Dusan Strutworks RACP Reinforcement Brace Style 1: Drilling Pilot Holes from Below and Chasing Threads Properly
Drilling From the Bottom Up on the Strutworks RACP Brace Install
The Dusan Strutworks RACP reinforcement brace Style 1 mounts at the rear axle carrier platform — an awkward spot to access from above. Drilling pilot holes upward from below is the practical way in, and a few details separate a clean install from one you’ll be revisiting later.
What the RACP Brace Actually Does
The rear axle carrier platform is prone to cracking on certain Mazda platforms, particularly under repeated track or hard road use. The brace ties the forward and rear mounting points together, spreading load across a wider footprint. Left unreinforced, the RACP can crack progressively. That’s a bad day anywhere, and a much worse one on a circuit.
Bit Size and Why It Matters
A 13/32″ bit is the commonly used size for these pilot holes — roughly 10.3 mm. That diameter leaves enough wall material for threads to grip solidly after chasing. Reach matters too. A 12″ extended-shank bit lets you get to the mounting points from below without dismantling more of the rear than necessary.
If the bit is skating at entry, punch a small dimple first. A center punch takes two seconds and keeps your hole where you actually want it.
Why Bottom-Up Is the Right Approach
Drilling upward means chips fall away from the cut rather than back into it. You can also see your entry point directly. Going top-down at the RACP means fighting past more components for a worse angle. Not worth the effort.
Clear chips every inch, especially near the rear mount where the metal tends to run thicker. A bit packed with swarf will bind, and a bound bit in a confined space can walk the hole sideways before you feel it happening. A small amount of cutting oil on the flutes before each pass makes a noticeable difference in chip clearance and bit life.
Chasing Threads vs. Cutting New Ones
Chasing is not tapping. When you chase threads, you’re running a tap through existing or slightly distorted threads to clean them up — you’re not cutting fresh from solid metal. The distinction matters because the force required is different. Treating a chaser like you’re cutting new threads is how you strip or cross them.
Back off a quarter turn the moment you feel resistance. Clear the flutes. Go back in. Do this at both the forward and rear mounting points — not just the one that looked rough. A half-chased thread gives false confidence at final torque, and that’s worse than knowing the thread needs attention.
Fitment Before Final Torque
Get all bolts started by hand before any go to final torque. The brace needs to sit flat against the mounting surface. Torquing one side fully before the opposite is even seated puts a twist into the brace and builds in a preload you don’t want. For torque values, use Strutworks’ own specs for the Style 1 — a generic chart for that bolt diameter is not a substitute for manufacturer guidance on a structural brace.