The T.H.O.R.P. System is the most realistic brake system ever made for sim racing. In any given racecar, the brake pedal is always hard. A hard brake pedal is faster (you can brake later) and it is required to proper trail brake and use your muscle memory to do so, as explained later. You can consider a racecar braking system as 2 stages:
The “soft stage”: When you apply pressure on the pedal, it will move 0,39-0,79 in (measured on the pedal plate), while you build up pressure, while the caliper pistons are traveling to and pushing the brake pads against the brake disc, and to compensate for the small amount of play in all the mechanical parts on the pedal system that is required for them not to seize up.
The “hard stage”: When hydraulic pressure is built up, the brake pads are squeezing the discs hard and all mechanical play is compensated. In this stage, your foot is basically “pressing against a wall”, because now your muscles are pressing directly against the hydraulic forces (the brake fluid). Since the fluid cannot be compressed, you will feel the pedal is hard. When a racecar driver complains about a “long” or a “soft” pedal, it is typically because there is air in the system, and since air CAN be compressed, the pedal will feel soft and long. The mechanics then bleed the brakes for air, meaning there is only fluid left in the system, and the pedal is once again hard after passing the “soft stage”.
In our quest to mimic the perfect racecar feel, we also designed a 2-stage system on our Invicta™ pedals with the T.H.O.R.P. brake cylinder:
The “soft stage”: Since we do not have a brake disc, caliper and brake pads in a simulator, we made the slave cylinder to mimic this. The slave cylinder is compressing an elastomer, and like in a real racecar, it will allow a pedal travel of maximum 0,79-0,98 in measured on the pedal plate. When full pedal travel is obtained, the slave cylinder will hit a mechanical stop, just like in a real race as described above. We supply different elastomers to mimic different feelings of the “soft stage” but the different elastomers will not change the pedal travel, only how much force that is needed to fully depress the pedal and engage the “hard stage”.
The “hard stage”: When the slave system is mechanically locked, you have 100% the same feeling as in a racecar, when the brake pads are fully pressed against the brake disc, and your muscles are pressing directly against the hydraulic forces. This is NOT simulated, this IS the same and identical feeling as in a racecar, and you can keep pressing the pedal up to a hydraulic pressure of 100 bar, which corresponds to 408 lbs of pressure on the pedal plate – the same as a real F1 car!
Besides from being able to calibrate and measure the pressure in bar, the 2-stage system is exactly the benefit you will get over a mechanical brake system. Most mechanical brakes are relying on the elastomers and a load cell to give you the racecar feeling. It will never be the same, because it is NOT the same! A load cell system IS a simulation and at best, you can implement a mechanical stop to simulate the “hard stage”, but unlike the T.H.O.R.P. system, your pressure readings in the simulator will also stop at that point, because your load cell will stop to physical deflect. And without deflection it will not meassure. In the T.H.O.R.P. system, pressure readings will continue despite the
slave cylinder has reached its mechanical stop (passed the “soft stage”). THAT is the Asetek Invicta T.H.O.R.P. hydraulic difference!