[eelnoraa]

Originally Posted by SwissBeemer

Usually what people feels as "being underbraked" is actually not the brakes themselves and not even the tires but two things:

1. The force it takes to reach a certain stopping power
2. The feeling when decelerating

Number one is always a bit higher with BMW's compared to say Alfa Romeos, and I prefer it a lot that way. Compared to Alfa's you really have to apply some pressure whereas with the Alfas a tad more than "resting your foot against the brake pedal" will already result in a pretty hefty stop, which I don't like as it makes it quite hard to dose the braking power adequately and you almost have to lift and hover your foot above the brake pedal to get the right amount of small force.

What is actually more often the case with cars feeling "underbraked" though is the "feel" when a car is decelerating which is mostly dictated by the front diving. On some cars it feels as if you are actually braking quite hard because the car is already leaning forward quite a lot, so it feels as if the car is already trying quite hard to stop, while it's actually not braking that hard but the lean makes it feel as if it is. This gives you the feeling of low stopping power because the car is decelerating less than what it feels it is and I think this is your issue here.

If you actually feel the ABS and it's still not enough you will need better tires first. Only when you don't feel the ABS even though you are really stepping on the brake and feel the brake pedal give in without any more stopping power is it when you know that you need modifications to your brakes, which is hardly ever the case. And even then other brake pads and better cooling will do A LOT of heavy lifting before you actually need to look at other rotors & calipers. Quite a lot of BMW's, even non-M models, are being driven on the Nordschleife in Germany with stock rotors&calipers, but better cooling & different pads. I personally only ever felt I need to modify my brakes once which was on my 135i that I was driving hard on the German autobahn with 420hp instead of the stock 306hp. Only after 3 decelerations from ~170mph down to around 60mph in quick succession is when I felt fading because the brakes were getting too hot. Custom cooling already solved this (airflow redirection) and different pads would've probably eliminated that issue on most racetracks as well. But again brake temperatures or power is not your issue if you're talking about coming to a stop at red lights. I'm quite sure it is actually No. 2 from above.

I can't really give you a solution here. A different suspension would certainly help but I don't think you'd want to get rid of the air-suspension. Other than that there's just braking harder and maybe looking at different brakepads. They can give you a very different feel that is maybe more to your liking.

This is well said. Under hard use, stock pad will not stand because it is selected for street use, to provide max brake performance at cold temp. This type of compound will fade when temp increase. Brake pads is usually the first thing experience driver swap out at track events

[jad03060]

FWIW, on a long grade downhill, you should not be riding your brakes! If you're using the cruise control, the computer will actually downshift, but if you're not on cruise, you should do the same thing...the engine has much better cooling than the brakes do. If you're going slow enough, you could let the descent control do it for you, but most of the time on the highway, you'd be going over the range that function will work.

[aaaaaaaaaz]

Originally Posted by eelnoraa

No it does NOT for street driving. If regular 50e brake can lock up tire and activate ABS, the any bigger brake won't help the car stop faster.
The limitation is always tires on street. What bigger big helps is dissipating heat, lower temperature for both rotor and pads, quicker recovery. This application shows up if you do multiple back to back panic level breaking (like in track events), or if you go down a very long steep hill where you need to ride your brake for a long time. Being able to lower temp also makes big last longer.

I'd imagine it will help when do spirited driving OVER LONG PERIOD OF TIME; maybe over really really long downhill driving when driving aggressively, as well as when towing a heavy trailer over mountain pass. Larger brake may help heat management a bit, but only relevant when used heavily over extended time.

On street driving, as others has pointed out, the tire is the limiting factor, not the brake. Stock brake is plenty strong.

[aaaaaaaaaz]

Originally Posted by jad03060

FWIW, on a long grade downhill, you should not be riding your brakes! If you're using the cruise control, the computer will actually downshift, but if you're not on cruise, you should do the same thing...the engine has much better cooling than the brakes do. If you're going slow enough, you could let the descent control do it for you, but most of the time on the highway, you'd be going over the range that function will work.

