Twin Clutch Deformed ? | FerrariChat

Twin Clutch Deformed ?

Discussion in '348/355' started by m.stojanovic, Aug 31, 2015.

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  1. m.stojanovic

    m.stojanovic F1 Rookie
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    Miroljub Stojanovic
    #1 m.stojanovic, Aug 31, 2015
    Last edited by a moderator: Sep 7, 2017
    I took straightness measurements of the friction surfaces of the steel plates of my twin clutch and found that all have assumed a conical shape as shown on the drawing. The rectangles represent the friction surfaces only. The surfaces of the plates are not worn into the conical shape, they are deformed (the bottoms follow the tops). Are the plates fabricated into slight conical shapes or have they been deformed due to overheating? All friction surfaces look like leopard skin and I can also see some bluing and rainbowing along the inner edge of the flywheel friction surface.

    The two clutch plates look almost new, 7.2 and 7.1 mm free thickness with very slight conical wear following the conical shapes of the steel plates but not at all to the same extent (perhaps the PO replaced the two clutch plates shortly before I bought the car).

    If the steel plates are indeed deformed, is it advisable to press them back flat first before machining? The flywheel has the deepest cone (and is most expensive).
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  2. Mitch Alsup

    Mitch Alsup F1 Veteran

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    #2 Mitch Alsup, Aug 31, 2015
    The plates are machine conical so that there is greater pressure on the outer ends of the friction plates (where there is greater area). This equalizes the wear over the whole surface of the clutch.

    Were this not none, the inside area would wear first.

    The amount of the cone (offset) is relative to the clutch disk pressure on the flywheel. More pressure implies more cone.
     
  3. m.stojanovic

    m.stojanovic F1 Rookie
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    #3 m.stojanovic, Aug 31, 2015
    Thanks Mitch, most excellent info.
     
  4. mad dog

    mad dog Formula Junior

    Jan 5, 2006
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    #4 mad dog, Sep 1, 2015
    The original dish on flywheel is negligible and was for ease of take up. A dish of those measurements will wear the friction plates unevenly.
    Especially the flywheel that is made to be machined but only by 15mm max.
    We also make sure any material taken off friction surfaces is put back on behind before a rebalance so make sure your local shop can do that.
    What's measurement across friction plates is wear even? That's a good indication all well.
     
  5. m.stojanovic

    m.stojanovic F1 Rookie
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    #5 m.stojanovic, Sep 2, 2015
    The wear of the clutch plates and the steel plates is minimal (12 k miles car); I can still see (here and there between the heat-patches) the images of the original machining marks on the steel surfaces. I first thought that the clutch plates might have been recently replaced by the PO but they were not as I found the same AP (hand written) numbers on he clutch steel assembly and on the clutch plates. The plates are 7.1 and 7.2 mm and fairly evenly worn across (inner to outer diameters). The steel friction surfaces have many brown/black patches (probably caused by heat due to slipping - the triple seal were leaking) and all friction surfaces are well glazed.

    So, I will not do any machining of the steel plates but just remove the glaze and the coloured patches and de-glaze the friction material on the clutch plates.

    Even though the original clutch plates still have a long way to go, I am not sure whether to use them back or get new ones. What is the advice here? The friction material does not appear to be oily, just glazed; or has the oil soaked deep into the friction material? I would appreciate some experience/opinions in this respect.
     
  6. mad dog

    mad dog Formula Junior

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    #6 mad dog, Sep 2, 2015
    Oil soaks in very quickly and easily and stays there.
    It slips and causes the heat marks mentioned which is then a cycle of wear and damage.
    for the price of relining i would always do that with a company that has good material.
    I always use a system of bonding onto new backing plates that are themselves riveted on so you get a double secure system that copes with any uneven surfaces far better.
     

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