Braking in rain

[kishdude]

Drove through a pretty bad rainstorm yesterday here in AZ... it rained so hard that everyone on the freeway stopped and turned on their blinkers. Blinding sheets of water were coming down. I also drove through two large puddles where I could feel the force of the water hitting the underside of my car and shooting out the sides. I noticed no difference in regen/braking performance and my car made it through the deluge and ensuing flooding just fine, even after giving my battery pack and brakes a thorough drenching.

Drove through the same rain with flooded streets and completely soaked car with no brake issues what so ever, but reading this thread is scary. Brakes not working as soon as you hit them is no laughing matter. For those having this issue, is it that every time your brakes are wet that this happens or only intermittent times?

 

[mknox]

For those having this issue, is it that every time your brakes are wet that this happens or only intermittent times?

For me, it's every single time. If I come out of a car wash it happens. If I drive in the rain or slushy winter stuff it happens. FWIW, it's been like this since new a year ago.

 

[wtgw]

Hello, 1st post. Car knowledge level: expert, although I know nothing about Tesla I'm interested.

A few things nobody mentioned: 245 width tires are moderate to narrow for a 4600 lb car of this performance. Wide tires do skate over water/rain much more easily than narrow tires but I don't think this is hydroplaning because the tires aren't terribly wide and the car is pretty balanced. Are you losing traction with the road? No idea, I've never driven a Tesla.

Ice pedal: I've had it twice and heard of it happening a few times to other people and it's not fun. I don't know the specifics of the Tesla system so I'm not speaking of the Tesla specifically, only cars in general. This usually happens when the ABS system gets confused and takes away the brakes. It's happened to me when I'm driving too fast on the street and I hit a pothole when braking. I've heard of it happening on the track when someone bumps a curb or the car is unloaded in a strange way. It's a known issue with Porsche and BMW that see the racetrack (and probably many other cars that don't see racetracks). On the track, unless you're running for money or your career as a pro, it's a good idea to pump the brakes before entering a hard brake because you want to be sure they're there, the pads can lose contact with the rotor for a number of reasons previously discussed, and slow in-fast out. It's not as fast but it's faster than a crashed car

Normal ABS operation: I've had the ABS kick on normally on ice, it takes away all braking authority because ABS is NOT a braking aid, it's a steering aid. It actually hurts braking under most conditions. Perhaps the ABS system is tuned too sensitive. You should feel the ABS pumping the brake pedal but I don't know about the Tesla since I don't know the systems on this car.

If you ever lose braking authority, a good idea is to completely release the brake and reapply them. Opposite of what your natural reaction is, to press harder and lock your elbows for the brace In any case, people in general follow way too close, especially in the rain and snow. Slow the F down.

 

[Discoducky]

Raining heavily today and did not experience any issues with braking. Several times down steep hills to a complete stop.

I'm not doing anything special to provoke this behavior. Going down a hill 4 to 6% grade in pouring rain at about 40MPH. Let normal regen scrub out about 20MPH then gently apply brakes to feel normal braking force coming to a stop.

 

[mknox]

Raining heavily today and did not experience any issues with braking. Several times down steep hills to a complete stop.

I wonder if the wheels have something to do with it, perhaps directing water flow towards the rotors??? I have the stock Tesla 19" wheels for what it's worth...

 

[Atebit]

For me, it's every single time. If I come out of a car wash it happens. If I drive in the rain or slushy winter stuff it happens. FWIW, it's been like this since new a year ago.

Has Tesla taken your car in for an extended period of time to try & reproduce? If you can consistently reproduce this, you seem to be in the minority. Which could mean you have a different problem than the rest as well I guess

 

[Gizmotoy]

If I come out of a car wash it happens.

Happened to me for the very first time yesterday, and I immediately thought of this thread. It feels exactly as everyone else described. I came out of a car wash, pulled into a parking spot to continue drying, and lightly hit the brakes. Nothing. So I pushed a little harder, to no additional effect. Then I stood on the brakes and it stopped (thankfully short of the curb). I was going maybe 5mph tops.

