The 7/9 Bils are super over-achiever. You're right about that! Seems specific to those cars? Someone moved a decimal point or reversed the compression & rebound damping #s or something crazy?IMO the Nivomats are a great feature on the 7/960 line. They are not a stiff shock like a Bilstein HD so if your car is truly intended to be used on the racetrack only, or you just want your Volvo to ride like a cement truck as many folks apparently do on here, you won't like them. But they have a great balance of ride vs handling for any kind of honest real world usage.
They last a long time too. And if you tow at all they will be a particular plus to you. My $0.02 would be just to get a fresh set of the stock setup and keep on rolling.
The 200 Bils or OE DeCarbon monotubes on GT/GLT/Turbo are still pretty mild/tame on a stock height car/matched to the springs properly?
The 7/9 Bil HD valving is ridiculous! Like a pogo stick to rattle all your fillings out/punch you in the kidneys?
240Turbos/GLTs came with DeCarbons with appropriate valving that Bilstein USA can rebuild, but '86+ Volvo gave up entirely on building mid-size 'driver's cars' & no more monotubes OE on any of them...
Slide the sleeves off the DeCarbons on the 240s and Bilstein USA can't tell the difference between them & Bil HDs and can preserve valving that matches the pretty mild 240T/GLT & GT springs pretty nicely/nothing too crazy?
Use the 240 dashboard mounted load leveler switch, air pump & some aux air bags inside the springs?
Then, you still have regular springs & shocks that last forever & the shock itself is a rebuildable monotube wear item instead of the shock failing w/the super soft nivomat model springs?
That said, the IRS 7/9s, the nivos drive real nice, especially with a modded G80 locker?
Nice huge fuel tank on sedans that can be used in conjunction with the 700 sedan aux fuel tank (no evap to worry about on a Diesel)...tow, auto load leveling, gets over slick snot good with the locker etc?
Volvo was super conservative & didn't trust IRS in snow etc where if it sagged none of the geometry would work right like the old solid axle cars, hence the nivos being universal on MK1 IRS...pretty logical.
Put any real weight on an IRS japanese IRS car and it'll twist up & drive sketchy &/or wear the tires in weird patterns...