News

What is this? Wire in slotted rotor

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

  1. TurtleFarmer

    TurtleFarmer Rookie

    Jan 13, 2020
    36
    Full Name:
    Jason S
    FChat experts,
    This is my first post! I've been lurking for a while and so far you've all answered just about every single one of my questions in the regular posts w/o having to submit replies or new posts. Thank you!!!

    So I'm in the middle of rebuilding the CV joints on both half shafts, and as I was putting a screwdriver into the slots of the rotor on one of the last bolts, I came across this bizarre little wire buried in the slots of the rotor.

    In the picture, I'm holding it in front of the rotor. However, I originally found it *in* the slots--in the same orientation that I'm holding it. In other words, each "lobe" of the wire was in a separate slot and the bottom of the wire was bridging between them. That bridging was nearest the hub, not on the outside of the rotor--which would have probably flung it out of the rotor a long long time ago. I had to rotate the affected rotor slots to the opposite side of the caliper to find room to wiggle it out from the inside of the rotor near the hub.

    So what is it? And how long has it been in there? It's definitely not a paper clip (metal gauge too thick). And the shape makes me think it was intentional. The "mild" surface rust had adhered it to the inside of the slots and had to do a bit of poking to loosen it. So it's been there a while.

    Also, again many thanks for the excellent info contained in these pages. It's made things fairly straightforward to debug. I do wish the search function was a bit more advanced...but, well, it seems this forum is the only thing that's free about owning a Ferrari, so I'm really not complaining.
    Image Unavailable, Please Login
     
  2. smg2

    smg2 F1 World Champ
    Sponsor

    Apr 1, 2004
    10,175
    Dumpster Fire #31
    Full Name:
    SMG
    I believe it's for balancing. Newer rotors have material ground off the outer edge.
     
    BigTex and Steve Magnusson like this.
  3. BigTex

    BigTex Seven Time F1 World Champ
    Rossa Subscribed Owner

    Dec 6, 2002
    72,788
    Houston, Texas
    Full Name:
    Bubba
    Balancing would be my guess as well, ……..although the process to spin a bare rotor and determine the location rather boggles the mind...and that wire can not weigh much....

    Thinking about it I would hazard a guess a parts guy stuffed it in there to have a place to mount a Part Number tag??

    That's really odd, have never seen one and I have stacks of spare rotors lying around....of course I will have to look in the morning!!!
     
    mike996 likes this.
  4. smg2

    smg2 F1 World Champ
    Sponsor

    Apr 1, 2004
    10,175
    Dumpster Fire #31
    Full Name:
    SMG
    It's a balancing hair pin, very common. More recently MFG switched to milling.
     
  5. TurtleFarmer

    TurtleFarmer Rookie

    Jan 13, 2020
    36
    Full Name:
    Jason S
    Wow--I've never seen a balancing wire for a rotor before either.

    So next question: Does this mean I should try to put it back? Similar to @BigTex note, I find it difficult to believe that the mass of this little wire actually makes a difference to the balancing of the rotor esp given the years of oxidation on both the rotor and the wire itself. You'd think that both the oxidation and the rotor wear have changed whatever "balance" this little guy was trying to hard to achieve.

    But if you folks think I should put it back, well, back it shall go.
     
  6. ClydeM

    ClydeM F1 Veteran
    Rossa Subscribed Owner

    Nov 4, 2003
    8,767
    Wayne, NJ
    Full Name:
    Clyde E. McMurdy
    I've seen this a few times in older cars/rotors. Yep, for balancing.
     
  7. thorn

    thorn F1 Rookie

    Aug 7, 2012
    2,619
    Tallahassee, FL
    Are you going to remove the rust/oxidation?
     
  8. TurtleFarmer

    TurtleFarmer Rookie

    Jan 13, 2020
    36
    Full Name:
    Jason S
    @thorn no immediate term plans to clean up or resurface the rotors. It would be *way* down the list.
     
  9. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Two Time F1 World Champ
    Rossa Subscribed Owner

    May 4, 2001
    29,953
    Birmingham, AL
    Full Name:
    Tommy
    Welcome to Ferrarichat
     
  10. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    330
    Afternoon Jason and welcome to ferrarichat,
    My 1987 328 has the same wire on the rotors, balancing purposes? Beats me, yet makes sense. Although with such small mass(the wire) and small rotor diameter(centrifugal force) I really don't believe that you would notice any vibration if it was removed.

    Just my opinion,

    John.
     
  11. Crowndog

    Crowndog F1 Veteran
    Rossa Subscribed

    Jul 16, 2011
    6,939
    Fairfield,Pa
    Full Name:
    Robert
    Was it for final balance or balance during surfacing at the manufacturing process?
     
  12. thorn

    thorn F1 Rookie

    Aug 7, 2012
    2,619
    Tallahassee, FL
    I would guess final balancing; as SMG noted, more modern rotors have an area that's cut/ground off to balance it. Balance (or lack of it) isn't really a thing when you're dealing with resurfacing a rotor - at least not that I've ever heard/seen nor done.
     
    Crowndog likes this.
  13. Crowndog

    Crowndog F1 Veteran
    Rossa Subscribed

    Jul 16, 2011
    6,939
    Fairfield,Pa
    Full Name:
    Robert
    The reason I asked was that the speeds at which they are spun during manufacturing is probably a lot faster than what we think of when resurfacing and therefore that little bit of weight might be more significant ? Just a guess.
     
