Rear Brake rotors - casualty of high regen.

[DKM_R1S]

Not sure if you'll pay labor for inspections or not, @DKM_R1S. Consider talking with the service advisor at your Service Center. They vary in knowledge and understanding (Portland SC is excellent), but they should at least try to give you reliable information.

***

What I learned from members of the other forum is: Brake pad and rotor issues can be complex. I'll give you what I think is the TL,DR version of a long and somewhat convoluted thread.

Regarding brake wear and corrosion, you can reduce the pad wear from FRICTION by turning off the poorly named "Regenerative Braking Assist" in the Vehicle --> Driver Assistance menu. This will stop the brakes from coming on automatically when the right pedal is programmed to request more deceleration (which must transform kinetic energy to recharge the HV battery) than the batteries will accept. Be aware that the right pedal response will feel different, based on battery temperature and SOC and other factors.

However, CORROSION makes the rotors more abrasive, so it can also cause excessive pad wear, and corrosion can be worse if you use the friction brakes less often. Near the ocean, with windy weather and salt spray and keeping vehicles outside, is also bad for corrosion.

I paid about $800 ro replace front brakes on our R1S at 40,000 miles. Since then, I've turned off "Regenerative Braking Assist" in hopes of wearing out the brakes less often. This should improve energy efficiency, but I don't know whether it improves brake pad wear or not.

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I hope this helps!

Thanks for the post. Yes, I also switched off the “Regenerative Braking Assist” in the very beginning. I am amazed at how powerful the R1 regen is. I’ve found that even when switched to “Low” the regen braking often is still enough to slow down the vehicle without needing to press the brake.

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[DKM_R1S]

Interesting thread. A bit dark to get decent photos of our R1s. My R1T has 72,000 miles with about 90% pad life remaining and smooth polished rotors front and rear. Our R1S has 31,000 miles with over 90 % pad life remaining and rotors that look new just like the R1T.

Regen Brake Assist has been on for both since mile zero.

thanks for the post. Very interesting about the R1T with 72K miles and perfect looking rotors. Out of curiosity, do you live in a region where road salt is used in the winter?

 

[Mark_AZR1T]

thanks for the post. Very interesting about the R1T with 72K miles and perfect looking rotors. Out of curiosity, do you live in a region where road salt is used in the winter?

What is road salt ...

 

[DKM_R1S]

What is road salt ...

I see. The “AZ” in your handle must stand for Arizona.

 

[BTOR]

Not sure if you'll pay labor for inspections or not, @DKM_R1S. Consider talking with the service advisor at your Service Center. They vary in knowledge and understanding (Portland SC is excellent), but they should at least try to give you reliable information.

***

What I learned from members of the other forum is: Brake pad and rotor issues can be complex. I'll give you what I think is the TL,DR version of a long and somewhat convoluted thread.

Regarding brake wear and corrosion, you can reduce the pad wear from FRICTION by turning off the poorly named "Regenerative Braking Assist" in the Vehicle --> Driver Assistance menu. This will stop the brakes from coming on automatically when the right pedal is programmed to request more deceleration (which must transform kinetic energy to recharge the HV battery) than the batteries will accept. Be aware that the right pedal response will feel different, based on battery temperature and SOC and other factors.

However, CORROSION makes the rotors more abrasive, so it can also cause excessive pad wear, and corrosion can be worse if you use the friction brakes less often. Near the ocean, with windy weather and salt spray and keeping vehicles outside, is also bad for corrosion.

I paid about $800 ro replace front brakes on our R1S at 40,000 miles. Since then, I've turned off "Regenerative Braking Assist" in hopes of wearing out the brakes less often. This should improve energy efficiency, but I don't know whether it improves brake pad wear or not.

***

I hope this helps!

Regenerative Braking Assist on Gen2’s is under “Vehicle” >> “Autonomy” and it is the very last option in that menu.

Mine has been enabled since day 1. Rivian recommends keeping it enabled. I would be surprised if this feature caused excess brake wear, be it pads or rotors. I think driving habits and brake use are the largest contributor to brake wear. As mentioned in the thread, driving environment will also be a factor.

 

[DCFC]

Hi, I’ve always used high regen with the idea that I could extend my brake life. For the most part I think this is true, however, I recently noticed when detailing my wheels that the rear rotors are not wearing evenly like the front. I can see some groove lines and also the wear pattern does not extend all the way to the edge of the rotors like in the front.

Is this a common problem with R1S? Mine is a gen 1 quad with 22” performance if that matters.

Perhaps they started getting some corrosion due to lack of use? I did test & verify they’re working by heavy braking and feeling they’re hot and generated some dust. I just think that during my normal driving habits, I’m not using the rear brakes very often,

Do you think I can salvage these rotors by switching to low regen and performing some intensive burnishing via heaving braking over an extended period of time???

Images: 1) passenger rear 2) driver rear.

What your pictures show is very LITTLE rear brake use. Because the rear pads are barely ever touching the rotors, they rotors are not getting cleaned up of surface rust and contamination. With an EV, it's a good idea to go do a hard stop to engage the mechanical brakes every so often. For my Polestar2, the owners manual actually recommends a hard stop once a week just to keep the rotors and pads clean and bedded.

I suggest to go find a nice and open road and do three hard stops from 45-60mph in a row. Then drive around for a bit to allow the brakes to cool before stopping. You should see the rear rotors cleaned up a bit.

 

[UnsungZero_OldTimeAdMan]

I don't buy the theory either. Dragging the rear brakes just doesn't seem like a safe thing to do from a vehicle dynamics and legal liability POV. It's more likely the pins aren't adequately lubricated or are too dirty, limiting the pad's movement and causing it to drag on the rotor.

 

[iamnid]

Regenerative Braking Assist on Gen2’s is under “Vehicle” >> “Autonomy” and it is the very last option in that menu.

I don't even have that option in my Gen 2 R1S

 

[Thedude]

What is road salt ...

It’s what places that don’t get very cold in the winter use on the roads.

 

[BTOR]

I don't even have that option in my Gen 2 R1S

Huh, that is odd. What rev SW are you currently on? I’m on the latest, 2026.15.30

 

[Tlohrenz]

If your pressing the brake, your not using much regen. My brakes are 20 months old and look like new. And I live in the Rocky Mountains. My regen setting is set to the middle setting.

 

[mkg3]

This completely does not make any sense, especially with the regen braking assist off.

Regen braking does not use friction brakes. the motor becomes the generator and converts the kinetic energy back to the cells. In other words, electric motor is used to slow the vehicle and not kinetic/friction brakes. This means that the only time Rivian uses friction brakes is when the driver applies the brake using the pedal or when it comes to a stop since brake hold is the only mode Rivian has when the vehicle comes to stop.

High regen is not the reason for the problem. There is something else causing the issue.

The rust may be due to the rotors being wet at some point and the friction brake only used to hold the vehicle when stopped - meaning that there isn't enough pad/rotor interaction to rub the rust off. As someone mentioned, as soon as the brakes are actually used, the surface rust will be wiped off.

As for non-even wear, perhaps there is a debris on the pad or that the pad material may have inconsistent surface or fractured element(s).

Without seeing the brake pad condition, in terms of uniformity and thickness, it is hard to know why the rotors look to way it does.

 

[R1T Preds Fan]

If using driver + or cruise it auto applies the brakes way more frequently than you’d expect until the system can determine the regen is strong enough to release the brake amount applied… only explanation that I’ve been able to find so far outside of manual brake use.

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