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  • Brake disc for M3

    Hello! On first place... sorry of my english, im from spain and its difficult to me...

    Im looking for new brake discs for my Evo II. I like to drive fast on the roads, but never track days or similar. So i want performance discs in the same diammetert than OEMs.

    A friend recommend me drilled Zimmerman discs, they look very well, but i have a photo of them and ive realised that drilling lines are the same on both discs, so ventilation ducts rotate oposite in right and left sides of the car.
    So both discs are the same but rotate in oposite way.
    I think this is wrong.

    Here is the photo of the four Zimmerman Sport discs, look for the drilling lines to see what i mean:



    Otherwise, here is a photo os M3 E36 Zimmerman Sport (drilled) discs. As you can see, front disc are drilled in oposite ways, and when you put them on the car, drilling lines and ventilation ducs rotate on the same way. Lets see:



    I hope ive splained it ok.

    Thanks!

  • #2
    Hi

    Keep up with the english. Not bad at all:-)

    I would not recommend the cross drilled Zimmermans, mainly due to the cross drills which act as stress risers. My car came with these discs, and they were almost new. However, 20min into my first time on track, my left front disc developed a large crack that ran from one of the cross-drilled holes to the edge. In my opinion, unless you buy very expensive discs that have been heat treated after the cross-drilling, then buy without cross drills. Having said that, it is probably fair to add that they will be fine for most street driving. I have now purchased the BMW Evo rotors that don't have holes or slots, and am hoping for better luck. If you want to stay at the Zimmerman price point, I would recommend to get them without cross-drills, but I admit that they are not as nice to look at.

    Now to answer your question. The internal vanes on the Zimmerman e30 rotors go straight out = they don't curve like the e36 rotors. This is also the case with original BMW Evo rotors. Therefore each of the three holes that appear to curve on the e30 rotor are actually drilled in between different vanes, as opposed to the e36 rotor where all 4 holes from one curve are drilled between the same two vanes following the curvature of the vanes. I am guessing they do this to save on tooling, but I don't think it has a functional impact.

    Regards

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    • #3
      I would also recommend the rotors without the cross-drilled holes. They are weak and can not be resurfaced if they become warped. The reason you see cross-drilled on the expensive high end cars is because they run a much thicker rotor that can stand up to the more aggressive driving. Compare our rotors to something off a Porsche or MB and you'll see the difference in size.

      Comment


      • #4
        i cant even remember how many sets of rotors ive warped from just street driving until i purchased Frozen rotors. Cryo treated rotors that are supposed to take more abuse. ive only run these about 1500 miles and so far so good. Are these things really better or am I just lucky and havent had had them in service long enough. other pls chime in here. chucker
        89 m3 "Ms. Bavaria"..... Cinnabar w/ Black Guts, Evo 2 cam, Miller War Chip, CF Intake, What's a cat?
        12 Avalanche "OJ" ..... Black on Black, Loaded, and Runs
        08 335i "Vanessa" ..... Black with Buckskin guts
        08 Jetta 2.0 Turbo "Joan Jetta"..... Red with Tan Guts

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        • #5
          BMW discs are pretty much the best you can get in standard size.
          If everything seems under control, then you're just not going fast enough...

          Comment


          • #6
            Hello!

            Thanks to all for your answers, it has been very helpfull to me.

            Now i understand why m3 e30 rotors are drilled in diferent way than m3 e36.

            I usually talk in a spanish forum (www.bme30.org) and some people told me the same about drilled discs and stress points.

            Ive asked for no drilled Zimmerman discs price, and tomorrow will ask for OEM BMW rotors on my BMW dealer. (my uncle is the owner)

            I only can say thanks for all your help

            P.S. : In my spanish forum, a friend did a rebuild of a Sport Evo, if you like to see, this is the link:

            http://www.marplatenses.org/phpbb2/viewtopic.php?t=7783

            Bye!!

            Comment


            • #7
              It appears that the difference is because the vains (vents) of the E36 rotors are curved and the drilled holes follow the curve. The curved vains are specific to the side of the vehicle to aid cooling - there are left and right side rotors.

              The E30 rotors appear to have straight vains for the front so although the drilling pattern is similar to the E36 rotors they're not following the vains you just wind up with one hole per vain. For the E30 there would not be a left and right rotor and I'm guessing the PN is the same for both fronts. Same scenario for the rear rotors since they have no vains.

              As mentioned by others the performance related to the drilling is questionable unless you want that look. Porsche rotors have the holes cast into the rotor to reduce stress while most aftermarket rotors have the holes drilled in after the fact making them more prone to cracking.

              Comment


              • #8
                In my experience Zimmerman rotors warp and crack pretty consistently I would not use any rotor that was drilled and not stress relieved (cryo) after. Brembo tends to be closer in quality & better value to OEM than other makes.
                Rich!

                Comment


                • #9
                  I cracked both fronts on my car during a track session. I would recommend the evo disks if you are staying stock size.

                  Comment


                  • #10
                    Originally posted by ///Morris View Post
                    I cracked both fronts on my car during a track session. I would recommend the evo disks if you are staying stock size.
                    You mean OEM evo 2 rotors?

                    Comment


                    • #11
                      I have cracked oem rotors on my car as well. I priced the zimmerman at about $71 each and the cryos on tirerack for about $138 a piece. I personally have no experience with the cyro treated rotors. This may be a classic example of you get what you pay for? Can anyone comment. Perhaps better air ducting would help to get heat away from the M3 rotor under hard braking.
                      There'll be Spandex jackets one for everyone ...

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                      • #12
                        Originally posted by Victorevo2 View Post
                        You mean OEM evo 2 rotors?
                        the only rotors available in the US have a part number superceeded to be the Evo 3 specs....the only ones available.

                        Comment


                        • #13
                          I always preferred blank brembo discs for road and slotted for track.
                          Fully Restored 1985 Corolla GT-S
                          1987 328ci SR20DET Drift Car (Will Convert to M3 Spec soon)
                          1989 Honda Civic Si-R Current Project
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                          • #14
                            Originally posted by Bruce View Post
                            the only rotors available in the US have a part number superceeded to be the Evo 3 specs....the only ones available.
                            After looking in ETK, ive found this reference (the only that appears):

                            ONLY APPLIES TO M SPORT E3
                            02BRAKE DISC, VENTILATED280X25 234112226813



                            Is it right?

                            Comment


                            • #15
                              yes, as Bruce indicated, there is only one rotor available for all E30 M3 models, it is the version from the Evo 3.
                              Mark Williams
                              Dallas, TX

                              Nothing says "welcome to the neighborhood" like a search... oh wait... looks like they are all gone! :rastajake:

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