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Rear suspension broken top outer bolt...

Discussion in '308/328' started by Rod, Jan 11, 2021.

  1. Rod

    Rod Formula Junior

    Jan 18, 2004
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    Rod
    I've just rebuilt the rear suspension on my 328..... I torqued all the bolts as instructed about a week ago.. any way noticed a bolt head on the garage floor and it turns out that the head has sheered off the top outer suspension bolt?? I've ordered a new bolt.... My question is... could I place a jack under the hub to take the weight and then use the new bolt to drive out the old bolt and into place?

    Appreciate any advice.. thanks


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  3. conan

    conan Formula Junior

    Nov 13, 2011
    358
    I think the safe way is to use a spring compressor to ensure there are no forces acting on the bolt. Then after reassembly, jack up the hub so the car just barely lifts off the jack stands, and torque the bolts in this state.

    And check that the bolt is not catching or is not seating properly against the frame. Maybe it sheered off due to some misalignment.
     
  4. sp1der

    sp1der Formula 3
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    The shock will only extend to the full rebound position anyway so the bolt should come out without resorting to any jacking etc, was the bolt re-plated, it could have become embrittled in the plating process?
     
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  5. mike32

    mike32 F1 Rookie

    May 13, 2016
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    Looking at the picture, the break looks to have 2 shades, ie the dull material is from a hairline crack that has been there a while, the more fresh light grey is where it finally failed. Hard to see exactly but i think this has been failing for a while. You might want to think of changing any more you have.
     
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  6. Rod

    Rod Formula Junior

    Jan 18, 2004
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    Simon, yes they were re-plated....not cheapest bolt either at £24 each So there is no load on the top outer? Is it just the inners that need torqued under load? Thanks


     
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  8. mike32

    mike32 F1 Rookie

    May 13, 2016
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    I bet they are stamped 8.8 on the bolt head- standard bolt from your corner tool store with ferrari tax. About £1 each
     
  9. yelcab

    yelcab F1 World Champ
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    Hm, you have not worked on this part of the car, have you? That bolt is not available anywhere else. It is about 10 inch long, with a Ferrari horse at the head. Even without the horse, nobody in town will have that bolt, that long, in metric for that application.

    When you find that £1 replacement, please post its source so we can all enjoy the savings.
     
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  10. yelcab

    yelcab F1 World Champ
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    If I were to do this, I would use a drift or a long screw driver and knock out the broken bolt and then replace it, and torque it while it is under load. Don't try to use the new bolt to chase out the old one. That is not its purpose.
     
  11. rosemeyer

    rosemeyer Karting
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    Aug 13, 2010
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    Rod,

    That looks like a hydrogen embrittlement failure. The location of the failure (at the bolt head), the timing of the failure (shortly after installation), and the appearance of the break (you can easily find similar images online for your reference) all point to this.

    High strength fasteners such as those found in your suspension require controlled baking after plating in order to minimize the possibility of brittle failure. Even then there is no guarantee. The best way to minimize this outcome is to avoid those plating processes that are more likely to cause embrittlement. I note that your bolts look to have been yellow zinc plated. Originally these were generally black oxide, a process that while not as rust resistant as zinc plating, has no associated embrittlement risks.

    Given the above, I'd encourage you to keep an eye on these assemblies for signs of any further problems. If there is any doubt, replacement of all the bolts is advisable. No need to pay the Ferrari tax if you go this route. The only thing is to ensure is that the fasteners are of the same grade as the bolts that are removed.

    Hope you don't mind the departure from your original question but, as this is a safety item, I thought it worth mentioning.

    Best Regards,
    Paul
     
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  13. Rifledriver

    Rifledriver Two Time F1 World Champ

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    They were always yellow zinc. And they are not high strength. They are standard strength class.
     
  14. rosemeyer

    rosemeyer Karting
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    Aug 13, 2010
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    Then that is a change in plating process that would have taken place on the 328. On the 308 and the 246, which are cars with which I am very familiar, these bolts are definitely black. I assumed that this carried over to the 328, a model that I have admittedly zero experience with. It is also worth noting in that case, that I do not know if the grade changed on the 328 as well.

    Regardless, the failure mode indicated in the OP's photo is consistent with a brittle failure which is why my advice to be vigilant remains.

