Adjusting Sim Pedals/Realism

[Deleted member 197115]

Discuss

 

[BrightCandle]

Which was inspired by this video from Karl Gosling

 

[blekenbleu]

In a real car, my left foot is mostly braced against a dead pedal,
to counter G force that otherwise confounds threshold braking accuracy,
motivating dead pedal addition to my sim pedal set.
Harness tensioning very much helps as a proxy for G-force braking feedback,
along with wheel slip tactile effects.

 

[Daniel R.]

I know from a race driver, that in an LMP2 he has around 50-60mm travel at max ~800N (~80Kg) of pedal pressure.
Especially the travel is very different to what a lot of smart sim racers think is correct....senseless discussions are mostly the result....

 

[Deleted member 197115]

The thing is that these 800N feel completely different in sim rig and the car.
In race car after brake is initiated the G-Forces push driver forward assisting with brakes, trying to simulate this pressure in home pedals you are just exerting yourself and breaking seat mounts without getting closer to reality.
Another thing I've learned recently is that F1 are using brake by wire for some time now, which allows driver to adjust brakes to their preference, resulting in softer pedals with more travel, times when they were hard as a rock are gone.

 

[blekenbleu]

brakes by wire

Another opportunity for thumb encoder tweaking.

 

[Emery]

There are many items on a car that affect brake feel (assuming brakes are properly bled):

• brake booster vs. no brake booster
• reinforced rubber brake hose vs. teflon hose in steel braid
• distance pads/shoes have to move before contact is made with disk/drum
• hardness of the pad/shoe at the current temperature

 

[Enzo Fazzi]

The thing is that these 800N feel completely different in sim rig and the car.
In race car after brake is initiated the G-Forces push driver forward assisting with brakes, trying to simulate this pressure in home pedals you are just exerting yourself and breaking seat mounts without getting closer to reality.

While this is true to some extent (G-forces will make up somewhere between 5 and 20% of braking force), it is no where near as much as people think it is. You're strapped in tight and you and the car are decelerating at the same rate. F1 drivers we worked with say that using 120KG with our Ultimate pedals is a good exercise for what it feels like in the real thing.

Another thing I've learned recently is that F1 are using brakes by wire for some time now, which allows driver to adjust brakes to their preference, resulting in softer pedals with more travel, times when they were hard as a rock are gone.

Current F1 cars have a brake-by-wire component, but it isn't a fully digital/electrical system. The pedal is still hydraulically connected to all four brakes, with seperate master cylinders for the front and rear. The front brakes are solely a traditional hydraulic system. The rear wheels get slowed down by 3 components; The brakes, engine braking from the ICE and regenerative braking from the electric motor.
To keep the car balanced, these 3 need to be dynamically regulated (also ICE and regenerative braking changes throughout the race/lap anyway, depending on what the driver needs/wants).

A pressure sensor in the brake pedal will relay to a computer how much the driver wants to slow down. The computer calculates how much brake pressure needs to go to the rear brakes and a valve at the rear master cylinder (similar to ABS systems) will open and close accordingly.

Brake pedal feel (travel) gets changed to what the driver prefers by swapping out parts of the hydraulic system. This is not the same throughout a season, as drivers typically prefer a different feel for Monaco than for say, Suzuka.

 

[Deleted member 197115]

While this is true to some extent (G-forces will make up somewhere between 5 and 20% of braking force), it is no where near as much as people think it is.

Enzo, thanks a lot for the insight.
Doesn't F1 during hard braking generates around 5G force pushing body forward, I would expect that this can contribute to more than just 20% of braking force. Also video in original post, not sure if you had a chance to view it fully, has feedback from pro GT and Formula drivers discussing difference in brake force generated by muscles alone in sim rig vs supplemented by G-force in car during braking application.
One way or another, it's definitely not 1:1 as many might think and you don't have to pump sim rig brakes at 1 ton pressure to get realistic F1 car feeling.

 

[Enzo Fazzi]

Enzo, thanks a lot for the insight.
Doesn't F1 during hard braking generates around 5G force pushing body forward, I would expect that this can contribute to more than just 20% of braking force. Also video in original post, not sure if you had a chance to view it fully, has feedback from pro GT and Formula drivers discussing difference in brake force generated by muscles alone in sim rig vs supplemented by G-force in car during braking application.
One way or another, it's definitely not 1:1 as many might think and you don't have to pump sim rig brakes at 1 ton pressure to get realistic F1 car feeling.

It pushes most of your body into the belts. At best, it'll only be the weight of your left leg and even then, it's not all of it.

The adrenaline of being in a racecar will do a far better job at making the brake pedal easier to push.

 

[RasmusP]

You could say that the big difference between simracing and real racing is that you're not pressing yourself into the seat while braking, but instead only lifting your body from the belts?

Must feel very differently for the body. Not for the leg, ofc.

At 4G and 70kg driver weight, you won't push yourself against the backrest until reaching 280kg brake force

 

[Deleted member 197115]

Anyone with pro racing experience at least GT level, not sports car track days, can confirm or debunk info in the video.
I'd say mechanically and physically it must be quite a big difference between just keeping your leg tense when it gets pushed by inertia of the body forward or actively extending it using muscles to generate force.

