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    Drilled brake discs.

    I haven't been on here in some time but now I'm after some help/info if anyone can, I'd appreciate it.

    I somehow warped a front disc which is obvious using my runout dial guage so I can be sure it's that, and one of my rear discs are quite badly grooved from a knackered/contaminated pad. I have bought a set of good quality drilled replacements that are also going to look miles better behind the rims.

    Now however, I'm a bit puzzled. The manufacturer (zimmermann - who I've used before) says that there is no left or right as per oe discs because there are no directional vanes inside - therefore left and right are identical. This means that the drilled pattern will run opposite directions on either side of the car because they are also identical.

    Does this sound right to users here? None I've fitted to cars before were the same as these, they've always been sided/handed.

    I know lotus and corvette do the same because it means they only manufacture one front disc and one rear, but to me it just seems odd. Click image for larger version

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Views:	77
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ID:	1254744


    Thanks in advance.

    #2
    Originally posted by Dean S550 View Post
    I haven't been on here in some time but now I'm after some help/info if anyone can, I'd appreciate it.

    I somehow warped a front disc which is obvious using my runout dial guage so I can be sure it's that, and one of my rear discs are quite badly grooved from a knackered/contaminated pad. I have bought a set of good quality drilled replacements that are also going to look miles better behind the rims.

    Now however, I'm a bit puzzled. The manufacturer (zimmermann - who I've used before) says that there is no left or right as per oe discs because there are no directional vanes inside - therefore left and right are identical. This means that the drilled pattern will run opposite directions on either side of the car because they are also identical.

    Does this sound right to users here? None I've fitted to cars before were the same as these, they've always been sided/handed.

    I know lotus and corvette do the same because it means they only manufacture one front disc and one rear, but to me it just seems odd. Click image for larger version

Name:	IMG-20201026-WA0014.jpeg
Views:	77
Size:	1.01 MB
ID:	1254744


    Thanks in advance.
    They look great mate how much where they?.

    Comment


      #3
      The hole pattern does not have a mandatory direction of rotation as it is designed to work correctly and deliver precisely the same performance and comfort irrespective of the side of the vehicle the disc is mounted on. It’s only if they have a directional drill pattern there is a left and right hand which the picture you provided doesn’t show so they will be fine mate.

      Comment


        #4
        These have a directional drill pattern they aren’t mustang discs but just to show the difference ​​​​​ I hope this helps and puts your mind at ease

        Comment


          #5
          Thanks for the info JB . The Discs were 307 all in delivered from AUTODOC, I figured if I've had trouble with Ford oem after just 10k miles then it certainly can't hurt to try third party as I haven't had any troubles with them before. If we were in America replacement rotors and pads are cheap as chips, but obviously here we get gouged into oblivion for most things.

          I have checked numerous places and the pattern seems right if a little odd to the eyes. brembo say their discs are not sided and the pattern direction is not dictated by side, only internal vane direction....

          Zimmermann only have 1 part number for the front and 1 for the rear, mustang vanes aren't directional therefore this must be correct......

          Comment


            #6
            Originally posted by Dean S550 View Post
            Thanks for the info JB . The Discs were 307 all in delivered from AUTODOC, I figured if I've had trouble with Ford oem after just 10k miles then it certainly can't hurt to try third party as I haven't had any troubles with them before. If we were in America replacement rotors and pads are cheap as chips, but obviously here we get gouged into oblivion for most things.

            I have checked numerous places and the pattern seems right if a little odd to the eyes. brembo say their discs are not sided and the pattern direction is not dictated by side, only internal vane direction....

            Zimmermann only have 1 part number for the front and 1 for the rear, mustang vanes aren't directional therefore this must be correct......
            you should notice a difference between them and stock better cooling as well

            Comment


              #7
              Originally posted by JBGT50 View Post

              you should notice a difference between them and stock better cooling as well
              I hope so, I suspect the brake issues I've had stem from when I first got the car but Ford were never interested due to the brakes being wear and tear items. The car had a build date of Sept 17 and I got the car may 18 so it had sat a long time in Belgium vhc prior to shipping. There were visible pad patterns etched into the discs when I got it and a few k later I have the warp and grooving issues. Poor show from them but hardly worth the battle to try and get them to step up.

