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      09-15-2014, 10:49 PM   #1
besiktas
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Didnt know M3 stock brakes were top performers!!!

Based on this publication from 2008, the stopping distance from 100km to 0 is very close to brembo powered ferraris.

For some reason I cant put the picture in the post so see the link.

http://www.brembo.com/en/car/origina...s/default.aspx

just hit X on right left corner to see the data when prompts for password
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      09-15-2014, 11:30 PM   #2
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That doesn't surprise me. The stock M3 brakes are very good for the street with great bite and short stopping distance. The problem is that they do not stand up to repeated hard threshold braking very well and begin to fade on the track.

The M3 and Brembo-equipped Ferraris might start off roughly the same, but the M3's stopping distances would start to grow considerably with lap after lap whereas the Ferrari's would stay pretty much the same.
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      09-16-2014, 01:05 AM   #3
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the m3 gts uses different brakes than the "normal" m3's
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      09-16-2014, 01:18 AM   #4
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Quote:
Originally Posted by a burrito
the m3 gts uses different brakes than the "normal" m3's
Regular E9X M3 is also on the list. I think this is what the OP was referring to.
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      09-16-2014, 01:38 AM   #5
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Big Brakes really shine during prolonged hard driving. They have more surface area and they're also able to cool down faster, especially if you have proper ducting.

The first few stops won't matter a whole lot, but if you're driving it right, you will notice some fade.
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      09-16-2014, 04:19 AM   #6
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Its the tyre grip (and how aggressive the ABS is set) that determines the stopping distance in single stop tests...you could put F1 brakes on an M3 and its not going to stop any quicker. "Bigger" brakes buy you greater thermal capacity and/or the ability to shed heat quicker. Whenever you see people say that they fitted Brembos and felt the improvement the first time they used them they are talking nonsense.
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      09-16-2014, 08:38 AM   #7
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      09-16-2014, 09:13 AM   #8
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SenorFunkyPants is correct. If your brakes are strong enough to lock up the tires/set off ABS, how sticky your tires determine how short you stop, not so much which calipers are on your car.
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      09-16-2014, 09:32 AM   #9
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Quote:
Originally Posted by Sapper_M3 View Post
Regular E9X M3 is also on the list. I think this is what the OP was referring to.
I missed that. Thanks for the clear up. BMW brakes in a pool of all CCB's. That's pretty cool.

However since all the car weights are different and the brakes are all different sizing isn't the result basically just a number?
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      09-16-2014, 09:48 AM   #10
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Quote:
Originally Posted by SenorFunkyPants View Post
Its the tyre grip (and how aggressive the ABS is set) that determines the stopping distance in single stop tests...you could put F1 brakes on an M3 and its not going to stop any quicker. "Bigger" brakes buy you greater thermal capacity and/or the ability to shed heat quicker. Whenever you see people say that they fitted Brembos and felt the improvement the first time they used them they are talking nonsense.
This.

The four things that matter for good single stop braking distances (from relatively low speeds like 60mph):
- Good tires
- Well set up alignment/suspension geometry
- Correct brake bias and ABS setup that isn't too aggressive
- Car's weight distribution

Size of the rotors, number of pistons in the caliper, etc.. have very little bearing since just about any brake system on a sports/sporty car can overcome tire grip on at least one axle at lower speeds. At higher speeds the amount of torque that the brake system can generate (which is related to size of rotors, caliper design, number of pistons, etc..) does become relevant since you won't be locking up tires at 150mph from braking even with ABS disabled. I have no idea where that delineation starts happening though.

But I can tell you that my 18 year old 993 out brakes my 3 year old M3 in panic situations mostly because of weight distribution and because the ABS system kicks in pretty late. I can lock them up pretty easily at 60mph for a half second or so before ABS pulses in that car.
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      09-16-2014, 11:12 AM   #11
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Quote:
Originally Posted by RudyP View Post
This.

The four things that matter for good single stop braking distances (from relatively low speeds like 60mph):
- Good tires
- Well set up alignment/suspension geometry
- Correct brake bias and ABS setup that isn't too aggressive
- Car's weight distribution
This is interesting, so holding all these controlled variables constant and equal between two identical M3s (for example). The larger brakes would make no difference other than heat dissipation etc.?

And if this is true then why is the GTS at the top of the pack? Which controlled variables are different with the GTS and the standard M3 for example? I know the wheel dimensions are exactly the same on the GTS as the ZCP package.

Just trying to learn this car, thanks for the information!

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      09-16-2014, 12:14 PM   #12
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How the manufacturer sets up the ABS can make a difference...maximum deceleration is achieved with the tyres "slipping" at between 10-30%..ie the tyres are turning 10-30% slower than they would if no brakes were applied. Maximum steering control is when the tyres are not slipping at all. So you have to choose your compromise.
Porsche set their ABS quite aggressively on some models - you can hear their tyres chirping at full ABS braking.
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      09-16-2014, 12:32 PM   #13
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Quote:
Originally Posted by SinfulM3 View Post
This is interesting, so holding all these controlled variables constant and equal between two identical M3s (for example). The larger brakes would make no difference other than heat dissipation etc.?
If identically set up, yes. But in real life they would probably make things slightly better or slightly worse bc different brake hardware always affects brake bias a little bit (due to differences in swept area, rotor size and pad radius). The good brake companies that design car specific OEM packages or aftermarket kits try to keep it pretty close to ideal but there's always some variation. Depending on which direction it goes it could be better or it could be worse in your low speed single stop scenario.

