There are two schools of thought on the how to set the Strength for wheel in iRacing… the problem is iRacing does things differently… The iRacing Slider does adjust the strength of the wheel but it does so by extending the range of the telemetry for the car by Moving the 100% point of the feedback… I am not sure how this works under the hood in regards to what Mika mentioned with Constant force in that it does possibly
alter FFB signal fidelity BUT on the flip side it Massively increases the CAR fidelity in Iracing (depending on the car).
Especially with you using the IR18 you probably want to set the iRacing Slider between 47 and 60 to allow the Car to have full fidelity of telemetry resulting in the full range of feedback. Then Adjust the SimuCUBE strength as needed to get the feel you want as far as strength… you can leave this the way it is for every car in iRacing and the cars will adjust to their relative strength based on their telemetry model (IE this is a set it and forget it type of thing. At this point though if you wanted to slightly increase output fidelity and intern strength you can then use the slider at lower settings to increase car feedback strength (just know the lower you go the more likely you are to clip the cars… I would not suggest going lower than about 35 in most cases as that is about the point that most of the GT cars clip… The Indy cars are much higher…
So basically my suggestions are as follows:
#1 - Increase your MMC in granity to the full 12.86A - Tomo short sets the MMC to 12 which reduces Max output to about 18.5Nm using 12.86A will give you the full 20. You can find a .drc to do this through the Motor, Encoder, and Centerpoint Wizard in the iRacing Hardware forums in the Firmware Settings and Information thread… http://members.iracing.com/jforum/posts/list/3573261.page#10702255
#2 - Set your iRacing slider to about 55Nm then adjust the Simucube strength to meet want you want use. IF you hit 100% and still want more strength then start lowering the Nm in iRacing. Note this will lower the point at which clipping will occur.
As for settings in that same thread a little further down I have the settings that I used when I was testing the Small Mige posted I tend to use a bit higher strength than many but at the same time my setup of the wheel is a lot less lively which means you can run higher strength longer without being beat up as much with the spikes that come from running low to no filtering.
One thing of note though with the iRacing Indycars… the base Setup they use for Road racing the cars is built around lower output wheels. If you are in an open set-up situation you can do the one change that the Real drivers supposedly run with that completely revises the steering feel and that is to change the steering pinion from the 8 tooth to the 6 tooth. This ONE change will reduce the telemetry steering output by around 30% which will then actually allow you to reduce the Iracing slider further without clipping the car.
Overall though in regard to changing strength and which method is better it really depends on the came… Because of the detriments to iRacing and the Telemetry output Range with iRacing I am under the opinion that leaving the SimuCUBE as close to 100% as you can get with the Slider set to cover the range of the car you are using or greater (up to about 65Nm) is the best method… For other games this might be different BUT I also like setting and forgetting so I am not one to change strengths or profiles all the time either.
Also in that thread linked there are a BUNCH of other different set-ups you can try. one thing to remember though is that Filtering does change feel a bit when reducing power levels so a setting set like mine if you run it at a lower power (Higher Nm or lower SimuCUBE %) it more than likely will change feeling and become even less lively… In this case you may have to make some adjustments (lowering Damping, Friction, ect)…
BTW last note… with the IndyCars they will naturally oscillate due to the tight steering parameters of the car in iRacing and the inherent instability of FFB - so basically you need to keep at least one hand on the wheel to naturally dampen the movement.
EDIT… Just looked at the picture… If those are your settings then you have already upped the MMC and I would suggest NO inertia (small mige doesn’t need help in moving) and I was actually lower .75% on friction and a little higher on damping 2.25%