Page 1 of 1

Question on Brake Pads & Brake Fluid Change

Posted: Fri Jan 08, 2021 2:05 pm
by Swapsafari
Hey Folks,

We just bought a 2017 BMW i3 from a dealer and the service for brake fluid is overdue from over a year ago. Also, the brakes seem not so strong when trying to make a complete stop. The car has only 33K miles so I assume these are original pads on the car. Does anyone know how long do the brake pads last on these cars and if it is about time to change them? I know it is dependent on the driving habits of an individual but I had read in my research on this vehicle that because its one pedal driving, the brake pads last a little longer than normal cars? My understanding is that you do a brake fluid flush and brake pads together? If anyone has done this before, what kind of $$$ are we talking about for getting it done at an independent BMW mechanic?

Any advice would be helpful!

PS: We have had the car for 4 days now and are absolutely loving it. Very happy with the purchase and glad that we made a switch to EV life.

Re: Question on Brake Pads & Brake Fluid Change

Posted: Fri Jan 08, 2021 8:35 pm
by 3pete
As you mentioned, brake pad life is highly dependent on driving style, even more-so on an EV (or hybrid) because of regenerative braking. 100k miles isn't unreasonable on a set of brake pads in the right conditions. The only way to know where you're at for sure is to measure the pad thickness which is a good idea anyway considering how important brakes are. I would wager your pads probably have more than half of their life left at 33k unless the previous owner liked to autocross the car.

I can't exactly help you on a dollar amount for the estimate but any (decent?) mechanic should be able to do brakes the same way they would on any other car because the only "complication" from it being an EV is that the pads won't wear out as fast. Prices should be in line with any comparably priced car.

For what it's worth, the two times I've unexpectedly slammed on the brakes in the i3, I've found the response a little bit disappointing. Even though it's a rear-engine, rear-drive, carbon fiber vehicle, it's not a sports car, and the rotors only do so much.

Re: Question on Brake Pads & Brake Fluid Change

Posted: Fri Jan 08, 2021 9:54 pm
by alohart
Swapsafari wrote:
Fri Jan 08, 2021 2:05 pm
My understanding is that you do a brake fluid flush and brake pads together?
That's a misunderstanding. One set of front brake pads and one set of rear brake pads have wear sensors that alert the driver when the pad thickness on the front or rear decreases below a certain thickness. Until that happens, it usually isn't necessary to replace the brake pads.

By contrast, BMW suggests that the brake fluid be replaced every 2 years due to moisture being absorbed by the brake fluid which could cause corrosion of brake components. Less likely in the i3, the brake fluid could boil under extreme braking conditions due to the boiling point decreasing as the water content increases. Should this occur, braking could become much less effective because gaseous brake fluid would compress reducing braking force.

Some of us feel that replacing the brake fluid every 2 years might be excessive. I just replaced the brake fluid in our 2014 i3 after it had been replaced 2 years earlier as part of the maintenance program included with our purchase. I didn't measure the old brake fluid's copper content or conductivity as an indication of its moisture content, but its color was indistinguishable from the new fluid. The new fluid is Bosch extended use fluid which is designed to remain safe for at least 3 years.
Swapsafari wrote:
Fri Jan 08, 2021 2:05 pm
Any advice would be helpful!
Because your car is over a year overdue for a brake fluid change, you should have that done. I have read of one independent BMW mechanic charging $125 for this service. There is nothing special about replacing an i3's brake fluid, so any reputable mechanic could do this. The cost is almost all labor with the brake fluid itself retailing for less than $15.

Re: Question on Brake Pads & Brake Fluid Change

Posted: Mon Jan 11, 2021 1:46 pm
by Swapsafari
Thanks for the feedback! I was thinking on the same lines to get just the fluid replaced. Will get the brake fluid done for the piece of mind. I tired looking for the brake pad indicator to see if I can spot the padding left but for some reason couldn't find it easier with i3 wheels. My mechanic should be able t tell me that.

Re: Question on Brake Pads & Brake Fluid Change

Posted: Mon Jan 11, 2021 2:23 pm
by alohart
Swapsafari wrote:
Mon Jan 11, 2021 1:46 pm
I tired looking for the brake pad indicator to see if I can spot the padding left but for some reason couldn't find it easier with i3 wheels. My mechanic should be able t tell me that.
On our 2014, the pad wear indicators are on only the left front and right rear brakes. It's easy to see the wear indicator wire exiting the rear of the caliper. It's not so easy to see the thickness of the pads without removing the deep offset wheels.

Re: Question on Brake Pads & Brake Fluid Change

Posted: Mon Jan 11, 2021 3:10 pm
by spartacus68
The main dealers will tell you that the brake pads and discs (rotors) will outlive the car. That's just nonsense. The i3 braking system, although it uses regenerative braking, is fundamentally vented discs up front and solid discs at the rear with a floating caliper. Brake sliders after 3-4 years will be sluggish and probably need re-greased, and the pads themselves may be grooved. A visual inspection isn't often enough, and a brake dismantle will always help, brake de-dust, file the carrier and wire-brush, copper anti-seize on the backs of the pads and grease the brake sliders. I use a product called ProSlip. Also a good opportunity to check dust sleeves.

The brake fluid change every 2 years is also worthwhile, and if nothing else it ensures the brake nipples are wire brushed and re-greased which will tend to seize up.

I think more than just driving style has an affect, but your physical location. This is my wife's i3 (2015/16) at 50k miles. The rear discs were completely shot. In addition - if you're doing this job, just renew the sensors, regardless if they haven't triggered. You'll find it will be brittle with age, and for just £20 GBP to replace it's a no-brainer. Water, salt and road debris all take their toll. :o

https://ibb.co/p3WV9VS
https://ibb.co/g4T1fVT
https://ibb.co/prKLw2B
https://ibb.co/p3WV9VS
https://ibb.co/ftb9f51
https://ibb.co/cX1GKgm

Re: Question on Brake Pads & Brake Fluid Change

Posted: Tue Jan 12, 2021 7:27 am
by eXodus
water in the break fluid may corrodes components of the break system from the inside. Had many master brake cylinders started leaking because of the lack of changing the fluid.

I think the boiling point, is a non-issue at a city EV which brakes mainly with regen.

Yet since everything at a BMW is expensive, I would change it rather often. Every 2 years a few bucks of maintenance. I mean, that's really the only thing you need to do at a i3.