Mugen Sport Suspension (Mugen SS) Install on the Acura RSX Type-S
Introduction
The Mugen Sport Suspension (Mugen SS) is a bolt-in strut package for the Acura RSX Type-S, mechanically the same chassis as the Japanese Integra Type-R (DC5). Each corner arrives as one fully assembled unit combining a matched spring, damper, and mount, so no spring compressor is needed anywhere in the job. The kit lowers the car by roughly 35 mm (1.4 inch) and firms it up with higher rates, a stated front rate of 279 lbs/inch and a rear rate of 458 lbs/inch, up from the factory springs' 207 and 413. Because the dampers are non-adjustable, the work amounts to a like-for-like strut exchange front and rear, with the one delicate task being separation of the front tie-rod ends. Owners consistently note the ride stays close to stock in comfort while cornering composure improves sharply, and that alignment typically remains within factory range afterward. Plan for an afternoon and recruit a second person, since several steps need one worker underneath and one in the trunk or engine bay at once. Adapted from a community writeup by conradb212 on Club RSX (https://www.clubrsx.com/threads/mugen-ss-diy-and-data-long.132932/), including corrections from the follow-up discussion.
Reference
Tools Required
- Ratcheting socket set with extensions (10, 12, 14, 17, 19, 21, 22 mm)
- 14 mm wrench, ideally a ratcheting box wrench
- Needle-nose pliers
- Torque wrench
- Gear (bearing) puller for tie-rod separation
- Factory RSX lug/tire wrench
- Floor jack (a second jack is very helpful)
- Jack stands
Parts Required
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Mugen Sport Suspension kit (four assembled strut units, complete front and rear)
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Two tie-rod cotter pins (supplied with kit)
-
Six 14 mm front tower flange nuts (supplied with kit)
Safety Warnings
- ⚠ Always support the car on jack stands before working underneath, and never rely on a jack alone.
- ⚠ Sheet-metal edges around the rear strut towers inside the trunk are sharp; the author cut himself there.
- ⚠ Steady the front strut as it comes free so it cannot drop onto the driveshaft boot or damage the brake line.
- ⚠ Do not use a standard pickle fork on the tie-rod end, as it will tear the rubber boot; use a gear puller instead.
Step-by-Step Instructions
1 Inventory the kit and note strut orientation
Unbox the four corner assemblies and the supplied hardware, which amounts to just two tie-rod cotter pins plus six 14 mm flange nuts for the front towers. Each rear unit carries a white paint dot on its upper mount; that marker must end up pointing toward the middle of the car once installed, so locate it before you start. Lay out your tools while the car is still on the ground: sockets covering 10 through 22 mm, needle-nose pliers, a torque wrench, the factory lug wrench, a jack and stands, and a gear puller for the tie-rod ends.
2 Loosen the rear upper mounts from inside the trunk
Begin at the rear while the wheels are still loaded. Fold the rear seat backs forward, open the hatch, and pry out the two plastic clips retaining the trunk-side trim panel. Bend the panel back to expose the pair of 14 mm flange nuts capping each rear strut. Crack both loose now: a plain 14 mm wrench reaches the forward nut, while the rear one needs a 14 mm ratcheting wrench and patience. Keep your hands clear, because the sheet-metal edges in this pocket are sharp.
3 Lift the rear and free the lower damper bolt
Raise the rear of the car, set it on a jack stand, and remove the wheel. Keep a second jack within reach. Take out the flange bolt at the base of the damper; if it will not slide, position the spare jack under the hub and load the suspension slightly to shift the shock until the bolt releases.
4 Remove the old rear strut and fit the Mugen unit
Have your helper spin off the two upper nuts inside the trunk so the factory assembly drops out. Raise the Mugen unit into place with its white dot facing inboard, and let the helper start, but not tighten, the two upper nuts. Line up the lower mounting hole with the bolt hole; this is the awkward part, and jacking the hub up or down to compress the spring usually brings the holes into register. Pass the lower bolt through.
5 Torque the rear fasteners and refit the trim
Bring the lower flange bolt and both upper flange nuts up to spec. The concealed rear upper nut is nearly impossible to reach with a torque wrench, so tighten it as firmly as the ratcheting wrench will manage. Reseat the trunk trim panel and secure it with its two plastic fasteners, then carry out the same rear sequence on the opposite side.
6 Separate the front tie-rod end
Move to the front, lift and support the car on a stand, and pull the wheel. The tie-rod end is the most delicate operation of the job because its rubber boot rules out a standard pickle fork. Withdraw the cotter pin and back the nut off until it sits just past the end of the threads. Seat the gear puller against the joint, slipping a small flat plate between the puller's point and the nut to guard the threads, then wind it down until the taper pops loose.
7 Disconnect the wheel sensor and brake line
Unbolt the wheel-speed sensor, held by a 10 mm nut, and the brake-line bracket, held by a 12 mm nut, from the strut body so both hang clear once the strut is out.
8 Remove the front strut assembly
Undo the two large through-bolts clamping the strut to the knuckle; the bolt head takes 19 mm and the nut takes 22 mm, and the factory lug wrench fits both. Have your helper back off the three 14 mm flange nuts on top of the strut tower in the engine bay. Steady the strut by hand as it releases so it cannot swing down onto the driveshaft boot or strain the brake hose, then draw it out.
9 Install the Mugen front strut
Guide the new strut up into the tower, keeping the driveshaft boot, brake hose, and sensor lead away from pinch points. Your helper starts the three upper nuts in the engine bay. Feed the two large through-bolts back through the knuckle and thread their nuts, then reattach the brake-line bracket with its 12 mm nut and the wheel-speed sensor with its 10 mm nut.
10 Reconnect the tie-rod and torque the front
Seat the tie-rod taper back into the knuckle, which draws in far more easily than it came apart, run the nut down, and fit a fresh cotter pin. Torque every fastener. Heed the correction raised later in the thread: the knuckle pinch bolts take 76 lb-ft, not the 101 and 116 lb-ft figures the original writeup listed. Those higher numbers belong to the camber-adjusting bolts described in the alignment section of the service manual. Repeat the front sequence on the other side.
11 Road-test and verify alignment
Lower the car and take it for a short drive to confirm there are no rattles or binding. Owners consistently report camber, caster, and toe landing inside Acura's factory range after this swap, so a camber kit is generally unnecessary. Even so, have a shop check the alignment before you put the car into regular use.
Pro Tips
- 💡 The kit ships as complete assemblies, so no spring compressor is required at any point.
- 💡 A basic universal gear or bearing puller (the author used a roughly $10 unit) separates the tie-rod ends cleanly without tearing the boots.
- 💡 Recruit a helper: several moments need one person under the car and another in the trunk or engine bay simultaneously.
- 💡 Aligning the lower strut hole with the bolt hole is the fiddliest part; gently jacking the hub to compress the spring brings them into line.
- 💡 King Motorsport is the authorized US Mugen distributor; the author paid about US$1,000 plus shipping.
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