              Comment


                #8
                Unfortunately Dean - you are going to have to take one of them back. It's defective!

                They are set out in trios of holes, inner to outer, and the top left (rear) has a blemish in production.

                One of the trios has become a duo. Therefore, cooling is defective by one hole and it will look odd on the car where everyone will point and stare at the deformed disc!!

                I am kidding you with its cosmetic / operational effect. But still interesting that one area escaped the drill bit.


                Just a word of caution, from my limited but very serious time with drilled / grooved discs. The structure is weakened. Drilled worse than grooved.

                I learnt this to my peril nearly. I had cracked discs from the weakened structure on 2 cars and decided to bin them all, there and then. I was not impressed because one motor (a 3rd one) had only just received these. I think I ran that motor for 6 months in trepidation with these newer discs on that nothing would happen - and it didn't - but then slung those as well.

                Perhaps I was unlucky. But someone then told me (guided me) that sometimes you make your own luck. When I spoke with this person, metal strength was a bit of a forté of his, this is in fact the conclusion. The structure had been weakened, coupled with an underlying defect, then they cracked.

                I questioned how come I would have seen 2 cracks on 2 separate cars. He based it down to a bit of misfortune but I had actually built in a bit of risk.

                HOWEVER, when I challenged him on the fact that race cars have these and there surely must be a positive in cooling, so how is it that the "professionals" don't believe this weakening in the structure.

                His response was "Cost". The issue with buying discs off ebay probably from China, where processes in production aren't so robust and cheapness all of the way, there could be issues. He didn't say there always are - but could be issues. You have to go up the cost tree some distance before you have both effective discs and ones that are strong.

                So I decided there and then that my braking didn't require £500 per corner (or whatever I needed to do) - and went back to solid/vented discs. Stayed there ever since.

                That's the objective response.

                OK, now the subjective one. I am only the messenger on this - there are several schools of thought - unlike the objective one above - and I am on the fence. By all means throw rotten fruit at me for this - but it doesn't bother me because I would blow where the wind in going on this one. I have never proven this and there are a lot of supposed experts out there - some probably are not. And I am not one either.

                Holed discs are actually not as effective, is the school of thought and they are only cosmetic. Look great, but don't do the deed!

                The science behind this is that for cooling, you need mass/size. You need surface area that is exposed to the air to cool the hot item down.

                The heavier the disc, therefore, increased mass and likely, the bigger is size, swept area, surface area to dissipate the heat. Now that the disc is made, drill holes in it. The effect is a lowering of all of these qualities.

                But airflow has increased around the disc as the holes allow more airflow, therefore, improve cooling.

                So you have the mass / size argument vs the extra flow of air.

                I have never tested this out so I don't know which breaks free of the other. And to be honest, there are so many variables when it comes to braking and stability, no one probably knows.

                Just keep a close eye on those discs though. They look good and sounds like you have spent decent money - got yourself out of the "zone". So should be good quality, rather than the Chinese versions I bought that were branded as something else.

                Comment


                  #9
                  Originally posted by Daz-RSK View Post
                  Unfortunately Dean - you are going to have to take one of them back. It's defective!

                  They are set out in trios of holes, inner to outer, and the top left (rear) has a blemish in production.

                  One of the trios has become a duo. Therefore, cooling is defective by one hole and it will look odd on the car where everyone will point and stare at the deformed disc!!

                  I am kidding you with its cosmetic / operational effect. But still interesting that one area escaped the drill bit.


                  Just a word of caution, from my limited but very serious time with drilled / grooved discs. The structure is weakened. Drilled worse than grooved.

