The first reason for choosing the Bilsteins relates to benefits associated with the mono-tube construction of the Bilstein struts. After many conversations with one of the Bilstein techs, I began to appreciate the benefits of the Bilstein mono-tube construction over the Koni twin-tube construction. While Koni is an excellent quality strut, one of its liabilities is that it exhibits rather significant cavitation across the valve resulting in considerable heating of the strut oil. The tech was able to cite shock dyno data to support the difference in cavitation between the two strut designs. He further explained how such cavitation adversely affects 'consistency in performance' via heat build-up of the strut oil.
The Bilstein exhibits nearly no cavitation across the valve, reducing heating of the strut oil. Also, because of the mono-tube construction, the oil is in direct contact with the strut body, thus providing improved cooling ability.
The second reason for choosing the Bilsteins relates to the size of the piston tube. The Bilstein piston tube is nearly twice as large in diameter than the Koni piston tube (1.573 vs. 0.856). With the struts serving triple duty (steering, damping, and load-bearing) in a coil-over application on a Mustang, I though this is one area where bigger just might be better as a larger bearing and cooling surface will likely provide some benefit.
After installing the Bilsteins, I was very impressed with their balance in ride quality and handling. The Bilsteins soak-up discontinuities in the road far better than did the Konis. Over the same roads that I've driven with the Konis installed, I found that the Bilsteins provided far less harshness over expansion joints and less chatter over broken pavement. With the improvement in ride quality, I though for sure I'd sacrifice some handling and responsiveness. I was pleased to find that I was able to push the car just as hard as with the Konis with no notable difference.
So, from a qualitative standpoint, I must say that I am extremely happy with the switch to the Bilstein struts.
