Racing Brake XT910 vs XT970

[talon720]

Hi guys, I used XT970 front / XT910 rear in my Model 3 (dual motor, not performance ) at a track day back in December and have a couple questions. See the first two photos after two 25-minute sessions - can anyone explain the irregular spots on the front rotors, and the non-uniform circular pattern on the rears? I have the RB Model S kit that has 355mm model S rotors and calipers up front, stock calipers in the rear. This was at COTA which has a straight where I reached 120-130mph and braked to about 40mph - I braked hard but not as hard as I could have, since I was new to the track and didn't want to push it the first time out on the new brakes.

For the front spots, I suspect this is because the pads weren't fully bedded in - what do you think? Before the track day I followed the RB bedding procedure, but it seemed much less aggressive than I've done in the past (8-10 hard brakings from 60mph down to 20mph, as Dave Zeckhausen recommends here: You are being redirected...).
Here is the RB bedding procedure for reference:

1. Make 6 to 8 brakings from approx. 30-35 mph. Do not go below 25 mph.
2. Make an additional 3 to 4 hard brakings from approx. 50-55 mph. Do not go below 40 mph.

The last photo is the front rotors after 3 months of street driving, with only moderate occasional braking beyond what regen provides - you can see the spots are gone.
I have a track day this week, so I'm going to try the Zeckhausen bedding procedure and see how it goes.

What do you think about the rear pattern? This is consistent on both sides of the car.

 

[Dangerous Fish]

Have you asked RB about it?

 

[destructure00]

Here is the RB bedding procedure for reference:

1. Make 6 to 8 brakings from approx. 30-35 mph. Do not go below 25 mph.
2. Make an additional 3 to 4 hard brakings from approx. 50-55 mph. Do not go below 40 mph.

FWIW that's the procedure for the 910. There's a more aggressive procedure for the 970.

MOTORSPORTS:

Racing pads must be properly bedded-in at race track conditions or undesirable result or premature failure may occur.

1. Seal all brake ducts, if any.
2. Make 6 to 8 brakings from approx. 60-80 mph. Do not drag brakes to a complete stop.
3. Increase speeds to simulate race conditions (at racing speeds) and make additional 6 to 8 brakings.
4. Remove brake duct seals. Allow 10-15 minutes for the brake system to cool down. Do not apply the parking brake during this cool down period.

A couple of us have seen odd pad deposits on the RB rotors.

 

[beastmode13]

The rear streaks are oxidation/aka rust from lack of use. It will go away once you gone through the bedding process.

fyi. Bedding is something you need to do consistently for our cars since the brake is barely used at all during normal driving. The bedded layer of material will wear away at low rotor temp, which is pretty much the normal state of our brakes. On a ICE the brake is used all the time, it will reach pad transfer temp during normal operations so the process of material removal and transfer balance itself out.

 

[ManManRoadDawg]

Thanks for that! Will a 245 tire stop faster than a 235 tire?

they'd be exactly the same.

The brakes don't stop the car, the tires do.

The only time you'd see a difference in pads is if you tested, say, 10 back-to-back-no-cooldown stops from 80-0 in a row.

One set of pads, the braking distance would begin to get longer after fewer stops than the other.

it'd never be shorter than stock though as brake upgrades can't do that- only tire upgrades can.

L M F A O ! ! !
Soooo...
A set of High Performance Fully Metallic Track Pads won't stop my Car any quicker than Stock Organic Brake Pads!?!
Now THAT is hysterical!

 

[bradhs]

L M F A O ! ! !
Soooo...
A set of High Performance Fully Metallic Track Pads won't stop my Car any quicker than Stock Organic Brake Pads!?!
Now THAT is hysterical!

His theory is once you hit max grip on the tires there's nothing more the brakes can do to stop you. Assuming you get there. I assume though that you'd get the tires to max grip much sooner with better brakes.

 

[MasterC17]

L M F A O ! ! !
Soooo...
A set of High Performance Fully Metallic Track Pads won't stop my Car any quicker than Stock Organic Brake Pads!?!
Now THAT is hysterical!

I'm sure @Knightshade will be here to roast you himself soon enough, but you clearly have no understanding of how brakes work.

The biggest BBK on earth will NOT stop your otherwise stock Model 3 faster or in a shorter distance than the stock brakes in a single-stop scenario. This isn't a theory, and it isn't unique to Tesla.

Track pads are designed to consistently stop the car over a broader temperature range, such that after ten 80-0mph stops they should be able to stop the car similarly the tenth time as they did the first time. Unlike the stock pads, which are at that point likely well outside of their ideal temperature range and would result in longer stops.

 

[Dangerous Fish]

As shown here:

 

[Knightshade]

L M F A O ! ! !
Soooo...
A set of High Performance Fully Metallic Track Pads won't stop my Car any quicker than Stock Organic Brake Pads!?!
Now THAT is hysterical!

It's actual factual. And one of the most misunderstood things in vehicle performance, so it's not surprising there's still folks falling for the myth brake upgrades stop you shorter. They don't.

Because that's how physics works.

MasterC17 covered this briefly and admirably, but If you'd like a much deeper explanation of why those pads not only won't stop you shorter but can not stop you shorter (all else being equal) I highly recommend this

GRM Pulp Friction

Author designs braking systems for major OEMs, teaches SAE master classes on brake systems, and has literally written books on the subject.

I can also quote you technical white papers from Stoptech or the FAQ from Brembo all telling you brake upgrades don't reduce stopping distance if you're still unsure.

Or if you'd prefer to more direct bit of physics evidence what I said was accurate, here's the actual formula for braking distance:


d=v^2/2ug

d=distance to stop
v=velocity of vehicle
u=coefficent of friction between tire and road
g=acceleration due to gravity (9.8 m/s on earth for example).

Notice it cares about your speed, the tires, and the road.
Notice it does not care about your brake pads (or rotors, etc)



Once you engage ABS (or lock the tires on non-ABS cars)-- which any production vehicle with stock brakes has been able to do for decades, moar brakes literally can not help in slowing you down.

Because your stopping distance is determined by the tires friction against the road not how sticky your pads are.

If you want to stop shorter- get better tires, not better brakes.



If you want to stop in the same distance on a race track on your 10th back to back no-time-to-cool-down stop, THEN your pads matter. But only in the sense of keeping your distances from INCREASING- they'll never be shorter the first stop than the stock system could have done.

(again the Pulp Friction essay gets into each specific part of braking systems, what they do, what they do NOT do, and why you might want to upgrade them even though they can not reduce your stopping distance)