October 13, 2012
I purchased 17x8.5" et40 Kosei K1 wheels a year ago from Tire Rack and have been very happy with them. Although I enjoy the occasional autocross and HPD event, my car is used as a daily driver. Before purchasing, I was a bit concerned about using them on a street driven car, and had read some older tales of cracking. So far, mine have held up to the demands of street driving, and I feel that the early tales of cracking are circumstantial. Ultimately, ANY larger diameter wheel with a lower profile tire will bend or break if you drive into a large pothole, and I don't feel the K1s are any more susceptible to damage in this regard. And while no wheel manufacturer will warranty damaged caused by potholes, Kosei does provide a 5-year warranty for structural integrity, which is nice peace of mind.
I installed Hankook Ventus V12 Evo tires in 245/40ZR17 on all four corners, and the overall fitment on my E36 was spot on. I did not have to roll any fenders or use spacers, despite being slightly lower than a stock M3. In the front of the car, there is just enough room between the lower spring perch and the inner sidewall to safely allow for a bit of tire flex under heavy load, and the same is true for the rear between the outer sidewall and the fender lip - a 100% perfect fit. On an E36 with a stock or mildly lowered traditional suspension (i.e. non coil-over) such as mine, 245/40 is absolutely as wide as you can go with these wheels without spacers and fender rolling.
Otherwise, despite not being the most beautiful wheels on the planet, I really like how these wheels look on my car. Rather than being flashy, they have a highly purposeful, track-oriented appearance to them which I appreciate. Since they have such an open design, the brakes are much more visible, making inspection very easy, but also showing off potentially unsightly rotor hubs and calipers.
Ultimately, my experience with these wheels has been extremely positive. I'd definitely buy them again.