  14. ragtop1

    ragtop1 Formula 3
    Silver Subscribed

    Nov 11, 2006
    1,968
    Ontario, Canada
    Full Name:
    Larry Warren
    brake wear indicator
     
    Saabguy likes this.
  15. rjlloyd

    rjlloyd Formula Junior
    Silver Subscribed

    Jun 19, 2014
    271
    Brisbane, Australia
    Full Name:
    Richard Lloyd
    It was always my understanding they were an anti harmonic noise spring, designed to stop ringing noise under braking
     
  16. Jbrauer

    Jbrauer Karting

    Oct 12, 2016
    109
    Pasadena
    For balancing. I just replaced my original factory rotors and they had that pin. The (OEM Brembo rotors) had the same pin. I would leave it in IMHO.
     
  17. ferrariowner

    ferrariowner Formula Junior

    Feb 21, 2014
    607
    Mansfield, TX
    Full Name:
    Ron
    Put it back in the same place you removed it
     
    Jbrauer likes this.
  18. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    5,443
    TX//Mexico/UK
    Full Name:
    Mike 996
    Hmmm...just wondering - if it's for balancing, did the manufacturer have a supply of different size (weight) clips for every possible balancing need or were all the rotors equally OUT of balance based on the manufacturing process so that only one specific clip was was necessary? BUT...seems like if they were all manufactured equally OUT of balance, they could have just as easily been all manufactured equally IN balance. ;)

    Not saying it isn't for balance but it seems an odd way to do it. I would think some spot-grinding or drilling would be more effective...
     
    Portofino and ragtop1 like this.
  19. ClydeM

    ClydeM F1 Veteran
    Rossa Subscribed Owner

    Nov 4, 2003
    8,767
    Wayne, NJ
    Full Name:
    Clyde E. McMurdy
    I found one in my 308's Brembo so I called them. They confirmed its for balancing.
     
  20. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    5,443
    TX//Mexico/UK
    Full Name:
    Mike 996
    #20 mike996, Mar 6, 2020
    Last edited: Mar 6, 2020
    Funny, I was going suggest they were NOT for balancing based on Brembo's web site which includes this statement re rotor balancing:

    "All discs are checked and, if necessary, balanced automatically during production.

    Discs are checked on an electronic test bench which spins the disc and measures any imbalance. If any imbalance is detected, the excess material is ground away to balance the disc perfectly.

    Not all discs need correction, and the majority are already perfectly balanced, making it unnecessary to machine material from the outer edge. This means that some discs may have a notch while others do not."

    Since they don't mention anything about clips, I ASSUMED they are not there for that purpose. My assumption, could, of course, be erroneous and that these clips were used back in the '80's but the idea of such a clip for balance still seems odd to me. It's not like the 1980's were an era of 'stone knives and bear skin rugs' (thank you Mr. Spock). If they could measure the balance during the manufacturing process, they could perform the necessary grinding to adjust the balance on a rotor rather than sticking a clip on it, as did the common rotor manufacturers. Again, did they produce a variety of these clips in different weights? Makes no sense to me.
     
  21. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    5,443
    TX//Mexico/UK
    Full Name:
    Mike 996
    I may have been unclear in the above post and the 20 minute limit to revise had occurred.

    I said this: "If they could measure the balance during the manufacturing process, they could perform the necessary grinding to adjust the balance on a rotor rather than sticking a clip on it, as did the common rotor manufacturers."

    In re-reading it, I realized that it could be taken as saying the common rotor manufacturers used a clip. I meant the opposite, the common rotor manufacturers back then (and now) balanced rotors if necessary by grinding, not by using clips.

    Sorry for poor composition
     
  22. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,949
    Austin TX
    Full Name:
    Brian Crall
    Still unclear what you are trying to say.


    A. How they balanced rotors in 1980 is and imagine this "Different than how it is done now"

    B. The wire is a balance weight.....Period.

    And C to the original poster. That is not a slotted rotor. A slotted rotor is something very different. It is a ventilated rotor.
     
  23. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    5,443
    TX//Mexico/UK
    Full Name:
    Mike 996
    What I'm trying - unclearly - to say is:

    In the 1980's (and much earlier) standard production rotors made by the common rotor suppliers in the USA were balanced then as they are now - by grinding/milling as necessary. It is (was) hard for me to imagine that Brembo, who from what I understand, was supplying brakes for Ferrari F1 cars back then, did not have the technology to balance brakes accurately by machining.

    I can certainly understand the IDEA of using the clips - pretty much like balance weights on a wheel. It just seems 19th century crude, especially for a vehicle capable of 150+ MPH but if that's how they balanced them, then that's the end of the discussion and my confusion over the clip's purpose!
     
  24. smg2

    smg2 F1 World Champ
    Sponsor

    Apr 1, 2004
    10,175
    Dumpster Fire #31
    Full Name:
    SMG
    Mill balancing is how it's done now, not that it wasn't possible then but the technology wasn't exactly in place. Instead the balancing was done with hairpins, much like wheels today with weights. With advances in CNC etc, the marriage of milling and balancing is possible, faster and more accurate.

    Keep in mind that rotors are cast, there's going to be imperfections, always. Loss rates are high as well due to this.
     
  25. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,949
    Austin TX
    Full Name:
    Brian Crall
    I am sure its robotics at this point and remain untouched until unboxed by the installer. Not done that way in 1980.
     

Share This Page