ULTIMATE IRS
The Total Package
Grannas Racing's Ultimate IRS (Independent Rear Suspension) Subframe is a high-performance upgrade designed to enhance the strength, handling, and durability of IRS-equipped Mazda FD3S RX7's. Engineered for drag racing, road racing, and street performance, this subframe is built to eliminate flex and wheel hop, ensuring better power transfer to the ground. Made from high-quality materials like 4130 chromoly and billet aluminum, it provides superior rigidity while reducing unnecessary weight. Designed specifically for the FD3S RX-7 (and other performance platforms), the Ultimate IRS Subframe allows for seamless integration with stronger axles and differentials, making it a must-have for enthusiasts pushing extreme power levels while maintaining IRS functionality.
This is a complete bolt-in rear tubular subframe for the 1993-1999 Mazda (FD3S) chassis. This is 100% chromoly, so it is not only lightweight but extremely strong. The weak, oem stamped steel subframe is around 30 lbs, this super strong chromoly tubular subframe is only 13 lbs heavier, weighing it at only 43 lbs.
This will make the entire IRS suspension more rigid. Removing the play and twist from IRS suspension systems is key in making it work better.
The subframe cradle uses all the factory mounting locations to the chassis and stock locations for all suspension arms. So, you technically could run all stock arms, but alignment due to no misalignment bolts (eccentric bolts) would not really be possible. So we suggest using aftermarket lower control arms. This is also designed to work with the factory spindle.
For the differential, it allows for both 8.8" or 9" Ford mounting. There is not enough room for the stock diff to fit with the cross brace we designed up front.
The subframe is available as a full kit with adjustable control arms, and differential.
Specifications
| Color | Raw or Satin Black or Custom Color |
| 9" Differential Choice | Spool (race use) or S-Trac LSD |
| 9" Gear Choice | 3.00 or 3.25 or 3.40 or 3.50 or 3.70 or 3.89 or 4.11 or 4.30 or 4.57 or 4.71 or 4.86 or 5.00 or 5.14 or 5.29 or 5.43 or 5.83 or 6.0 or 6.2 or 6.33 or 6.50 |