2011 rear brake vdc engaging unexpectedly after new coilovers

[wired00]

So very strange issue going on.

I just replaced a set of old coilovers (AST) + very light 5kg springs with something more track focused. I got MCA Pro sport with 10KG springs. So fairly significant upgrade in stiffness.

I also got a full alignment etc. The strange thing is straight after test driving i noticed on reasonably tight corners and not especially fast speeds i feel the rear right side wheel apply braking force unexpectedly. Id immediately think VDC strangely kicking. Yet i dont see the light on dash coming on which i might see at the track.

Its also NOT throwing error codes...

Anyone have any idea what could be going on?

I saw someone mention that this can happen under when a tire pressure is low and loaded up during heavy cornering since it can throw off the individual wheel speed sensors. But tire pressure is high at 34psi all round. Additionally that would light up with the traction control light on dash, again that is NOT happening.

I have not tried clicking the button to partially "disable" VDC to see if that stops the problem, i will try that, but i have to solve this crazy problem for normal road drivability. Its simply unsafe to have a brake unexpectedly apply and cause the car to steer left!

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[rtv900]

not sure about our subarus, but I have a vehicle with the same features and in addition to wheel speed sensors it also has suspension position sensors on each wheel.
The position data is part of the stability control system. I never would have guessed that would be used also but while working under the car one time I saw little lever arms attached to the A-arms that pivoted in small electronic devices and asked about it and was informed it was part of stability control.

So in your case all I could guess is maybe your coilovers are significantly different enough from stock that the system is expecting different body movement around certain turns at certain speeds and when it doesn't get that it trips the system to react.

Other than that I couldn't think of anything that system could pick up on.

[wired00]

Very interesting. Ill try investigate. I will say the car already had coilovers (ast 5100). But yah it might have been set to those. For sure the setup is substantially different. The thing is, regardless though, if VDC kicks in the light should appear on dash. That is what really confuses me. Or If a fault... The. A fault code. Neither happens.

Btw i forgot to say its a 2011 wrx hatch.

[wired00]

Ok yeah, rom initial look online it doesn't seem the 2011 model came with any sort of suspension ride height sensor. It appears later models possibly did

[wired00]

Ok the issue doesnt occur when the traction control button is turned "off"

[rtv900]

The light should still blink, so that is weird. When I had issues with mine the light would come on for sure. Not that I couldn't tell by the nightmare operation when it happened but still.

Also, mine had a traction control disable AND a stability disable, they are two totally different functions.
Just curious if turning your off turns both systems off????
Because on mine they are controlled separately

[Elbert Bass]

If you pulled the axles during the swap you may have contaminated the ABS reluctor ring in the bearing. It is magnetic and small bits of metal/rust can cause your issue. And no - your model has no ride height sensing. Also if you pulled the wheel speed sensor is it fully seated - did you crack the tip - pinch the wire?

[AliBenn]

^^^^this fur sure