[derek.megyesi]

Hi all,

I have a question. I just dropped $900 for new back brakes on my 2020 BMW 430Xi Grand Coupe

Anyhow, the gal at the Service Desk told me that I can extend the life of my brakes by using my cruise control to de-accelerate vs. pressing the brake itself.

Truthfully, I never considered this option. Doesn't the cruise control (de-accelerate) option use the brakes regardless? How else would the car slow down?

[asbrr]

It does not use the brakes, it just coasts, and the drag from the road/wind along with "engine braking" when throttle is reduced is what slows the car.

That's not really going to be practical in stop and go traffic, it's a dumb suggestion honestly.

[thatgarrett]

Nope, if you have dynamic cruise control your car will brake to maintain the set speed, maybe if you have the LIM style instead of the SET it is as described above but it definitely makes use of brakes

Note “dynamic” is the standard US cruise control, the radar based one is adaptive or something like that and has even stronger braking capabilities

[asbrr]

ah apologies - I have an old car and haven't kept up I guess lol, that makes sense for dynamic cruise control.

I suppose the cruise control does a better job of "modulation" and will extend life, that's the thinking? Still skeptical it will make a huge difference, if OPs driving is all city stop and go, nobody is using dynamic cruise control in those situations I'd think...

[thatgarrett]

I actually haven’t been the biggest fan of the braking feature on rolling hills, it seems to over brake and then over accelerate, where an old “normal” system would be smoother. In most other traffic it’s fine though, pretty smooth application of brakes where you wouldn’t notice it’s happening at all

[sgtwilko]

In my case, using cruise control on hilly roads regularly has definitely caused accelerated brake wear. Like the OP, I had to prematurely (~20k) replace disks and pads because of it. Bottom line, switch cruise control off in situations where it will often have to hit the brakes for you. This cruise side effect has been confirmed by my BMW service advisor when I had the brakes replaced. Not that this guarantees any accuracy🙄
My 2 cents.
SgtWilko

[casualDIYer]

Extend the life of the rear brakes?

I take my car to the track 7-8 days a year. I’m on the same set of rears I put on 2 years ago and likely have 1 more year. How much life should I have? So, do you want to use $200 brake pads to stop the car or your $11,000 transmission? If you want to save money on your BMW, trade it in for a Civic or Corolla.

Brakes are for safety. Cruise control for convenience. There is no comparison.

[thatgarrett]

It’s not a choice between the transmission and the brakes, but a choice of how the brakes are applied, so that line or reasoning doesn’t apply here…

The DSC pump can generate braking force to apply the brakes to slow the car in the F3X, a variant of this pump is used in the active cruise control models that can generate even greater braking force for collision avoidance and active cruise control function. The question here is if letting the cruise control brake via the DSC pump is easier on the rear brake pads than just pressing the brake pedal, especially on a decline. The pump can vary braking force to each wheel (that’s how DSC works and why you can code in different brake variants for different proportioning of the brake force)- but no one yet has a definite answer if the braking split is easier on the rears or not. I’d personally be more interested in brake fade over a long decline using cruise control vs manually pulsing or engine braking, or if cruise control would call for more engine braking in addition to applying the brakes