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      08-06-2008, 02:26 PM   #45
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Quote:
Originally Posted by swamp2 View Post
Absolutely not.

3. Is about routing air flow around the vehicle on to the brakes.
4. Is all about the rotor design. A two piece floating design with cast iron rotor and aluminum hat pinned together as per stock M3 design is great. It allows much more thermal expansion without generating thermal stress. As well care must be taken to properly design the internal fins of the rotor again for cooling
5. Is the weight of the system. Too little weight with the same heat generation will cause a much larger rise in caliper and fluid temperature.


ok so 3. has absolutly nothing to do with the brake in any physical form.. so scrath that...

and 4. the weight of the braking system?.. directly related to heat transfer... wtf r u talking about.... maby you ment the weight of the car....
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      08-06-2008, 02:34 PM   #46
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First of all I appreciate everyones response. For the most part everyone stayed adult about it. I was really curious.
I disagree with most of you on the track car issue. I think the M3 is a FINE track day vehicle. In fact I would love to take one to the track and I have alot of friends who drive them when i am there with the GT3. I didnt want an arguement I HATE flame wars.
I am not a troll, I have had two 335i's one Z4M and my favorite is my current X5 4.8iS Hot rod SAV. Just a luxurious fun family truckster than has the best V8 exhaust note I have heard on any truck. If I was a Porsche Troll I would have a Cayman (Z4M was more fun) and a Cayenne S ( X5 4.8iS is better looking and faster!)
The other thing I agree with most of you is that the current M3 brake package is fine for most buyers. I just love the styling and I miss the brake caliper asthetic value a nice caliper adds. The M3 is the best package I have found in the price range.
So I think we have put this to bed. There will be more to come since I found out that BMW has contracted with Brembo.
Just remember one magazine single stop test doesnt mean they are the best brakes. It comes down to your 15th lap at Willow springs and you are coming down the front straight at 140 and you go deep into turn one. IS there going to be some fade and how much. If I buy an M3 I would certainly head to Willow as soon as I could. I think its that good.
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      08-06-2008, 02:56 PM   #47
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Quote:
Originally Posted by KINGLEH View Post
ok so 3. has absolutly nothing to do with the brake in any physical form.. so scrath that...

and 4. the weight of the braking system?.. directly related to heat transfer... wtf r u talking about.... maby you ment the weight of the car....
Kingleh, Swamp is on target here, so no point in arguing. He is pointing out the other factors that affect braking performance more than the number of pistons. Airflow has everything to do with that.

Weight of the rotors constitute thermal mass for heat to be dissipated effectively without melting down everything in sight. Creating friction between the pad and the rotor by applying pressure is just one part of the deal. Dissipating the generated heat effectively is the other. If the rotors do not have adequate thermal mass to transfer the heat and dissipate it away from the calipers, the brakes will be in trouble. (Keep in mind the majority of the rotor is not in contact with the pad, and is surrounded by cooler air, and thus heat transfer via convection between rotor and air.)
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      08-06-2008, 03:00 PM   #48
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Quote:
Originally Posted by KINGLEH View Post
and 4. the weight of the braking system?.. directly related to heat transfer... wtf r u talking about.... maby you ment the weight of the car....
If you have to ask ...

Technically, he should have said mass of the system. It has to do with heat capacity. The greater the mass of the rotor, the more heat input it can take for a given rise in temperature.
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      08-06-2008, 03:03 PM   #49
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Quote:
Originally Posted by lucid View Post
... Weight of the rotors constitute thermal mass for heat to be dissipated effectively without melting down everything in sight. Creating friction between the pad and the rotor by applying pressure is just one part of the deal. Dissipating the generated heat effectively is the other. If the rotors do not have adequate thermal mass to transfer the heat and dissipate it away from the calipers, the brakes will be in trouble. (Keep in mind the majority of the rotor is not in contact with the pad, and is surrounded by cooler air, and thus heat transfer via convection between rotor and air.)
Wow! No wonder you go by lucid.
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      08-06-2008, 03:04 PM   #50
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Quote:
Originally Posted by Radiation Joe View Post
Paul,
I know what I'm talking about. If you were at Laguna two springs ago (07) for either the BMW or Audi track days, and you were running in the advanced group, you were probably out braked by my M3.
Ahh, BMW CCA (based on the advaned group) that explains it. Yea at those speeds I can believe they hold up just fine.
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      08-06-2008, 03:15 PM   #51
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I should add by biggest gripes with BMW brakes is not the number of pistons they have or the weight of the setup. The have/had two major flaws.

