Tyre friction/interaction with road surface

[Lazza]

What we're talking about is the dropoff in torque as you start to understeer, yes? We're not talking about the difference of one STS value to another.

Of course. I'm just saying that having lower STS will make a drop in force, that started somewhere in the higher end of FFB, more apparent, because the change (delta) will be bigger.

With 1STS it'll feel like the dropoff almost never happens, with 0 STS, it'll feel like the dropoff happens almost immediately. This is obviously just due to the change in linearity, but essentially it is also a change in the timing of that dropoff relative to vehicle behavior.

... I can easily feel the change in the dropoff when i change the STS for example, but again, it's not in the amount of torque that it happens, but in how soon it happens relative to vehicle behavior, that's why it's easy to feel it, since i can correlate it to what the car is actually doing in the corner. It's not that hard to correlate when you're going into a corner and you feel the steering start to lighten, VS going into that same corner at roughly the same speed with relatively the same amount of steering angle, and the weight still remains without dropping away, or dropping away much later into the corner, it's actually very obvious.

Regarding the first statement, it just sounds to me like you're feeling the extra FFB dropoff as a faster response - because the FFB is obviously dropping faster, as it's dropping farther. (e.g. 80%->70% might become 80%->60% with a low STS - so each time period there's twice as much change). That faster rate of change makes it easier / quicker to feel, hence the suggestion to lower STS to help feel it. (once you add in driver reactions all bets are off - if you perceive it better you'll catch it quicker, and it never drops as far, etc)

Second paragraph, and labouring the point on feeling 0.001 change, as you say roughly the same speed, relatively the same amount of steering angle - the error (in a scientific sense) in your controls lap to lap completely dwarfs the miniscule change to STS you're talking about, which is why I doubt - even if you are exceptionally dextrous - you'd be able to spot it in blind testing. Obviously the 'let go of the wheel at constant speed' test is another matter.

 

[green serpent]

I tried the Honda NSX and the USF2000 with an STS of 0.1. I drove them in the rain at different ffb multi values (0.60 & 1.0). I couldn't for the life of me feel a drop in torque during various amounts of understeer. I would think that in the rain, once the front end has lost grip, there would be an obvious change in steering weight. From what Paul has said, I'm sure there is some difference, but nothing that I can perceive through a g27. It really doesn't effect my driving too much, because I've come to know pretty well when I'm understeering, but it kind of breaks my suspension of disbelief. Next time it's raining I'll be sure to do a huge understeer around a corner, see what it feels like and report back my findings (just joking).

 

[Lazza]

Rain actually might not help much, because your peak force will already be lower. (I have done what you said in the rain by the way, could feel the drop and then a chattering as the tyres skipped across the tarmac - roundabouts are good for something )

You can definitely feel it with a G27, but it is less obvious when you have higher caster in the setup because it keeps overall forces quite high despite the tyres sliding.

 

[unknwn]

I know what the curve does and how it appears, it doesn't change the fact that i still feel hardly any difference in this drop off in feedback when understeering relative to the rest of the feedback regardless of the STS value, since this effect is near the middle of the range so the relative change isn't very dramatic. We're not talking about going from 1STS and suddenly switching to 0STS while in the middle o driving. When you're driving with a constant change in this curve, the drop off in feedback in the way that was described earlier would still be a very subtle difference, what changes is the overall feel and response of the torque levels.

I'm positive that if you go from 1STS to 0STS then you'll feel a big difference in every way i'm sure, and the way that drop off feels would probably also be very different as long as you're using the same FFB multi. However, that's not what's being done, you can only relate the feedback to what's happening before and after a certain point that you're feeling for in the moment that it's happening, it's not switching to a lower STS only when you want to feel this drop off.

I have T300@75% force (which has inbuilt compression). Changing STS to 0.7 (which kind of negates inbuilt compression) in rF2 changes the the understeer feel from barely feeling anything to "wow, i can feel the car". The wheel has only few nm torque, yet the difference is great.
Setting 0.3STS provides even greater feel of understeer (or any other forces) at upper range, however that improvement is not worth loosing feel of the lower end forces, at least on my low torque wheel.

 

[Lazza]

If you actually adjust the FFB multi so that the two different STS settings are producing roughly equal amounts of torque, then you shouldn't feel a huge difference between the two, not only that but you probably won't see a big difference in the pedal overlay plugin either.

So every time you adjust STS, you're adjusting FFB? What makes you think anyone else was talking about doing that?

If you're adjusting FFB so that your 'normal forces' are around the same, with varying STS levels, trying to work out the relative effects of the different STS slopes is a more complex exercise. Bearing in mind 100% with STS 1 is exactly the same as 100% with STS 0 - when the FFB mult isn't changed. Literally everything I was saying regarding STS was just changing the STS, just like the original suggestion (which you were questioning) meant to just change STS. 90% of your oversize posts just became completely irrelevant in terms of what I was talking about.

