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Talk about brakes

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    Talk about brakes

    I've worked since 2001 in a brake specialist shop. All my mechanic friends call me a "brake nerd". There's a lot of good info on this site about how to work on our brakes but i just wanted to talk a bit about brake systems overall and common things they DIYer doesn't know to look for.

    First I'm going to spend a minute talking about rotors and pulsations. I think this area needs a brighter light shed on it than what I've found while browsing.

    Rotor Basics

    There are a few important specs a rotor needs to meet in order to be "good"
    Minimum Thickness/Discard Spec : your disk must be thicker that this
    TIR : Total installed runout. This is the total stacked runout in your wheel end assembly
    some vehicles also have a "machine to" spec but not hondas so I won't talk about it again.

    What is a "warped rotor"?

    The term warped doesn't technically mean anything. What most of us picture as a warped rotor is called lateral runout. When a rotor has excessive runout it will push the caliper back and forth on the guide-pins as it passes through the caliper assembly. Assuming the disk is uniform in thickness and the pads and pins are moving freely you will not feel this when you brake (the piston is NOT being pushed back into the caliper bore) but you might hear a cyclical squeaking or chirping sound.

    So what causes pulsations?

    When you feel that shaking, usually first noticable at high speeds, what your feeling is disk thickness variation (DTV). In this case your disk is not the same thickness all the way around and as a result the piston is getting pushed back into the caliper as the thicker part of the rotor passed through and pushed back out again by your braking as the thinner part passes.

    Where did the DTV come from?

    Lateral runout leads to DTV. Imagine the disk spinning, a pad on either side, excessive runout in the disk. As the high side on the disk passes the outer pad it pushes that pad out, which pulls the whole assembly outward. On each revolution the outer pad pushes against the same spot on the outside plate of the rotor. The same thing is happening 180 degrees around on the inside. Over a period of time this will lead to uneven wear and uneven distribution of pad material on the rotor. Congratulation we have achieved Disk Thickness Variation

    Thats neat and all but the solution is the same so whats it matter?

    When you replace a rotor (especially on a HOR car like most of ours still are) its important that the TIR (total installed runout) falls within spec. Most of us don't have runout gages and I would't suggest going out to buy one unless you plan on being a full time brake nerd like me. What I would suggest, and what I always do on a HOR, is use a knuckle mounted on the car brake lathe to achieve perfect 0 TIR. I know most people don't have one (even most shops don't) but its worth the legwork to find someone in your area who can do it for you and its usually not very expensive. If your taking my advice here it may have already dawned on you that if your going to have the rotor machined on the car after you change it you may not need to change it at all. All but the most severely "warped" rotors can be machined true again in as little as .010" - .020". I wouldn't recommend getting too close to the discard spec, but if your measuring .040" or more above discard I would machine the existing rotor.

    If your ROH just be sure that the mounting surfaces are clean, and if you remove your rotor for servicing be sure to index it to the hub and install in the same position it was removed from.

    The next most common source of lateral runout is uneven wheel torque. Always hand torque your wheels to 80 ft/lbs in a star pattern (specs vary but for us its 80) and make sure any shop that touches your wheels does the same.

    Now a small bit on pads

    Pads are by far the most boring piece of the brake puzzle. When they are close to worn out change them.
    They come in a variety of compositions and price ranges. You get what you pay for here so bear that in mind when choosing your pads, cheaper pads tend to be more prone to noise issues as well as excessive wear to your rotors.

    The pads are your best indicator of the health of your caliper, so with that in mind lets move on to calipers.

    Calipers

    When your working on your brakes look for abnormal wear patterns in the pads. If everything is working normally all four pads in an axle set should wear very close to the same. If your inboard pads are worn further than your outer pads then your caliper piston is not retracting. If the outer pads are worn further its a problem with the guide pins or outer pad sticking in the hardware. You can buy rebuild kits that include the seal and dust boot and rebuild them yourself or just buy some remans but I wouldn't ignore it, as it leads to reduced friction life, noise issues and if you combine this with that excessive TIR we talked about earlier it will exacerbate that situation obviously.

