall WAY down on the importance list.
Buy the best pads for your application that you can afford.
Be aware of the limitations of these pads, and don’t out drive them. Remember, no matter how fast you go eventually you have to stop.

Fluid –
Regular street level fluid on a NORMALLY driven street car – change every two years.
Good fluid that sees aggressive driving on the street – change once a year.
Good fluid that sees heavy autoX usage on a “race on Sunday drive to work on Monday car” – change a couple of times a season at the very least.
Good fluid that sees hard track use – fresh fluid for each event.

Rotors –
Buy good rotors. Not unknown cheapy ebay ones that you have no idea who made them.
Slotted – not really necessary unless you are heavily racing in the rain
Drilled – NO NO NO a thousand times NO!
Two piece, semi-floating or fully floating – there’s a time, a place and a budget for these. 99% of the cars on this board will never need this time place or budget. Quite honestly they are not necessary unless you're REALLY into autoX or the track, and chances are if you are into those things I'm not going to tell you anything you don't already know about them.

Turning the rotors – if you feel they need it then do it, but don’t fall into the “warped” rotor myth. If you can see pad impressions on the rotors then get them lightly turned after a trying a bed-in (see below). Why this way - because "warped" rotors are actually uneven pad deposits. With light deposits you can scrub them off using a bed-in.

NEVER run a rotor that is below the recommended thickness spec. It’s just not worth the risk. Period.


General tips on pads, fluid or rotors –
Brake squeal – this is actually a vibration you are hearing. It’s the pad backing plate chattering against the pistons. Anti-squeal rubbery goop is supposed to help prevent this. I’ve never really cared for it. For many years I ran a good grease on the backing plates and it worked just fine. Until! I got a suggestion to run high temp anti-seize instead. I gave it a shot. I will never go back to grease.

Fluid – Use good fluid for your application. Please note – DOT 5 is NOT what to run in our cars. It’s a silicone based fluid made for preservation of lines in classic cars. DOT 5.1 is the stuff to look at for actual driving if you choose to use a DOT 5 series fluid.

Whenever you replace pads OR rotors, not both, but EITHER you should do a bed-in process. Here’s the process I have used for years:
45-10 using medium pressure 3-4 times
Drive to cool for a little bit
55-10 using medium pressure 3-4 times
Drive to cool for a little bit
65-5 using hard pressure but not locking them up 3-4 times
Drive for 20 minutes to cool them.
If you must come to a stop in that time do so gently, and just hold the car at the stop with the least amount of pedal pressure that you can (or use your hand brake).


Please note, you can do a bed-in process at any time. In fact, if you are starting to feel a slight vibration in your wheel during light braking due to pad deposits do a bed in process before thinking about getting your rotors turned.

Do not forget to do this on a new car. The factory or dealer does not bed the pads for you as part of their PDI.

(I know this doesn't apply to MINIs, but it might be helpful to someone)
If you are changing shoes as in on drum brakes do each side one at a time from start to finish. This way you can go and look at the other side in case you forget how it goes back together (and you will forget).

Couple of general points –
Use brake cleaner spray to clean machining oil and finger oil from rotors
Use brake cleaner spray and a rag to clean up stuff in there.
If you use an airgun for spraying dust out don’t breathe it. While pads are no longer made with asbestos I’m sure breathing that crap still isn’t exactly good for you.
Wipe things down so you can see what you’re doing.
Apply grease or anti-seize to the slider pins on the frame that holds your pads in place.
Apply grease or anti-seize to the backing plates of the pads
Apply grease of anti-seize to the clips that hold the backing plate tabs

 

Clint -
Thanks for posting this - a lot of good information

What's your opinion on SS brake lines vs. OEM rubber ones? I have SS lines but I truly can't feel a pedal difference.

 

Why not? (I understand your only talking MINIs and not other cars ... I presume).

That is really nice of you to provide your expertise. Very nice.

 

I happen to like SS lines, but keep in mind that's on the Subaru where pedal feel isn't that great in the stock setup. We'll know more when our R56 comes in, and we start to look at things.

 

I'm talking all cars. There are three reasons.

First, they crack, and the holes are stress risers.

Second, your vaned rotor is basically an air pump. Move as much air over the vanes as possible to shed heat absorbed by the rotor material into the air as much as possible. The walls of the rotor are the walls of your pump. When you go drilling holes in the walls of your pump you start to make it less effective.

Third, less thermal mass. The rotor is designed to absorb heat generated by friction of the pad on the contact surface. The more mass the more heat it can absorb, and store. Storage is important because shedding that heat to the surrounding air takes longer than it does to put heat into them. You start taking mass away and you start to affect the absorbtion and storage capabilies.

