Lee from Koni checked in on another forum, here is a copy of what he had to say:
"Hello all, my name is Lee Grimes and I am the Automotive Product Manager for KONI Shocks. I have been working with Greg and Joseph to get these new Z-car parts to market and help answer some questions. He pointed me to this discussion to maybe give some clarity or assistance.
A bit over a year ago, Motorsport Auto came to KONI to see if we could revive and modernize our offering for the early 240Z, 260Z, 280Z and 280ZX. Needless to say we jumped at the chance to offer proper products for these important cars. Off and on through the years KONI has offered the traditional red painted KONI Special strut inserts with internal (off the car) adjustment for 240Z through 280ZX. In the late '70s-and early '80s KONI also offered an externally adjustable version for these cars excluding the ZX but they were discontinued by the mid-'80s. Now was time for an update.
With Motorsport Auto as an exclusive partner stepping up to take full production run volume, we developed and tested new externally rebound adjustable (knob adjustable on the car) yellow painted KONI Sport strut inserts for these cars and a externally adjustable rear shock for the ZX. We started with the external adjustables from the 1980s as the launching point and even used the same part numbers this time with the SPORT suffix in the part numbers. We then updated the internals a bit (it was no slouch to begin with back then though) to more modern seals and guide components and set the valving to work well with either factory stock springs (starting baseline adjustment at or near full soft) or performance lowering springs for performance street, autocross, track day, etc. use (starting baseline adjustment about 1/2-3/4 turn up from full soft setting).
Like all KONIs, the adjustment range is about 100% so they are twice as firm at the maximum setting than at the minimum setting. This is a very large range of adjustment so we suggest that you start in the lower end of the range, drive it for a bit to get a feeling for it, and then tune accordingly from there for your ride and handling preference. I think it will be very rare that people will use more than 1 turn (about 50% higher than full soft) for normal use when they are new. Because the adjustment range is so large, it allows you to compensate for wear over extended time, tune it high for an autocross or track day, and then quickly turn it back down for street use. Because the range is so large, it is possible to overdamp the car for your needs and actually make it more harsh and have less grip than needed so do not just turn it way up figuring that "more is always better". Although these could be used for a dedicated track and racing car, their needs and expectations are different and we do have other racing options (e.g. 8610 RACE and 8611 RACE) where street handling and ride quality, high mileage longevity, etc. are no longer important. These new Z-car Sports are targeted to take you from stock Z- car to just shy of all out racing. They carry KONI's limited lifetime warranty against defects and materials to the original purchaser as long as tht person owns the car registered for street use.
Regarding the discussion about bump rubbers, you can use a good condition OE type bump rubber for a Z-car, one of the black urethane ones that Motorsport Auto sells, or the KONI Racing Silastic bump tops made for use on a 22mm piston rod. KONI does not have a specific bump stop length suggestions as different ride heights and springs will determine what length you need. The important part is that you have some bump rubber installed to keep the strut or shock from bottoming out internally which can cause internal damage that will cause loss of function and will not be covered under warranty.
The first production runs of the fronts and rears for the 240Z, 260Z, and 280Z are currently in-transit from KONI in The Netherlands due in mid-March. The 280ZX fronts are in-transit as well but the 280ZX rear shocks are awaiting final production due to to different component sourcing but will be here ASAP.
Please be clear that these were specifically developed only for these Z-car applications and they are not crossovers from some other vehicle. Because these parts are exclusive to Motorsport Auto and no other KONI dealer has access to them, we will not be listing these part numbers on our official KONI websites for North America www.koni-na.com
or Europe www.koni.com
. If you have any questions, please contact our Technical Staff at [email protected]
or 859-586-4100 Option 6 from M-F 8-5 Eastern time."