The SPL rear knuckle bushings replace the rubber factory knuckle bushing with a low friction PTFE-lined spherical bearing. Replacing the OEM rubber bushing eliminates deflection under heavy acceleration and braking loads that leads to unwanted geometry changes, and prevents binding by allowing the knuckle to smoothly articulate. The reduced deflection also translates to improved driver feedback from the tire and better overall response. We use the largest possible FK bearing, to increase longevity and reduce NVH, mounted in a 6061-T6 aluminum housing precision cut with +/- .001" tolerance to insure proper fitment.
Technical
Reduced Wheel Hop
Keeps the Tire Planted
The OEM knuckle bushings deflect under load. This deflection stores and rapidly releases energy back into the suspension which feeds the wheel hop cycle. The SPL spherical bushings eliminate this deflection, reducing the chances and severity of wheel hop.
Faster Response, More Stability
No Deflection Under Load
The OEM knuckle bushings deflect under both braking and acceleration loads, contributing to a floaty, disconnected feeling. SPL spherical knuckle bushings eliminate this deflection and provide more predictable handling.
Smoother Articulation
Less Bushing Bind and Rubber Bounce
The OEM knuckle bushings resist compression and rebound travel and act like an underdampened "rubber spring", generating ~15 lbs of bind force per inch of travel, which is 0.25 kg/mm at the wheel, or equivalent to changing the rear spring rate by 0.42 kg/mm, not a trivial amount!
However, unlike the coil spring, the bushing bind will resist compression AND rebound. Basically, any suspension movement (up or down) results in binding force, with a dead zone of no resistance where the trailing arm was bolted to the bushing previously. This acts like a torsion bar and generally complicates suspension tuning and handling behavior.
Benefits
- Reduced Wheel Hop
- Lightweight: 0.674 lbs (306g) / 0.337 lbs (153g) per Side
- Improves Throttle and Braking Response
- Improves Braking Stability
- Maintenance-Free, US Made, PTFE-Lined FK Bearings
Materials
- 6061-T6 Aluminum Bearing Shells and Spacers
- PTFE-lined FK Spherical Bearings
Featured On
Devin's VA STI Track Car
Fez's GR86 Track Car
Noise, Vibration, and Harshness (NVH)
The SPL rear knuckle bushings are a moderate contributor to NVH. The rear traction arm knuckle bushings are an active part of reducing the felt vibration from potholes, rough pavement, and other road irregularities. By replacing one of the OEM rubber bushings with a spherical the longitudinal compliance of the suspension is reduced.
If combining the rear knuckle bushings with a spherical traction arm as well, then the rear knuckle bushings will add a similar amount of NVH as the traction arm. When combined with the solid subframe bushings it eliminates all longitudinal bushing deflection and will result in a noticeable amount of NVH over rough roads. Running larger tires with taller sidewalls at lower pressures and high-quality shocks will improve the NVH.
Applications
2021+ Toyota GR86 (ZN8)
2013 - 2021 Toyota 86 / Scion FR-S (ZN6)
2013+ Subaru BRZ (ZC6/ZD8)
2008 - 2014 Subaru Impreza WRX / WRX STi (GR/GV)
2015 - 2021 Subaru WRX / WRX STi (Inc. Type-RA) (VA)
2022+ Subaru WRX (VB)
2013 - 2023 Subaru Crosstrek (GT/GP)
2009 - 2018 Subaru Forester (SH/SJ)
2014 - 2018 Subaru Forester (SJ)
2010 - 2019 Subaru Legacy (BR/BM/BN)
2010 - 2019 Subaru Outback (BR/BS)
ADDITIONAL FITMENT INFO
WILL THIS FIT A ...
We limit the above applications to known fitments from testing and research. If you're unsure if this is the proper part for your application, send us an email.
THIS SHOULD FIT MY CAR
Occasionally, parts will fit other vehicles not listed above. If you believe, or know, this part will fit your vehicle, send us an email and we'll work with you to confirm proper fitment.
Replaces OEM Part Number(s)
This is a list of known OEM part numbers. OEMs constantly make changes to part numbers due to part updates, suppliers, etc so this may not be a complete list.
Toyota
SU003-00366
Subaru
20254-CA000
20254-FG010
20254-VA000
20254-FJ010
20254-XA00A
Installation Instructions
SPL GR86/BRZ/GT86/FT86/WRX Knuckle Bushing Install Instructions
