When I upgraded my front brakes from single piston sliding calipers clamping onto (IIRC) 260mm discs over to a 4 piston 294mm disc combination that would fit inside the 15 inch wheels on the car at the time they had to be tested and approved and signed off by engineer and an engraved modification plate fitted in the engine bay and paperwork forwarded to the Transport Department.
There was an improvement but I found that the rears were locking but never the fronts under hard braking at the track.
Put simply when I braked the rears had 100% pressure applied to the discs and the fronts approximately only 80% which was not ideal so I had a WILLWOOD bias adjuster installed in the engine bay ( it is not road legal in the cabin where anyone could change the setting without the owners knowledge )
This allowed me to progressively reduce pressure to the rears and allow more pressure to the fronts until I found the ideal setting so now I can apply more pedal pressure without locking the rears and stop shorter OR brake harder much later safely.
Another benefit is that there are no hi performance pads available for the rears of the car in the pic whereas there are many different pads for the fronts and the adjuster allows me to adjust the front to rear pressures IF needed to allow for different friction levels between the pads.
http://www.wilwood.com/MasterCylinders/MasterCylinderValves.aspx
There was an improvement but I found that the rears were locking but never the fronts under hard braking at the track.
Put simply when I braked the rears had 100% pressure applied to the discs and the fronts approximately only 80% which was not ideal so I had a WILLWOOD bias adjuster installed in the engine bay ( it is not road legal in the cabin where anyone could change the setting without the owners knowledge )
This allowed me to progressively reduce pressure to the rears and allow more pressure to the fronts until I found the ideal setting so now I can apply more pedal pressure without locking the rears and stop shorter OR brake harder much later safely.
Another benefit is that there are no hi performance pads available for the rears of the car in the pic whereas there are many different pads for the fronts and the adjuster allows me to adjust the front to rear pressures IF needed to allow for different friction levels between the pads.
http://www.wilwood.com/MasterCylinders/MasterCylinderValves.aspx