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Do our brakes need "excersise?"

For the first time in quite a while, I had to panic brake, and it really seemed like the brakes were a bit "mushy" and slow to react. I stomped on the brake pedal as hard as I could and the car did stop in time but I was wondering if our brakes need any "exercise" every now and then since they are used so infrequently due to regen.

I wonder if any type of layer builds up over time that could reduce the effectiveness of the brakes.

What's the best practice for making sure the brakes are in a state of peak performance? Is it a good idea to do a panic stop from a certain speed in a safe setting every month or few months?

Look forward to hearing any advise or theories about what best to do!
 

whitex

Well-Known Member
Sep 30, 2015
6,912
8,806
Seattle area, WA
Long time Tesla driver here. I always do a quick brake check when leaving the house, and sometimes a hard brake to scrape whatever build-up is on the brakes. Especially when it rains and the car has been sitting there fore a couple of days, the first brake will not be as effective, and sometimes it takes some hard braking to fix it. It can be a little unnerving, which is why I now do a quick test as soon as I start rolling. I rarely use mechanical brakes, most of my braking is regen, but I want to know that the mechanical brakes are ready for action if needed.
 
I recently learned that Model S/X front brake inner calipers can get stuck in place if they are not used heavily occasionally. Also, in areas that get snow and they put salt on the roads, you should yearly use a ceramic brake grease so there is free movement of the pads in the caliper. Even if the inner caliper gets stuck in places the brakes will still work, but not as well, and can cause problems with the rotors and bearings. I'm surprised the service centers in the rust belt don't check them when cars come in.
 
I had a similar issue where it wasn’t braking straight. After inspecting the brakes I had stuck pads. Now every fall I disassemble the brakes and re-lube everything for the winter.

my service advisor suggested turning off regen and when getting off the highway use the brakes harder to clean them off every so often.

doing both of these things has helped and I haven’t had the problem happen again.
 
Wish the Tesla brake software would periodically "exercise" the brakes, as the car knows best how often the brakes were used to bleed off any debris or layer of whatever that builds up.

For example in Mercedes cars, even if it just rains (the car knows that due to the operation of the wipers) every now and then, it automatically applies an imperceptible amount of braking to clear/clean the brakes so maximum brake force is available in the rain.

I can see Tesla expand on this feature to take into account the "relative dormancy" of brakes in EVs and apply slight braking as needed to ensure brakes are always at peak performance. Tesla should add this feature!

From the Mercedes Website:

" When you´re driving in the rain, Automatic Brake Drying applies just enough brake pressure to sweep built-up water from the discs."

2019-09-18_12-51-16.gif
 

Skotty

2014 S P85 | 2020 3 P19"
Jun 27, 2013
2,538
1,987
Kansas City, MO
In my opinion, it's good to use the brake every now and then (while moving at modest speed; this is in addition to using brake every time you are at a stop). Just the occasional quicker than regen stop from modest speed should be enough. I always like to use the brake shortly after a car wash also to remove the immediate rust buildup that occurs after being directly sprayed with water. You can temporarily set regen to low also; just remember to turn it back to normal after.
 
What's the best technique for cleaning any residue from brakes not used in a while but would not cause harm/warping to the brake pads?

I've heard something about 2-3 quick 60-5 mph slowdowns so you don;t fully stop but engage the brakes and then disengage around 5mph so you are not sitting on hot brakes while fully stopped. Does that make sense?
 

whitex

Well-Known Member
Sep 30, 2015
6,912
8,806
Seattle area, WA
Your brakes should be used every time you dome to a stop. They aren't used as much with regen, but they are used.
The way I drive I usually use brakes under 5mph, and often not at all since I see red lights ahead of time and time my arrival so that that I don't have to come to a complete stop at all. Same on a highway heavy traffic, just leave more room and anticipate traffic speed. Even occasional full stop from under 5mph doesn't clear the brakes from rust and rain mixure, when they feel like they are not braking full strength - in that situation, a fast brake from ~40mph tends to clear them - that could cause an accident with someone behinds me, which is why I try to do that with nobody behind me.

I just developed a habit of brake check when leaving and a purposeful braking to scrape the rotors when needed.
 

dark cloud

Active Member
Apr 14, 2018
2,203
2,570
BC
What's the best technique for cleaning any residue from brakes not used in a while but would not cause harm/warping to the brake pads?

I've heard something about 2-3 quick 60-5 mph slowdowns so you don;t fully stop but engage the brakes and then disengage around 5mph so you are not sitting on hot brakes while fully stopped. Does that make sense?

I would say one of these stops is more than sufficient. You can actually hear the sound of the pads scraping rusty rotors. A couple of rotations at any speed with moderate force and they should be good. With more moisture of course one may need more heat to dry them.

But there are 2 concepts going on here: The first is the cleaning of the surface of the rotors, which what you are getting at with this post, and the second is exercising the calipers to break up dirt/corrosion between the pads and the caliper sliders in order to prevent future seizing: You don't necessary have to wear the brakes to achieve this. The pads can be forced into the rotors promoting movement of the pistons, and the pads in the caliper sliders just as effectively at a stop as when driving and slamming on the brakes. So if the rotors are sufficiently cleaned why wear them and the pads out any more than you need to? A couple of times a day stopped at a traffic light just push the hard on the brakes.

