Braking in rain

[Ven Rala]

I had this problem recently when it was raining heavily and was driving on I-95 for about 2 hours. Every time I braked it too several seconds for the car to actually start slowing. It felt like I was pressing on nothing, but after I braked a couple of times within a minute, the brakes worked as usual. But a few minutes go by and again I had to brake hard for several seconds before I actually felt the car braking, this was of course very concerning as the only time I really use the brakes is when I do emergency braking, otherwise I just keep a safe distance and let regen slow me down.
After this rainstorm, the brakes worked as usual again. So my question is: because I don't use my brakes very often is there water that is getting on the brakes that is decreasing friction to prevent it from properly stopping?
In the past with light rain, I did not notice this problem. Or is there a problem with my brakes that I should have the service center check?

 

[SarahsDad]

Sounds like hydroplaning.

 

[Doug_G]

Never had that happen on my Model S, but if your brakes are soaking wet it might take a moment for them to properly grip. They're the same sort of system as every other car on the road. But it would only be a brief moment.

Did it just feel like several seconds, or did your brakes literally do absolutely nothing for several seconds?

 

[ElectricAvenue]

Sounds like hydroplaning.

Doubt it. The driver would have felt the car skid maybe even sideways slightly and I assume ABS should have kicked in.

 

[jerry33]

Like Doug, I've never had this happen in my Model S either. Usually, it's the opposite--they're a bit grabby when wet.

 

[Discoducky]

What is your regen set to? Are you not feeling any brake force from regen or just the brakes themselves? If regen is set to 'low' it might feel like the brakes are slow to respond as the is pretty heavy.

 

[Morristhecat]

I've had almost the exact thing happen to me the other day during a hard rain. I had to really hammer down hard on the brakes to get them to do anything. It wasn't just a low regen thing, it was quite different. It went away after a few stop. It was as if there was too much water on the brake rotors and the calipers were hydroplaning.

 

[stopcrazypp]

It could be wet rotors. However, like jerry says, wet rotors should tend to be grabby. I guess it must be REALLY wet for it to not respond. In that case, you may have to brake really hard to clear off the water (using the heat of the friction).

 

[stevezzzz]

To the OP: is there any chance you were pressing on both pedals simultaneously, by mistake? It can feel like a brake problem if you do. Of course there is an audible warning and a message on the driver's console, too, but if it catches you by surprise you might not notice them.

 

[cinergi]

I've had this happen in every car I've ever owned if the rotors/pads/whatever are completely soaked (e.g. I drove through a deep puddle). That includes the Model S.

 

[mknox]

Yep. First time I noticed it was coming out of a car wash. Almost rear-ended someone. I've had brakes get a little weak when wet on past cars, but nothing like with the Model S. I'm used to it and aware of it now, but do wonder what it is about the Model S pads and/or rotors that makes it so much worse than other cars I've driven.

 

[bluetinc]

I've had the same thing happen on my S.

Peter

 

[greensprit]

Some cars (like a BMW 3 series I used to own) will automatically lightly cycle the brakes when it is raining out to ensure that the pads are always dry and ready to apply maximum braking power. (they are linked to the rain sensor for the windshield wipers). Not sure what impact this might have on efficiency though, though I'd imagine it'd be quite small. Given the large size of the MS rotors it might be a feature Tesla should implement.

 

[Ven Rala]

I definitely was not hydroplaning, there was no loss of control, just the brakes didn't seem to slow the car down.
Regen was working fine, so I should correct to say the car was slowing down due regen, but not from the braking.
It did feel like several secoonds, though in retrospect it might have been more like 2-3 seconds, but that is a long time when braking on a highway.
I definitely was not pressing on both pedals, I know there is the alarm that goes on when that occurs.

 

[Discoducky]

We have a term: Aquaplaning!

http://www.tirerack.com/brakes/tech/techpage.jsp?techid=78&

 

[Morristhecat]

I talked to my local SC guy about this. Apparently Tesla is aware of this issue and they are trying to figure out a solution.

 

[bhuwan]

I've had this issue repeatedly on my car; never had it on my Lexus.

 

[Chris]

I can confirm the OP braking issues. I had this happen a few times and it is very scary since there is no warning. This is no hydroplaning but the actual brakes not responding to brake pedal input. Has always been related to wet weather and it was worst after the recent snow and cold temps. One time I almost hit the front of my garage and the other time my turn on a side street was much faster than anticipated because the car would just not slow down. My workaround for the time being is to hit the brakes occasionally when it it wet which seems to help

 

[Gizmotoy]

I talked to my local SC guy about this. Apparently Tesla is aware of this issue and they are trying to figure out a solution.

Is it the rarity of using the brakes causes the pads to soak with water, reducing their grip until you burn off the moisture? Or is it the electric brake booster not functioning properly? I notice the booster is slow to respond in the morning after coming out of sleep. It would be obvious in that the pedal requires a lot of additional effort: is the pedal feel normal when this occurs?

I've had mine out in the rain a few times and haven't noticed anything, but I'll be certain to save some extra distance next time.

 

[Ven Rala]

I'm not sure if I feel better that others are having this issue as well. I hope there is a fix.