Quote:
Originally Posted by SinfulM3 View Post
And if this is true then why is the GTS at the top of the pack? Which controlled variables are different with the GTS and the standard M3 for example? I know the wheel dimensions are exactly the same on the GTS as the ZCP package.
I guess I wouldn't put too much stock in this chart other than it showing that all of these cars brake well. The difference between the regular M3 and the GTS is a little over 4%. Not a huge difference assuming they tested both cars on the same piece of track on the same day, practically rounding error if these results are from different times (atmospheric conditions, humidity, etc.. will have an impact).

But assuming that is a repeatable difference, my hunch would be:
- Is the GTS lighter?
- Suspension geometry differences (e.g., you want very flat, very straight front tires under breaking - toe and camber are both bad for braking distances)
- Brake bias is bound to be different even if they wanted both to be pretty close
- Perhaps ABS differences - maybe BMW programed a slightly higher threshold
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      09-16-2014, 01:57 PM   #14
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Quote:
Originally Posted by RudyP View Post
This.

The four things that matter for good single stop braking distances (from relatively low speeds like 60mph):
- Good tires
- Well set up alignment/suspension geometry
- Correct brake bias and ABS setup that isn't too aggressive
- Car's weight distribution

Size of the rotors, number of pistons in the caliper, etc.. have very little bearing since just about any brake system on a sports/sporty car can overcome tire grip on at least one axle at lower speeds. At higher speeds the amount of torque that the brake system can generate (which is related to size of rotors, caliper design, number of pistons, etc..) does become relevant since you won't be locking up tires at 150mph from braking even with ABS disabled. I have no idea where that delineation starts happening though.

But I can tell you that my 18 year old 993 out brakes my 3 year old M3 in panic situations mostly because of weight distribution and because the ABS system kicks in pretty late. I can lock them up pretty easily at 60mph for a half second or so before ABS pulses in that car.
I don't have scientific evidence, but my experience tells me that brake compound makes a difference as well (at the very least in initial bite). When I have my race compounds on, braking force with 25% pedal travel is like doing 50-75% pedal travel on my street pads.
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      09-16-2014, 02:00 PM   #15
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The rear wing on the GTS is going to help some...less rear lift or positive downforce will allow a bit more rear bias on the ABS.
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      09-17-2014, 10:19 AM   #16
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Quote:
Originally Posted by Sapper_M3 View Post
Regular E9X M3 is also on the list. I think this is what the OP was referring to.
I was. Thanks.
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      09-17-2014, 02:32 PM   #17
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Quote:
Originally Posted by SinfulM3 View Post
This is interesting, so holding all these controlled variables constant and equal between two identical M3s (for example). The larger brakes would make no difference other than heat dissipation etc.?

And if this is true then why is the GTS at the top of the pack? Which controlled variables are different with the GTS and the standard M3 for example? I know the wheel dimensions are exactly the same on the GTS as the ZCP package.

Just trying to learn this car, thanks for the information!
The GTS has larger tire sizes and a higher grip tire than an OEM M3.
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      09-17-2014, 02:49 PM   #18
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Is it any wonder why the world has a love affair with European cars?
That answer is very clear... It was your personal choise buying... driving an ///M3 !
BTW....My battery charger is European too, but you knew that already !
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      09-17-2014, 04:09 PM   #19
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My love for European cars aside, I am sorry but you are still a heel for choosing to connect the charger directly to your battery.
=> http://www.m3post.com/forums/showthr...0#post16648620
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      09-17-2014, 09:24 PM   #20
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Quote:
Originally Posted by RudyP View Post
I guess I wouldn't put too much stock in this chart other than it showing that all of these cars brake well. The difference between the regular M3 and the GTS is a little over 4%. Not a huge difference assuming they tested both cars on the same piece of track on the same day, practically rounding error if these results are from different times (atmospheric conditions, humidity, etc.. will have an impact).

But assuming that is a repeatable difference, my hunch would be:
- Is the GTS lighter?
- Suspension geometry differences (e.g., you want very flat, very straight front tires under breaking - toe and camber are both bad for braking distances)
- Brake bias is bound to be different even if they wanted both to be pretty close
- Perhaps ABS differences - maybe BMW programed a slightly higher threshold
Your right, did a bit of research and found out that the GTS is lighter by just over 100 lbs. It also uses wider tires 255-35 and 285-30 instead of 245-35 and 265-35 like ZCP. The suspension geometry differences are also noted in this release: " Featuring a transmission and suspension configuration which has been optimised for the racetrack," Unsure about ABS but knowing BMW they probably had their tweaks and changes in the ABS too! Makes sense...thanks for the information!!

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      09-18-2014, 03:25 AM   #21
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The weight change isn't going to make a difference. If an M3 stops from 60mph to zero mph in 34m, with all else being equal if you removed 100lbs of weight, the M3 would still take 34m to stop.
Fitting Brembos will not change the braking distance (single stop).
A small change in the tyre size will not change the contact patch by any significant amount.
A small change in front suspension settings will not affect the braking distance - in fact a more track oriented set up would probably make it worse.
A "stickier" tyre compound would shorten the braking distance.
An increase in load on the tyre (reduced lift/increased downforce) will shorten the braking distance.
Optimising the ABS for shortest braking distance will unsurprisingly shorten the braking distance.
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      09-18-2014, 02:57 PM   #22
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Quote:
Originally Posted by SenorFunkyPants View Post
The weight change isn't going to make a difference. If an M3 stops from 60mph to zero mph in 34m, with all else being equal if you removed 100lbs of weight, the M3 would still take 34m to stop.
.

I have heard that before but I just can't buy it. Weight seems to me to be the main variable. Taken to the extreme if I were to load all my gold bars equally around my car thereby doubling the cars weight I can only imagine the stopping distance doubling if not more. I realize the tires would have increased traction or grip but momentum would still kill the stopping distance. If increased weight helped traction more than increased weight hurt acceleration then dragsters have a much different look.
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