Saw these some time back .. joined up on this forum yesterday so thought i'd share (can't see that they've been discussed before?)
These are an option on the ABT (German tuning co) modified audi RS4.
Rather than a full cover (i'm assuming to allow brake cooling) they are essential a "ring" running around the outer edge of the wheel.
I did some research and found a technical paper that looked at various designs of wheel covers and this sort of design was very effective - i'll dig out that paper and post it here if can find it.
Other advantage of these vs. a full cover is that it keeps the lug nuts accessible so removing the wheel will be possible with the cover in place.
I might look to make up some similar covers for my wheels.
More info:
https://www.abt-sportsline.com/compa...imited-series/
https://uk.motor1.com/news/260350/ab...heel-for-sale/
Oh, and they are a little pricey..
Looks like similar tech is used on the ABT formula e car:
https://www.motorsport.com/formula-e...7672/12797672/
Thoughts?