Dried off the car and they worked fine for the rest of my trip.

I will definitely mistrust wet Model S brakes in the future.

I've wondered before if my brake pump is weak. When I get to the car in the morning, there's no stored brake assist (the pedal is extremely stiff). In an ordinary vehicle, you have one or two good pushes of the brakes stored even if the pump isn't running, and the lack of that would indicate a leak in the brake lines. Is that normal with the Model S electric pump? Anyone else with trouble stopping in the wet experience that?

 

[Atebit]

I wonder if this could be some kind of intermittent hand-off issue between the regen & mechanical braking systems? IIRC people say the regen bails out around 5 MPH. Maybe in some cases the mechanical brakes aren't taking over at low speeds. Not sure why water would cause this. Though I thought I remember reading in one thread where someone experienced a similar lack of braking when pulling into their garage at a slow speed.

 

[Discoducky]

I wonder if the wheels have something to do with it, perhaps directing water flow towards the rotors??? I have the stock Tesla 19" wheels for what it's worth...

So do I. Are you driving through high standing water? Something that would cover part of a caliper? Also, when it is raining I'm more careful in my following distance to be sure that I never need hard or quick braking and let regen scrub most of the speed.

 

[mitch672]

So do I. Are you driving through high standing water? Something that would cover part of a caliper? Also, when it is raining I'm more careful in my following distance to be sure that I never need hard or quick braking and let regen scrub most of the speed.

The issue is especially bad in extreme cold and wet conditions (under 20 F), in those conditions regen is mostly or totally disabled, and there is essentially no regen, so you can't count on it to slow you down, you lift your foot off the accelerator and the car continuos to travel at essentially the same speed. Which is why diminished front brakes are so frightening, trying to stop a 5,000 pound Model S.

It doesn't have to be raining, if the vehicle has been outside all day, in wet / damp weather, the rotors and brake pads are wet, and just don't work well.

 

[mknox]

So do I. Are you driving through high standing water? Something that would cover part of a caliper? Also, when it is raining I'm more careful in my following distance to be sure that I never need hard or quick braking and let regen scrub most of the speed.

Nope. It is really noticeable coming out of a car wash. That is understandable since the rotors would be soaked, but again, I've never noticed anything nearly like this on any other car. Also happens just driving on wet and/or slushy highways. Service is going to take a look for me (as soon as I can get it in -- my fault not Tesla's as I've just been so busy).

 

[Gizmotoy]

Nope. It is really noticeable coming out of a car wash. That is understandable since the rotors would be soaked, but again, I've never noticed anything nearly like this on any other car. Also happens just driving on wet and/or slushy highways. Service is going to take a look for me (as soon as I can get it in -- my fault not Tesla's as I've just been so busy).

Let us know if they find anything. I was contacted by my SC about my experience the other day, but the only time I've ever seen it is that one time coming out of a car wash, and I'm not sure that alone warrants them doing a full investigation. For now I'm just increasing my following distance in the rain, which given the record drought, I haven't seen much of.

I've wondered before if my brake pump is weak. When I get to the car in the morning, there's no stored brake assist (the pedal is extremely stiff). In an ordinary vehicle, you have one or two good pushes of the brakes stored even if the pump isn't running, and the lack of that would indicate a leak in the brake lines. Is that normal with the Model S electric pump? Anyone else with trouble stopping in the wet experience that?

My very nice contact at my SC walked me through this. It sounds like energy for 2-3 pumps of the brakes should be stored in the booster when the car is turned off. There was some speculation that I'm somehow eating into this reserve when I park. Considering the car turns on when you press the brakes from the driver's seat (and thus powering up the braking system) I'm having trouble envisioning how that could occur, but I suppose it's possible. I'm going to pay closer attention to when this occurs to see if I can pin down something I'm doing to cause it.

