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Spherical bearings or custom machine solid a-arm bushings?

Discussion in '308/328' started by luckydynes, Jan 28, 2009.

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  1. luckydynes

    luckydynes F1 Rookie

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    #1 luckydynes, Jan 28, 2009
    Hey all,

    I just put "mono balls" on my 911 track car and I luv 'em.

    I want to do the same to a 308. I've had the polyurethane bushings on my car for 10+ years so I want to try something new.

    So my question is should I use off the shelf spherical bearings or make some kinda sleeve/bushing arrangement? The movement of my 911 suspension requires the bearing be spherical ... don't think it's necessary for the 308 but seems easier than making everything.

    No matter which route I go I'll incorporate grease fittings which I did for my 911 setup.

    Thanks for the input,

    Sean
     
  2. Hans

    Hans F1 Veteran

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    #2 Hans, Jan 28, 2009
    On the rear suspension, the bottom A-arm is used to set toe-in by inserting a whole bunch of shims. The top A-arm is fixed - no shims.

    If I loosen the bottom fixtures on mine, the natural position that results has way too much toe-in. And so the shims push the wheel toe-out against the push of the bushings. If using bearings, I can see no way that this setup will NOT eat up your bearings, if you'd be able to shim the bottom at all...

    What you'd really need is to be able to shim at least one of the top attachment points as well (or use an oblong bolt hole there). Then bearings would work, IMHO

    Hans
     
  3. fastradio

    fastradio F1 Rookie
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    #3 fastradio, Jan 28, 2009
    Sean,

    Boxer's use a sleeve/metal bushing set-up in the front suspension (no rubber)...If you take a look in the Boxer section/Repair threads, you'll see my detailed process for rebuilding them, as well as many photos of the set-up you're describing.

    Sounds like a great project.

    David
     
  4. luckydynes

    luckydynes F1 Rookie

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    #4 luckydynes, Jan 28, 2009
    Thanks David.

    Is it similar to the outer bushing setup on the rear of the 308 by any chance? They have a thrust washer setup in there. That seems like a lot more work then putting spherical bearings in there don't you think?

    Also the spherical bearings would prevent any possible binding that Hans mentioned ... I don't think that should be an issue with a conventional sleeve though .. just spherical seems easier but is it maybe a thrust issue? Acutally wouldn't think so 'cause I thought I recall seeing Modena and Norwood aftermarket arms with heim joints on the inner attachment points.

    Appreciate the input all,

    Sean
     
  5. fastradio

    fastradio F1 Rookie
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    #5 fastradio, Jan 29, 2009
    Sean,

    Yes, the BB front bushing/sleeve set-up is very similar to the rear of a 308. The Boxer set-up also uses a front and rearward facing thrust washer on each of upper control arms. The lower control arms, where they attach to the chassis use a rubber/metal bushing, like all the other 308 and 328s, except that is of a larger diameter. (I've replaced these with the Energy Suspension poly bushings.)

    In terms of difficulty to convert to a spherical bearing set-up, the collar that the BB uses to support the pin/sleeve set-up, could, I believe, be installed in the 308 control arm without too much effort. However, I'm not 100% certain if the i.d. of the BB arm and the 308 arms are the same...

    Although spherical bearings have a precision advantage...and pose less of a concern when it comes to mis-alignment/binding issues, particularly in the rear, due to camber and toe adjustments, I think they're too rigid for "street use".

    I had both a Lotus Europa and Alfa Romeo 2000GTV that had custom control arms fitted with spherical bearings. Although these cars handled extremely well, bearing life was short along with pretty harsh ride characteristics.

    Good luck,
    David
     
  6. luckydynes

    luckydynes F1 Rookie

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    #6 luckydynes, Jan 29, 2009
    Thanks for the input.

    Sean
     
  7. luckydynes

    luckydynes F1 Rookie

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    #7 luckydynes, Oct 18, 2009
    Getting ready to do something with this.

    Thanks again for the input David ... did the short life setups you mentioned have grease nipples?

    I'm back to thinking of doing spherical bushings and incorporating grease nipples. What kind of life should I expect from them? I've tried asking this on the P car forums and it seems like there's a lot of difference based on:

    1. The quality of spherical bushing used ... some real junk was used in some of the kits apparently.

    2. LUBRICATION!!! None of the 911 monoballs have grease nipples incorporated. I put some on my 911 and it didn't make the ride any more harsh ... that car has rigid motor mounts and huge torsion bars so she's pretty stiff anyway. My 308 has 375# f 325# r springs with the QA1's set at 10 & 8 respecitively ... meaning my arse is knumb anyway :).

    3. I was concerned about the thrust loads during braking with the spherical joints which is why I contemplated going to the trouble of the thrust washer setup. I have the aftermarket poly grahpite bushings and I can see some compression in them from braking forces on the front ... really deformed one of the washers in there and was making for some interesting braking characteristics (running the full race Porterfield pads).


    Cheers,

    Sean
     
  8. mk e

    mk e F1 World Champ

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    #8 mk e, Oct 18, 2009
    Sean,
    I've seen ball bearings used too. They will handle a LITTLE misalignment and might give better life. Maybe....

    On the spherical solution, grease fittings are a start, but rubber boots of some kind are pretty important to life as well. You are talking about what is basically just like the ball joints on the outside and they normally aren’t long for this world once the boot tears.


    Good luck with it.

    Mark
     
  9. luckydynes

    luckydynes F1 Rookie

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    #9 luckydynes, Oct 18, 2009
    Thanks for the input ... I just saw spherical bushing seals at Summit ... I found something that worked on my 911 to keep the dust out but these seals are specifically for the spherical joints.

    cheers
     

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