Rear Brake rotors - casualty of high regen.

[DKM_R1S]

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.

Sponsored

 

[Time2Roll]

If the pads are worn evenly I would not worry too much about it.
OK to reduce regen for 90 days and see if you like the result.

I would do no hard stops unless to avoid collision.

 

[Motoarzon]

I always keep it on "low" regen. Mine are the same. Grooves and wear not like the fronts. Have about 20,000km on the vehicle and 1.5yrs old

 

[RBM3]

If I recall correctly, the gen 1 uses the rear brakes more when Highway assist/ACC is enabled. Something to do with the system requirement to use breaks while engaged regardless of regen ability. Kind of a holdover from ICE cars which similar adaptive cruise control features.

 

[Zathras]

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.

I wonder what difference the R1 being front-biased has to do with this? The R2 is rear-biased. Would that make a difference?

 

[BTOR]

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.

Well I’ve had my 2025 R1S DM set to max regen since day 1. I have somewhere north of 15,000 miles (24,000+ km). All 4 of my rotors still look brand new. I almost never touch the brake pedal. Picture is of the passenger side rear but representative of all 4.

I’m not sure I buy in to the max regen root cause explanation. Do you drive a lot in wet, gritty conditions? I would think it would take more than just brake pads to scar the rotors like that (unless they were extremely worn). Didn’t notice your geographical location? Perhaps road salt caused some corrosion?

I would not attempt to perform any type of self corrective action. If you notice your braking is compromised, I would have the SC take a look at them immediately. If your braking seems normal, I would make a note of it and have the SC look at them on your next visit.

 

[DKM_R1S]

Well I’ve had my 2025 R1S DM set to max regen since day 1. I have somewhere north of 15,000 miles (24,000+ km). All 4 of my rotors still look brand new. I almost never touch the brake pedal. Picture is of the passenger side rear but representative of all 4.

I’m not sure I buy in to the max regen root cause explanation. Do you drive a lot in wet, gritty conditions? I would think it would take more than just brake pads to scar the rotors like that (unless they were extremely worn). Didn’t notice your geographical location? Perhaps road salt caused some corrosion?

I would not attempt to perform any type of self corrective action. If you notice your braking is compromised, I would have the SC take a look at them immediately. If your braking seems normal, I would make a note of it and have the SC look at them on your next visit.

We do live in the Chicago area, so frequent driving in road salt. I wonder the fact that yours is a Gen 2 Dual makes any difference?

 

[BTOR]

We do live in the Chicago area, so frequent driving in road salt. I wonder the fact that yours is a Gen 2 Dual makes any difference?

This is only a guess on my part but I would think unless there was a well know issue with the Gen1 rotors, they sourced the same part for Gen2's.

Many rotors are cast iron or alloys with a high iron content which means they rust easily. It is very common. Some manufacturer's put coatings on the rotor surface to reduce the rust but obviously, this is silly, these coating wear out quite quickly from normal braking. The rust is generally only a surface rust. Our rotors on our old Acura MDX would rust within hours after driving in the wet. They would then make this awful rubbing noise on the next drive for the first few miles before the caliper pads would rub and clean them up.

But on ICE vehicles this surface rust cleans up immediately each drive upon braking. On an EV with regen, this might not be the case. Add salt, and you might get a rust/corrosion combo. In the event you brakes don't clean it off immediately due to regen braking, it's possible that it gets severe enough to where it can wear and scar the rotors when the caliper pads do make contact. This is all very speculative on my part but I suppose possible. I would think other Rivian owners in the midwest where different concoctions of sodium chlorides are used to alter the freezing temperatures of road water might be seeing similar conditions.

You might try using your brake pedal to assist the regen braking if you don't already and see if you notice any changes in the rotor wear patters over time. I wouldn't expect the change to occur overnight. Caliper pads are relatively soft and the steel is hard so it might take a few months before you notice anything.

Just some ideas and thoughts. Again, I would not do anything out of the ordinary to try and correct the situation. What you are observing might not be that unusual. Hopefully some other Rivian owners in the midwest will chime in.

 

[BTOR]

As some of the other posts noted, I guess there might be some differences between Gen1 & Gen2 when the brakes are applied via regen (rear vs front bias). I'm not sure if this is known or speculative. I would try to get a confirmation on those differences if they in fact do exist.

I do notice at times that my brake pedal depresses on its own when using regen to slow the vehicle. If I lightly place my foot on the brake pedal I can feel it depress or move away from my foot. I don't notice it all the time which tells me it only happens under certain conditions or situations. I haven't done it enough to figure out which conditions or situations trigger it. I also try to use the brake pedal periodically just to keep the calipers pistons moving and their seals lubricated. Maybe old school, but it is what my common sense tells me to do.....

 

[DKM_R1S]

Thanks for your reply. I’m on the fence as to if I want to add this to my service ticket for next month’s service appointment. I don’t feel like there is anything wrong with the brakes. Just visually the rotors don’t look that great and now I have developed an infatuation with everyone’s brake rotors, can’t stop looking and comparing.

by the way, the original rear rotors on my 2023 Model Y look very similar to my R1S, so maybe it’s how and where I am driving these vehicles. I used FSD / Driver Assist quite often.

 

[DKM_R1S]

As a follow-up question, if I ask Rivian to take a look at my brake rotors during a previously scheduled service appointment, should I plan on Rivian charging me a labor rate just to look at them? So far I have paid zero dollars for all 17 of my service visits (except for the replacement of the glass roof).

 

[BTOR]

Thanks for your reply. I’m on the fence as to if I want to add this to my service ticket for next month’s service appointment. I don’t feel like there is anything wrong with the brakes. Just visually the rotors don’t look that great and now I have developed an infatuation with everyone’s brake rotors, can’t stop looking and comparing.

by the way, the original rear rotors on my 2023 Model Y look very similar to my R1S, so maybe it’s how and where I am driving these vehicles. I used FSD / Driver Assist quite often.

You may have answered your own question based on how your Tesla rotors looked.

I completely hear you regarding your infatuation.

I have my own little story. My rear derailleur hanger on my nicest road bike somehow got bent and caused the derailleur cage to be slightly angled in towards the rear wheel. It still shifted perfect so I didn’t think much of it at first. But I found myself looking at every rear derailleur on every bike I saw. They ALL hung straight. Once I determined it was the hanger and NOT a bent derailleur, I was able to straighten it with the proper tool and all was good. A new derailleur would have set me back $900. Yep, a Shimano Dura Ace Di2 rear derailleur cost that much…. OUCH!

 

[Dave Cundiff]

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!

 

[R1T Preds Fan]

This ^^^ make sure to turn off the regen brake assist… on my Gen 1 T I’m at roughly 80k and turned that off immediately. Just had service done last week and still at 90+% pad/rotor life acc does still apply the brakes in some situations but I’ve gotten accustom to disengaging it prior to allow the regen to engage sooner and avoid the brake applying…

 

[Mark_AZR1T]

Interesting thread. A bit dark to get decent photos of our R1s. My R1T has 72,000 miles with about 80% 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.

Sponsored