    Also look at the dust boot around the piston and make sure its not torn or melted, lift it up a little and make sure its clean and dry inside. If theres brake fluid in there its leaking, rebuild or replace.

    As far as the caliper hardware goes, I recommend replacing the hardware clips (shiny pieces that fin in the bracket) every time you change the pads. These parts can be bought in a kit very cheaply and also come packaged with several different brand pads and pretty much any reman caliper. Pull the guide pins out and clean and relube them with a silicone based paste.

    Fluid

    Keep it clean! Dirty brake fluid, especially when left for long periods of time in a system, causes all kinds of problems with hydraulic components.

    NEVER EVER EVER use anything other than dot3 or dot4 brake fluid in a street car. Racing fluid is not hygroscopic and will allow water to pool in your brake system causing corrosion.

    ANYTHING petroleum based will RUIN EVERY HYDRAULIC COMPONENT in your brake system.

    Bleeding


    The best way to do this is with a pressure bleeder. I realize that most people don't have one and will probably just have their buddy push the pedal while they open and close the bleeders. When you do it that way there's a few things you should understand about how a master cylinder is made to avoid damage.

    The primary seals in your master are situated at the front edge of an aluminum piston. There is a steel screw called a piston stop block protruding into the bore that is there to prevent the piston traveling so far down the bore that it passes the outlet ports thereby releasing all hydraulic pressure. Understand that your piston will only travel that far down in the event of a hydraulic failure (your creating one by opening the bleeder valve). The important thing here is to be gentle when depressing the brake pedal and don't let it go all the way down until it bottoms out. If that aluminum piston and rubber seal slam that steel screw it will do damage, its just a question of how much damage was done. Our cars have enough master cylinder issues without us damaging them while bleeding our brakes.

    Drum brakes

    Drum brakes work a little differently than disks but your still using hydraulic pressure to force a stationary friction material into a spinning metal surface to make a stop (converting kinetic energy into heat energy via friction). Inspect the wheel cylinders by lifting the dust boots on the ends up and looking inside, if its clean and dry its fine, if its wet or corroded replace it. I suggest changing the springs every time you do the shoes. Our shoes usually last a long time and those springs have been back there stretching and releasing, heating and cooling the whole time. The spring kits aren't much so don't cheap out. Use you parking brake regularly to maintain adjustment in the rear brakes.

    I hope this is helpful to anyone who reads it, I didn't really intend to have such a long write-up when I started this but one thought leads to another I suppose. Feel free to ask for clarification if you don't get what I mean or anything else brake related you might need help with.
    Last edited by SlimmTex; 01-26-2014, 04:32 PM. Reason: Fixed some typos, made it easier to follow

    #2
    whats your take on proportioning valves? ie: when someone does a rear disc conversion? or if they convert ABS to nonABS?

    Also Stainless braided brake lines?

    I know when I disabled my ABS system on my coupe due to an expensive leaking modulator failure, adding a 40/40 integra prop. valve was my only route, rather than pay 8-900 for a new modulator which isn't cost effective for the benefits of ABS. I feel my braking even without ABS is more controllable up until lockup and I can modulate it quite well with this setup. It seems to balance the braking more front to rear vs. when I was ABS equipped which always used to only ABS lock the fronts vs. the rears.

    I've also got stainless lines which made my car's brake pedal feel that much better and stiffer/solid. I feel this helped contribute to the good modulation I'm getting after doing the nonABS conversion

    Btw, I think the best brake setup using OE parts is Legend GS/LS 2 piston calipers, 25mm wagon rotors, and 25T brackets. I found it to be highly resistant to any DTV as you put it.