I actually still have doubt on this. I personally love to use engine braking, but there are some argument modern turbocharged engine is not designed to do engine braking; also higher RPM may reduce life of transmission, engine and engine oil. It sounds like make sense but I don't know how relevant it is.

[eelnoraa]

Originally Posted by alanzyy

I'd imagine it will help when do spirited driving OVER LONG PERIOD OF TIME; maybe over really really long downhill driving when driving aggressively, as well as when towing a heavy trailer over mountain pass. Larger brake may help heat management a bit, but only relevant when used heavily over extended time.

On street driving, as others has pointed out, the tire is the limiting factor, not the brake. Stock brake is plenty strong.

It depends on how spirited. basically the situation needs to be repeat hard breaking from high speed. In SF Bay area back roads, I cannot thinking of a case where I can make this happen, either too small road not high speed enough (highway 9), or too big not and too straight (highway 17), we dont need much slow down to make the next turn.

[jad03060]

My previous BMW was the first one that downshifted itself when using the CC on a long downhill...

FWIW, if you have the OEM towing package, if your vehicle would normally have the stock brakes, they get updated to larger ones as part of that package...an aftermarket towing hitch typically doesn't get that, but may already have an upgraded brake package.

I haven't had my current vehicle through a long downhill where it may have needed to downshift to prevent it from over speeding that just backing off of the throttle couldn't manage the speed.

[eelnoraa]

Originally Posted by alanzyy

I actually still have doubt on this. I personally love to use engine braking, but there are some argument modern turbocharged engine is not designed to do engine braking; also higher RPM may reduce life of transmission, engine and engine oil. It sounds like make sense but I don't know how relevant it is.

Engine should be fine. With auto transmission, you cannot over rev engine by down shifting. It just won't allow. Oil pump is driven by timing chain, so as long as crank is rotating, oil pressure will be there for lubrication. I would say at the same RPM, engine braking will have less wear than by combustion.

Turbo should be fine as well. when foot off gas paddle, boost pressure is completely released by boost relief valve. Also since no boost, exhaust volume will be low as well, so turbine isn't spooling up.

It isn't great for transmission especially for low gears, say 1st and 2nd. These gear gives the most shock to the drive chain. It also depend on what speed you are shifting into these gears. If you are doing 50mpg and shift into 2nd, you get that jerk, it isn't good.

In general, use brake to slow down, not engine or transmission. But in case of long steep down hill, it is where this is justified. What is the other option?? let brake fade and overheat?

[cptcolo]

I have a 2023 X5 45e with the M-Sport Breaks and Michelin Pilot Sport 5 tires (the new Max Performance Summer Tires they released last year). Overall the braking performance is pretty dang good. I would like to drive a 45e or 50e with the regular breaks to see the difference. I was told after I bought my car by a different BMW salesman that the compound in the M-Sport breaks is superior and match the car better.

The braking does not feel as aggressive as a 2018 Chevy Corvette C7 Stingray or a 2023 Porsche Boxster GTS 4.0 (two other cars I recently got to drive together). I also find the throttle response slightly behind those two cars too.. but those two are sports cars and the 45e is a 5,700lb SUV. During 'spirited' driving sessions you really have to be aggressive with the breaks and throttle to get it to respond somewhat quick. I also felt like partially turning off the traction control helped quite a bit with the brake response and acceleration.

[gadgetfreak2024]

Originally Posted by jad03060

FWIW, if you have the OEM towing package, if your vehicle would normally have the stock brakes, they get updated to larger ones as part of that package...an aftermarket towing hitch typically doesn't get that, but may already have an upgraded brake package.

I forgot about this fact. I do have the OEM hitch. So I think I should technically already have the best brakes available from the factory on a 50e in the US.

Very interesting feedback from everyone overall. As a lease I’m disinclined to upgrade the pads. I haven’t had the occasion thankfully for any emergency braking, so I have not been into the point of needing ABS. As such I can’t speak to emergency performance.

