The stamping seam creates a tire NO-GO region: approximately 0.5” from the bottom of the support; cutting a tire would be a very bad thing to do. As luck would have it, this NO-GO region is not an issue as even under the most extreme suspension compression scenarios, the tire will not hit the seam.
With the current tire size, 265/35/18 and with our current wheel offset, this does not become a factor when the wheel is turning at full lock. Some drift teams that have modified the tie rods for more steering angle with very aggressive wheel offsets have had to cut and flatten this hexagon enclosure, however with our Requirement 4, we set this as the physical limit of how far back the fender would touch since we did not want to perform any sort of frame modification.
Another thing we noticed during dissection was the fender liner showed damage from tire abrasion near the corner reflector area on the OEM bumper. The bumper mates with the fender using an internal clip-in mechanism with the frame attached to the underside of the headlight and the fender’s mounting edge being directly bolted to the corner light. Since the material of the OEM bumper was very flexible, we could design into the fender a re-position of the corner light out approximately 20mm to allow for a non-interference with tire compression and provide some top coverage of the tire to minimize tire poke. This +20mm continues along the top side of the fender, following our upper vent edge.
Another thing we noticed with the FR-S/BRS OEM fender was that underneath the fender emblem insert, it was a completely sealed except for a small slit to allow protrusion from yet another frame stamping. However the chassis behind there was actually quite open and had a decent air pathway to the engine bay. We decided to place an opening within this recessed area that would allow for the OEM emblem to still be inserted, but with minor modification, could turn it into a functional vent (ala BMW). I’d have to use Khiem’s thermocouples to prove this— I’ll take temperature measurements soon and post in a follow up article to prove that hypothesis.
With our physical hard-limits in place and proportional measurements taken from our CG render, we began the plug building process. This involved a lot of skilled metal work and frequent spot measurement checks.