front springs...
-Progressive brand popular, but they are one rate fits all. i had them. unimpressed. ditched them for...
-Race tech, much better. you get a spring rate that is "fitted" to your usage and weight. not everyone is the same.
https://www.racetech.com/ProductSearch/2/BMW/K75%20C-S-RT/1992-95#210 is heavy for a stock rear spring when it was new. 30 years later the spring is softer than it was, and guaranteed the damper is shot. rebuilding waste of time. just get a new one. can't go wrong with Ted's
https://www.beemershop.com/ there are a range of options.
I have
K75S #1 progressive front/ progressive 465 rear. works ok on track. that is all this bike gets used for.
K75S #2 Race Tech front/ Fox DA rear. works great on track or street
K1100RS Race Tech front/ Progressive 465 rear. has not been on track, but very happy with sport touring riding
K1300S Wilbers DA front and rear with ESA function deleted. freaking awesome control...track or street.
A good suspension makes a HUGE difference in how a bike rides and handles. It is not a place to ignore or cheap out if a bike is to be enjoyed.