Brake Performance Issues in wet weather?

[scaesare]

MOD NOTE: I'm editing this asking for the mods to delete this thread, as I had not initially seen another thread already covering this, so to avoid duplication I've copied my info there. Thanks.

Just got a call back from service center. They were able to detect some brake feel issues in a test drive, and did a fluid flush/change. Although that service is not specified until two years, I have ~22K miles on mine, and they said they've seen a few times cars with higher mileage for their age with similar issues...

Again great service from the folks in Rockville.

OK, so I'm resurrecting this from earlier in the month.

I got the weird brake feeling again a few times with the heavy rains the last couple of days. When I initially hit the brakes for the first couple of seconds it feels very much like either air in the lines, or "brake fade" if you've ever had it: the calipers just don't seem to be grabbing. After a few moments it will then start to grab and slow me down.

I did some testing, and here are my observations:

- It appears to happen when the car is first driven after sitting in wet conditions for a bit (a couple of hours).

- After the first instance or two in a driving session it stops being as prevalent (but can still happen to some extent)

- It does not appear to be tires losing traction/hydroplaning: I had a section of parking lot where I could test and under identical conditions it would happen the first time, but not subsequent times

- It is not the ABS system. I can feel that kick in, and deliberately engaged it during testing to compare... this is different.

- I've not had it happen in dry conditions


I've never had a disc brake car act like this when in good order. It's very disconcerting in that it it can easily double stopping distance when it happens if in mid-speed traffic.

I'm wondering if the same rust/scale build-up that we notice on the rotors, and that may cause them to stick when parked over night, might be reacting with the moisture and preventing good brake-bad friction until it's been "scuffed off" after the first few braking applications in a given session?

Has anybody else experienced anything like this?

 

[mibaro2]

My car is a few weeks old. It has been raining here for the past 2 days, and my car was parked out in the rain all day today.
The only thing different that I noticed when I drove it was my brakes squeaking. Other that that, the braking was fine.
Could be that my car is new and won't show your symptoms until it has a few more miles on it.
My .02 cents.

 

[Xenoilphobe]

your brakes are wet if you use regen the motor is the braking element so the wet rotors are not really being used

 

[SeminoleFSU]

There have been numerous discussions on brake fade in wet conditions. Just do a search (top right)... IIRC, it has to do with water being directed onto the discs and lack of brake use in general because of regen. An owner who complained a lot wrote about a mod they did on his sig model s to help deflect water away or something

 

[scaesare]

your brakes are wet if you use regen the motor is the braking element so the wet rotors are not really being used

True, however the initial wet brake application in the S feels drastically different than all of the other disc brake vehicles I've ever driven or owned.

 

[yobigd20]

there is a brand new TSB Tesla just released that replaces the rotors with heavier rotors and brand new brake pads to address the braking issue and brake squeaking issue. I just had my rotors replaced last week and haven't had these issues since.

 

[scaesare]

Thanks yobigd20, I just read the other thread on this and my experience is identical.

I should also point out that the service center flushed my brake system to address this when I first mentioned it here (they proactively called me about my posting here). I'll give them another ring...