Project 987.2 Cayman S, Cup Car Suspension for the Street!

The rod end and the fork are threaded in right and left-hand threads so adjustment is easy, just crack the jamb nuts and turn the rod, no need to remove the ends to adjust!  The forks bolt to the eccentric in the lower control arm.

The rear toe rods use spherical bearings and eliminate all the soft rubber.  They also use pinch bolts so you can simply loosen them and turn the rod to quickly adjust the toe settings. The outer pivot point is raised to reduce toe steer over the stock parts on a lowered car.  Fine adjustment of bump steer can be done with shims.

The front tie rod ends shank is longer than stock and raises the outer pivot point to have built in bump steer correction for a lowered car. Additional bump steer adjustment can be done via shims under the spherical bearings to finely adjust bump steer.

The front tie rod adjusters also have a pinch bolt to allow for fast toe adjustment.

To give the car a rear tie-down/tow location and to stiffen the subframe, we used this brace from Rennline. The brace is adjustable for length and allows preloading of the subframe for additional stiffness.

12 comments

  1. Ok, I really like the idea of using the HLS to do rake; will be cool if that works well. Do you know what the roll centers end up like on these things when lowered and strut inclination? I was looking at a bunch of more modern McPherson strut cars and trying to figure out what they’re doing for geometry lately.

    1. I am waiting for the right springs to come in so I can figure stuff out and get it all set up. Next article.

      1. Cool, looking forwards to it. I’m in the middle of some some relatively weird design work for an SCCA car so wanted to sanity check some stuff before I start machining a bunch of NLA parts; I’m basically mulling over changing steering axis inclination on 1st gen RX-7 knuckles.

        Whole project is going to be going relatively slowly because I have a one month old daughter now, but I figure if I’m going to the extent of having shock pistons made for struts and doing cambered floater hubs on a live axle, might as well be thorough.

        1. You can look to off road and circle track parts for camber floating live axle hubs. Some Mustang guys run that stuff on drift cars too. I am in the middle of figuring out how to control scrub on a strut suspension with really wide tires. My first idea got banned by FD before we could even make it.

          1. I’m cribbing design of it from circle track practice certainly, but scaling down – the circle track stuff with the right features all tends to be 5×5″ bolt pattern and all the affordable good 15×7 wheels (yay SCCA rules) are 4x100mm.

            I assume you’ve seen the Revoknuckle, Superstrut, and the dual pivot lower control arm solutions… I’ve been thinking of the same thing and how to get something like that through the rules. Only about 9.5″ of tread width, but on slicks, and I’m not sure power steering is in the weight budget.

          2. What about something like the Chevy Cruze WTCC front strut – they had a big bracket moving the strut around the tire which could let you sink the knuckle deeper into the wheel.

  2. “The anti-corrosive construction is one of the reasons why KW Clubsports have a limited lifetime guarantee.” The KW Clubsports do not carry a warranty as stated by KW’s web site, unlike the other models. Unless you’re referring to another guarantee, thought I’d point that out for those in the market.

  3. Nice program !
    I like the pinch bolts instead of jam nuts to lock the alignement settings ! Far more convenient and precise.
    The Rennline brace doesn’t look that well engineered though, it’s more for show than actual stiffness.

    I’ve had a really good result with tightening the front end with a triangle brace on the front subframe, where there is usually just two stamped steel braces, I have a solid piece that triangulates the whole subframe instead and the difference is quite noticeable ! Should be even more so with full spherical bearings suspensions !

      1. It’s a Ultra Racing brace. I’m sure you can easily fabricate one like it. But it was very cheap.
        It protrudes a bit underneath the car, but no big deal on mine, it never touched anything (and I’m lowered).
        Check out their strut brace too, looks much stronger than the rennline 😉

  4. I’ve been running Tarett parts for 15+ years on my aircooled cars, top notch stuff that is built to last. We recently added the Tarett cockpit adjustable sway bars to our 987.1 Cayman racecar and they are awesome too. It’s so nice to be able to make adjustments on the fly without losing time on track or having to roll around on 100+ degree asphalt between sessions.

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