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Old 03-06-2008, 10:46 AM   #41
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Originally Posted by villanovakid View Post
you justify it by stopping and preventing a major accident that regular brake wouldn't have prevented ?
Stopping distance is generally limited by traction, and bigger brakes do not increase traction. So bigger brakes do not equal shorter stopping distance in a single incident.

What they will do is increase the ability to modulate the brakes AND shed heat faster. In a panic stop, the ABS system on a modern car eliminates the driver's modulation anyway. So what you gain from BBKs like this is primarily their ability to continue to deliver top braking performance after many frequent stopping incidents.
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Old 03-06-2008, 10:55 AM   #42
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Originally Posted by Xcelratr View Post
Stopping distance is generally limited by traction, and bigger brakes do not increase traction. So bigger brakes do not equal shorter stopping distance in a single incident.

What they will do is increase the ability to modulate the brakes AND shed heat faster. In a panic stop, the ABS system on a modern car eliminates the driver's modulation anyway. So what you gain from BBKs like this is primarily their ability to continue to deliver top braking performance after many frequent stopping incidents.
Related, the common "do I need a BBK?" question:

http://www.uucmotorwerks.com/alcon/need_a_bbk.htm

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Old 03-06-2008, 02:38 PM   #43
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Originally Posted by Xcelratr View Post
Stopping distance is generally limited by traction, and bigger brakes do not increase traction. So bigger brakes do not equal shorter stopping distance in a single incident.

What they will do is increase the ability to modulate the brakes AND shed heat faster. In a panic stop, the ABS system on a modern car eliminates the driver's modulation anyway. So what you gain from BBKs like this is primarily their ability to continue to deliver top braking performance after many frequent stopping incidents.

i thought if under same conditions, like same car same tires, same pads, same everything

BBK slows down the car faster and in less distance than stock?
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Old 03-06-2008, 03:03 PM   #44
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Originally Posted by villanovakid View Post
i thought if under same conditions, like same car same tires, same pads, same everything

BBK slows down the car faster and in less distance than stock?
What I think he's saying is that the stock brakes on our cars are already powerful enough to exceed the traction limitations of the typical street tires we have. Clamping down with stock brakes and clamping down with a BBK will not alter the point at which you lose traction and that is the limiting factor.

A BBK isn't clamping down on the rotor any harder than the stock brakes which might, as you've speculated, give you the ability to lessen your speed more rapidly and/or stop in less distance. Rather, a BBK gives better pedal feel by clamping the pad down on to the rotor more evenly (floating caliper vs. fixed multi-piston) and it also allows for better heat dissipation because of caliper material choice and size (surface area).

Now, if you use a different pad material, its a different story, but you can change pad material on the stock brakes. BMW brakes are excellent to start with, which is why a BBK has never been at the top of my mod-list, but they offer real-world and track-world benefits that we all can appreciate and benefit from beyond simple stopping distance numbers.
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Old 03-07-2008, 12:47 AM   #45
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Originally Posted by Rob Levinson * UUC Motorwerks View Post
Related, the common "do I need a BBK?" question:

http://www.uucmotorwerks.com/alcon/need_a_bbk.htm

- Rob
Rob, I'm consistently impressed with the writing on UUC's website.

The FAQ you linked to is well-written, is short on slick sales lingo, long on facts about whys/hows, and skips the overstated claims or misleading omissions that such "tech" items are often riddled with. Well done.
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Old 03-07-2008, 01:50 AM   #46
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i thought if under same conditions, like same car same tires, same pads, same everything

BBK slows down the car faster and in less distance than stock?
JCz04 is correct, and the article Rob linked to on UUC's website has very good info. I'm going to expand the explanation and hope I don't bore you to death.

Since your car's stock brakes are powerful enough to lock up all 4 tires at any road speed, increasing braking power will not shorten the stopping distance. All it will do is get the tires to lock up faster, or with less effort on your part. But the braking distance will be the same.

The tires exert the greatest force on the car (and therefore slow it down most rapidly) just before they lock up. Exert less braking power than it takes to lock them up and you're not slowing the car down as fast as you can. Exert too much braking power, you'll lock them up and will take longer to stop. But since locked tires don't stop the car as quickly as damn-near-locked tires, being able to lock the tires up faster or more easily (by increasing braking power via a BBK or race pads or ss lines, etc) doesn't allow you to stop the car any faster.

So the only way to shorten the stopping distance is to increase the traction available at each corner so that the tire can exert more force on the car without locking up. Wider tires, stickier tires, suspension that slows weight transfer from front to back, lower C of G that limits ultimate weight transfer will all increase traction.* Bigger brakes will not.