Having said that I religiously service (clean and lubricate with silaramic grease) the calipers every 6 months due to the climate I live in. Here is the latest recommendation from Tesla

Screen Shot 2019-09-18 at 6.16.33 PM.png

Also the easier the pads retract the less resistance and therefore the lower the energy used, and we all want maximum range, right? some of us analyze rolling resistance differences as small as 1% when we buy our tires, but don't thing about pad friction on the rotors. One can easily tell how much your pads are dragging by jacking up the car, putting it in tow mode and rotating the wheels.

I am more concerned with your "mushy" comment. How old is the brake fluid? Has it absorbed too much water? That is a cause for a soft feeling pedal. If it is 3-4 years old it probably needs changing. You can test for this but it is so cheap to change the fluid why not get fresh stuff in there every 2 years and not worry about the risk of rusting out the whole brake system?


Screen Shot 2019-09-18 at 6.20.30 PM.png
 
I would say one of these stops is more than sufficient. You can actually hear the sound of the pads scraping rusty rotors. A couple of rotations at any speed with moderate force and they should be good. With more moisture of course one may need more heat to dry them.

But there are 2 concepts going on here: The first is the cleaning of the surface of the rotors, which what you are getting at with this post, and the second is exercising the calipers to break up dirt/corrosion between the pads and the caliper sliders in order to prevent future seizing: You don't necessary have to wear the brakes to achieve this. The pads can be forced into the rotors promoting movement of the pistons, and the pads in the caliper sliders just as effectively at a stop as when driving and slamming on the brakes. So if the rotors are sufficiently cleaned why wear them and the pads out any more than you need to? A couple of times a day stopped at a traffic light just push the hard on the brakes.

Having said that I religiously service (clean and lubricate with silaramic grease) the calipers every 6 months due to the climate I live in. Here is the latest recommendation from Tesla

View attachment 456470
Also the easier the pads retract the less resistance and therefore the lower the energy used, and we all want maximum range, right? some of us analyze rolling resistance differences as small as 1% when we buy our tires, but don't thing about pad friction on the rotors. One can easily tell how much your pads are dragging by jacking up the car, putting it in tow mode and rotating the wheels.

I am more concerned with your "mushy" comment. How old is the brake fluid? Has it absorbed too much water? That is a cause for a soft feeling pedal. If it is 3-4 years old it probably needs changing. You can test for this but it is so cheap to change the fluid why not get fresh stuff in there every 2 years and not worry about the risk of rusting out the whole brake system?


View attachment 456476

Thanks for the super informative post! My car is just about 2 years old so the brake fluid should be fine. is this something they check during the annual service or do you have to ask them?
 
The reason the brakes get soft is the edges of the pad get bound in the caliper and stop floating.
Caliper provides ample pressure to flex the metal pad backer till the friction material contacts the rotor. As this keeps happening the friction material wears away at the center of the pad and the springiness of the backer keeps resetting to straight. This results in the pad sitting further and further from the rotor and the piston having to travel ever further before it actually drives the friction material against the rotor.

This is why they have begun recommending lubrication of the brakes periodically, that keeps the pads floating in the caliper.
 
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dark cloud

Active Member
Apr 14, 2018
2,203
2,570
BC
Thanks for the super informative post!

It took you 2 months to see it? :D

My car is just about 2 years old so the brake fluid should be fine. is this something they check during the annual service or do you have to ask them?

Are you still doing annual service? you must be one of the few who do. Honestly no idea what they do. You are going to have to ask them if they check the brake fluid with a test strip at such a young age. At 2 years they may not bother; just opening up the master cylinder on a humid day may increase the water content from say 1.8 to 2.0 percent so is it worth it? My personal opinion is, it is not so much the decreased performance for a passenger vehicle but to the fact that the more water in the brake fluid the more it attacks the corrosion inhibitors in the fluid and the more corrosion of the brake lines occurs. By the time you use a test strip testing for copper sediment isn't the damage already occurring? getting fresh fluid with 0% water for $100-$150 bucks every 3 years is money well spent, if you car about the longevity of the car.

This is why they have begun recommending lubrication of the brakes periodically, that keeps the pads floating in the caliper.

And don't forget the parking brake (if you have a separate caliper) Mine were totally seized and dragging slightly at just over 3.5 years of age. (Used Dec 2014 car, I bought it May 2018, I assume the parking brake has never been inspected/lubed) I bought a different set off eBay and replaced them, and once removed put one of them on the bench and soaked the sliders in penetrating fluid for days, and bent my punch on the pins; they did not budge. Pin sliders rusted solid in the caliper body, and one pad did not slide on the rusty pins at all. Totally seized, the calipers are garbage. They still functioned as parking brakes as they put enough pressure on the rotor to hold the car, but the drag probably cost a few Wh/km of energy.

IMG_0517.JPG
 
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