 

[Joe]

For estimating STS for realism, one may plot the Steering shaft torque vs lateral-g, the slope is called "STG".
For BMW 116i, is about 5.9 Nm/g:
https://pdfs.semanticscholar.org/be76/5954e4119af3aa258d2e3b3622ff63d19f70.pdf
(see fig 3 in the paper).
I had old Corvette GT data (with STS=1) and plots shown STG is about 9 Nm/g. it is about 1.5x of the real BMW.
If I want the Corvette to be like this BMW, I would lower down the STS to 0.66 (1/1.5= 0.66)

Just a thought.....

 

[Korva7]

Joe i think you should change ffb multi, instead of STS to do that.

Here's picture about what STS does. Lowering sts will amplify torque changes on higher force levels.

 

[unknwn]

I wasn't implying anyone was talking about it. I'm adjusting the ffb multi so that the weight during the point of this understeer dropoff is similar between sts changes. How else would you distinguish the difference between overall steering weight change vs the change in this dropoff point if all of the forces are completely different between the changes?

If you're saying the sts changes the weight of the wheel then that's common sense but still doesn't mean that the particular effect during understeer alone is more dramatic with a lower sts.

It literally means that understeer effect (or any other effects will be pronounced - spiky/peaky) at upper force output range and more numb at lower end when setting lower STS but leaving same FFB multiplier.
This is the first time I have noticed you mentioning to change FFB multiplier when adjusting STS, which now gives a different perspective of what you telling.
Either way adjusting both STS and FFB mult should provide quite different final output. I imagine above STS graph by Korva7 where low STS has increased mult, and high STS has decreased mult, the low STS curve would still look more progressive except that top part will be clipped off because of higher mult.

 

[Joe]

Joe i think you should change ffb multi, instead of STS to do that.

Here's picture about what STS does. Lowering sts will amplify torque changes on higher force levels.

No, I dont think so. The FFB muliplier is physics-less (scaling paramter).

 

[Korva7]

But if you want to lower the force you get in cornering to 66% from the original, shouldn't you frop ffb multi from 1.00 to 0.66?
If you drop STS to 0,66 the cornering force doesn't necessary drop to 66% from original force.
If you are at 100% ffb output in certain corner, dropping sts doesn't change the force you get in that corner at all.

 

[Euskotracks]

Yeah that makes sense, but that's just not what I'm seeing in the pedal overlay or feeling. I've already said that probably there is some difference, but my point was that i can barely distinguish the two different sts settings even when i actually do increase the ffb multi with the lower sts to reach up to the 90% ffb range so that it matches the higher sts. That's where the difference should be biggest and i can't really feel the difference with my AF, yet it's supposed to help someone with a G27. I can barely see the difference in the overlay too so most likely this drop isn't significant enough in the first place to really feel it any better by adjusting the ffb settings.

It may be because the forces only are leveling off, rather than dropping at all. then it would feel very similar for different sts values. That's why i asked if Eusko had telemetry to show what was actually happening within the physics during this behavior, to which he said he didn't need it, even though he was the one emphasising the use of said telemetry to understand what is really going on under the surface.

If you reduce STS to increase the torque drop when losing grip, is beacuse that situation was occurring at high FFB levels where STS will have the desired effect. If when doing this you need need to adjust FFB multiplier, you are certainly doing it wrong. You need to maintain average FFB level to notice the effect.

The initial STS=1 situation should close to but not higher than clipping state. Without changing anything else but STS you should feel higher drop with lower STS values.

I think Lazza already explained this in other words some posts earlier...

 

[Joe]

I thought we already addressed this issue last year. In classic or real case, a racing tire does have a peak friction coffi at about 8-12 degree of slip angle. hence one will feel ffb drops after that angle. But, in rF2 new tpre model, they no longer use slip angle as variable to model the friction coffi curves. I posted data seemed suppot this finding....no such peak, except the 2-3 degree peak which is due to self-alig-torqe.

 

[fsuarez79]

I'm experiencing the same problem but with a T300RS.
Ironically, I had a Logitech G920 and the FFB on rfactor 2 was spot on. I could feel the tires at all times with any car at any track (high and low forces) however my paddle shifters started acting weird so I decided to order a T300RS and no matter what I change in the wheel profiler and the ffb in-game settings, I can't feel the road at all with the T300RS except when doing tight corners. All the low forces are gone.
I'm using the FFB overlay plugin so I know I'm not clipping. After reading this post I increased the STS but that didn't make any difference either.
Funny enough, Automobilista with the T300RS now feels like rfactor 2 used to feel like with the Logitech, but I like rfactor 2 much more so I'm about to return the Thrustmaster to the store and go back to my faulty Logitech.

 

[fsuarez79]

Have you tried testing the linearity? I'm not sure how either of those wheels you have work, but i remember with the T500 if you increased the total strength in the control panel settings, then you would create a very non-linear FFB, where the strength would start dropping near the peak, and if you looked at it in a graph it would look like a hill where it steadily gets less steep towards the top. It was basically the opposite near the bottom. The best compromise was usually around 70-75% if i remember correctly.

