A note from Kevin Bird - The Technical Director at Bird's Auto
In the world of car suspension development, there’s always room to improve. Settling for “good enough” can leave you stuck in place, unable to push the boundaries of what’s possible. This was our realization after years of fine-tuning suspensions for BMW models, from the E92 3 Series to the E87/8 1 Series, both of which earned high praise from press and customers alike. But when the M135i came into play, we knew we couldn’t rest on our laurels.
Reassessing Expectations: The M135i Journey
Using data from previous models, we recalibrated our setup for the M135i, adjusting to the unique characteristics of its chassis. The results? As expected, the suspension handled beautifully. Yet, despite early success, challenges still emerged that hadn’t appeared in previous models. After numerous refinements, the feedback from both the press and our customers confirmed our belief: we were on the right track.
A Game-Changing Encounter
However, true progress sometimes comes from unexpected places. At a charity event track day, we reconnected with James Weaver, a legendary sports car driver. After testing our Z4 35i, James had some feedback—both positive and constructive. He suggested reaching out to his long-time colleague, Peter Weston, a renowned chassis engineer.
The M235i: Collaborating with Experts
When the M235i demonstrator arrived, we applied our M135i suspension setup and got the expected results. But, inspired by James’ suggestion, we sent the car’s detailed measurements to Peter Weston. His level of precision was astonishing—he requested data we hadn’t even considered, like unsprung weights, center of gravity positioning, and bump stop stiffness. After two full days of meticulous measuring, we provided the required information.
Peter’s response came back with two new suspension settings, and we quickly had Bilstein re-valve a set of dampers to his “Revision A” specification. Testing with both Peter and James in cold, damp conditions brought immediate improvements, but it was clear that further gains could be achieved. Revision B was on the horizon.
The Power of Iteration: Revision B
Three weeks later, Revision B was installed, including changes to spring rates, damper curves, track width, and even tire choices. The results were nothing short of transformative. The improvements to ride quality, steering feel, and overall body control were leagues ahead of anything we had achieved before.
Most impressively, the traction and grip levels reached unprecedented heights, even in challenging weather conditions. What seemed like minor adjustments delivered a suspension setup that exceeded our wildest expectations.
The Takeaway: Continuous Innovation
This journey taught us that the best results aren’t achieved by settling for a “proven formula.” True success comes from constantly reassessing, refining, and pushing beyond what you think is possible. Our latest suspension tune on the M235i stands as proof that there’s always more to discover—if you’re willing to look.