However, that's not to say that you don't get anything out of upgraded brakes. BMW factory brakes are excellent. But if you do spirited driving on the street, some track days, or any kind of road racing, you can see a performance gain from a well-designed BBK simply because it has the ability to shed heat so much faster than the OE brakes.

So while your stopping distance into the first corner might be the same with OE brakes vs a BBK, by the time you get to the 4th, or 12th or 35th corner, the BBK is probably going to be managing it's system temperature much better than the OE brakes and delivering better feel, modulation, initial bite and ultimate clamping force. All of which adds up to a happier slow-down situation.

The floating vs fixed, and 2+ piston vs 1 piston, and slotted vs drilled vs solid vs 2-piece, and rubber sleeve vs metal bushing factors all contribute as well. There's also the maintenance part of it, how much are replacement pads and rotors, where can you buy them if you're in a jam, how easy are the pads to replace, do the pad mfgs pay contingency in your series and .

So anyway, don't install a BBK and think you can stand on the whoa pedal a lot closer to the off-ramp than you did before. If you expect to magically stop shorter, you're gonna be disappointed, it doesn't work like that. But by all means, install a BBK and enjoy the consistent braking performance even after many many laps of hard driving.

It doesn't hurt that they look dead sexy, either.

I hope this helps.

* Making the car lighter without greatly lessening the sum of the normal forces acting on the 4 contact patches will lessen the energy the tire's traction has to overcome. So that also will shorten braking distance, but that's a different subject.
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Old 03-07-2008, 12:07 PM   #47
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^ nice post
what i was implying with that was like before i drove the 350z and they had 2 brake options (OEM 1piston vs. OEM Brembo)

The tests were done comparing the 2

The stopping distance of OEM vs. brembo were similar in a sense that they were around the same distance but brembo always stopped a couple feet shorter than OEM and obviously the distance stretched as the brakes got heated up... but the thing im trying to stress on is even initially brembo brakes on the same car with same tires stopped shorter than OEM 1 piston

Obviously in the REAL WORLD 1-5 feet from 60-0 or 100-0 does not sound like a whole lot but considering that it can result in "near miss" from that 1 foot of extra stopping power or a real accident....

^ thats what im thinking ... but you know everything is hypothetical lol
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Old 03-07-2008, 12:12 PM   #48
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Quote:
Originally Posted by villanovakid View Post
^ nice post
what i was implying with that was like before i drove the 350z and they had 2 brake options (OEM 1piston vs. OEM Brembo)

The tests were done comparing the 2

The stopping distance of OEM vs. brembo were similar in a sense that they were around the same distance but brembo always stopped a couple feet shorter than OEM and obviously the distance stretched as the brakes got heated up... but the thing im trying to stress on is even initially brembo brakes on the same car with same tires stopped shorter than OEM 1 piston

Obviously in the REAL WORLD 1-5 feet from 60-0 or 100-0 does not sound like a whole lot but considering that it can result in "near miss" from that 1 foot of extra stopping power or a real accident....

^ thats what im thinking ... but you know everything is hypothetical lol
I'd be curious to know if there was a difference in the pads used on each of the two brake options on the 350Z for the test. Also, its likely that the OEM 1-Piston on a 350Z is not nearly as good of a performer as the OEM offerings on our BMWs. If the stock option is so-so to begin with, a BKK is going to stop the car faster, because the limiting factor is no longer traction but rather the caliper/rotor design itself. The fact that BBKs don't stop our cars in any shorter of a distance is mostly a function of excellent stock brakes that are already capable of exceeding the traction threshold.
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Old 03-08-2008, 09:52 AM   #49
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I'd be curious to know if there was a difference in the pads used on each of the two brake options on the 350Z for the test. Also, its likely that the OEM 1-Piston on a 350Z is not nearly as good of a performer as the OEM offerings on our BMWs. If the stock option is so-so to begin with, a BKK is going to stop the car faster, because the limiting factor is no longer traction but rather the caliper/rotor design itself. The fact that BBKs don't stop our cars in any shorter of a distance is mostly a function of excellent stock brakes that are already capable of exceeding the traction threshold.
but can you really undermine the quality of OEM?
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Old 03-08-2008, 10:00 AM   #50
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but can you really undermine the quality of OEM?
Why not? OEM doesnt automatically indicate quality or, more accurately, performance! Why do you think we all spend so much money on modifications?

