Weak brakes on my M3

[MikeRTX]

I have to use my brakes every now and then, and they really seem weak. For instance, I had a traffic light go yellow on me yesterday, making me have to use the brakes, and they didn't "bite' like I'm used to with other cars. I had to press hard to get the car stopped.

Is this because I'm having to fight the inertial nature of the drive motor?

I moved my wife's ICE car the other day and I kept standing it on it nose after being used to driving my M3. I'm halfway afraid if I had to do a panic stop it wouldn't do well.

Does anyone else experience this, or is mine not working right?

 

[dsgerbc]

Have you performed the Tesla-recommended maintenance, where they pull the pads, lubricate their sides and caliper pins?
If not, do it now before you really need to use your brakes.

 

[MikeRTX]

Have you performed the Tesla-recommended maintenance, where they pull the pads, lubricate their sides and caliper pins?
If not, do it now before you really need to use your brakes.

No, the car is only 2 weeks old and has only 700 miles on it. But I appreciate the heads-up.

 

[Zcd1]

Which version of the 3 do you have?

My 3P’s brakes are STRONG, but the pedal feel is softer than my wife’s Q5.

 

[dsgerbc]

No, the car is only 2 weeks old and has only 700 miles on it. But I appreciate the heads-up.

Go into the service menu (software menu, press and hold 'model 3', enter 'service' as a password when prompted) and perform the brake burnishing routine. If that doesn't help, open a service ticked via the app.

 

[Dangerous Fish]

As per the post above, you need to bed the brakes in. It makes a big difference.

 

[dsgerbc]

As per the post above, you need to bed the brakes in. It makes a big difference.

Technically, it's the Tesla delivery team that needs to do it.

 

[Zcd1]

Curious that people are suggesting there’s an actual problem with the brakes, rather than perhaps the brakes just feel different than the OP’s other vehicle…

 

[dsgerbc]

Because Tesla brakes aren't special in any way in their design, but are somewhat special in their use patterns. OEM Tesla 3 pads that are in good working order usually have a decent initial bite. I've rented a few 3s from Hertz over the past year. Had to do some quick pad re-bedding on several (due to weak brakes as in OP) and it was fine afterwards.

 

[Knightshade]

Curious that people are suggesting there’s an actual problem with the brakes, rather than perhaps the brakes just feel different than the OP’s other vehicle…

Correct answer marked

The only thing playing around with pads, rotors, etc do is change the "feel" of the system- in an emergency stop it'll work just the same as any other modern vehicle. If you want to reduce stopping distance better tires will do that, "better" brakes won't.

 

[Dangerous Fish]

Technically, it's the Tesla delivery team that needs to do it.

Is that the team that hands you your key card and says "your car is parked over there"?

 

[dsgerbc]

in an emergency stop it'll work just the same as any other modern vehicle. If you want to reduce stopping distance better tires will do that, "better" brakes won't.

This is patently false. Brake pads need a healthy transfer layer of pad material embedded in the rotors to work properly.
That transfer layer degrades if one doesn't use brakes much ( which is hard to do in an ICE car but pretty easy in a Tesla), and then brakes don't perform as they should, adding tens of feet to emergency braking distances.

 

[Knightshade]

This is patently false.

Except, it's not.

If you wanna disagree with physics that's on you.

First- the poster asking has a car that's 2 weeks old with 700 miles on it... his brake pads have not "degraded" due to lack of use. (I'm also curious what the mechanism you imagine would "degrade the transfer layer" of brakes not being used but that's a tangent)

But back to the physics of why different pads/rotors/etc do nothing but change the feel not the stopping distance:


Here's a guy who literally writes books on brake system design, teaches SAE master classes on the topic, and has designed braking systems for major car OEMs explaining why what I said was accurate if you need more info.

GRM Pulp Friction

Couple relevant quotes:

Ths part might surprise some and offend others, but it is a big misconception that changing brake pad material will magically decrease your stopping distances

or the money shot:

You can take this one to the bank. Regardless of your huge rotor diameter, brake pedal ratio, magic brake pad material, or number of pistons in your calipers, your maximum deceleration is limited every time by the tire to road interface. That is the point of this whole article. Your brakes do not stop your car. Your tires stop the car.