 

[RasmusP]

I'd say mechanically and physically it must be quite a big difference between just keeping your leg tense when it gets pushed by inertia of the body forward or actively extending it using muscles to generate force.

But that's not how Enzo said it would be and also not what I said.
Or am I misunderstanding you?

If you move 3cm forward under braking until the belts stop you, you can only press the brake by 3cm until you'll have to actively use your muscles.

The leg doesn't know the difference, it has to extend actively.
Your upper body though will get pushed against the backrest in simracing but will hang in the belts in the real car.

Basically while simracing, you're laying on your back with the brake pedal above you in the air and you have the press it.
In the real car you're hanging in a harness above the floor with 2 people sitting on top of you and the brake pedal is on the floor.

Your leg has to actively extend in both cases and won't know the difference. Your body isn't moving. At least it surely won't in F1 and high level GT racing where you're strapped really tight into the belts.

 

[Deleted member 197115]

Only leg itself is 5 times heavier and there is no harness to stop it, and even harnessed body moves significant enough distance to cover pedal travel.
Would be really interesting to hear from practitioners, like in OP video, we can theorize all day long.

The way I see it, driver starts braking extending his leg covering initial "soft" portion of pedal travel, car starts decelerating creating G-forces pushing body forward (whatever the distance harness allows) assisting in the final few cm of pedal travel that gets progressively heavy. Leg gets heavier too, helping with effort as well.
Plus as most race pedals have relatively small travel distance, it's mostly pressure on the pedal itself, not the movement that creates braking force, so we don't need a lot of harnessed body movement, but there is always will be some regardless of high tight you fasten it.

 

[stigs2cousin]

As stated above I´m not qualified to post her since my experience is limited to a (my personal ) sportscar although equipped with semi slicks and upgraded brakes (Ferodo DS1.11, DTM level according to Ferodo)

and an older Touring Car, (E36 with race slicks, containment seat and 6p harness)

In both cases you feel the deceleration forces on your chest belts, your butt stays glued to the seat bottom.
That what the contour of the seat bottom and the lapbelts are for.

I also don´t remember my leg elongating or detaching, so the additional forces onto the brake pedal should be limited to the extra foot movement caused by the deceleration forces.

The whole body moving forward is even more improbable in a formula position:

MFG Carsten

 

[stigs2cousin]

And on the topic of brake travel:

I really like the feel of "kicking the brick" but drive way better with a measurable amount of brake travel, especially at corner entry.

Since aquiring the new brake rubbers for my Sprints I´ve twice changed to a softer setting and am now in my happy place with aprox 15mm travel.

MFG Carsten

 

[RedBull48]

And on the topic of brake travel:

I really like the feel of "kicking the brick" but drive way better with a measurable amount of brake travel, especially at corner entry.

Since aquiring the new brake rubbers for my Sprints I´ve twice changed to a softer setting and am now in my happy place with aprox 15mm travel.

MFG Carsten

I had a very similar experience with my sprints using the new elastomers. I also find them much easier to modulate.

 

[Deleted member 197115]

On Simtrecs I've found happy medium between too hard and too soft using their "Sportish car" settings with medium 15mm elastomer, it's like half way between Sport and Race.

 

[Deleted member 197115]

Found interesting study on brake pedal stiffness effect on driving performance.
Short conclusion, it's a wash, drivers adapt to whatever is thrown at them.
One excerpt from the doc

Finally, the simulator fidelity needs some discussion. Although the
characteristics of the pedals as well as the vehicle models were realistic and
representative, there may have been unrealistic aspects to the driving simulation as
well. In the real world, decelerations induce an extra pedal force as a result of the
mass of the driver’s leg.

And few quotes from Quora

I’m a physics grad and have raced up to Formula Renault, which is around 2–3g tops. In theory, yes, but the harnesses holding your pelvis and torso, plus the way you sit, with bum lower than knees, means that only your leg weight, nothing more, is assisting pushing the pedal. It’s not an effect I’ve noticed, although it is a conscious (although small) effort to hold your legs upright in corners, so there is something going on. If you drive a single seater like a road car, your legs flop from side to side as you corner.

F1 cars and Indy cars generate up to 6 Gs when braking. That means a leg plus pants leg and shoe must experience around a hundred pounds of force on the pedal just from momentum. I know that it takes around 250 pounds of pressure to apply the brakes of an F1 car and I think that's because the driver would otherwise have a hard time modulating the brakes coming to a high speed corner because of the G force.

And from some old discussion on this very board.

Don't know if true, I was told once that in real-life (open-w / proto / gt) they reach these pressure numbers (like 150kg) only under high speed braking where the gforces are actually helping by making the leg weight more. If someone could confirm that...


Yes, we had that discussion somewhere before. G forces help to put extra force in a real car (or a kart) when braking, unlike in a fixed home seat+pedals.

I personally see little point in anything over 50 kg, more than that starts to turn driving into a gym session.

 

[Deleted member 1066209]

And on the topic of brake travel:

I really like the feel of "kicking the brick" but drive way better with a measurable amount of brake travel, especially at corner entry.

Since aquiring the new brake rubbers for my Sprints I´ve twice changed to a softer setting and am now in my happy place with aprox 15mm travel.

MFG Carsten

Yep, I'm also much faster with a softer pedal that has more travel. My immersion is ruined, but the lap times take precedence.