One other thing since I know it's going to come up. Outgassing - folks will tell you that it's to allow the organic compounds to gas off the pads without creating a layer of gas between the pad compound and the rotor. This was true in the old days, but modern pads do not outgas.

 

Hmm ... I presumed you were talking MINIs but all cars?

So I guess I better take my car back to the dealer since it comes OEM with cross drilled and slotted rotors and they have no clue as to how to properly engineer a car. Statements like

"... they must be able to go through 25 consecutive cycles involving full acceleration to top speed, followed by deceleration to 62 mph (100 km/h) without fading." Source

are meaningless?

Sigh ...

 

Sigh indeed. The holes are there for bling.

Here, let me give you little something to think about on those holes -

Give me an inch on this and agree with me that the holes are stress risers. I guess that one would be pretty easy to understand, and I'm pretty sure a number of folks are going to agree with me on that one.

So - how do help keep cracks from forming at the edge of the hole. Well, there's a couple of ways. 1) we could chamfer the bore. Would be good, BUT even better is if while we were at it we 2) peen the hole. No problemo. Just chamfer it when you drill the holes, and peen it with something like a ball bearing and a good hard thwack with a heavy hammer (seriously, this is a legit form of doing this).

Bingo - problem solved..... well, not really. How are we going to chamfer or peen the inside edge of the bore?

Now, I knew that the cross drilled thing was going to bring up some argument. It always does. Let me point you to a little something you might enjoy reading:
http://iwsti.com/forums/showthread.php?t=67007

This thread was started by a gentleman over on one of the Subaru boards who has done quite a bit of homework to put it together. Quite honestly, the information he has put together, and others have contributed explains things quite nicely.

In the end, I'm not trying to be a jerk. Just trying to impart some of the knowledge that I have learned. Please keep in mind you are, despite what I say, entitled to your opinion.

 

Whoa ... nice link

From your link "Porsche rotors are the only "crossdrilled" rotors I would ever consider putting on my car"

Bling? No, they have a legitimate reason to be there. The cars are meant to go from your driveway to the track and back.
I was objecting to the word "all". But your link just verified that "all" was not the right word to use. I wasn't really trying to dump on you but I really think Porsche knows "just a little bit" about building sportscars and race cars.

That article was very informative and just verifies my point. In fact, Porsche does know how to properly engineer a car since every Porsche sportscar sold (not sure about the Cayenne SUV) comes with cross-drilled brakes.

BTW, "the red brakes" as he referred to (the Calipers) are Porsche Design, built by Brembo to Porsche specs that are uniblock ... one single block of metal. Not the same as regular brembos. If you read the literature it says they are cross drilled to improve wet weather response and unsprung weight but the cars also have engineered air flow to ensure cooling on all parts of the brake assembly. The ceramic rotors are an entirely different league.

So I guess we agree now ... it does NOT apply to all cars

The technical literature also describes the engineering of the air flows to ensure cooling of to the entire brake assembly.

Cracking is a real problem but after reading from people who track all the time, microcracks don't matter unless they connect the holes which is "supposed" to be very rare unless the car is extensively tracked. In that case, the rotors are just disposable items anyway but for normal street use ... they wouldn't be able to sell the cars if OEM parts cracked easily. (IMO)

Thanks for the insight ... I think the use of the word "all" was probably the wrong word Now I don't have to go back to my dealer and ask to have them fill in the holes

 

Very good and valid points. I'll concede that the word "all" was probably a bit too inclusive.

 

Good links and articles, but as always is a matter of application, I my case I had drilled rotors on my 90 mustang, (bear brakes) and 2000R (brembos) 2004 cobra, and on a 02 MKiv 1.8T and never had a problem with warpping or distress ... Its more cosmetic yes, but if there were this bad and such a no no no, they would not make them anymore, specially the last set I got for my R56 MCS which comes from BMW, and the JCW kit would came with regular rotors...I totally agree with buying stuff from Ebay, you have to be careful of quality...BUT if I see any problems with the rotors I just had installed by a Certified BMW/MINI Mechanic I will post.

 

I can now answer this question based upon more driving time with the car.

I feel that SS lines will improve the pedal feel on this car. The stock brakes really aren't bad at all (the tires are a different story). They get good initial bite, and are easy to modulate. They would be even easier with the improved feel that SS lines would provide.

