Ceramic brakes?

[Lmirafuente]

Someone took pictures of the stamping on the back of the 20" wheels. They are 20x8.5, ET48. The center bore is still unknown.

Thank you!

Sponsored

 

[SeaGeo]

Thanks for all the information!

I ask only because I saw a post on the Tesla Plaid brakes catching fire when used in track-like conditions.

https://jalopnik.com/watch-a-tesla-model-s-plaids-brakes-catch-fire-during-t-1848169116

The video had them going up to 100MPH then braking hard and they did it several times and was testing the temperature of the rotors after. Not a typical SUV/Truck thing, but got me wondering. The guys on the video were upgrading the Tesla Plaid brakes.

Thanks again for the info!

Regarding the wheel offsets...that has still been an illusive bit of data.

Reason for asking is looking at potential after market options.

I originally configured 22"s on my LE then moved to 20". I may just get both but wanted to check on what is out there on the market that can suppor the R1's....

The plaid's issue is also because the breaks are undersized for the weight of the car (as you saw), and even driving it hard on some twisties has been shown to make it unsafe. Based on their break size, I suspect Rivian has sized their breaks to handle sustain truck and tow loads without regen.

 

[DuckTruck]

I haven’t seen ceramic brakes mentioned, and wouldn’t expect them to be much use for an EV.

The Rivian is a very heavy vehicle, but like other modern EVs the regen means that brake requirements are actually pretty modest.

AFAIK the real advantage of ceramic brakes (apart from bragging rights) is longevity and lack of fade under repeated applications such as on a track. It’s hard to imagine a use case on the Rivian where they’d be better than standard brake materials.

The bright yellow caliper paint already confers most of the advantages, without the significant expense. This is also true of Porsches that aren’t actively running on a track.

I can't wait to read this to my Porsche buddies! Ten bucks says one of them will splash me with their Chardonnay within fifteen seconds of me finishing the story. Their reflexes aren't nearly as good as they think they are. ?

 

[AbqEV]

I’m also assuming this question was about carbon ceramic rotors. While I agree with others, this would likely be overkill, and comparing the braking issues of the Tesla plaid is likely a different animal. Unlike the plaid, Rivian is already using 6 piston (Front) calipers and what looks like 4 piston out back, larger rotors, and with regenerative doing most of the work, brakes should be great on the Rivian.

As to potential advantages of the carbon ceramic approach -
They would substantially reduce unsprung weight/rotational mass, I would guess about 15lbs a corner, and that’s a lot. This would likely translate into noticeable acceleration increase but more importantly it would increase range. I’m sure someone could do the math, but I’d suspect it would add another 50mi of range. As an example, the Tesla Plaid gets almost 50mi longer range with the lighter (9 lbs lighter each) 19” wheels/tires than with the optional 21” in wheels. I’m sure there’s a mile or two in there from aerodynamics and other factors but it’s primarily weight reduction. Other comments point out that yes they would be expensive (probably in the $10k range for just rotors) but they would likely last the lifetime of the vehicle given the extensive use of regenerative braking. Probably a relatively short ROI if you factor in the likely range increase.

 

[Lmirafuente]

I’m also assuming this question was about carbon ceramic rotors. While I agree with others, this would likely be overkill, and comparing the braking issues of the Tesla plaid is likely a different animal. Unlike the plaid, Rivian is already using 6 piston (Front) calipers and what looks like 4 piston out back, larger rotors, and with regenerative doing most of the work, brakes should be great on the Rivian.

As to potential advantages of the carbon ceramic approach -
They would substantially reduce unsprung weight/rotational mass, I would guess about 15lbs a corner, and that’s a lot. This would likely translate into noticeable acceleration increase but more importantly it would increase range. I’m sure someone could do the math, but I’d suspect it would add another 50mi of range. As an example, the Tesla Plaid gets almost 50mi longer range with the lighter (9 lbs lighter each) 19” wheels/tires than with the optional 21” in wheels. I’m sure there’s a mile or two in there from aerodynamics and other factors but it’s primarily weight reduction. Other comments point out that yes they would be expensive (probably in the $10k range for just rotors) but they would likely last the lifetime of the vehicle given the extensive use of regenerative braking. Probably a relatively short ROI if you factor in the likely range increase.

Interesting! $10K upgrade to ceramic vs $10K for max pack…..hmmmm

….wonder if we could get a group volume discount to drive that $10K down….if we could truly increase range…..

 

[Lmirafuente]

I wonder if Rivian would offer a Ceramic Brake upgrade if they can guarantee a range increase of xx miles…. I bet that would sell if the range increase was at minimum of 50 miles….and the cost was ideally less than $5K….thoughts?

 

[Joe schmoe]

I'm very skeptical that range gains would approach 50 miles from switching to carbon rotors. That would be about 16% or so which is a -huge- number. 50 miles on the plaid is from a much higher baseline range, is the incremental gain is less significant. Also, the Tesla is vastly more efficient at converting kWh to miles, so small improvements make more difference.

I agree that they would reduce unsprung weight (which by itself wouldn't have much impact on range). They would also reduce rotating mass as you noted, but I'm guessing the real thing you want to look at is the polar moment of inertia. Reducing weight near the axle doesn't do nearly as much as going to a lighter tire or rim.

If you could source a suitably durable carbon fiber -rim- you might be on to something

 

[DuckTruck]

I'm very skeptical that range gains would approach 50 miles from switching to carbon rotors. That would be about 16% or so which is a -huge- number. 50 miles on the plaid is from a much higher baseline range, is the incremental gain is less significant. Also, the Tesla is vastly more efficient at converting kWh to miles, so small improvements make more difference.

I agree that they would reduce unsprung weight (which by itself wouldn't have much impact on range). They would also reduce rotating mass as you noted, but I'm guessing the real thing you want to look at is the polar moment of inertia. Reducing weight near the axle doesn't do nearly as much as going to a lighter tire or rim.

If you could source a suitably durable carbon fiber -rim- you might be on to something

I'm not Bill Nye, the Science Guy (even though several friends say I look like him), but I'd think the biggest advantage to range by greatly reducing the rotational mass would be in stop-and-go traffic. Once you're out on the highway and up to a constant speed, does changing the rotational mass impact the range as much?

In this case I'm talking about wheel, hub, disc, and tire combos that have the same coefficient of drag and rolling resistance, but weigh different amounts. At a constant speed, I can see there being a slight difference, but I wouldn't think it would be that great of an impact on range.

Bill Nye is a huge E.V. guy (and, apparently, a very handsome man). If you're lurking out there, Bill, jump in here and educate us! ?

Sponsored