Quote:
Originally Posted by ecomodded
I am curious of the benefit these would provide,Off hand without really understanding their use i am thinking that a spat ahead of the tire would be of benefit by reducing the amount of air that will pass over the rolling tire, thereby reducing the air resistance on the rotating tire. The rear of the tire spats seem like they would restrict the air from leaving the rotating tire, causing unneeded drag.
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I was just reviewing the Coventry papers that were on a thread here. There is one by Jeff Howell on Wheel-Wheelarch drag. They tested various front and rear fender skirt combinations and deduced that 80% of the drag penalty came from the exposed lower wheel(tire).
In other words, even with front and rear side skirts a majority of the drag came from the air slamming into the front of the tire. I believe that is why tire spats are becoming commonplace, especially on Asian and German cars.
In another Coventry paper they tested "underfloor wheelarch blanking" on an Audi A2. They reduced drag by closing the gap between the belly pan and the tire. The tire spat may solve two problems by managing the airflow hitting the front of the tire and the turbulence of the wheelwell. Super slippery aerodynamic cars would utilize canoe-style boattailing in front and behind the tires. This is not practical for road going vehicles. A mini airdam (spat) in front of the tire can streamline the air around the tire and possibly prevent some turbulence in the wheelwell. Unfortunately, we do not have access to windtunnels to see what the perfect placement and size would be. The best we can do is to seek out similar vehicles and try to copy what the major manufacturers have done. I have been amazed to see how small some of the spats are in front of the rear tires of some Toyota SUVs (often smaller than a deck of cards). If you discount the hours of testing in the windtunnel, it is a cheap, easy fix for the automakers.