    Best Regards,
    Paul
     
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  15. mike32

    mike32 F1 Rookie

    May 13, 2016
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    Regardless of the length, its still a plated standard bolt, we used make parts for the ejection seats which had this yellow finish but this was a passivation process over the cadmium plating to seal it, in the days when it was still used. Cannot say i have ever seen yellow zinc plate.
     
  16. yelcab

    yelcab F1 World Champ
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    It is a custom Ferrari bolt (with the Ferrari horse embossed on the top of the head). Judging from the attention to details this OP is trying to accomplish here, he is unlikely to replace it with a bolt without a Ferrari head for this car. I am not questioning the plating or strength, just the $1.50 price tag you gave for this bolt. By weight alone, it's worth $10 at the hardware store if anybody carries a bolt that long. With the prancing horse on its head, it's $40 easy. I would gladly pay that price from a Ferrari supplier just to save myself the hours searching around town for a similar bolt.
     
  17. ProvaMo

    ProvaMo Karting
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    Jun 29, 2004
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    Similar to what Mitchell states, the process I would use is: Unload the suspension, use (optimally) a rod of the bolts major thread diameter to push the residual bolt out, reverse the process to guide/court the new bolt in with the rod. No need to torque the outboard bolts under load, they are full floating to the center ground bushings (unlike the inner rubber loaded bushings). If this was hydrogen embrittlement due to the plating, it would (obviously/potentially) raise concerns regarding the other suspension bolts. v/r Paul
     
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  18. Rifledriver

    Rifledriver Two Time F1 World Champ

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    I have worked on these cars for 45 years. I own a 328, I just finished a suspension overhaul on a 308, have my own TR on the hoist now and am in the process of doing one on a 246 and have done them on 365's. All are yellow zinc.
     
  19. yelcab

    yelcab F1 World Champ
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    That same bolt is used on 308s back to the 308GT4. Same bolt, same finish, same yellow zinc, same horsey on the end, $57 from a known US vendor.
     
  20. Rifledriver

    Rifledriver Two Time F1 World Champ

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    They are also 1.25 mm thread. Not a standard for 12mm bolts making sourcing them outside more difficult and more costly..

    $1 apiece? I'll take 3 boxes full.
     
  21. conan

    conan Formula Junior

    Nov 13, 2011
    358
    What is the length if this one? I recall I may have some bolts for suspensions on other cars I have worked on.
     
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  22. miketuason

    miketuason F1 World Champ
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  23. mike32

    mike32 F1 Rookie

    May 13, 2016
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    Just reading up on the yellow finish, it appears the yellow finish is a layer on top of the zinc plate using Chromates in a passivation process, so it is similar to the process we used on top of the cadmium. Had to come from somewhere as zinc being a silver/ grey colour.
     
  24. mike32

    mike32 F1 Rookie

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    I had a look on e bay and available in m12x150x1.25. In yellow finish. About $5 to $6 each. If it was 1.5 pitch then they go for around $1.5 each.
     
  25. Rifledriver

    Rifledriver Two Time F1 World Champ

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    It is called yellow zinc. Silver is called clear zinc.
     
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  26. ProvaMo

    ProvaMo Karting
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    My 1979 308 GTS USA Rear, Upper, Outer bolt is 156mm long, from under the head of the bolt (i.e. does not include the head)
     
  27. conan

    conan Formula Junior

    Nov 13, 2011
    358
    The bolts I had was 212mm long with 1.5 pitch ... so not working.

    However, I found a Lada/Chevrolet Niva part for the shocks, 15542221.
     
  28. pshoejberg

    pshoejberg Formula 3
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    #25 pshoejberg, Jan 11, 2021
    Last edited: Jan 11, 2021
    Do not over complicate this. Do as Rifledriver indicates; Buy one new yellow zinc original (If it's not NLA) bolt from Ferrari and change out the broken one using a method were you don't use the new bolt as a drive out tool. Ensure to apply correct tightening torque on the nut. It's not uncommon to see a broken bolt on +30 years old car that has been tampered with by god knows who. Drive the car and be happy.

    Price at Ferrariparts UK: 35 BP
    Price at Superformance: 25 BP

    I guess it is the same bolt at both places and I guess it is an aftermarket bolt as well = No horsey on head. Ferrariparts will call it Maranello approved, hence the 30% higher price...-:)

    Best, Peter
     
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