[aiweili]

Hi Guys,

My new 21 X5 45e now has about 2000 miles on it. And I still experience very slight pulsations when braking. It almost feel likes a ABS kicking in but much more subtle. It doesn't happen every time though. Any thoughts?

Thank you in advance!

[SmartSaves]

Mine is 4 months old MY21 X5 40i MSport with mild hybrid, currently has 3300 km. I am having similar pulsating shudder when I press brake pedal to slow down, especially from about 80km/hr. Initially I thought it is related to brake energy regenerative system, but it is more and more feels like brake pad deposits issue or some form of rotor warp. With Covid car is sitting in garage longer, don't know if that has anything to do with it. I also tried brake pad bedding by slowing down form about 80 km to 10km/hr repeatedly about 8 times and driving without braking immediately afterwards (as much as possible) to cool down the pads and rotors; however, the shudder is still there. Booked an appointment with dealership next week to find out what is going on.

By the way, BMW use Continental developed MK C1 brake-by-wire system.

Here are two helpful videos on brake pad bedding and rotor warp:

[SmartSaves]

Here is another similar thread with similar reported issue, but the original poster didn't report back on the resolution (if there was any):

3rd brake replacement on 2019 X5, help!

https://g05.bimmerpost.com/forums/sh....php?t=1803991

[aiweili]

Originally Posted by SmartSaves

Mine is 4 months old MY21 X5 40i MSport with mild hybrid, currently has 3300 km. I am having similar pulsating shudder when I press brake pedal to slow down, especially from about 80km/hr. Initially I thought it is related to brake energy regenerative system, but it is more and more feels like brake pad deposits issue or some form of rotor warp. With Covid car is sitting in garage longer, don't know if that has anything to do with it. I also tried brake pad bedding by slowing down form about 80 km to 10km/hr repeatedly about 8 times and driving without braking immediately afterwards (as much as possible) to cool down the pads and rotors; however, the shudder is still there. Booked an appointment with dealership next week to find out what is going on.

By the way, BMW use Continental developed MK C1 brake-by-wire system.

Here are two helpful videos on brake pad bedding and rotor warp:

Thanks for sharing. I also booked a appointment with dealership next week to have the car checked out. Please keep me updated!

[SmartSaves]

The dealer is saying the brake-pedal shudder/pulsation issue is caused by pad deposit on the brake rotors. Apparently this is a common reported issue. Given the COVID situation it is plausible because I am not actually driving as much and the vehicle is sitting in the garage for days at a time. Their assessment is that it should go away as I drive more.

However, I am quoting an interesting paragraph from the article below:

"… pedal feel can be tuned by engineers using driving simulators to give a more aggressive response on track and a more relaxed response in traffic. Another advantage is that pedal travel doesn't increase when the brakes take a beating and get hot. What the driver actually feels is a simulator built in to the MKC1 that generates the sensation normally fed back through the hydraulics, only it remains consistent however hard the brakes are working."

https://thebrakereport.com/continent...wire-benefits/

Because the brake feel is simply a simulation built into the MK C1 system, in theory, the vibration caused by warp rotors should not be felt on the brake pedal, perhaps only should be felt by other vehicle vibrations, for example body/steering/dash is shaking. Hopefully someone with more knowledge on this brake-by-wire system will educate us.

[SmartSaves]

Check this post on recall:

https://www.bimmerpost.com/forums/sh...php?p=27522920

[aiweili]

Originally Posted by SmartSaves

Check this post on recall:

https://www.bimmerpost.com/forums/sh...php?p=27522920

Just got feedback from the dealer that the pulsation is normal on newer X5 45e models. I pushed back on that.

I asked what is causing this pulsation. Assuming that it is normal, what is the purpose of this designed pulsation?

I have not received any notice on the recall you mentioned though.

[aiweili]

Actually just was told by the dealership that it's normal because

"when you get to the end of the travel you will feel a pulsation. Its the system pressurizing and releasing pressure. Also you have multiple systems slowing down the vehicle. You are feeling a little of that as well."

Will you buy that answer?

[SmartSaves]

This explanation doesn't make a lot of sense to me. When brake pedal is pressed and travelled closer to the floor every car does bit of body shake/vibration. Here is my scenario:

Driving about 80 km/hr.
Seeing a stop sign and slowly pressing the brake pedal with the aim to stop.
I feel slight pulsating pedal at the beginning when I start pressing the pedal (NOT at the end when the pedal is closer to the floor).