Overheating has not been a problem, but then again one of the first things I did was remove the dustshields. In a more roadrace setup I would want to run some ducting to them, but for short autoX runs, and daily driving they seem to be fine.

Overall, I think that you'd really really have to be pushing hard to justify (from a performance standpoint) of going straight to a BBK without trying some other things first. I personally feel that with the stock calipers and rotor size there is a good amount of room to play with by just using the following:

- more performance oriented pads - at the cost of noise and dust
- different fluid - since I don't know what MINI puts in from the factory I don't know how far I can push it and start to recognize when it's about dead. By changing to a fluid I know well I can make this judgement easier.
- SS lines - for the feel and better modulation
- Ti backing plates - keep the heat out of the caliper pistons as much as possible
- remove the backing plates
- brake ducts - for road race conditions

Beyond that there's a few other one-off tricks you can do, but I don't really think anyone (other than us) will go that far.

 

Wow. That's a lot to take in.

I do know this, having cross drilled rotors will prevent the stupid dime-a-dozen brake shops from telling you that your rotors HAVE to be turned everytime you take your car to them.

I swear I had a GMC Sonoma that everytime I took it in for an inspection or because of a squeek, they told me my rotors had to be turned. I put cross drilled rotors on and continued going back to the same shop for 5 more years, and they never once played the "your rotors have to be turned" game.

 

Just wait until all the shops have equipment to blanchard grind. then it'll be back to the same game for slotted or drilled rotors.

If they want to bug you just ask them what the runout numbers are, and how close they are to min. service thickness. I'm betting they can't tell you to which you can reply "well, how do you know they need to be turned?" Oh, be sure to say this AFTER you get your inspection pass sticker.

 

As a seasoned Autocrosser and Time Trial and competitor i can't add very much to what cboggess has written, It is all very true and should live by it.

I can add these additons, the bettter the brake fluid the more water soluble it is so it gathers more humidity. That is will cause concatination/air bubles to form causing the fluid to boil. - THis is why better fluid needs to be changed often. I only used Dot 4, MOTUL RBF 600. Castrol makes better but it costs like 50 bucks a liter.

The cross drilled rotars are as cboggess stated and not good for track use. They are good for offroad condition or for rain condition, the holes will allot more pad contact since the water/dirt can get pressed into the holes, but for best braking in street/track on a road car you want blanks. I personaly used groved discs on my track car so that i will remove the glaze that forms on my pads and remove the gases better, but i never really senn much benifit for the cost.


Cheers.

 

Thanks Cboggess. The information you've provided in this thread reinforces little bits of theory I've adopted over the years. I haven't changed much about the brakes on any of my cars so it remains theory. I drive the MINI a little harder than any of my previous cars and may want to do just a couple of things.

What you say about changing the fluid is interesting. In the past when I've done brake repairs and had to bleed them it has been the most tedious part of the job, often involving recruiting the mechanically disinterested to help. Surely there must be a tool, method or technical innovation which makes changing the brake fluid something one does as race preparation rather than preparation for purgatory. What am I missing?

 

On my other cars, I've used one of these. There's a learning curve, but the premise is that you lightly pressurize the master cylinder with a generous amount of new fluid in this bottle to replace any you are pulling through the lines. When it's set right, you merely go to the far corner, open the bleeder until you've got the air out (or get fresh fluid if that's your goal). Then move to the next wheel. Just mind the seal on the master cylinder, place a safety rag around it, and don't run out of fresh fluid or you'll start all over again.

 

gravity bleed is my method.

You just need to open up all the valves and put loops in the drain lines. Open the MC and let gravity and potential energy work for you.

 

Loops in the drain lines? I can't even begin to guess what this may mean. For example, I didn't know there were drain lines. Are these just vinyl tubing pruchased for the purpose? Is the point that the drain lines fill up with the fluid that was in the car and the new fluid replaces it?:impatient

 

Yeah you put a vinyl tube in in a loop that then drains into a container. Put it so that the top of the loop is the highest point of the tube+caliper. The bleed nipper you use should be at the top of the caliper if for some reason the bleed nippel is on the bottom you will have to unbolt it and hold it upwards for air to get you. You do this setup for all brake calipers and open up all the nipples. Open up the master cylinder and it will flow down to the open vavles but the loops put some hydraulic resistence on the flow and air will make it's way out. I like this method cause it is easy, i can do it myself and is not soo messy. If i need to flush the system i do not use this system. And for emergency track side bleeding, speedbleeders work well.

http://www.speedbleeder.com/

 

I have always used the 2 man pump system, but I've been giving some thought to rigging something up with my vacuum pump to give that a try.