Allow NA Miata to Upgrade to NB Miata Rear Suspension Uprights
#38478 from Chris Dilluvio · Rule change · TB 25-08 (2025-08 Fastrack)
In ITA Spec Lines, Mazda MX-5 / Miata (90-93), change Notes as follows:
"Spec Miata floor pan modifications allowed. Reinforcement of the differential housing ears is allowed for the purpose of
repairing or reducing breakage at the factory stress riser “notch.” The 90-93 Miatas may convert to the 94-05 differentialassembly. This conversion includes the driveshaft and half-shafts. The original 90-93 model rear suspension uprights must beretained. NA 90-97 cars may use the OEM Mazda 99-05 (NB) model year rear uprights. NA cars upgrading to the OEM Mazda NB
rear uprights must use the NB rear uprights on both sides of the car, Miss-matching of rear uprights is not allowed. Any final
drive permitted so long as it fts in an unmodifed housing."