Project Acura RSX, Improving the Stopping Power!

You might have been following the progress on our 300 whp pump gas K engine over the past few weeks which went onto a 2005 DC5Acura RSX Type S.  With serious power on tap, in building our sleeper, we had to upgrade the stopping power to match our engines much-improved performance.  To upgrade our brakes we turned to Stoptech who we feel is an industry leader for racing performance brakes that are compatible with a car’s OEM systems.

Our first stop into the land of better braking (bad pun) was to get Stoptech’s Trophy Kit P/N 83.058.4300.R3 for our RSX. For cars using the OEM hydraulic system, we have always felt that few companies can rival Stoptechs engineering and the ability to maintain a car’s proper hydraulic and mechanical balance, thus keeping systems like ABS happy.  Most other brake companies have three different piston sizes for their calipers while Stoptech has over 30. This enables Stoptechs engineers to get the hydraulic proportioning perfect with a nice firm pedal.  Most other aftermarket big brake kits in our experience usually have too much front brake bias and often have soft long pedals from having to adapt calipers designed for race use dual master cylinder pedal boxes on an OEM single master cylinder hydraulic system.

For the front brakes on our RSX, we opted for StopTech’s Trophy four-piston ST40 caliper equipped system finished in electroless nickel plating. The Trophy kits differ from the standard StopTech systems in more than just their finish. The calipers are CNC machined down to reduce weight after careful FEA analysis so weight is removed without sacrificing the stiffness of the calipers. Generally, this saves about a half-pound from each caliper. Trophy kit calipers are also not powder coated, but rather hard anodized or in our case nickel plated. Unlike powder coat, hard anodizing and nickel plating will not deteriorate or burn off with heat. They are also a very hard, corrosion-resistant and durable surface finishes and to scratch them, you actually have to damage the base metal.

The ST40 caliper is very stiff, part of the ST40’s stiffness is attributable to the black CNC machined billet aluminum bridge that spans the open area of the caliper and is bolted to the caliper body in 4 places. This is a solid part that will resist the calipers’ tendency to spread under load. The bridge is also why in StopTech’s benchmark testing, their calipers are among the stiffest in the industry. The bridge is an aid to assure a hard brake pedal and helps braking efficiency by assuring all the hydraulic force is transferred to the brake pads. A stiff caliper helps assure a consistent brake pedal and even pad wear.

The ST40 Trophy caliper body starts with a 6061 aluminum forging. Forging is the strongest way to form aluminum as it refines the grain structure and orients the grain along the geometry of the part. 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 ST40 caliper also has durability enhancing features like stainless steel abutments to prevent the brake pads steel backing plates from digging into the aluminum caliper body


  1. I’ve noticed that no one makes 2-piece rotors for stock sized rotors. I would have thought the weight savings from the iron hub will still be worth the trouble, but it seems that the market does not demand for it.

    Any insights on that?

    1. Because it would be pointless to offer something like that. Stock rotors are good if you are running stock sized tires with stock type compounds. When you run more aggressive tires and suspension you quickly overwhelm the stock brakes in track use, with aggressive pads, the car might stop but the rotors will become damaged, rapid wear heat checking and warping.

      1. are S2000 rotors the same as RSX? Cause there are 2pc options for that… although same logic applies as to why its kind of a waste of money…

        1. Yup, anyone who is really serious about tracking the S2000 upgrades to a BBK now. It only took a decade of telling people that, ha. The crowd of, “oh, I just bring spare stock rotors because they crack every two track days” is much smaller now.

  2. Would you recommend going to a bigger rear brake on a FR car with more even weight distribution, or do they tend to do well with just a more aggressive pad as well?

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