 

[neroden]

Nope. It is really noticeable coming out of a car wash. That is understandable since the rotors would be soaked, but again, I've never noticed anything nearly like this on any other car. Also happens just driving on wet and/or slushy highways. Service is going to take a look for me (as soon as I can get it in -- my fault not Tesla's as I've just been so busy).

Tell me if you find anything out. I've seen some odd behavior coming out of car washes as well. I haven't had noticeable trouble in other conditions. My brakes get used much more heavily compared to everyone else's thanks to the constant hills around here, though. (And even more so in the winter because I have limited regen on every single in-town trip.) So my relatively heavy brake usage probably makes a difference; probably cleans the water/ice off the rotors faster.

 

[ACDriveMotor]

FWIW I have not yet experienced this issue driving around Seattle in some pretty heavy rains. No issues with car washing either. Though I hand wash my car, so maybe there is something about car wash that more completely soaks the rotor/caliper. I suppose I am a fairly spirited driver so my brakes get some work-out even with regen.

For those experiencing this do you regularly use brakes or do you try to regen to a near-stop most of the time?

Nov'13 delivery. For those experiencing, what is your vintage?

 

[mknox]

It sounds like energy for 2-3 pumps of the brakes should be stored in the booster when the car is turned off.

When my car was new, it would hold this vacuum reserve, but from about the 6 month of ownership point on forward, the pedal is "hard" when I get into the car in the morning. As soon as I "start" the car, the vacuum boost is immediately restored, so I'm not particularly worried about it. It has nothing to do with the problem when wet.

- - - Updated - - -

For those experiencing this do you regularly use brakes or do you try to regen to a near-stop most of the time?

Most of my driving is on the freeway, so no, the brakes don't get used much. My last (ICE) car was on the original pads and rotors after 4 years and 80,000 miles, so that should give you some idea of my brake use. With its re-gen, the Model S brakes likely get used even less. Having said that, I never had wet brake problems either from a car wash or from driving in the rain with any other car before. They're fine 99% of the time. It just gets a little scary when they're wet, but I'm kinda used to it and expecting it now.

 

[SeminoleFSU]

Something is definitely weird with the MS brakes. I've had my freeze/lock many times after washing my car and parking it in my garage wet. And overnight (without it getting below freezing) my brakes would be literally stuck... and when I put it in reverse, I have to give it juice to unbreak them... when it does it makes a horrible snapping noise... and they don't all unsnap at once, so it is very jarring and scares the daylights out of you. first time it happened to me I thought I ran into the garbage can or something

 

[lolachampcar]

The freezing thing is simply the pads "rusting" to the rotors. I've had several Brembo equipped cars that have done that including my MS.

 

[SeminoleFSU]

It's new to me Guess I haven't had any cars with high performance brakes

 

[Doug_G]

My Roadster does it all the time - just need a humid day. My old Infiniti would do it sometimes. Model S is actually much better.

Sticking to the pads is no big deal. Break it loose, do a couple of stops, back to normal.

 

[Gizmotoy]

When my car was new, it would hold this vacuum reserve, but from about the 6 month of ownership point on forward, the pedal is "hard" when I get into the car in the morning. As soon as I "start" the car, the vacuum boost is immediately restored, so I'm not particularly worried about it. It has nothing to do with the problem when wet.

Having worked on a lot of brake systems (though in a maintenance capacity), while unlikely, I can think of at least one thing that could cause them to be related. If your brakes are doing two things which are not normal, you should probably at least consider the possibility that they're related.

It's more likely to simply be the pads, though. Brembo pads have kind of a reputation for being weak when wet. Do we know if that's what Tesla used (Edit: It is, I saw the proof in another thread)? My last car used OEM Brembo calipers and rotors, but Ferodo pads, probably for that reason. I did a track day in a school's prepped Acura TSX in the rain that used Brembo calipers/pads and they instructed us to make a little jab on the brakes at the end of the straight, let off, and then "pull the chute" into a tight S turn. In all likelihood we're just seeing something like that, exacerbated by high-pressure water shot right into the brakes.