    PS. I just got a job at Link Engineering a few months back so I deal with these terms on a daily basis. You're pretty much correct in everything you mentioned above. Still learning the job as an EIT, I think its fun testing all these vehicles, especially the new 15' Shelby with CCM rotors

    member's ride thread
    93' EX Coupe H22A w/ P2T4 Sir 5spd 191whp 155 wtq
    99' Lexus LS400 157k VVTi V8 gets up & goes...new DD
    91 Accord SE 176k
    97' Honda Odyssey 199k miles...$485 spare van for my parents

    Comment


      #3
      i've been told on facebook that racing brake fluid will make my dead stock F22 powered auto trans Accord alot faster in the 1/4 mile


      back to reality , thaks Slimmtex for a great writeup concerning brakes

      but one point

      i always heard the term hydroscopic when it came to brake fluids pooling water, i haven't heard hygroscopic

      and when i have replaced caliper(s) in any car i always tried to do a complete brake bleeding with fresh fluid
      http://i220.photobucket.com/albums/d...82408002-1.jpg

      Comment


        #4
        Originally posted by Losiracer2 View Post
        whats your take on proportioning valves? ie: when someone does a rear disc conversion? or if they convert ABS to nonABS?
        The valving on a disk/drum vehicle has to be a bit different because drum brakes are held in a released position by strong return springs so you would definately want to change to the apropriate prop valve. From everything I've read on the subject the integra valve is the way to go, although i imagine you could use an adjustable aftermarket one as well. I think the preset honda one would be easier since it's already set and you don't need to fiddle with it. It would be the same thing if you did an ABS delete since the valving is built into the ABS unit.

        Also Stainless braided brake lines?
        Stock rubber hoses stretch a small amount when you apply your brakes and you can feel that in the pedal, braided stainless steel ones don't so the pedal will feel firmer and more responsive. A definite upgrade in my opinion, just make sure to use hoses that have a DOT tag attached. If there's no DOT tag they aren't street legal and more importantly you don't have anyway of knowing if its made to high enough standards to trust. Remember that if you have a brake hose blow then you lose your hydraulic pressure to that half of the system (our cars have a diagonally split system so RF and LR are on the same hydraulic circuit, LF and RR on a different circuit), the two wheels affected will not brake at all and the pressure generated in the other half of the system will be greatly reduced. This means a stopping distance suddenly WAY longer than what you anticipated, not to mention you'll bottom out that piston into the stop block while your crapping yourself and trying not to wreck.

        Btw, I think the best brake setup using OE parts is Legend GS/LS 2 piston calipers, 25mm wagon rotors, and 25T brackets. I found it to be highly resistant to any DTV as you put it.
        the 2 piston legend caliper has more piston surface area than a sigle piston caliper. Pascals law says that pressure in a hydraulic system is transmitted equally to all points in the system so a greater piston surface area means more area for that pressure to work against. This is why I agree that the two piston caliper is a great way to go.

        I mentioned in the first post that brakes stop your car by converting the kinetic energy into heat energy via friction. A rotor with more mass will be able to dissipate that heat more efficiently. Think of holding a paper clip over a candle, it will not take long before it gets to hot to handle. Think of holding a piece of re-bar over the candle, you could probably hold it there all day without the other end getting hot. So a bigger rotor runs cooler and will be more resistant to developing runout problems as well as more resistant to heat fade.

        Originally posted by bobbycos View Post
        i've been told on facebook that racing brake fluid will make my dead stock F22 powered auto trans Accord alot faster in the 1/4 mile
        I've also been told if you ad a little brake fluid to an auto that is slipping it will buy you 6 months or so. I don't know nearly as much about transmissions as I do brakes so I wouldn't really know whats the deal there.


        back to reality , thaks Slimmtex for a great writeup concerning brakes

        but one point

        i always heard the term hydroscopic when it came to brake fluids pooling water, i haven't heard hygroscopic

        and when i have replaced caliper(s) in any car i always tried to do a complete brake bleeding with fresh fluid
        When I first started learning about brake fluid more in depth I thought i was mis-hearing what was being said. I thought surely its hydroscopic because hydro=water. It turns out hydroscopic isn't actually a word (Firefox wants to correct it to hygroscopic, google does the same thing).

        http://www.fouragesofsand.com/2011/0...groscopic.html

        I just found out that a hydroscope is an optical device used for viewing objects far below the surface of water.
        Last edited by SlimmTex; 01-26-2014, 05:59 PM. Reason: fixed some formatting

        Comment


          #5
          whats your opinion on a street driven car getting better rotors?

