Project E39 M5: StopTech Front & Rear Trophy Kit Installation
In our Brake Refresh Article we maximized the capabilities of our E39 M5’s OE braking system by using StopTech’s Sport Axle Pack, which includes slotted rotors, stainless steel braided brake lines and Sport (formerly Street Performance) brake pads. Front brake ducting was also added in order to improve on our project’s susceptibility to brake fade. Though these improvements left us with a braking system that performed better than stock, the E39 M5’s stock system has a lot of room for improvement.
It is puzzling why the M cars of the E39’s era stubbornly stuck to using cheaper production single piston floating calipers. Exceptionally puzzling for the E39 M5 considering one of its main rivals, the S55 AMG, came equipped with 4-piston race inspired fixed calipers. Let’s also not forget the M5’s properly sized, but extremely overweight front rotors. The front one piece full steel rotors weigh almost 27 pounds each! That is a lot of un-sprung weight we could potentially save.
Many of our project cars are equipped with race level big brake kits that come with fixed multi-piston calipers, larger and better ventilated rotors, and their components are usually much lighter than their stock counterparts. The improved performance and weight savings we’ve achieved with our choice of brake components in the past is exactly what we want for our M5. We will look to achieve our goals by using a modern state of the art braking system from the brake experts at StopTech – the highly coveted Trophy Kit.
StopTech also has a 4-piston caliper upgrade kit for the E39 M5 in case your wheels specs limit you to a smaller front caliper. We chose the 6-piston caliper for its much larger brake pad area. The M5 is a heavy 4,000 pound car so it needs all the brake you can put under it!
Part of the ST60’s stiffness is attributable to the CNC machined 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. Also why in StopTech’s benchmark testing, their calipers are among the stiffest in the industry.