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  1. #1
    14 PSI Boost
    Join Date
    Jul 2018
    Location
    Brooklyn NY
    Posts
    59

    The rear suspension tweak thread

    While looking up SVO rear suspension treatments I noted only a handful of posts and they were 10-15 years old and weren't particularly informative. I thought it might be a good idea to make a thread where the pros and cons of rear suspension tweaks or add-ons for the SVO could be compared. From what I've understood, the SVO front is fairly competent so I concentrated only on the rear. I don't know anything about any SVO rear suspension tweaks and upgrades but I do know a little about Watts links and Panhard Bars so let's start there:

    Watts Link is an in-genius system that creates a snakelike vertical path for your stick axle rear. It restricts the movement of the axle off the road plane so both wheels keep contact. Simplified, it is two parallel panhard connections configured so that the arc of one is offset by the other. This eliminates any lateral movement of the axle and maintains wheelbase geometry. Its main criticisms are its additional weight, its sometimes inconvenient mounting, its unexpected asymmetrical roll center dynamics (more on that later) and its expense.

    Panhard Bars are simple structure connections of the frame to the axle so as to restrict the movement of the inside rear off the pavement with leverage. It has two main mount point styles with many variations:
    Single Mount - which forces you to commit to a given assymetrical lever point.
    Mirrored Mount - which allows you to reverse the assymmetry of the lever point to suit the bias of your racetrack (ex: more/deeper left than right turns).
    The main criticism of the Panhard Bar is its sagitta (arc offset travel). A pivoting lever creates an arc that the axle must follow and so the axle will float laterally as it travels up and down. This sounds terrible in theory but in the real world it isn't so bad and there are steps that you can take to minimize the effect. A common example is a 30" bar with 6" of suspension travel has about 5/8" total sagitta so if you center your installation properly your axle will only float 5/16" on either side. Tires at speed have sidewalls that deflect nearly 10x that amount!

    Baby, it's all about how you roll. At first glance the Watts looks like the more elegant solution. No lateral axle deflection, no frame geometry distortion, case closed, right? Even if we disregard the higher cost and weight of a Watts Link we still have to deal with body roll center dynamics. When you corner hard left in a typical Watts setup, the rear sits down nicely and everything is very predictable and tight but turn right with the same intensity and your a$$ has risen and become looser. It's still balanced and both wheels are still contacting but there is definitely a change in handling. For an experienced driver who knows his car, this is acceptable and can be factored into a race strategy but for someone who hasn't had much time in a Watts, it can be very unsettling to have the same car be neutral going right and oversteering going left. This same dynamic happens with Panhard Bars but if your mounts are mirrored, you can much more easily switch them for the best compromise. Conversely, better Watts Links can mount below the pumpkin to reduce or eliminate these issues if you're willing to sacrifice ground clearance. It's always a game of compromise because nothing is perfect with cars.

    Okay, know we know the different types of rear suspension upgrades but can we fit them in our SVO? Will they play nice with my subframe connectors and my exhaust system? Do I have to do irreversible and cosmetically annoying mods to get them in? This is where you guys can help make this thread worthy of stickiness. All you need to do is sound off with what you've tried and the result. In not much time, we'll be able to gather a database of working combinations. If I missed any types feel free to include them in your replies and we'll give'm a once over. Ditto for tweaks available with the stock setup.

    To start us off, we have a great example of a Watts install by @svono50 linked here.

    For those considering the track bar, a link to Maximum Motorsports install instructions are linked here.
    Last edited by yldouright; 07-18-2018 at 06:52 AM.

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