Servicing outer a-arm bushings on Daytona | FerrariChat
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Servicing outer a-arm bushings on Daytona

Discussion in 'Technical Q&A' started by Telerding, Mar 21, 2006.

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  1. Telerding

    Telerding Formula Junior

    Sep 30, 2004
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    Tom Elerding
    #1 Telerding, Mar 21, 2006
    I am going thru refurbishment of my Daytona suspension. At the rear, the outer ends of the a-arms have a multi part bushing assembly that has pressed in teflon coated bushings and a top-hat shaped "pin" that rotates inside this bushing. The pressed in bushings are cylindrical, and split along the length of the cylinder. When pressed in, this split closes as it is inserted.

    I ordered new bushings and had them pressed into the outer end of the a-arms. To my HORROR, I find that in 7 out of 8 cases neither the new nor the old pins will fit into the new bushings. There is either NO difference in the diameter of pin and bushing or VERY LITTLE difference in diameter.

    So, I am left with either (1) removing bushings, honing out bushing carrier bore, and re-pressing in bushings or, (2) honing down the outside diameter of the pin. I am guessing that perhaps 0.001" is all that is necessary.

    Alternative (2) is theoretically easier, as long as there is no hardening or other surface preparation of the pin.

    As an aside, alternative (1) is used by Patrick Ottis, but then he has access to all the tools!

    Anyone have experience to weigh in on this??? Anyone else solve this problem?

    Tom Elerding
    Daytona S/N 16333
     
  2. Llenroc

    Llenroc F1 Veteran
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    Vern
    #2 Llenroc, Mar 21, 2006
    Tom, Not sure why your bushings are fitting that tight I have not had that problem before but, I thought I would give you info on what I have done on 308s, 512 and my 355C with similar bushings. Apply a little grease, preferably synthetic,(I have used Redline) to the bushing before assembly. I know they have a teflon coating but this seems to help them last longer. IMHO I don't think you can mill down the pin because its hardened steel, honing out the carrier fitting would probably be the best bet. Regards, Vern
     
  3. Telerding

    Telerding Formula Junior

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    Tom Elerding
    #3 Telerding, Mar 22, 2006
    Thanks, Vern:

    I was afraid this might be the case.

    I think I am going to do a test case, where I hand pick pins for the bushings on one a-arm. Then I will use a heat gun to warm up the a-arm end and dry ice to cool the pin to get it to fit.

    There is a trial fit test in the Daytona shop manual that talks about assembling the a-arms to the hub and after tightening, verifying that the a-arms drop under their own weight. In this test the rubber o-rings are supposed to be left off, so maybe I can observe the pin flange to make sure the pin is rotating as well as the thru-bolt. That's really what is important.

    What you don't want is the bolt to be rotating inside the pin as the a-arms/hub move up and down. This would put the wear on the thru bolt (metal to metal) rather than in the bushing (metal pin to teflon bushing surface.

    Tom
     
  4. Llenroc

    Llenroc F1 Veteran
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    #4 Llenroc, Mar 22, 2006
    Tom, After I had answered yesterday on your question I thought about the heat effect also but was wondering after things had cooled down would the pin fit too tight and prematurely wear the teflon coating. I liked your idea of honing the bore on the A arm. This would allow a few thousands of play(just enough for easy movement) for some movement of the pin without rubbing off the teflon because a over snug fit and if you add a little grease to the bushing it should wear much better. Regards, Vern
     
  5. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Brian Crall
    #5 Rifledriver, Mar 22, 2006
    If the steel inner piece (hat bushing) does not just slide in with the slightest push it is too tight and the teflon will be destroyed in no time.

    I don't know if OE parts are being used in this case or not but many of the parts being used that are being supplied by Ferrari for cars in TR and earlier period are being made for Ferrari by vendors, in some cases different vendors and the original specs have not been followed. In some cases it is in the materials, in some it is dimensional. Many of the parts being sold by Ferrari for older cars are just no good.

    If on the other hand they are reproductions made by someone outside Ferrari it sounds as though they just missed the size by a little.

    It sounds as though more space needs to be provided for the outer bushing.
    It could also be a case of the teflon coating having been applied a little too thick and to open up the holes in the arm may just leave you with a loose bushing.
     
  6. Telerding

    Telerding Formula Junior

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    Tom Elerding
    #6 Telerding, Mar 22, 2006
    Gentlemen:

    After pondering the issue, and looking at your latest responses, I have come to the conclusion that the heat/cold approach might end up with pins too tight, and as you stated, could end up with high wear on the teflon.

    I am going to try and mix-match the pins and bushings to see how many I can get in without any heroics. It may not be that many, unfortunately.

    For those with a definite fit problem I will have to press out the bushings and open up the bushing carrier bore just slightly to give just enough clearance for the pins to be hand fit.

    I have decided to invest in an "inexpensive" press to get these things in and out by myself. I hope I can find a correct size hone for my drill press.

    Thanks for the advice, and I'll keep you posted on the results.
     
  7. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #7 Rifledriver, Mar 22, 2006
    A simple arbor press would work just fine I think. No need to go to the expense of a hydraulic unit.
     
  8. Llenroc

    Llenroc F1 Veteran
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    #8 Llenroc, Mar 22, 2006
    Hi Brian, Have you used the grease technique? in your experiance is that ok. I have done this several times and it seemed to work but you would obviously have had more experiance as to weather this is helpful or not. The teflon seems to wear off fairly quickly is the reason I started doing the light film of grease. Regards, Vern
     
  9. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #9 Rifledriver, Mar 22, 2006

    I have always lubed them. Over the years with different stuff but as you have I also use Redline now. I use it on everything, I even use it on my target rifles.
     
  10. Llenroc

    Llenroc F1 Veteran
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    #10 Llenroc, Mar 22, 2006
    LOL. That's funning you say that, I have found that I can't fuction very well in my mechanical life without Redlind in seems that it works for alot of stuff.
     

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