Sensitive/overboosted brakes on MYP?

[holmgang]

My MYP has a long, soft, brake pedal travel before it meets the resistance zone. In that travel it also induces up to 10bar at the master cylinder (shown in vehicle service menu) making the brakes feel very ‘touchy’

My M3P almost doesnt have that soft travel zone at all. You have to apply a bit of pressure to induce 10bar.

Is this typical for MYP? Can you fix it by replacing a spring or something?

Also does anybody know what is the Brake Stiffness Test is in the service menu, and how to pass the Gateway Unlock to access it? At the Unlock, no movement on the left or the right stalk can satisfy the “turn signal active position”

 

[holmgang]

on the service manual doesn't look like there's any spring or anything as 1 mechanical control of the brake firmness.

car is new and pedal is not spongy so it shouldn't be an issue of line bleed either... just very soft travel

 

[Dangerous Fish]

The brakes are going to feel different on any car based on it's model, age, how well the system is bled and holds it's pressure, how the pads were bedded and all sorts of other reasons.
We've owned 2 Model 3s and a Model Y and I can't say the brakes felt that much different between them all but they all came out of the factory at different times and may have revised parts on some or all which could affect brake feel.
From my testing, 10bar before you are fully pressing the pedal is not that unusual and if you have tested multiple times you'll be building more pressure in the system each time you press the pedal so that value will increase.
Last week 4 of us (M3P owners) ran the brake stiffness test on our cars at a track day we were on and the results varied from 55 to 76 bar (minimum should be 31, maximum 80) so make of that what you will. As it happened, the car with the best brake feel (to me) measured around 65 but I put that down to it having the new pads, fluid and discs just before the day more than anything else.
To unlock the gateway put the turn signal all the way up and press the brake pedal at the same time.

 

[holmgang]

Mine is a late 2023 Berlin build, but the car is extremely low mileage.

I pressed the brake multiple times. It doesnt build up pressure sequentially like in most cars, but seems to relax or reset after a few presses. Anyway, the 10-15bar is from the reading that feels representative of the pedal pressure and travel during normal travel: really light for 1.5 inches or so.

What is the Brake Stiffness Test anyway? Nothing on the web describes what it does and how it works.

 

[Dangerous Fish]

The test pressurizes the system to see if the fluid has been fully bled.

 

[holmgang]

both cars passed the stiffness test at 65 bars. M3P has in-spec range of (31,80) and MYP has (36,80).

i suppose this is measuring the cylinder pressure at maximum pedal travel/pressure. mildly useful to know, though says nothing about firmness at the beginning of travel.

 

[Dangerous Fish]

The Model 3 does suffer from movement of the master cylinder due to flexing of the bulkhead where it attaches. LHD and RHD braces are available which help to reduce this flexing. Some of what you feel in the first part of pedal travel could be this unless Tesla strengthened the MY mounting.
I've only seem braces sold to fit the M3 and they wouldn't fit a MY.

 

[ngng]

I bled my system and bed the pads and it made a big difference.