For those who want to use a polyurethane bushin, Harrison Motorsports and AKG offers a 75D hardness. 75D is by far the hardest polyurethane compound available on the market for a BMW and will tremendously improve many aspects of a race car's handling characteristics. AKG's 75D polyurethane bushings utilize the correct compound polyurethane required to control a racecar's suspension geometry during the rapid movements a race car experiences on the track. For those who want to go a step further, we also offer aluminum bushings for most models.
High performance street cars will see a noticeable increase in performance with AKG's medium durometer bushings. These would include 80A, 85A, 90A and 95A durometers. These bushings utilize the most ideal hardness and compound for street/performance use, providing for an increase in performance without a large increase in NVH (Noise/Vibration/Harshness).
Softest <-> OEM - >Powerflex Street -> AKG Street & Powerflex Race -> AKG Track <-> Hardest
Powerflex offers a choice of Street or Race (track) hardness in most of their bushings.
Powerflex Street at approximately 75A, is harder than OEM bushings, but softer than AKG's Street (95A)
Powerflex Race at approximately 95A, is softer than AKG's track hardness (75D)