This weekend I was instructing at the Mass Tuning event at Watkins Glen. I saw three cars with Racebred splitters. All of them had their splitters mounted upside down.
What do I mean, aren’t splitters just flat? Sometimes and unfortunately yes, but even when they are flat, a splitter behaves essentially as a wing; there’s high pressure on top, and low pressure beneath, and the difference creates downforce. The low pressure undersides of wings and splitters produce much more downforce than the high pressure top sides, and so flow attachment beneath these components is critical.
Racebred only rounds the leading edge on one side of the splitter, and that’s where they put their logo. So people think that’s which way the splitter goes, logo side up. But the underside of the splitter is what matters, so it’s the bottom of the leading edge that needs rounding!
I mentioned this to one guy and he said, “but the texture is on the top side.” Waitaminute. You think putting texture on the blade is a performance enhancement… on the pressure side? The pressure side is of little consequence; any modifications you’d do to reduce flow separation (texture, whatnot), would be under splitter, not on top of it!
It’s understandable that customers don’t know the fundamentals of aerodynamics; it’s not their job. Their job is to buy things. They trust manufacturers to have done the research and give them the products to go faster. So it’s a shame when aerodynamics manufacturers literally don’t know which side is up.
Look, I don’t want to just pick on Racebred. Putting your logo on the wrong side of your splitter is endemic in the aerodynamics manufacturers community. Look around and you’ll see lots of manufacturers who round the wrong side of the splitter blade.
And when they do round it, it’s like just breaking the edge a little bit. The leading edge of the splitter should be as thick as possible, with as much radius as possible. On the underside of the splitter. This is one reason an Alumalite splitter screams “Amateur!” But I digress.
If you have an aftermarket splitter, do yourself a favor and examine which side the rounding is on. In most cases you’ll want to flip that embarrassment upside down. If the splitter isn’t rounded on either side, round the heck out of the underside leading edge.
At this event, and really at every event, I see a lot of splitters with unused real estate on the outside edge. This does nothing, because it doesn’t change the direction of air. All you’re doing with this extra width is inviting contact with hard objects.
A small kicker here is an easy way to increase the pressure differential above and below the splitter. Or put a fence on it and reduce downstream losses. But do something with this extra width people!
These and other mistakes are in my Your Splitter Sucks article. If the manufacturers can’t get it right, at least you have the information to fix it.
Occam's Racer 
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