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Originally Posted by dyong
Agree. The design has no concavity like the CSL. For me too big a wheel = more road friction => less fuel efficiency and poorer performance. Unless you track the car and up the engine performance > 500hp++, otherwise for a street car it serves no purpose.
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you CAN NOT have a concave wheel on a 1 series if it's produced at the proper offset in a wide wheel design. and these wheels DO have concavity to them. of about 1-1.5". You will never see the same concavity that you do on an 18x10" M3 wheel with a Low offset. Look at the drawings above, and you will see there is no place for the spokes to go. The spokes are straight but very much NOT flat. The narrower CSL wheels are actually CONVEX at first, and then bow in around the hub area.
These ARC-8 wheels are 18". The 18" wheels that come stock with the 1 series are extremely heavy. I'm not sure what you're basing your road friction figures off of. These ARC-8 wheels are significantly lighter then stock. It can be measured in either improved full efficiency, greater acceleration, or shorter braking times depending on how you drive. You need less HP to turn a lighter wheel. This is why people buy lighter wheels. If your car weights less, it takes more HP for it to accelerate. Removing unsprung weight (wheels/tires/brakes) effects the car 6-10 times more then chassis weight.
I believe you are under the assumption that your stock wheel/tire package is lighter then what these wheels with tires would be. Which is incorrect. Even if you have 17" wheels/tire. These are still lighter, and would be a weight saving improvement.
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Originally Posted by trboboost91
any plans for a 17"??
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The wheels already exist in a 17x9" et42 design. And 17x8.5" et40 are on the way. It's aggressive but a few people are running that 9" setup on the 1 series for autocross and track applications.