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  • Brake cooling; removing disc "guard"?

    The brakes on the Z3M seem to fade quite easily as standard and even with uprated pads they seem to struggle to cope with light trackday use. I remember a post a while back by Exdos who found the air ducts (through the front spoiler/bumper) to be next to useless on a back to back test; I'm just wondering if the air that these ducts provide is deflected somewhat by the brake disc guards? I've never run with them fitted on my 205 GTi and not had problems.

  • #2
    Well, I guess if you improve the air flow you will get a little less fading, but honestly, I think the brakes are one of the weakest parts of this car.
    I intend to upgrade mines as soon as possible.

    Comment


    • #3
      Chris, you're right, the front air ducts do absolutely nothing for brake cooling.

      As it happens, I've just embarked upon another round of my DIY mods, one of which is brake cooling. When I had the wheels off last week to fit the K-Mac front top mounts, I had a good look at how I might easily redirect some air towards the centre of the discs, which I think will be a better mod than removing the inside guards. I think I've found a way of doing this without cutting into any of the plastic panels or even the disc guard itself. I shall take some photos of my prototype fittings as I install them and I shall then try fitting the parts just on one side only so that I can see what temperature difference I get between the opposite side which I'll leave OEM for comparison. I'll post the results on here. From my reading, I've seen it stated that good brake cooling is equivalent to increasing the disc diameter by 2", so if this is true, then the OEM 315mm discs cooled would be equal to 365mm discs. We'll see. One thing I know though is that fitting cooling to the brakes is a hell of a lot cheaper than new brakes.
      Last edited by exdos; 14-08-2007, 06:10 PM.
      /// Exdos ///
      "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

      Comment


      • #4
        Looking forward to your results exdos. Maybe worth doing a quick temp check on the side you are going to modify and the "control" side before you make your mods to to ensure that both are heating up by the same amount?

        Just a thought. If you had a slightly sticking caliper or something else that would cause uneven heating then this will be highlighted before and test is done.

        keep us posted as brake fade does my nut in a bit but dont want to spend the £££'s on a brake up grade if there is a far cheaper way.

        Regards

        David
        EX: S50 Black with Kyalami Orange/Black Leather. Becker Bluetooth/Ipod HU.
        Now: S50 Black/Black with Ap Racing brakes and Race logic

        Comment


        • #5
          What about this? http://www.davidparis.org/coupe/brakeducting.html
          S50 - '99 Imola Red/Red-Black
          Mods - KW V3, Powerflex Bushes, Wiechers Strut Brace, H&R ARBs, FOX exhaust, KT4 New Racer 18" wheels, Pagid racing brake pads (yellow), Motul rfb600 racing fuids, untill now ;)

          Comment


          • #6
            I think the location of the the pipework on the front of the wheel arch will cause problems, especially with 18'" or 19" wheels.
            /// Exdos ///
            "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

            Comment


            • #7
              Originally posted by exdos View Post
              I think the location of the the pipework on the front of the wheel arch will cause problems, especially with 18'" or 19" wheels.
              Works just fine with a little smaller duct and little different routing. But ducting isn't easiest job to do and I see no reason to use it on street.

              I bet this is the ultimate solution for brake cooling without changing the brakes. I know many race cars using the same method.
              S50 - '99 Estoril/Estoril-Black
              Mods - KW 3 Coilovers, H&R ARBs, Raid steering wheel, Wiechers Sport half-rollcage & strut brace, Simota CAI, Powerflex front and beam bushes, Beyern Mesh 18".

              Comment


              • #8
                I've recently knocked up some simple brake ducts and fitted them on to my MC last weekend.



                I've driven in the company of two different members of the forum since; one with a Stoptech BBK kit with OEM wheels and the other member with OEM brakes and wheels but with uprated pads (I have Red Stuff pads all round and BBS RXII wheels). Using a digital pyrometer to take temperatures of the discs immediately after stopping from a drive, I found that rear brake temperatures are similar in all three cars and therefore these act as a gauge for the consistency of all the readings. The Stoptech record slightly lower or similar temperatures to my own front brakes, but the OEM front brakes recorded more than 30 degs C hotter than mine, after a spirited drive of about 8 miles followed by about 5 minutes of slow driving through a town before temperatures were recorded.

                I made the cooling ducts out of a metre length of 2" flexible brake duct hose which I bought off ebay for £15 including p&p, some 2" aluminium tube and a few scraps of aluminium sheet I had lying around, 4 stainless steel jubilee clips and some cable ties.