          (drilled, slotted, drilled and slotted)

          also what type of pad material would you recommend for said rotor?

          Comment


            #6
            Drilled and slotted rotors are sweet looking behind some nice rims, but that's going to be the only benefit you'll get out of them. Another thing worth thinking about is the fact that if you attempt to machine a drilled/slotted rotors with traditional brake lathes the bits will move slightly due to tool push as they cross over the holes and slots, making one side of the hole higher than the other.

            As far as what pad composition to run, it boils down a lot to your personal preference. Metallic pads tend to feel more aggressive when you stop and i find them easier to lockup the wheels, usually more dust wheel collect on your rim with a metallic pad as well. Ceramic pads usually have a bit of a gentler application and a more linear friction through the stop.
            A good quality ceramic is my favorite in pretty much any Honda. Of course the OE is a good choice. If you want a good pad without spending to much coin Centric makes a nice line called Posi-Quite that comes with the hardware kit (105.xxxxx are the ceramics 104.xxxxx are metallic), Carquest blue box (also comes with hardware). Or if your really want the best look at Hawk Performance.

            Comment


              #7
              When you say that the piston isnt retracting and the inner pads get worn more, what steps exactly should i do to address this problem?

              Comment


                #8
                Sorry I didnt reply sooner, just didn't see till now.

                Replace or rebuild the caliper. I intend to make a video showing how easy they are to rebuild but I'm not sure when.

                Comment


                  #9
                  Originally posted by SlimmTex View Post

                  Bleeding


                  The best way to do this is with a pressure bleeder. I realize that most people don't have one and will probably just have their buddy push the pedal while they open and close the bleeders. When you do it that way there's a few things you should understand about how a master cylinder is made to avoid damage.

                  The primary seals in your master are situated at the front edge of an aluminum piston. There is a steel screw called a piston stop block protruding into the bore that is there to prevent the piston traveling so far down the bore that it passes the outlet ports thereby releasing all hydraulic pressure. Understand that your piston will only travel that far down in the event of a hydraulic failure (your creating one by opening the bleeder valve). The important thing here is to be gentle when depressing the brake pedal and don't let it go all the way down until it bottoms out. If that aluminum piston and rubber seal slam that steel screw it will do damage, its just a question of how much damage was done. Our cars have enough master cylinder issues without us damaging them while bleeding our brakes.
                  Some of the best information, I think I blew mine out bleeding the brakes.

                  Comment


                    #10
                    Great post, some really great information in here. Thanks!

                    Comment


                      #11
                      bump a good post!


                      UKDM 93 CB3 Page (1) H22A U2Q7 LSD
                      UKDM 91 4ws Page (3) OEM Minter
                      NOW H22A U2Q7 SWAPPED

                      Comment


                        #12
                        Yes this is a great post OP. I want to ask what can be done about non abs driving in heavy rain? Drive slower? What I discovered is that by applying. the brakes while in a higher gear usally stalls the motor, but also brings the wheels to a slower speed. VS when its dry and I down shift (engine brake) and apply the brakes to stop sooner without sliding. Just an observations.

                        Comment


                          #13
                          Originally posted by 8ball View Post
                          Yes this is a great post OP. I want to ask what can be done about non abs driving in heavy rain? Drive slower? What I discovered is that by applying. the brakes while in a higher gear usally stalls the motor, but also brings the wheels to a slower speed. VS when its dry and I down shift (engine brake) and apply the brakes to stop sooner without sliding. Just an observations.
                          drive slower and manually pump the brakes

                          Comment

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