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My 2018 LR RWD M3 needs new tires and service - Keep it or Trade?

Knightshade

Well-Known Member
Jul 31, 2017
13,673
23,267
NC
Well, in California, it is. Brake fluid should not "take on water"

And yet, it does.

It's inherent to the nature of the fluid.


Your personal anecdotes don't trump basic chemistry.

Some light reading for you-

Brake fluid 101: What it is and how it works

Why do you need to change your brake fluid?

DOT 3, 4, and 5.1 brake fluids are hygroscopic. That means they absorb water from the humidity in the air around them. Even with the brake reservoir lid tightly sealed, eventually enough moisture will contaminate the fluid.

What's so bad about water in the brake fluid? Well, brake fluid is incompressible under pressure, and since it has a high boiling point, the heat from your brakes isn't enough to cause it to boil. But water has a much lower boiling point. If the moisture-contaminated brake fluid starts boiling, it creates gas bubbles. Gas is compressible. So when you step on the brake pedal and create hydraulic pressure in the brake system, instead of that force being transferred to your brake pads in order to grip your rotors (or drums) and slow your car down, that force is wasted compressing that gas.


In more practical terms, it could mean your brake pedal just sinks to the floor without stopping the car. That, friends, is very bad.

Water in your brake system can also cause rust, which can gum up the small passages in the brake lines or brake hardware, and cause your brakes to work improperly or even drag – a situation where the brake pads don't disengage from the rotor or drum, creating friction and heat, and perhaps causing even more damage.
 

ebmcs03

Active Member
Dec 22, 2017
2,191
1,353
So Cal
Well, in California, it is. Brake fluid should not "take on water", and in my meager experience of sixty years of driving, twenty of which were in Missouri, I NEVER had any problems with brake fluid "taking on water", and I NEVER changed brake fluid, usually putting on over 100K miles on my cars.

In my not so humble opinion, most of these maintenance places are a scam.

Brake fluid for a Tesla is more than 2 years lifespan prob 5 or more before I really am going to consider a flush. Brake fluid in a Porsche is more susceptible if you track it and heat cycle it.
 
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SageBrush

REJECT Fascism
May 7, 2015
12,789
17,091
New Mexico
Your personal anecdotes don't trump basic chemistry.
As I understand the basic chemistry, water uptake is primarily a function of ambient humidity and brake use -- mostly related to heated fluid.

So while you can say that brake fluid is hygroscopic, that does not tell you the rate of uptake.

My opinion: light footed Tesla drivers can safely test the fluid with a strip every couple of years.
 
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TLLMRRJ

Active Member
Dec 19, 2019
2,054
2,452
Houston
Well, in California, it is. Brake fluid should not "take on water", and in my meager experience of sixty years of driving, twenty of which were in Missouri, I NEVER had any problems with brake fluid "taking on water", and I NEVER changed brake fluid, usually putting on over 100K miles on my cars.

In my not so humble opinion, most of these maintenance places are a scam.

Good to know to never buy a used car from you.

Funny how people that don't understand anything about cars and maintenance know so much. Flushing the brake fluid is about as hard as rotating the tires. Once the tires are off, it's super easy, and brake fluid is inexpensive. Why people like you are afraid of routine maintenance is just ridiculous.
 
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Reactions: SageBrush

Knightshade

Well-Known Member
Jul 31, 2017
13,673
23,267
NC
As I understand the basic chemistry, water uptake is primarily a function of ambient humidity and brake use -- mostly related to heated fluid.

So while you can say that brake fluid is hygroscopic, that does not tell you the rate of uptake.

Never said otherwise.

The other guy was claiming it simply shouldn't take on water at all. Which is demonstrably false.


My opinion: light footed Tesla drivers can safely test the fluid with a strip every couple of years.


That is literally what Tesla tells you to do.

Car Maintenance.

Tesla said:
Tesla recommends testing brake fluid for contamination every 2 years and replacing as needed.
 

SageBrush

REJECT Fascism
May 7, 2015
12,789
17,091
New Mexico
A google search on brake fluid flush manufacturers reccs found a lot of variation, but every 2 years is common, as is every 45k miles. I find the mileage interval interesting and supportive of a rule of thumb (perhaps not true in high humidity areas) that brake fluid aging correlates with brake pad wear in average use cars.

'Hobbit' the supreme Prius hacker tested his brake fluid at 100k miles and found it in like new condition. He surmised that his minimal use of friction braking preserved the brake fluid.
 
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Watts_Up

Active Member
Mar 4, 2019
3,754
2,730
In a galaxy far, far away
The question is - would you hang onto it, or trade into the Model Y similarly equipped (nearly $16K plus my car in trade),
or upgrade to the Model S ($41,500 plus my car).
It seems to me that hanging on to my M3 makes the most sense, but I'd welcome your thoughts.
You also need to include the sales taxes and DMV registration.

But I think in NC, car sales taxes are only 3%.

Note: NC states taxes are between 4.75% and 7.5% depending of which county you live.
 

geometro

Member
Jun 24, 2015
448
900
Austin
NONONONONO. I'm a woman, and I didn't even get taken like that. Don't do it. My car is also a 2018 LR RWD with 25K miles, and I just had a mobile ranger come out and do a two year service for less than $200, which some people would argue is still too much. I don't need tires - yet- but when I do I'm NOT going to Tesla. Go to a place like Discount Tire or Costco. No only will you get a better price, but you'll have access to road hazard insurance, something Tesla doesn't offer. Most places now know how to lift a Tesla correctly. And if you don't buy your tires from Tesla, you don't need an alignment from Tesla.

Do not agree to this estimate.

what was included in your two year service?
 

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