If you follow NASCAR closely, you know that one of the areas teams have tried to get an advantage in is rear suspension, specifically working to build in rear aerodynamic sideforce, to help cars turn better through the corners.

In a somewhat unusual move Wednesday afternoon, NASCAR announced a rules change that go into place this weekend at Phoenix International Raceway, site of the penultimate racing weekend of the season.

The sanctioning body sent out a tech bulletin pertaining to Section 20.14.2.I-1 Truck Trailing Arms of the Sprint Cup rule book.

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The bulletin, which pertains to both the Sprint Cup and XFINITY Series reads as follows:

"Truck trailing arm mounting slugs may be used to locate the truck trailing arms on the truck trailing arm mounting brackets.

"If used, truck trailing arm mounting slugs slots must be perpendicular to the slots on the truck trailing arm mounting brackets."

A NASCAR spokesman said the new changes were designed to keep teams from getting an advantage in rear yaw or sideforce, and that the changes would be part of the 2017 rules package.

Friday at Phoenix International Raceway, we'll know who it helped and who it hurt.