1: Poor airflow to the rotor which prevents proper cooling of the rotors. Its the high temp that they reach that causes the fade and rapid wear of components.

2: The pads are a royal PITA to change. Why do I have to unbolt crap to change the pads? On proper calipers I pull one or two pins and just slide the pads out.
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      08-06-2008, 03:57 PM   #52
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What is the difference between sizes of pads between the Brembo/Stoptech/PF/AP offerings to the stock caliper?

The sliding calipers have been used with great success with the Vettes. My prior Z06 was great with pads/fluid/lines/ducts...until the caliper spread and pad taper was unmanageable. A caliper replacement from Stoptech would pay for itself in two years of track days, with the additional longevity of the pads. Most people who race the Vettes (in T1) replace the stock calipers yearly to combat the taper problem. But I will say that the size of the pads were twice the size of the E36M3's that my friend owned. I couldn't believe how small a surface area those pads had compared to my Z06's pads.

The point is that the sliding caliper is an old, heavy, outdated design that really has no place on an M-car costing roughly $70K. I'll no doubt change lines/fluid/pads and add ducts, as BBK/calipers cut into the track-day budget too much. I'm also less than thrilled thatthe rotors are drilled, but we'll see how things go first.

Be good,
TomK
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      08-06-2008, 04:32 PM   #53
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Quote:
Originally Posted by enigma View Post
I should add by biggest gripes with BMW brakes is not the number of pistons they have or the weight of the setup. The have/had two major flaws.

1: Poor airflow to the rotor which prevents proper cooling of the rotors. Its the high temp that they reach that causes the fade and rapid wear of components.

2: The pads are a royal PITA to change. Why do I have to unbolt crap to change the pads? On proper calipers I pull one or two pins and just slide the pads out.
I have not tried to change pads on the E92 but I know that on my previous E30 race car we could change front pads under a caution without losing a lap.Remove 1 bolt and swing the caliper out of the way and push the pistons back at the same time and you were good to go in under 3 minutes.
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      08-06-2008, 04:37 PM   #54
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Quote:
Originally Posted by enigma View Post
Ahh, BMW CCA (based on the advaned group) that explains it. Yea at those speeds I can believe they hold up just fine.
Ouch. I'd like to be able to keep up with the A group at BMW CCA events.

Lucid: Thanks for succinctly pointing out the obvious!
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      08-06-2008, 05:53 PM   #55
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Quote:
Originally Posted by swamp2 View Post
This topic has been beat to death here. Braking performance is dominated by many things above piston count. Assuming you have enough brake power to lock at any speed you then have, roughly in order of importance:

1. Brake pad compound - provides enough friction and fade resistance
2. Swept area per vehicle weight - provide braking power
3. Brake thermal management/cooling (cooling flow and rotor design) - prevent rotor warp
4. Rotor design (floating, internal cooling fins) - prevent rotor warp
5. Brake system mass, i.e. rotor size (for thermal mass/management)
6. Proper brake fluid
...
...
7. Number of pistons in brake caliper

It is fairly obvious from your post that you are more worried about aesthetics compared to actual performance. Don't get me wrong I love the killer look of a flashy/racy BBK but it is not really money well spent.


and
tires
car wt distribution
not to mention driver skill

for a street car floating calipers are the way to go...
for a race car where pads/rotors are changed frequently, fixed...

the Bosch Automotive Handbook seems to imply floating is a better all around system...
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      08-06-2008, 06:04 PM   #56
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the C&D test is very valid...
100-0 1/2 g stop
20 seconds
100-0 max g
20 seconds
100-0 max g
20 seconds
100-0 max g
20 seconds
100-0 max g
20 sec
repeat until failure

one cycle takes ~ 5(20) + 5 (5) ~ 125 sec, 2 minutes...
the 335i did not fail, but the warning light came on after 7 cycles!
35 100-0 stops in 14 minutes...
pedal travel increased 1.5 inch, the PCCB's ~0.75"
pedal force, 18 lbs to 23 lbs or so

the M3 brakes are much better and the tires larger...it would only perform better:
larger rotors
cross drilled
aluminum hats
floating
more mass

think about it

btw: the PCCB's performed no better than the std 997S brakes
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      08-06-2008, 06:13 PM   #57
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I don't think anyone is complaining the M3s brakes are ineffective anywhere except on a race track while being pushed very hard.

