TEIN Flex A Coilovers

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Get the ultimate DD Coilover Set for your 2015+ WRX/STI.

  • Full-Length Ride Height Adjustment Feature - Ride Height Adjustment with Little or No Change in Ride Quality
  • Twin-Tube Structure - For Low Resiliency & Securing Sufficient Stroke
  • Damping Force Adjustment System - 16-level Linear Damping Force Adjustment System
  • Complete Kit with Upper Mount - Exclusively Designed Upper Mounts are Included

FLEX A is equipped with new feature "Hydraulic Bump Stopper (H.B.S.)" which has been tested and proven effective in the world's harshest motorsports including World Rally Championship and European Rally Championship. When a lowered vehicle goes over big bumps, urethane or rubber bump stopper often causes a big upward jolt and/or rebound and can disturb controllability. On FLEX A, H.B.S., mounted inside the shock absorber, effectively generates damping force near and/or at full-bump, to absorb big impact smoothly. Comfortable ride in vehicles even at full occupancy will revolutionize the industry




When Hydraulic Bump Stopper is not actuated, as shown in the left image, the valve (green part) is floating and is not blocking the oil flow through the base valve. Damping force is generated just as same as the shock absorber without H.B.S. through the base valve port and the friction of stacked shims. Once the piston rod strokes further than the certain point, as shown in the right image, the valve is pushed down to activate H.B.S. The port is made narrower, limiting the oil flow, to generate high damping force only near and/or at full-bump.
The relief valve installed suppresses the sudden rise in damping force, when the inner pressure exceeds the certain level.
By changing the components, operating point and/or damping force specification of H.B.S. can be modified, to optimize the settings for wide variety of vehicle models.




Considering the use of larger tires/wheels and the lowered ride height, FLEX A uses twin-tube system, in pursuit of ride comfort on streets.

In order to maintain the ride quality on streets with rough spots here and there, a shock absorber has to have sufficient stroke, be low-frictional and move smoothly.
As an oil chamber and a gas chamber are not arranged serially in a twin-tube system, it is easy to secure enough stroke. Also, low gas pressure keeps friction low.

Its smooth stroke movement makes it possible to follow rough and bumpy road surfaces quite well, offering supple ride at low speed and stable ride at high speed.


For more info check out TEIN's Product page:



Ride Height Range (F): -3.17~-0.27in (-80.33~-6.67mm)
Ride Height Range (R): -3.37~0.53in (-86.67~14.33mm)
Spring ID (F): 65mm
Spring ID (R): 70mm
Spring Length (F): 175mm
Spring Length (R): 175mm
Spring Rate (F): 448lbs/in (8kgf/mm)
Spring Rate (R): 392lbs/in (7kgf/mm)