Steering Torque Capability
Emery has covered the detail above, but let's put some numbers on it so we can see what it does and when to (not) use it.
Let's say we have 2 cars:
- A: Track day car, light, quite narrow tyres, no downforce to speak of. Has a nominal max steering torque of 9Nm.
- B: Modern formula car, big tyres, lots of downforce. Max steering torque around 25Nm.
Note: Nominal max for each car is chosen based on 'normal' inputs. That usually won't include things like a 45° kerb strike at 320kph, since that would generate huge forces and everything else would pale in comparison. This nominal max is actually an important parameter to get right, the recent Reiza bundle just had adjustments in this area to help the content better compare to the existing rF2 content.
In each of those cars the game scales the calculated steering torque in accordance with the nominal max value. So assuming your wheel does 4Nm, if car A has a current steering torque of 6Nm, the game can see that's 66% of the car's maximum, so it outputs 66% FFB to your wheel, which then produces* 4 x 66% = 2.66Nm. If that same car produces 9Nm at a particular moment, your wheel will go full power and produce 4Nm; if the simulated car produces 12Nm because of an unusually large deviation or impact, your wheel will still produce 4Nm (it can't go any higher).
*how much force your wheel actually produces we'll get to in the second section
This is all fine, and generally how things work with normal consumer wheels. Whether you jump into car A or car B, you will experience a range of forces (depending on the situation) ranging from 0 to 4Nm at your wheel, based on where things currently are in relation to each car's maximum. Let's step it up a notch.
You go out and buy a 25Nm direct drive wheel. Fantastic.
You drive car B, and it's transformed. You're feeling the actual forces the (simulated) car is generating; road surface + tyre + steering geometry produces 5Nm? You can feel it. High speed cornering producing 22Nm? You can feel that too. Your wheel matches the car and you're 1:1 with what you'd feel in real life (excepting game inaccuracies).
What about car A? Well, not so good. Those calculated forces in the range 0-9Nm (in the car) are now stretched over 0-25Nm by your wheel. You catch a lazy slide, overcorrect, the car rocks back and instead of the solid 5Nm you'd get in reality your wheel is hitting you in the wrist/jaw with nearly 14Nm. Driving a passenger car is like doing a workout, and if you think you're going to nudge anything you better take your hands off the wheel or you could injure yourself.
Solution? You could adjust the vehicle-specific FFB Mult down, so the forces better match reality. Hope you know what sort of forces you'll encounter so you can get the right value. And then do that for every car, occasionally forgetting you haven't yet and getting a shock when you jump in.
The better solution? Change Steering Torque Capability to 25. In car B (or anything with even more force) the game will let you feel the full power of your wheel. But jump in car A and the game can see its nominal maximum is only 9Nm, 36% of what your wheel can do. It will then scale all forces by a factor of 9/25, so you feel everything correctly in car A without needing to change anything else. (added bonus: higher forces that would have been lost previously [ >9Nm], are now sent to your wheel)
Any car with a higher nominal max than your wheel can do, will get scaled 0-100% like before. Anything lower will be scaled down so that it produces correct forces, instead of being too powerful and not matching reality.
What happens if you adjust this parameter with your consumer wheel?
As above, if you set it to 4 nothing will change. I think there are no cars in the game that produce a maximum as low as 4Nm, so the game will continue to scale everything to your wheel and all cars will potentially produce your full 4Nm at the wheel, but generally a little less (so you can continue to feel detail).
If you think that cars scaling sounds like a good idea and put it on 25, your wheel will produce 4 x 9/25 = 1.44Nm in car A
at full power. Most of the time somewhat less, sometimes a lot less. Now you can barely feel any detail, and overall forces are weak.
So: if you have a powerful wheel and want cars that should feel lighter than your monster wheel to actually feel lighter, set the Steering Torque Capability to suit your wheel. Otherwise, leave it.
Steering Torque Sensitivity
First, this defines the way the range of 0-100% force is scaled to your wheel. The standard is a straight line, so 50% maximum force (in the car) is given to you as 50% strength at your wheel (assuming 100% is full force from the car; these are all intertwined a bit). If you raise it, 50% in the car will produce more force at your wheel, and the opposite is true for lowering it. So higher sensitivity will give you generally more force, lower will generally produce less force, while in both cases not changing where 0 is and what 100% means. (same concept as the input axis sensitivity in the game)
There are two main reasons to adjust this:
- To change the general level of force,
- To correct shortcomings in wheel behaviour.
The first is as described above: if you have a weak wheel, you might find that during mid-corner with mid-level forces you aren't really able to feel changes as you lose and gain traction at either end of the car. By dialing up the sensitivity you can give yourself more force (and therefore bigger fluctuations, easier to feel) in normal situations, while not losing detail up near 100% because you haven't simply scaled all FFB up (though it will flatten out a bit, so it's personal preference on what sort of compromise you'd prefer). Lowering sensitivity to adjust overall FFB probably isn't as common by itself, and certainly not with a consumer wheel.
The second reason is a topic of much debate. There's a theory that your wheel doesn't produce forces in a linear manner. The game might say 50% but your wheel doesn't produce 50%. Maybe it's only producing very low force at lower percentages, and doesn't catch up until you reach full force (so all intermediate forces are too low). Or it might try too hard to give lots of power up the top and make 90% hardly any different to 100% (at your hands), making it difficult to discern details at high loads.
There was a program made which pushed the (unloaded) wheel with varying forces and measured how quickly it moved, and used these results to produce a graph of wheel linearity. By careful analysis of that graph and adjustment of the sensitivity and other parameters (like minimum torque, effectively raising the 0-level of your wheel) you can make it more linear and give better awesomeness in its feedback. In theory.
On the other hand, electric motors (which wheels usually have) tend to be quite linear when static, as they're based on the principle of induction. Half of full power will produce very close to 50% of full force, much closer than suggested by the aforementioned program and probably close enough that you won't feel any difference. Note this is when you're holding the wheel still.
In practice, you'll generally be holding the wheel but it'll often be moving a bit. The wheel's response may change in that scenario in comparison to holding it still, though how much is anyone's guess (I've seen a static test, but I don't know if anyone's gone to the trouble of measuring a moving wheel's response - and this would be motor dependent, so there's not much chance you could find someone testing your wheel so you don't need to).
In my opinion, for hands-on driving, the wheel's generally moving slowly enough at times when you want to feel the forces that just leaving the wheel (and sensitivity) as-is will probably suffice. If you have a fast responsive wheel and do a lot of drifting, and want the wheel to rotate properly, you may want to look at that program (it's called Wheelcheck) and adjust the sensitivity so that its 'free' movement is closer to reality.
If you feel that FFB forces tend to be too weak on your wheel, and increasing overall FFB doesn't do enough (make sure you don't go too high, or you will lose detail at high forces which isn't any fun), you could try increasing the Steering Torque Sensitivity so that your wheel feedback is generally stronger.
While you're there, consider adjusting the minimum torque (that one's in the game, too) and see if that improves your feel.
Wow, that got a bit lengthy. Sorry about that.
