What is this? Wire in slotted rotor | Page 2 | FerrariChat

What is this? Wire in slotted rotor

Discussion in '308/328' started by TurtleFarmer, Mar 1, 2020.

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  1. mike996

    mike996 F1 Veteran

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    Mike 996
    #26 mike996, Mar 6, 2020
    FWIW, I replaced a lot of (US) brake rotors back in the day - long before 1980 and I never saw one of those clips in a rotor. There were plenty with little mill marks or drillings, indicating that some balancing had been required. Admittedly, my experience at that time was almost totally US cars. That pic of the clip in the first post is the first time I have ever seen such a thing.

    I continue to learn stuff almost daily! :)
     
  2. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
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    Brian Crall
    #27 Rifledriver, Mar 6, 2020
    About 99% of Detroit's rotors and back in the day brake drums are all made by one contractor in Canada. They are huge and pretty advanced. But yes, typically you'd see them drilled somewhere. Or drums would have a weight welded on them.

    Since Ferrari has had vented rotors up until around the mid 90's weights of some form are shoved in the vent holes.
     
  3. TurtleFarmer

    TurtleFarmer Karting
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    Jason S
    #28 TurtleFarmer, Mar 10, 2020
    Alright, to wrap this thread up: Thanks to all who chimed in and helped educate. Sounds like these wires are added as part of the balancing procedure for the rotors (or, at least, they were back in the day). Also, thanks to @Rifledriver for pointing out my original incorrect reference to these as "slotted" rotors--they are indeed "vented" rotors.

    Lastly, while many folks recommended the wire go back in, I've decided to run w/o it. Three reasons:
    - That wire weighs 1.3g. I haven't weighed the rotor, but I'm pretty sure that it's a minimum of 8kg. That's 0.016% the mass of the rotor and it's center of gravity is roughly 3.5" from the centerline. From a physics standpoint, that is going to have very little impact on the balancing of the larger mass. Particularly at << 2000rpm and with an add'l ~15kg tire/wheel hanging off of it at an even wider annulus. The balancing of that tire/wheel are going to have a much more significant impact on the overall balance of the system.
    - As can be seen from my picture, the whole rotor system and the wire have seen a lot of oxidation. Whatever balance was achieved at the factory is highly likely to have changed significantly with the passage of time (altho I suppose you could argue that the steady wear of the rotor from the pads would have kept it in balance over time?)
    - The most important reason: on attempt to re-insert the wire, it disintegrated (it was *really* rusty). So the wire doesn't really exist anymore, at least not as a single piece.

    Hoping to have everything back together in the next few days. I'll re-post if I find that my right rear is shaking the car apart :)

    Thanks again to all the responses. I sincerely appreciate the expertise of this forum.
     
    mike996 likes this.
  4. mike996

    mike996 F1 Veteran

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    Mike 996
    #29 mike996, Mar 11, 2020
    Also,some shops can spin-balance the wheels on the car and the rotor balance is automatically included. Of course, this means that if you remove a wheel for some reason, you should reinstall it so that the same wheel mount holes are mated to the same studs.
     
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