Summary: IMO brake feel isn't smooth, and learning to modulate the brake up and down to avoid shudder. My 15 year old car has better brake feel in comparison when it comes to pulsating issue. It doesn't bite and brake as fast as the X5, of course, but brake travel is smooth. I am really hoping this slight shudder goes away as I drive more.

[nZtiZia]

what's considered "new"? I have a 2020 week 49 45e... no brake pulsation in 2000 miles.

[jad03060]

Brake by wire is a different animal than purely hydraulic systems especially when you have a hybrid involved with regeneration. With the 45e, on light brake pressure, you may not actually be engaging the brakes at all, then, it may blend in the hydraulic brakes, and at the end towards the stop, blend back out the regeneration. Personally, I think BMW has done a good job on that software blending operation.

I know the 45e does that, but I'm not as familiar with the mild hybrid system...it may do some regenerative braking, too...something is recharging their 48vdc battery, and it makes sense to use some regeneration since they have the ability...anyone know for sure?

[SmartSaves]

Mild hybrid should have very similar brake regenerative system compared to 45e.

I documented my findings what the MY21 40i does when braking and decelerating here:

https://www.bimmerpost.com/forums/sh...php?p=27580104

[iamlosthelp]

Originally Posted by jad03060

Brake by wire is a different animal than purely hydraulic systems especially when you have a hybrid involved with regeneration. With the 45e, on light brake pressure, you may not actually be engaging the brakes at all, then, it may blend in the hydraulic brakes, and at the end towards the stop, blend back out the regeneration. Personally, I think BMW has done a good job on that software blending operation.

I know the 45e does that, but I'm not as familiar with the mild hybrid system...it may do some regenerative braking, too...something is recharging their 48vdc battery, and it makes sense to use some regeneration since they have the ability...anyone know for sure?

I've been experiencing the same thing as OP. The light, subtle vibration from the brake pedal when I press on it.

Is this normal? It's my first time driving an electric/hybrid. Or should I get it taken to the dealership to look at?

[ApexG5]

Originally Posted by SmartSaves

The dealer is saying the brake-pedal shudder/pulsation issue is caused by pad deposit on the brake rotors. Apparently this is a common reported issue. Given the COVID situation it is plausible because I am not actually driving as much and the vehicle is sitting in the garage for days at a time. Their assessment is that it should go away as I drive more.

However, I am quoting an interesting paragraph from the article below:

"… pedal feel can be tuned by engineers using driving simulators to give a more aggressive response on track and a more relaxed response in traffic. Another advantage is that pedal travel doesn't increase when the brakes take a beating and get hot. What the driver actually feels is a simulator built in to the MKC1 that generates the sensation normally fed back through the hydraulics, only it remains consistent however hard the brakes are working."

https://thebrakereport.com/continent...wire-benefits/

Because the brake feel is simply a simulation built into the MK C1 system, in theory, the vibration caused by warp rotors should not be felt on the brake pedal, perhaps only should be felt by other vehicle vibrations, for example body/steering/dash is shaking. Hopefully someone with more knowledge on this brake-by-wire system will educate us.

I have been having the same issue and just got it resolved. Have them look at your control arm bushing. My front left failed and it caused a vibration that felt like a warped rotor even at the lightest touch. It just sucked because I couldn't find a bushing by itself. The control arm was a little under 400.

[SmartSaves]

Originally Posted by ApexG5

I have been having the same issue and just got it resolved. Have them look at your control arm bushing. My front right left failed and it caused a vibration that felt like a warped rotor even at the lightest touch. It just sucked because I couldn't find a bushing by itself. The control arm was a little under 400.

Thanks for sharing your findings. Did you replace both control arms? I presume those were lower control arms?

[ApexG5]

Just the lower left control arm. That's the one.

[jonesy16]

Noticing the same in my '21 45e at about 34k miles. Seems more pronounced when braking starts from a higher speed (50mph+). If I'm just cruising around town at 20-40 with light braking then I don't notice anything. I usually just let regenerative slow me down if I know I have to stop, it's when I have to apply more brake pressure that I notice it, so it certainly could be deposits on the rotors from minimal use. At first I thought it was just the transmission having some rough downshifts as it ran through the gears but now I'm not sure what to think.