                  I learnt this to my peril nearly. I had cracked discs from the weakened structure on 2 cars and decided to bin them all, there and then. I was not impressed because one motor (a 3rd one) had only just received these. I think I ran that motor for 6 months in trepidation with these newer discs on that nothing would happen - and it didn't - but then slung those as well.

                  Perhaps I was unlucky. But someone then told me (guided me) that sometimes you make your own luck. When I spoke with this person, metal strength was a bit of a forté of his, this is in fact the conclusion. The structure had been weakened, coupled with an underlying defect, then they cracked.

                  I questioned how come I would have seen 2 cracks on 2 separate cars. He based it down to a bit of misfortune but I had actually built in a bit of risk.

                  HOWEVER, when I challenged him on the fact that race cars have these and there surely must be a positive in cooling, so how is it that the "professionals" don't believe this weakening in the structure.

                  His response was "Cost". The issue with buying discs off ebay probably from China, where processes in production aren't so robust and cheapness all of the way, there could be issues. He didn't say there always are - but could be issues. You have to go up the cost tree some distance before you have both effective discs and ones that are strong.

                  So I decided there and then that my braking didn't require £500 per corner (or whatever I needed to do) - and went back to solid/vented discs. Stayed there ever since.

                  That's the objective response.

                  OK, now the subjective one. I am only the messenger on this - there are several schools of thought - unlike the objective one above - and I am on the fence. By all means throw rotten fruit at me for this - but it doesn't bother me because I would blow where the wind in going on this one. I have never proven this and there are a lot of supposed experts out there - some probably are not. And I am not one either.

                  Holed discs are actually not as effective, is the school of thought and they are only cosmetic. Look great, but don't do the deed!

                  The science behind this is that for cooling, you need mass/size. You need surface area that is exposed to the air to cool the hot item down.

                  The heavier the disc, therefore, increased mass and likely, the bigger is size, swept area, surface area to dissipate the heat. Now that the disc is made, drill holes in it. The effect is a lowering of all of these qualities.

                  But airflow has increased around the disc as the holes allow more airflow, therefore, improve cooling.

                  So you have the mass / size argument vs the extra flow of air.

                  I have never tested this out so I don't know which breaks free of the other. And to be honest, there are so many variables when it comes to braking and stability, no one probably knows.

                  Just keep a close eye on those discs though. They look good and sounds like you have spent decent money - got yourself out of the "zone". So should be good quality, rather than the Chinese versions I bought that were branded as something else.
                  Thanks for the info I don't track the car and to be honest am puzzled as to how I warped a stock disc in the first place, I very much suspect the surface was compromised from surface deposits and stuck pads that led to hot spots, and eventually, distortion. I would normally get them reface with such low actual wear but have had some troubles getting any local engineers that can accommodate mammoth discs. I don't expect to feel any real benefits of the drilled rotors but as I intend to paint up the brembos at the same time I thought I may as well 'complete the look' while I'm there.

                  I've had mixed success in the past,
                  my 5 series was comparably heavy and powerful and the discs held up fine on that after the stock 2 piece ones picked up a warp on one side. prior I had slotted rotors on a silvia S15 with ksport brakes and they worked great but made some noise, this was different in that it was a powerful car, but weighed around 1200kg tops and the rear caliper was a dedicated 2 pot alloy job with the handbrake being a shoe in disc setup that I fitted from a skyline - these were a really effective setup.

                  I beleive these are purpose built as drilled discs which gives me more confidence, I agree that almost all the ones on ebay are your basic discs that have been machined after the fact, some even catching vanes on the way through which can't be a good thing.

                  I guess I'll just have to get used to smart arses telling me I've fitted them the wrong way round on one side .

                  Comment


                    #10
                    Oh, and I too noticed the 'error' with the 2 drill holes , but it appears it's by design for whatever reason according to the illustration on the site... Perhaps balance? Click image for larger version

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                    Comment


                      #11
                      That's fine and you sound like you have purchased yourself a set that are waaaaay beyond the ebay rubbish.

