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2021 XC40 P8 - Bursting Blue
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I vaguely remember something about the OPD system using actual brakes in aggressive situations; could they be activating for you? What if you turn off OPD and brake aggressively yourself -- same sound? I'm kind of wondering if there's some obstruction on your rotors/pads/etc and actually applying brakes in motion is creating this sound.
 

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Discussion Starter · #3 ·
I vaguely remember something about the OPD system using actual brakes in aggressive situations; could they be activating for you? What if you turn off OPD and brake aggressively yourself -- same sound? I'm kind of wondering if there's some obstruction on your rotors/pads/etc and actually applying brakes in motion is creating this sound.
I'm going out soon to try the regular driving mode and see if I still get the sound when braking.
 

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2021 XC40 P8 - Bursting Blue
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In my unspoken theory that some grit or debris was in/around the rotors/pads -- If you're mechanically inclined, I might inspect the rotors for scoring/damage, which might mean putting it on jacks to either remove the wheel and look at the back of the rotors or just crawl under and inspect them from under. Might be able to do it all without jacking it up. While there's not much one can do about it without replacing rotors/pads, it might give you some answers.

I'm actually curious to put it up on ramps and see all the bits underneath. So very different from the ICE's I've lived with (and shade-tree-mechanic'ed) since I started driving many years ago.

I hope you get it sorted out. I'm getting to where I never touch the brake pedal now, I have a good sense for how soon to let off the go pedal brake for a stop line, etc. I LOVE the OPD mode.
 

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Discussion Starter · #6 ·
In my unspoken theory that some grit or debris was in/around the rotors/pads -- If you're mechanically inclined, I might inspect the rotors for scoring/damage, which might mean putting it on jacks to either remove the wheel and look at the back of the rotors or just crawl under and inspect them from under. Might be able to do it all without jacking it up. While there's not much one can do about it without replacing rotors/pads, it might give you some answers.

I'm actually curious to put it up on ramps and see all the bits underneath. So very different from the ICE's I've lived with (and shade-tree-mechanic'ed) since I started driving many years ago.

I hope you get it sorted out. I'm getting to where I never touch the brake pedal now, I have a good sense for how soon to let off the go pedal brake for a stop line, etc. I LOVE the OPD mode.
Thanks for the advice. I'm with you on OPD -- only issue is when I get back in my ancient 4Runner, it's hard to switch back to actually using the brakes.
 

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In ev cars regenerative breaking is used predominantly for deceleration. It is possible that the actual break pads will not be used for days. Any moisture will result in the disc getting rusty and hence a grating sound.

This is exacerbated if you get the wheels wet or leave the car in the rain.

Solution break hard ( not abs hard just harder than regenerative hard ) from say 40 to 10 a few times. This will clean the rust off the pads.

Interesting experiment. After exiting the high way notice how cool your break pads are. Try it with an ice car and see the difference.

I was told that the software has been updated so that that pads are used sometimes to keep the pads clean. I read that vw’s do this, not 100% sure if the p8 does.
 

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I had car work done. Part of it they cleaned the car which means brakes got wet. When I picked it up the discs were all rusty and the car made grounding noises. Sped up ton40 breaker hard to 10 a few times and voila shiny discs and no grinding.
 
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