                If you closely inspect the dust-guard on the inside of the front brakes, you'll see that it doesn't completely cover the entire disc and that there is a hole at the centre just in front of the bottom of the damper. If you rotate the disc whilst looking through the hole, you can see that air can enter through the dust guard and blow between the two faces of the ventilated discs.



                So, I cut a short length of ali tube, and welded a "T" piece onto it with a hole I'd drilled through it, so that the "T" piece fitted between the damper and the disc guard so that I could pass a cable tie through the hole to secure the ali tube to the damper. I fitted a second cable tie around the tube to keep the tube securely in a position from which it couldn't easily move. I attached about half a metre of the flexible tube to the ali tube with a Jubilee clip.

                [imghttp://www.z3mcoupe.com/photopost/data//500/53BDWheel1.jpg[/img]


                I'd previously spent a bit of time assessing the best place to fit the mouth of my brake duct and I'd identified the rear corner of the front undertray on each side, just in front of the ARB, because air passes straight through the front grille, just above the bumper, from a zone of high pressure. I made a little orifice out of the ali tube and welded a small side to it in order to make a crude funnel and attached the tube to the ali orifice with another Jubilee clip.




                I found that fitting the orifice tube with the tube pointing directly into the wheel arch placed the least stress on the flexible tubing. I rotated the steering from full lock in both directions and cut the flexible tubing to the perfect length by trial and error, so that when it was fully extended, it was not stretched or taught, and when concertinaed in compression, it was not crushed against anything solid nor was it too slack. Getting the length of the tubing spot-on should ensure that the tubing lasts a long time and that there's no pressure on the two ends of attachment, causing the ali fittings to move.

                Now that I've trialled this idea, I shall now make a much better aluminium fittings, and with them, I'd expect to see even better brake cooling.
                /// Exdos ///
                "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

                Comment


                • #9
                  Excellent work, exdos.

                  30 deg C is a pretty big difference. I'm curious as to why the StopTech BBK runs cooler, as the one that fits under OEM wheels have discs that are barely any bigger than OEM. It's not obvious to me why the extra pistons in the caliper would improve cooling.

                  Paul

                  Comment


                  • #10
                    Originally posted by pdwarren View Post
                    Excellent work, exdos.

                    30 deg C is a pretty big difference. I'm curious as to why the StopTech BBK runs cooler, as the one that fits under OEM wheels have discs that are barely any bigger than OEM. It's not obvious to me why the extra pistons in the caliper would improve cooling.

                    Paul
                    The owner of the MC with Stoptech brakes is, by his own admission, an extremely light braker, so this might explain some of the difference between his brake temperatures and mine.

                    Likewise, the Stoptech discs, calipers and pads are bigger than my OEM brake kit, and since the energy required to stop an MC travelling the same route together, at similar speeds, will be the same, the heat created by stopping will have a larger mass of disc and brake kit volume to absorb heat in the Stoptech BBK than OEM, therefore a slightly lower temperature of the Stoptech discs. Does that sound right?

                    The clearance of the Stoptech brakes with OEM wheels is minimal, but there is still clearance nonetheless.

                    I can't justify the expenditure of about £1.5k on a BBK when I can achieve effective brake cooling for £15 plus my own time in making bits and pieces. That's the fun that I get out of devising mods using OEM parts as the basis.
                    Last edited by exdos; 09-09-2007, 01:55 PM.
                    /// Exdos ///
                    "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

                    Comment


                    • #11
                      Yea I don't find their ultimate braking power is a problem, just the ability to cope with any kind of heat seems to be a problem.

                      I've just recently fitted some brand new floating discs (about £210 from Euro Car Parts ) and they look pretty nice and shiney behind the alloys again now. Was having problems with wheel wobble under braking that seemed to get worse when warm, usually it's from pad material and "cleans" up after a while but it never did, I've also found that skimming the floating discs doesn't seem to work and can still cause vibration. Anyway the new discs now are super smooth and quieter!

                      Whilst I was changing them my dad had a quick look (mentioned removing the backing plates to him) and he noticed the hole that Exdos pointed out as the entry point for air, the disc acting as an impellor drawing air through the disc so removing the backing plate could impare this airflow route - just that with the standard setup there isn't much air being forced in, so Exdos' ducting should be what's required.