You could try what's explained in this thread: https://forum.studio-397.com/index....actor-2-the-key-to-being-in-the-zone-d.42931/

Yes, I did read it and actually I used that wheel profiler setup to begin with (60%). I couldn't feel any low forces so I increased it gradually up to 85% but the wheel just kept feeling harder and harder to turn but low forces were still missing.
I remember when setting up the Logitech, the big game changer was the "FFB Minimum torque" (which I had at 8% with that wheel) but I tried a range from 0% and all the way up to 25% with the T300RS and with some settings it feels better than others but still no low forces and the ffb feels completely fake (unlike the Logitech).
I'm pretty sure the problem isn't the wheel but me not being able to set it up properly but I can't think of any more settings to play with.

 

[fsuarez79]

That sounds a lot like what i was experiencing with the T500. I was constantly holding the steering back instead of letting the self aligning torque more or less work itself like a real car. The only thing that helped was to lower the STS, not increase it. Increasing it makes high forces even more exaggerated and low forces would make up a much smaller portion of the total range of forces.

So, maybe you should try to lower the STS? Just a guess.

No harm in trying. I think that's the last thing that's left for me to do....if it doesn't work, it'll be going back to the store!! I'll try it when I get back home.
Thanks a lot

 

[Lazza]

Higher STS (above 1) would boost lower forces, but I'm not sure that's the best solution (certainly isn't a root cause). Have you turned FFB smoothing right down?

*But definitely keep the control panel at default (60%?), otherwise you start correcting corrections...

Out of the box the general forces should feel pretty strong, so something's definitely not right. Try a fresh player folder?

 

[Lazza]

When i'm driving the USF2000, the FFB through those S's at Suzuka: With STS at 1, the peak cornering forces were producing FFB% of up to 90%, possibly even more. When i drove those same corners with my STS set to 0.272, those same cornering forces were only producing about 45-50%, maybe close to 60% FFB.

Question is: if you then raise your FFB Mult, what happens to the 90% 'flat' (STS 1.0) forces? An FFB Mult of 1.11 makes 90% -> 100%; a higher Mult will make 85% -> 100%, next step 80% -> 100%, etc. Peak cornering forces are now clipping. Does STS help? Depends how it works... if it maps incoming 0-100% values to new 0-100% values, then as you say yourself all those new 100% values will end up all still being 100%. In other words, by compensating for very low STS with quite high FFB Mult, you can actually create clipping in forces you'd like to be feeling. If it works that way.

 

[Boldaussie]

A very simple way to test if caster is applied correctly in physics or not , which is readily apparent with as little as one degree difference in real life, is to simply run one side at maximum and the other at minimum and drive the mod. The vehicle should want to always steer towards the minimum value on a straight and level surface and more so under braking condition..

The same will apply to see if camber is applied in physics. Ensure caster is set to equal values and simply make a degree or more camber difference between sides and the car should pull to the closer to 0 degree camber side under a braking condition.

From my experience the camber is usually correctly modeled by mod physics, caster is not aside from giving a different ffb feel. Caster does far more than just give a heavier feel. Caster in combination with SAI is largely responsible for camber change on turns giving positive camber on the inside tyre and negative camber on the outside tyre.

Most mods also strangely run anti ackerman and in combination with caster induced camber change, this should reduce to almost nil inside edge wear on the inside tyre in turns and this is rarely true.

 

[Joe]

no friction coffi peak on oversteering found on rF2 tyre model, data from corvette gt new car:

It seems no ffb peak and drop corresponding on this regard, except for self-align-torque at 2.5 degree (note: a light peak at 12 degree need some one to validate... could be true if that can be repeated):

you would not experience a feel on ffb as a real car on oversteering (if the peak at 12 degree shown above was due to other effects, like bounced/drop by hitting sideway or epex, etc):

 

[fsuarez79]

Higher STS (above 1) would boost lower forces, but I'm not sure that's the best solution (certainly isn't a root cause). Have you turned FFB smoothing right down?

*But definitely keep the control panel at default (60%?), otherwise you start correcting corrections...

Out of the box the general forces should feel pretty strong, so something's definitely not right. Try a fresh player folder?

I played with the settings again yesterday for about an hour (wheel profiler, STS, FFB minimum torque, individual car FFB, smoothing always zero) and I never found a setting that made me as happy as I was with the Logitech in terms of realistic feel and tire friction.
I decided to plug in my G920 again and I was even able to dial it in with Automobilista and R3E. It has also decided to work fine these last couple of days (was having issues with the paddles not working for a matter of seconds or switching functions at the middle of a race. Not really a hardware issue, more like a software issue) so as long as my G920 keeps working I'm happy with it. I already packed the T300RS back again and returning it to the store later today.
Thanks for the help