Does offset affect brake clearance?
Thereof, does wheel offset affect performance?
On most OEM wheels, offset is positive (contact patch slightly inboard), and it can have a major effect on steering feel and stability during acceleration and braking. The distance between the center of the tire's contact patch and the point where that line touches the road is the scrub radius.
Subsequently, question is, is lower offset better? A lower positive wheel offset will typically result in the wheels being more flush to the fender, giving the vehicle a more aggressive look. A lot of people that choose a much lower offset end up modifying other components on their cars to compensate for fitment (i.e., rolling fenders, adjusting camber).
Keeping this in consideration, how much clearance do you need between brake calipers and wheels?
We recommend a 2mm minimum of clearance from our calipers to the wheel spokes. If you have 1.5mm without spacers you should be OK, but if your car exhibits any level of knockback or hub flex you might end up with contact if you autocross or track the car.
What happens if the wheel offset is wrong?
Too much positive offset (the wheel sits too far in towards the car) can cause damage to inner suspension and brake components from the inside lip. This can lead to poor handling making the car unstable at speed. Sometimes the rubbing will happen on the thin inner sidewall of the wheel causing a rupture of the tire.