                      I paid dearly on that one. But it was a lesson learnt.

                      There probably are 2 ways of fabricating these. I don't know this for certain. But I wondered whether the holes are made as part of the manufacturing process or the discs are made as solid and someone with the 8mm/10mm bit goes drilling afterwards.

                      To me, the latter sounds dangerous. But to be honest, I don't really know the production process of these.

                      Comment


                        #12
                        The hole pattern will be to do with the number of vanes as the pattern will be designed not to compromise any of the webs during drilling.

                        It can be quite hard on some vented disks to get a balanced pattern - what you are seeing is the result of that.

                        Holes aren’t for cooling as such. They allow the layer of hot gas that builds on the pad surface to escape allowing the pad to work as intended (so I was told).

                        WD

                        Comment


                          #13
                          There is quite a bit of info about braking and pads - some of it, I am sure is myth. Some possibly the truth. The thing is that many have a view, many are right and yet many oppose each other.

                          I wasn't aware of that hole reasoning, WD. So thanks for that!! It starts to make some sense why these may not be afflicted to warping in the same way.

                          It does though depend on which view you support on how a disc warps.

                          For me - and I am not the font of knowledge on this - I have difficulty in believing the metal (cast iron) actually distorts. But to many - maybe some of you - that is disc warping. The cast has distorted by heat and runs out of true alignment.

                          The school of thought I follow is pad layer adherence and a thin film of pad is laid on the disc. This helps with the friction for braking. The disc is constantly being layered with this film (adherence) and then cleaned as well. So this microscopic layer never stays in situe - as in there is adherence, and then cleaned, then adherence, then cleaned etc. Runs through cycles in this way.

                          Where we speak of the physical disc being warped, my personal dismissal of it is due to the temperatures required to make the cast move. A typical disc will become molten at about 1200 deg C. Probably as the cast is not pure, the temp is lower. But it is certainly north of 1000 deg C.

                          Pad and normal braking operation tend to run at between 100-200 deg C. Under an amateur racing set up, 300-400deg C (which is why when you take the car on the track, they do recommend uprated pads and discs to not only brake better with heat, but also withstand it as well). Then the pro's will see 500-600 deg C. But they are running real expensive stuff.

                          So the gap here is the 1000 deg C where the molecules in the cast iron start to become mobile and what we normally see as 200 deg C or 300 tops under operation temps. That gap is not, IMHO, going to trouble a cast disc.

                          What I follow - but it is all subjected to opinion and rumour - but based on my logic - the pad suffers with the heat and adheres to the surface, perhaps, a little too much, such that the cleaning process cannot be fully completed. This starts to build a layer. Still microscopic in measure, but a layer that is thicker than the rest of the disc. With the failure / partial failure of being able to be cleaned, it becomes (for want of a better description) part of the disc itself. The "warping" is the build up of debris on the disc, not the disc distorting.

                          I may be telling you stuff you already know - so make my apologies. Conversely, this description is rubbish and needs to be thrown in the bin. Again, apologies. Whatever way you believe is true, I can see the value of the holed discs in allowing the surface temps to be lowered to stop the pad from adhering too much to the disc.
                          Last edited by Daz-RSK; 27-10-2020, 07:00 PM.

                          Comment


                            #14
                            I'm always open to as much info as I can get so thanks all regardless.

                            When I say warped, I don't necessarily mean 'warped'. I just class it as such whenever there is a discrepancy on the dial guage outside of tolerance when rotated , to me warped is just a general diagnosis. This could be uneven wear, pad deposits etc. My passenger side front measured 0.14, not dreadful but enough to get a definite groan from that corner when trying to shed speed from anything above about 60mph. It's a heavy car and under braking is when I find it notices most, even on pedders coilovers set to 10 back from full hard.

                            Usually as I say I'd just get a skim and give the pads a rough up with some emery paper, but I want to do the calipers anyway so in for a penny, in for a pound.

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