Subaru WRX Master Cylinder Brace from Radium Engineering Radium Engineering has developed a master cylinder brace for the Subaru WRX STI; which is constructed out of 6061 billet aluminum to help reduce firewall flex while supplying a firmer pedal feel. The brace uses pre-existing threaded holes in the engine bay which requires no drilling or modifications of any kind. Due to the master cylinder flexing in an arcuate path, a specially designed CNC machined foot contacts the master cylinder to counteract the arc movement. Preload is adjusted with an anodized aluminum green bolt then locked in place with a jam nut.