However, that doesn't change the fact that the caliper design is painfull to work with and they will fail under track conditions.

Should you expect a street cars brakes to hold up on a race track, normally no. However they do market the car as suitable for those purposes.


Quote:
Originally Posted by ArtPE View Post
the C&D test is very valid...
100-0 1/2 g stop
20 seconds
100-0 max g
20 seconds
100-0 max g
20 seconds
100-0 max g
20 seconds
100-0 max g
20 sec
repeat until failure

one cycle takes ~ 5(20) + 5 (5) ~ 125 sec, 2 minutes...
the 335i did not fail, but the warning light came on after 7 cycles!
35 100-0 stops in 14 minutes...
pedal travel increased 1.5 inch, the PCCB's ~0.75"
pedal force, 18 lbs to 23 lbs or so

the M3 brakes are much better and the tires larger...it would only perform better:
larger rotors
cross drilled
aluminum hats
floating
more mass

think about it

btw: the PCCB's performed no better than the std 997S brakes
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      08-06-2008, 06:31 PM   #58
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Chaps

Before I beign, would like to preface this with the fact that my brembo bbk for my e92 just arrrived and I had ordered it before I got the car.

I might not be as experienced as you chaps but I have 20+ track days under my belt, have done various advanced driving courses and been to the ring a couple of times for BMW driver training.

Just wanted to report on the actual performance of the braking system in the car (regardless of the rotor size, material, piston numbers etc). I did a track day in my E92 at Mondello park here in Ireland a few weeks ago. Its a tight track that is very hard on brakes.

Personally, I was surprised that the brakes didn't fade as badly as I would have expected. Sure there was fade, bu it was manageable. I found that if I was doing 4-5 lap stints, laps 4-5 were dodgy, but 10 minutes in the paddock and I was ready to repeat with typically good performance for laps 1-3 again. If you forget the fade issue, in terms of stopping distance the brakes are right up there and more than enough to trigger abs and make my ps2's the limiting factor.

In terms of diagnosing the fade, the nature of my pedal travel suggested it was a pad/fluid issue rather than any issue of clamping force.

So in fairness, I had to reckon that changing hoses, changing the stock fluid to dot 5.1 or somethign and putting a set of performance pads on the car would give you a braking system that will work for 95% of people.

Yes I am glad I have my brembos, but I recognise that its a function of looks and ease of pad change as much as anything (because I probably could have made the above changes far cheaper and had a decent system)

Mick
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      08-06-2008, 06:34 PM   #59
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I don't think anyone is complaining the M3s brakes are ineffective anywhere except on a race track while being pushed very hard.

However, that doesn't change the fact that the caliper design is painfull to work with and they will fail under track conditions.

Should you expect a street cars brakes to hold up on a race track, normally no. However they do market the car as suitable for those purposes.
the pads can be changed in minutes...I've done it...

they will not fail...100-0 35 times in 14 minutes?
that's a lot of energy dissipation...

good pads (at the expense of rotor wear)
solid bushings (at the expense of NHV)
SS lines, no real negatives
HiTemp REGULARLY CHANGED fluid

and you're good to go...the reason the Porsche may outlast the M3, is ~400 lbs of weight, the brakes are no more efficient...but then again, 2 different design objectives...
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      08-06-2008, 06:44 PM   #60
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Quote:
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Kingleh, Swamp is on target here, so no point in arguing. He is pointing out the other factors that affect braking performance more than the number of pistons. Airflow has everything to do with that.

