Fishey

The first 3 years of ownership the Stance GR+ might come close to being at the same level as a spring/Koni combination. At 5 years in the Stance GR+ will already be suffering pretty heavily from nitrogen loss in the free piston. At 10 years the Stance GR+ will not even function as a shock anymore. Its the same problem I see pretty often from customers with older coilover setups. An example a 20,000mile Viper ACR with dynamic racing shocks (I looked this up says ACR came with KONI Competition (Monotube) but I swear they were dynamic not that its important) felt like driving a pogo stick simply because of pressure loss.

Cheap Monotube Coilovers are a compromise of A. Performance or B. Durability you cannot have both because of physics and I should note by cheap I mean every single monotube ever built that doesn't have a nitrogen charge port to be re-pressured. Since extremely few non-external res shocks have a charge port then you can expect that you basically need to get external resevoirs if you want to not be considered "Cheap". Anyways, to the physics! of Monotubes because of the very nature of the design a Monotube cannot perform good and be durable at the same time. To make a shock last on the street without being rebuilt every other year they have to add significant sealing pressure/surface to the free piston or they run the highest possible pressure when new so as they drop pressure the shock will actually get better. As you add this sealing you create friction and friction causes the piston to stick and that means your initial shock response is extremely poor. This makes for a bad ride quality (like Bilsteins HD's for example) and a major reduction in overall shock performance expecially on the street. This of course is all done so the shock will last longer but usually even doing this will only make the shock last at a decent level of performance for about 5 years before they start to drop off. The alternative being that you can get a good performing monotube with lower free piston friction that gives good ride and performance like most Motons/Ohlins/Penske type shocks but they don't last long before they start to drop in performance becuase that free piston will leak out its nitrogen quicker due to less sealing they tend to lose about 5psi a month or 100psi every 2 years. The pressure loss is reduced as pressure from the shock lowers since there is not as much pressure pushing against the sealing surface. When it does that on cheap shocks you have to rebuild them since you have no way to get nitrogen back to the other side of the free piston. On high end shocks you simply go to a nitrogen tank and re-fill them to the proper pressure (for awhile anyways but eventually you will have to rebuild due to nitrogen on oil side but you can do this yourself since they are built to be serviced). Now, also on most cheap coilovers (D2 and a few others excluded) lowering significant amounts can cause a massive reduction in performance simply because the shocks serial layout. This can cause major issues with valve piston to free piston distance and so the shock will not behave properly. Now on the D2's you can adjust the shock body so its not that big of a problem but on many other brands this isn't an option.

So why do you even want Monotubes for the street performance? Monotubes better design and heat disipation? Well, they will not perform better then a twin tube if they have high stiction on the free piston or running completely the wrong shock pressure (overpressure) for the valving. Even if they don't Monotubes really don't do any better then a twin-tube unless they get hot and on the street your not stressing the shocks enough to build up heat very often if at all. So go with spring/shock combo for the street is my advice and enjoy not having to service your suspension for many years. Hell, just last year we had a on track incident that broke a front strut on our 944 race car. So we went back to the shop that night to find what we had on the shelf and a set of 1989 Koni Yellows (double adjustable) + Coil Conversion off a Turbo S M030 car with 150,000miles were our only option. A bit soft on compression but rebound seemed to be great. The car went back together in the morning and we ran it to a podium finish. That is 23 year old shocks with 150,000miles going to the podium (3rd). I can't think of any mono-tube that could even think of doing that.