                      With the BBK kits, the caliper may make a difference, I would guess being multi piston it's alunimum which means it will act a cooling heat sink whereas the standard iron calipers are rubbish in this regard!

                      Exdos, do you suffer from brake fade/judder when hot or are you just experimenting cooling them down? Im currently running Yellowstuff pads and have yet to give them any proper hard use but so far they seem ok.
                      Last edited by c_w; 09-09-2007, 05:41 PM.

                      Comment


                      • #12
                        Originally posted by c_w View Post
                        I've just recently fitted some brand new floating discs (about £210 from Euro Car Parts ) and they look pretty nice and shiney behind the alloys again now. Was having problems with wheel wobble under braking that seemed to get worse when warm, usually it's from pad material and "cleans" up after a while but it never did
                        I'm in exactly the same boat. I got judder once after a track day and it eventually went away. It happened again after the next track day and it doesn't seem to be going.

                        I considering going for a BBK, but don't know whether it's worth doing without putting bigger wheels on.

                        Paul

                        Comment


                        • #13
                          Originally posted by c_w View Post
                          With the BBK kits, the caliper may make a difference, I would guess being multi piston it's alunimum which means it will act a cooling heat sink whereas the standard iron calipers are rubbish in this regard!
                          To experience the difference between the heat sink capacity of aluminium and iron, all you need to do is use a grinder on the two different metals and hold the part in your hand. Aluminium gets much hotter. Ouch!

                          Originally posted by c_w View Post
                          Exdos, do you suffer from brake fade/judder when hot or are you just experimenting cooling them down? Im currently running Yellowstuff pads and have yet to give them any proper hard use but so far they seem ok.
                          I don't find the stopping power of OEM brakes a problem, although I've experienced brake judder since fitting H&R ARBs. I've attributed this to the drop-links being placed under too much compressive loading when there is rapid weight transference to the front of the car under heavy braking and wobbling like Rolf Harris' wobble-board when under load. I've since fitted meatier Whiteline adjustable drop-links at the front and solid brake bushings all round and the juddering seems to be much reduced. Since the H&R ARBs are twice as stiff as OEM, IMHO this is too much for the OEM drop-links which are fine under tension but poor under compression, thus uprating the front drop-links is also required at the same time as uprating ARBs.

                          I ditched the OEM pads for Red Stuff all round 2 years ago and I think these are better than OEM. They work well when cold and operate silently at all times. They have the added bonus of not making your wheels filthy.

                          My brake duct cooling interest is driven more out of my liking for experimentation and knowledge, and because I can do these things myself. I think BMW has done a great job with the MC in OEM state, but if you go over it with a fine tooth comb, as I like to do, there are a few relatively simple tweaks that are begging to be done, which can improve things some more and for very little expense.

                          I know you think the OEM brakes are bad on track days, knock up some simple devices and try cooling the brakes for your next track day. If you can't get the aliminium tube to make the ends for the flexible tubing, then give me a shout and I'll see what I can do for you.
                          Last edited by exdos; 09-09-2007, 06:20 PM.
                          /// Exdos ///
                          "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

                          Comment


                          • #14
                            Exdos,

                            Just a thought; have you considered integrated the air hoses and your brake guards ?

                            I.E: cut a hose-shaped hole in the brake guard, and seamlessly join the two items together to provide a direct air feed close to the disc surface ?

                            Rgds, Will

                            Comment


                            • #15
                              Hi Will,

                              Yes I have, but I'd rather have something that easily attaches and remains securely fastened but can be detached rather than have a permanent modification. Also, I don't really want a round hole facing the inner disc, like other brake cooling kits available for BMWs because this would tend to cool the inner face of the ventilated discs more than the outer face, which could create a whole new set of problems. The actual hole in the OEM dust guard is more banana shaped, a sort of curved slot, which feeds air into the centre of the disc so that the impellor action of the rotating disc itself creates air flow between the discs and therefore cools both sides of the disc equally. I think the basic OEM idea is rather good but during times of heavy use, it just needs a bit of help in getting more air from a fresh source.

                              Now that I've done a sample testing of the cooling effect with very crude fittings to get a ball park figure, I've got further ideas for better fittings. I might even cast some aluminium parts that fit precisely onto the guard which are shaped perfectly to the aperture.
                              Last edited by exdos; 09-09-2007, 07:33 PM.
                              /// Exdos ///
                              "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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