So while changes to different parts of the brake system may affect certain characteristics or traits of the system's behavior, using stickier tires is ultimately the only sure-fire method of decreasing stopping distances.

he then goes on to explain why you might want to change parts of your braking system despite it NOT having any impact on stopping distance, including:

Modifying your brake system component sizing (brake pedal ratio, master cylinder piston diameter, caliper piston diameter, rotor diameter) can be performed to adjust the feel of the car to suit the driver's tastes. Some drivers prefer a high, hard pedal, while others prefer a longer stroke. In this regard, tuning your brakes is a lot like tuning your shocks: every driver likes something different, and there is no right answer within certain functional limits. These components can be adjusted in small steps to achieve a feel that the driver prefers.

Which again, is what I already told you that you seem to disagree with for some reason.


Or, if all that is too long for you to read, look up the actual physics formula for stopping distance.

Notice it doesn't ask, at all, about your brake pads. The only part of the vehicle it cares about is the amount of friction the tires of capable of applying to the road.

 

[MikeRTX]

Go into the service menu (software menu, press and hold 'model 3', enter 'service' as a password when prompted) and perform the brake burnishing routine. If that doesn't help, open a service ticked via the app.

Thanks! I'll give that a whirl when I have time to go through the process.

 

[gsmith123]

But back to the physics of why different pads/rotors/etc do nothing but change the feel not the stopping distance:

You can even (sort of) prove this yourself. Find a back road or big parking lot and try a full emergency stop from 30 or 40 mph to zero. You'll noticeably feel the ABS pulsation through the brake pedal when you stomp it.

If the car was not maxing out the brake traction force available at the road-tire interface there wouldn't be any need for the ABS to do it's thing.

Incidentally, I'd highly recommend every driver do this sort of test with their car (especially a car that's new to them). For practice and to get a feel for how the car feels under maxing braking. It's good to get a sense of how car braking distances actually are. I'm always pretty amazed how fast a car stops if you stand on the brakes at 20 mph, it's feels so quick.

 

[Mcgugupapa]

I have experienced the same thing today with my 2 days old car with 50 miles on the OD. The brakes seems to be weaker than ICE car….

 

[dsgerbc]

Except, it's not.

If you wanna disagree with physics that's on you.

You are confusing two things. Sure, tires are certainly important. They limit the MAXIMUM deceleration you can achieve with a properly functioning brake system.
But look up the physics of how brake pads actually work. The coefficient of pad to rotor metal friction is considerably lower than the coefficient of friction between the pad and the transfer layer embedded in the rotor from proper pad bedding. The link you gave does not talk about pad betting at all, so, it pretty much assumes proper bedding.

Improperly (or not at all bedded pads) will not let you utilize the maximum braking traction your tires could supply.
Transfer layer formation needs brake rotor to heat up a bit for the pores in the metal to open up and take in the pad material. If you never brake hard enough, the transfer layer will degrade. If the PDI Tesla team never did the brake burnishing, there won't be any kinda of transfer layer to begin with.

 

[Rocket_man]

Go into the service menu (software menu, press and hold 'model 3', enter 'service' as a password when prompted) and perform the brake burnishing routine. If that doesn't help, open a service ticked via the app.

As per the post above, you need to bed the brakes in. It makes a big difference.

Technically, it's the Tesla delivery team that needs to do it.

Thanks, I need to check out the bed-in procedure. I hardly ever use the brakes, but they do feel like freshly replaced pads before being bed-in. When I get a chance I'll give it a shot.

 

[Dangerous Fish]

This is one of my front discs when I picked up the car.

And this is after some bedding. You can see how the face of the disc has changed. You want to try for a uniform appearance across the whole width of the rotor on all the disc faces.

 

[Knightshade]

You are confusing two things. Sure, tires are certainly important. They limit the MAXIMUM deceleration you can achieve with a properly functioning brake system.

Yeah I'm not though.

Take a fresh out of the factory, nobody bedded the brakes, Tesla (or any other new car).

Now do a single emergency stop.

Does ABS engage? (I guarantee you it does)

That means you already have the maximum decel the tires can deliver.


Bedded brakes will insure that stop (and all stops) feel better.

They will also insure longer life of the entire system because you won't end up with uneven deposits on the rotors (which is frequently misdiagnosed as "warped" rotors-- which is another common braking myth).

That second reason in particular is why you definitely should bed you brakes.

But they won't change how short the car stops.