How does it feel when PSM engages?

[PhoenixBlue]

Was thinking it might be the arms, but it’s not a clunk sound, more like a series of hard rattles. Will a worn LCA do this?

Originally Posted by ike84

If your LCAs in the rear are shot, you will get wheel hop coming around hard turns. Do you ever hear a clunk coming from the rear if you hit a box around 15-20mph? If so, it's the LCAs.

When traction control activates, all it does is kill power momentarily. No braking to my knowledge.

If it were your traction control, the juddering should stop when you disable it.

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[ike84]

Originally Posted by PhoenixBlue

Was thinking it might be the arms, but it’s not a clunk sound, more like a series of hard rattles. Will a worn LCA do this?

When accelerating through or out of a hard turn a bad LCA will cause wheel hop. It can be a rather violent (depending on the amount of acceleration) juddering in the rear as the wheel literally bounces in the vertical axis, losing/regaining/losing traction as it does so. Google wheel hop or wheel skip and I'm sure there will be a good video on it.

Truthfully, if you're on dry haven't and on a street, it's really quite difficult to break the rear end loose. I'd be surprised if that's what's going on, unless you are intentionally trying to do so.

The "clunk" sound does happen during turns, it is only when going over bumps during straight line driving at low speeds. It's just another tell tale sign of a worn LCA.

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[PhoenixBlue]

Is the LCA the “Coffin” control arm? I’ve replaced that recently, but not the longer (trailing?) arm as circled in the photo attached. Could it not be the sensors and this mechanical part instead?

Also, this sound comes from the front end, and not the rear…

Originally Posted by ike84

When accelerating through or out of a hard turn a bad LCA will cause wheel hop. It can be a rather violent (depending on the amount of acceleration) juddering in the rear as the wheel literally bounces in the vertical axis, losing/regaining/losing traction as it does so. Google wheel hop or wheel skip and I'm sure there will be a good video on it.

Truthfully, if you're on dry haven't and on a street, it's really quite difficult to break the rear end loose. I'd be surprised if that's what's going on, unless you are intentionally trying to do so.

The "clunk" sound does happen during turns, it is only when going over bumps during straight line driving at low speeds. It's just another tell tale sign of a worn LCA.

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[ike84]

Originally Posted by PhoenixBlue

Is the LCA the “Coffin” control arm? I’ve replaced that recently, but not the longer (training?) arm as circled in the photo attached. Could it not be the sensors and this mechanical part instead?

Also, this sound comes from the front end, and not the rear…

No, it would be part 5, the part that runs front to back.

The rear LCA helps to keep the wheel planted, so when making a hard turn under acceleration the inside corner will hop. I think this is true especially since (in the rear) these are the drive wheels and are more prone to doing so.

I don't know if what I am saying is true for the front end though. A bad rear LCA will not affect the front wheels, but I would assume a bad front one might. Someone else may be able to chime in on that.



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[PhoenixBlue]

Thanks! Then it might be these arms in the front then. Maybe I’ll get them changed and see how it goes. I’m just entertaining the speed sensor/wiring hypothesis as the “juddering” feels rather regular, similar to an ABS feeling, but only on the inside wheel when turning.

Oh and to your previous question, yes I was intentionally taking the sharp corners at speed to try to get close to the grip limit of the car. Feels like I can get to within 80-90% of the limit before the juddering comes on (but only on power).

Originally Posted by ike84

No, it would be part 5, the part that runs front to back.

The rear LCA helps to keep the wheel planted, so when making a hard turn under acceleration the inside corner will hop. I think this is true especially since (in the rear) these are the drive wheels and are more prone to doing so.

I don't know if what I am saying is true for the front end though. A bad rear LCA will not affect the front wheels, but I would assume a bad front one might. Someone else may be able to chime in on that.



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