When driving in competition experienced drivers use the brakes for far more than simply stopping. Although use of the brakes always slows the vehicle the pilot of a race car also uses the brakes to shift the weight of the car and thus affect the the turning radius, suspension behavior, and to reposition the wheels of the car when the wheels have broken traction. To this end the driver may use either the pedal (acting on all four wheels) or the handbrake (acting only on the rear wheels) In addition to this pedal or handbrake choice the bias (pressure ratio) between the rear and front wheels may be adjusted through the use of a proportioning valve (for systems with a single master cylinder) or a "bias bar" for systems with separate front and rear cylinders. This adjustment can be critical for maximum braking performance because changes in the suspension and tires as well as conditions on the road affect the optimum brake pressure bias.
Why is a new system needed? A new system of intuitive brake control would reduce the complexity of the current foot/hand system by allowing the driver to actively modulate the bias of the brakes by rolling their pressure on the brake pedal itself. It would also allow for compound braking maneuvers that were formerly clumsy or impossible. For example with the current setup a driver entering a gravel hairpin fast must brake hard, release the brakes to steer into the corner, handbrake to induce oversteer, release to regain traction and swap to the accelerator to maintain oversteer. With the new system the driver would brake hard with their foot in the conventional position to slow then shift the pressure on the pedal to their toe "rolling the pedal forward" (as if it were mounted to the floor) this would shift the brake force away from the front wheels increasing their steering force while increasing the force on the rear brakes, locking the rear wheels and forcing the car into an oversteer skid. Once the desired degree of skid is achieved the driver may relax the toe of their foot restoring normal brake pressure or return to acceleration. In this way an extended into the corner skid transitions smoothly into a drift without the driver taking their hand off the wheel. The need for dramatic jerks of the wheel is reduced as is the amount of road required to flick the car around a corner is reduced.
What are the basic parts of the system? The system is assembled in two parts, the first is a pair of master cylinders stacked atop one another rather than side by side as is the usual arrangement. Each has its own rod and linkage acting independently. The second part of the system is a modified brake pedal. This pedal is taller an lies somewhat lower than its conventional counterpart. Force applied directly to the center of the face of the pad places direct pressure on the fulcrum of the bias bar, the position of the fulcrum being adjustable for the purpose of adjusting static brake bias. When pressure is applied to the upper portion of the pedal it pivots slightly increasing the pressure on the upper rear brake linkage this is allowed to the point that application of pressure to the upper third of the pedal will only apply the rear brakes but is limited such that a forceful application of the brakes brings both circuits into action. The action of the pivot is such that the degree of bias induced by pivoting the brake pedal is defeated when the brakes are forcefully applied (driver is stabbing the pedal brutally to lock the wheels, all the wheels should lock even if they hit only the top of the pedal).
Although I have described this system, for reasons of simplified imagery as requiring two cylinders stacked it would be just as simple to use currently existing side-by-side cylinders with a slightly more complicated linkage. To all those who think that this idea is bad because it would serve little purpose in a NASCAR or F1 car you are quite correct, this idea is for rally cars and their ilk. If you skipped to the last paragraph hoping I would sum up, sorry no such luck. If you didn't get it but think you might if I clarified something, please ask! Cheers and greetings to rally enthusiasts everywhere. Down with Lobe, victory to the Swedes!-- WcW, Sep 14 2009 sounds good to me... why isn't it like this already ?-- FlyingToaster, Sep 14 2009 Don't farm tractors already have split brake pedals for the left and right wheels? Great for traction in mud, can be locked together for road use or left separate for hilarious unexpected tarmac skids.-- pocmloc, Sep 14 2009 Such a system would be illegal on road cars in the UK. I believe it is forbidden even to have a bias adjuster acccessible from the drivers seat.
Rally cars have to be road legal.
I'd need to check, but I'm pretty sure most race rules would also forbid the system as described.
Tractors have 'fiddle brakes' with a left/right split to aid steering in deep mud etc.
If I understand correctly, your system is similar to the tractor system but with a fore/aft split.
Motorcycles have always had seperate front and rear brakes, although a few have linked systems.
I'm not sure the rolling foot pedal would be as intuitive as you think.
(+) for the idea, but it's unlikely to be applicable in practise.-- Twizz, Sep 14 2009 as to the complaints about deleting annotations, no, I just double posted the idea, then deleted the first incomplete post, I could see no way around it.
I think I made it pretty obvious that I'm talking about a Front/Rear split. As to the road legal aspect of rally standards I can only speak to the law here in the US where adjustable brake bias is perfectly legal. Since road racing and rally rules are very change and innovation averse it is likely that the safety of the device would need to be demonstrated in less conservative fields such as drift racing or AutoX. Then the technology would need to be homolgated into a production car. I admit that this is a very high bar for acceptance. Sad really-- WcW, Sep 14 2009 random, halfbakery