I think it will just be a matter of getting used to the extra weight and the corresponding need to brake a little harder and a little sooner. It remains an issue of physics and it feels to me that whatever upgrades BMW did make on my particular setup — as others have pointed out — in day-to-day street use the impact is not particularly discernible.

[TurtleBoy]

Originally Posted by gadgetfreak2024

I forgot about this fact. I do have the OEM hitch. So I think I should technically already have the best brakes available from the factory on a 50e in the US.

The MSport brake rotors are a little larger than what you have: 395x36 + 370x24 v 374x36 + 345x24.

[gadgetfreak2024]

Originally Posted by TurtleBoy

The MSport brake rotors are a little larger than what you have: 395x36 + 370x24 v 374x36 + 345x24.

I do have the M Sport package. So with the hitch do you not get the larger rotors?

[aaaaaaaaaz]

Originally Posted by gadgetfreak2024

I do have the M Sport package. So with the hitch do you not get the larger rotors?

See the image I posted in early reply. You get a larger brake than standard 40i one but smaller than the red/blue one.

There is a normal brake for 40i
There is a larger brake you get with 50e or tow package (grey)
There is the largest brake you only get with m-sport pro (blue/red)

[TurtleBoy]

Originally Posted by gadgetfreak2024

I do have the M Sport package. So with the hitch do you not get the larger rotors?

No, you do not as in larger than MSport. They are smaller than the MSport brakes and the same size and the standard 50e brakes.

[gadgetfreak2024]

Originally Posted by TurtleBoy

No, you do not as in larger than MSport. They are smaller than the MSport brakes and the same size and the standard 50e brakes.

Confused… so what (if any) options can one choose on a 50e to get larger than standard (for the 50e) brakes?

[TurtleBoy]

Originally Posted by gadgetfreak2024

Confused… so what (if any) options can one choose on a 50e to get larger than standard (for the 50e) brakes?

As shown in my initial post, the MSport brakes are the largest rotor size. The standard 50e brakes and the brakes with the tow hitch are the same and are a bit smaller.

[gadgetfreak2024]

Originally Posted by TurtleBoy

As shown in my initial post, the MSport brakes are the largest rotor size. The standard 50e brakes and the brakes with the tow hitch are the same and are a bit smaller.

Right. And I guess my confusion is I do have the M Sport trim and the M Sport Pro package. So don’t I have those M Sport brakes with the largest rotor size?

[SwissBeemer]

Originally Posted by gadgetfreak2024

Right. And I guess my confusion is I do have the M Sport trim and the M Sport Pro package. So don’t I have those M Sport brakes with the largest rotor size?

You do. At least in Europe these bigger brakes come with the M-Sport Pro package if I remember correct.

[gadgetfreak2024]

Originally Posted by SwissBeemer

You do. At least in Europe these bigger brakes come with the M-Sport Pro package if I remember correct.

Ok thanks. Since I pretty much chose every option other than leather, I was confused as to how I might have missed on maxing out the brake capabilities. And that’s and important consideration given the original reason for starting this thread…

Thanks

[TurtleBoy]

Originally Posted by gadgetfreak2024

Right. And I guess my confusion is I do have the M Sport trim and the M Sport Pro package. So don’t I have those M Sport brakes with the largest rotor size?

Yes, we said you did earlier. Just having the tow hitch does not get you the largest rotors.

[johneric2005]

Originally Posted by gadgetfreak2024

I’m 2500 miles into our 50e ownership. I find the vehicle is a bit underbraked for its heft. Wondering if anyone else feels the same or if perhaps there is something with my car. What are others’ opinions?

I am about the same mileage in and find the brakes are fine. But, I have this odd "clunk" sound when I come to a full stop. If I stop quickly from a higher speeds there is no sound, but slow approach to full stop, it literally clunks as the pads grab? I was told its normal and its the Pads Shifting. Anyone else have this?