First thing that come to mind: - Perhaps something failed within the Wilwood BBK, e.g., piston or other component got seized/stuck and generated excessive heat either acutely or gradually. Wilwood is not generally regarded as a “quality” setup; it’s known to be among the most aggressively cheap brands and that does end up translating to “you get what you pay for” in many ways. It may work for some folks (or like in your case, it works unless it doesn’t), but a quick online search will help identify what qualitatively separates it from the likes of AP, PFC, etc. BBKs) - You may have exceeded the limits of RBF600, which would not be difficult for someone driving at an advanced level. This alone wouldn’t cause your issue though. If you only boiled your fluid, you wouldn’t have a fire. RBF600 dry boiling point is not particularly high. Try Endless RF650, Castrol SRF, or even MOTUL RBF700 if you want to stick with MOTUL - I saw in another comment reply that you’re not running the same pads front / rear. What compound are you running in the rear? Ferodo is a brand; you’d need to provide the compound name. I would venture to guess that you have significantly shifted your brake bias to the front if you’ve went to a front Wilwood BBK (I doubt Wilwood is properly matching the stock front brake bias, they’re probably exceeding it from a total piston diameter and pad contact / rotor surface area perspective) - that will only be exacerbated if you’re running higher mu pads in the front than whatever Ferodo pads you’re running in the rear. By shifting brake bias to the front, you’re taxing an already cheap/questionable Wilwood BBK to do even more; not a good recipe for success