Project E39 M5: StopTech Front & Rear Trophy Kit Installation


The ST60 caliper body starts with a 6061 aluminum forging. A forging is the strongest way to form aluminum as it refines the grain structure and orients the grain along the geometry of the part. Here you can also see the two pairs of spring clips under the bridge that put tension on the brake pads in order to help prevent brake squealing noise from vibrations.


After forging the Trophy calipers are CNC machined to reduce weight in a secondary operation. You can see much of the CNC created lightening pocketing in the picture above. The ST60 caliper has durability enhancing features like stainless steel abutments to prevent the brake pads steel backing plates from digging into the caliper body and high-temperature silicone rubber dust seals that protect the main seals from dirt and ensure a long service life. Most racing type calipers have no dust seals which creates the need to frequently rebuild them if the car sees a lot of street long-term use.

Additionally, and which is perhaps StopTechs biggest competitive advantage in the market, is that StopTech makes their caliper pistons in 1mm increments. This allows StopTech to proportion each brake kit to hydraulically match the OEM brake system exactly. This assures that ABS and various electronic vehicle stability control and proportioning systems will still function correctly as designed by the manufacturer. Other manufacturers of big brake systems have at the most 3 piston sizes to choose from.

StopTech also does extensive on car tests to validate the brakes’ performance including repeated high speed stops with temperature monitoring, stopping while turning and a J-Turn test to assure vehicle dynamic system compatibility with the more powerful brakes. To our knowledge, no other aftermarket big brake upgrade company does more intensive validation and electronic compatibility testing than StopTech.


We attended StopTech’s testing in the past – it is a real good read!

Part 2 of the article showing how StopTech does on track validation. 


To go with the ST60 front calipers we had to of course upgrade the rotors to StopTech’s two-piece AeroRotors.


The front AeroRotors are made of an iron alloy formulated for a consistent coefficient of friction over a wide range of temperatures as well as dimensional stability. They are a two-piece design with an alloy hat machined out of super strong 7075 aluminum that saves a lot of weight. The front brake rotors are 355mm in diameter and 32mm thick vs the stock rotors which are a heavy one-piece design that are 345mm in diameter and 32mm thick. Weight difference = 8 pounds each! The StopTech AeroRotor gives us a larger rotor and an 8 pound weight savings.


The StopTech AeroRotors float on the hat. This means that they have about 0.012″ of free movement between the hat and the rotor.


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