Weight of the rotors constitute thermal mass for heat to be dissipated effectively without melting down everything in sight. Creating friction between the pad and the rotor by applying pressure is just one part of the deal. Dissipating the generated heat effectively is the other. If the rotors do not have adequate thermal mass to transfer the heat and dissipate it away from the calipers, the brakes will be in trouble. (Keep in mind the majority of the rotor is not in contact with the pad, and is surrounded by cooler air, and thus heat transfer via convection between rotor and air.)

number is pistons is irrelevant.. its the design of the caliper..


a multi piston caliper is a type of design.. the number of pistons doesn't really matter... like 6 or 8 pots.. whatever...

im not arguing the number of pistons.. im arguing the design...



and i totally agree with the air thing....


its hot here!.. 105 today!!.. i cant think straight..
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      08-06-2008, 06:46 PM   #61
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Quote:
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I don't think anyone is complaining the M3s brakes are ineffective anywhere except on a race track while being pushed very hard.

However, that doesn't change the fact that the caliper design is painfull to work with and they will fail under track conditions.

Should you expect a street cars brakes to hold up on a race track, normally no. However they do market the car as suitable for those purposes.
M3 is not an Elise and it does weigh a couple of pounds more, if that is your comparison point.
I have had some of experience with M3 brakes (E36/8) and some with my new E-93 (6 days) and I have to admit that I have been very impressed with the braking and absence of fade. And yes, I brake Hard and Late. I have not found any reason to even look at a BBK or changing calipers.
The new design for the backing plates is dramatically better for pulling in air to the disk. Pull off a wheel some time and look. It would be nice to see some ducting, but that can be fixed with a little channeling of air.

As far as changing pads. It takes me a little longer at the track to change the 12 pads on the front of my mechanically challenged friends Z06 as it takes to change both of my fronts. Oh yeah, he goes through a set of CHEAP Z06 pads every 2 track days.

BTW the stock pads held up fine until the last session of 6 days. Although the car will never see the track again with stock pads because of the wear and price. Rotors be damned. Surprisingly, I think this tank stops as short as my MCoupe.
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      08-06-2008, 07:02 PM   #62
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the reason the Porsche may outlast the M3, is ~400 lbs of weight, the brakes are no more efficient...but then again, 2 different design objectives...

ur on crak
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      08-06-2008, 08:01 PM   #63
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ur on crak
Or haven't seen the size of the pads.



BTW...what brakes are used here, sliders or multipiston?...


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      08-06-2008, 09:17 PM   #64
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ur on crak
sounds like you have personal experience with drug abuse...seek help

I gurantee the 997 (non PCCB) would stop better with the m3 brakes...

obviously you are not an engineer, nor do you have any technical comprehension what so ever...pick up a book once and a while...

997S F/R rotors 13" and 13" (the 997 are only 12.5/11.8, lol)
M3 14.2" and 13.8"

that's a big difference in area...

which has greater swept area? which rotor friction ring weighs more ?(although the m3 complete rotor may weigh about the same due to it's aluminum construction)

are the 997 brake rotors floating?
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      08-06-2008, 09:19 PM   #65
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Art I cant take you seriously if you are going to quote car and driver really.

Car and Driver has NEVER executed a Valid test EVER! You are an engineer?
for who?

Everyone knows those guys are a bunch of hacks. Not only that I can attest
having track experience in all three designs for Porsche that the
PCCBs are much better than the iron brakes on a 997, I have driven both
iron brakes on my 993 Twin Turbo and the Gen I PCCBS on my 996 GT3 and the Gen II
PCCBs on my 997 GT3 I can tell you from experience the reduced unsprung weight helps in so many ways and then there is no fade which I was able to experience on my TT on track days in the 100 degree days of summer. I dont care what a bunch of hacks from some rag say. I know better. Period. And IF you are a real engineer as am I you should
know to use better sources for information. Really. Please dont go to the track and get in a conversation and start quoting Car and Driver or Road and Track. I dont want you to get laughed out off the grounds.
The very idea that you are saying M3 brakes are better than a 997 is getting rediculous
Nobody would seriously argue that
Try going to Rennlist or 6Speed online or Ferrari chat and argue that point!LOL!
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      08-06-2008, 09:27 PM   #66
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Art I cant take you seriously if you are going to quote car and driver really.

Car and Driver has NEVER executed a Valid test EVER! You are an engineer?
for who?

Everyone knows those guys are a bunch of hacks.
+1

There are magazines that do real testing. Car and Driver and Motor Trend are not on that list.

As to those talking about "swept area", yes it helps, but its a long way from the most important factor.
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