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Prepared Lower Control Arm Rule Clarification - D.8.

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  • Prepared Lower Control Arm Rule Clarification - D.8.

    8. Any dampers may be used. Damper attachment points on the body/frame/subframe/chassis/suspension member may not be altered. (Rule a.2 seems to contradict this statement) This installation may incorporate an alternate upper spring perch/seat and/or mounting block (bearing mount). No damper may be capable of adjustment while the car is in motion, unless fitted as original equipment. MacPherson strut equipped cars may substitute struts, and/or may use any insert. This does not allow unauthorized changes in suspension geometry or changes in attachment points (e.g., affecting the position of the lower ball joint or spindle). Threaded collars and camber plates are allowed.

    a. Camber kits, also known as camber compensators, may be installed. These kits consist of either adjustable length arms or arm mounts (including ball joints) that provide a lateral adjustment to the effective length of a control arm. Alignment outside the factory specifications is allowed. The following restrictions apply:

    1. On double/unequal arm(e.g.wishbone,multi-link)suspensions, only the upper arms OR lower arms may be modified or replaced, but not both. Non-integral longitudinal arms that primarily control fore/aft wheel movement (e.g. trailing arm(s) or link(s) of a multilink suspension) may not be replaced, changed, or modified.

    I.E. Honda, Mitsu, anything with an upper AND a lower control arm you can replace ONE but NOT the trailing arm and per rule 12 they cannot have metal bushings

    2. On arm-andā€strut (MacPherson) suspensions, Adjustable camber plates may be installed at the top of the strut and the original upper mounting holes may be slotted. The drilling of holes in order to perform the installation is permitted. The center clearance hole may not be modified. Any type of bearing or bushing may be used in the adjustable camber plate attachment to the strut. The installation may incorporate an alternate upper spring perch/seat and/or mounting block (bearing mount).

    Camber plates are still allowed, but this says nothing about replacing lower arms, more on this later...

    3. On swing or trailing arm suspensions, the main arms may not be modified or replaced, but lateral locating links/arms may be modified or replaced.

    Here's the question, on a Subaru for example, you have one trailing/locating arm running fore/aft and two lateral links on each side, per this wording, you could replace those four lateral links yes?

    4. The replacement arms or mounts must attach to the original standard mounting points. All bushings may not be moved or relocated on the arm, except as incidental to the camber adjustment. The knuckle/bearing housing/spindle assembly cannot be modified or replaced.

    Pretty clear cut


    Now here's the discussion part, per rule 8.a.3 all PA Subaru's should be able to replace all four rear lower lateral links correct?

    Lastly, there's a known issue on all Subaru's with steel front lower control arms, they rust out and fail in spectacular fashion:

    Could we start a discussion on allowing either OEM aluminum LCAs in PA or possibly aftermarket LCAs on MacPherson style suspension? So long as the attachment points and geometry don't change it fits the spirit of the above rules while allowing racers to have a safer vehicle over a longer period of time while keeping cost down and offering very little in the way of weight changes (2# per arm). Without this allowance, there's a pretty clear advantage to vehicles with multi-link suspension in the form of being able to replace arms with adjustable aftermarket arms.
    Last edited by Crawlerado; 07-12-2017, 01:08 PM.

  • #2
    Are you suggesting that the Subaru aluminum lower control arm is "safer" than a *good condition* steel arm? (Note: good condition arms are readily available in the used market)

    What problem are you trying to solve?


    • Crawlerado
      Crawlerado commented
      Editing a comment
      For those of us that drive our vehicles year round and live in climates where salt and rust are the norm that would mean preemptively replacing parts so we don't have a failure.

      The simple and economical solution would be using a non-ferrous arm. However, given the current wording of the rules if you have a car that has MacPherson style suspension you're SOL whereas if you own a vehicle that has multilink you're free to replace up to four control arms.

  • #3
    I get it - I live in the rust belt. But if your arm is so bad that you shouldn't be rallyxing on it, you probably shouldn't be driving it on the street either. Again, they are readily available in good condition still, and for cheaper than STI arms. So I don't follow your logic at all.


    • #4
      Someday those parts will no longer be available (look at what's happening with Civics in STC now)

      The main point is there's already an allowance to replace LCAs on multi-link cars. Is there a reason we don't have that allowance for MacPherson vehicles?


      • #5
        The allowance is for a performance upgrade that the McPherson strut setup gets by slotting the strut tabs, which is also allowed.

        What your are asking for is outside the spirit and intent of the allowance for multi-link cars.


        • #6
          I would *think* that aftermarket control arms/links are allowed as long as they are an OE fit type replacement part, such as you might buy from Dorman or MOOG. Same geometry, bushing locations, material type, etc.

          Aluminum arms are far stronger than stamped steel, when talking OE to OE. Granted you can reinforce steel arms a lot more easily, but that isn't allowed until Modified either.