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Group N Hardened Bushings

STI hardened rubber bushings, either sold as a kit or individually, to improve handling, traction, and steering response. Rubber hardness is increased noticeably over stock parts (on all models including STI) but is within the limits for Group N use. Manufactured with the same quality and on the same production line as the OEM bushings.

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Manufacturer: STI


  • Subaru Impreza MY1993-2007

What bushings should I use for the front control arms of my USDM MY04-07 STI? There are no uprated Group N bushings for this application. RST-2020R and RST-2020L front control arm rear bushings will fit WRX applications but not USDM STI. The inside diameter of the bushing sleeve will not fit over the transverse link shaft. RST-2021 front control arm front bushing fits only GC8 (MY1993-2001) applications. The width of the bushing changed starting with MY2002 models so this bushing cannot be used. Its possible that no uprated bushings were ever offered for this application because the bushing durometers are already fairly high in the STI front control arms.

How can I determine if I need RST-4154 or RST-4154X for the RH side of the rear diff front crossmember? There is a production date of 01/2002 for the changeover. However, visually they can be identified by the height of the bushing. The earlier models use the same bushing for both sides. The later models will have a taller bushing on the RH side compared to the LH side and therefore will take RST_4154X for the RH side.

How do these bushings compare to urethane bushings? These are rubber bushings with a higher durometer than the factory ones. In terms of hardness they are comparable to most aftermarket urethane bushings. However, urethane and rubber bushings operate differently. Urethane bushings rotate in a sliding motion around the center sleeve and require lubrication. If the lubrication washes out or dries up the bushing may begin to make noise and can wear prematurely. A rubber bushing, on the other hand, has no sliding motion under normal conditions, but instead the material twists or distorts around the center sleeve to allow the suspension arm to articulate. A rubber bushing will not wear unless the material deteriorates. Exposure to heat, chemicals, ozone, UV light, etc. can break down the rubber.

How difficult are they to install? Installation requires the use of a hydraulic press. Some bushings use an outer metal sleeve that may need to be split in order to press the bushing out of its bore. Installing the new bushings without damaging them may require the fabrication of special tools. It is a job best left to a skilled professional.