I don't doubt that the OEM 1-piston brakes on the 350Z are of high quality but its certainly possible that the lower-level brakes, the 1-pistons, do not perform at the level of our BMW brakes. That said, remember, there are tons of other factors to consider such as weight transfer while braking, cooling characteristics, etc.
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Old 03-08-2008, 02:55 PM   #51
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Originally Posted by villanovakid View Post
^ nice post
what i was implying with that was like before i drove the 350z and they had 2 brake options (OEM 1piston vs. OEM Brembo)

The tests were done comparing the 2

The stopping distance of OEM vs. brembo were similar in a sense that they were around the same distance but brembo always stopped a couple feet shorter than OEM and obviously the distance stretched as the brakes got heated up... but the thing im trying to stress on is even initially brembo brakes on the same car with same tires stopped shorter than OEM 1 piston

Obviously in the REAL WORLD 1-5 feet from 60-0 or 100-0 does not sound like a whole lot but considering that it can result in "near miss" from that 1 foot of extra stopping power or a real accident....

^ thats what im thinking ... but you know everything is hypothetical lol
There are 2 possible reasons the Brembo stopped shorter. Well, there are 3, but assuming Nissan and Brembo advertising dollars didn't "affect" the test methodology, we'll say there are 2.

First, even though the rate of deceleration is limited by the traction level of the tire, the braking system takes a certain amount of time to go from 0 to maximum clamping force. And the car covers ground during that time. If the Brembo kit is more rigid, or the pad material bites faster, it's possible that it gets to maximum clamping force in less time and so stops the car sooner. Even if it's only 0.05 seconds, that's 5 feet at 70 mph.

However, that's not usually the case because the time the BBK gains from its rigidity and friction materials it loses because it needs a larger displacement of brake fluid into the caliper to move its pistons, which takes longer.

Second, it could be that the rigid structure, the increased swept area or the better design of the friction materials of the Brembo will allow the ABS to modulate the braking force better and keep the tire closer to the rotational slip angle that's ideal for maximizing deceleration. Because it's not dealing with as much flex and it gets faster reactions to lowering/raising/lowering the brake pressure with the Brembos, it can be more precise in it's management of the whole process, producing a better result.

It's also possible that the ABS software packages are different and the engineers spent more time optimizing the software for the Brembo option.

Anyway, this is all sound in theory, but the real test is whether it stops the car faster or better in the real world. Hope this helps clarify.
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Old 03-09-2008, 02:34 PM   #52
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Originally Posted by Xcelratr View Post
There are 2 possible reasons the Brembo stopped shorter. Well, there are 3, but assuming Nissan and Brembo advertising dollars didn't "affect" the test methodology, we'll say there are 2.

First, even though the rate of deceleration is limited by the traction level of the tire, the braking system takes a certain amount of time to go from 0 to maximum clamping force. And the car covers ground during that time. If the Brembo kit is more rigid, or the pad material bites faster, it's possible that it gets to maximum clamping force in less time and so stops the car sooner. Even if it's only 0.05 seconds, that's 5 feet at 70 mph.

However, that's not usually the case because the time the BBK gains from its rigidity and friction materials it loses because it needs a larger displacement of brake fluid into the caliper to move its pistons, which takes longer.

Second, it could be that the rigid structure, the increased swept area or the better design of the friction materials of the Brembo will allow the ABS to modulate the braking force better and keep the tire closer to the rotational slip angle that's ideal for maximizing deceleration. Because it's not dealing with as much flex and it gets faster reactions to lowering/raising/lowering the brake pressure with the Brembos, it can be more precise in it's management of the whole process, producing a better result.

It's also possible that the ABS software packages are different and the engineers spent more time optimizing the software for the Brembo option.

Anyway, this is all sound in theory, but the real test is whether it stops the car faster or better in the real world. Hope this helps clarify.
but ... hey ... honestly lol if i have a choice to stop on a dime between stock 1pot 12" OEM brakes or Alcon 4pot BBK... i'd pick not pick OEM
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Old 03-09-2008, 04:44 PM   #53
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but ... hey ... honestly lol if i have a choice to stop on a dime between stock 1pot 12" OEM brakes or Alcon 4pot BBK... i'd pick not pick OEM
Derrrrr!
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Old 03-10-2008, 09:57 PM   #54
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Edit - I won't comment. Good luck with the sale.

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Old 03-15-2008, 11:20 AM   #55
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quick question as i was reading through your "do i need a bbk link" rob,i noticed the question regarding operating costs how do the operating costs compare between your new alcons and your "trite and true" wilwoods? debating on how much more broke do i need to be
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Old 06-03-2010, 06:22 AM   #56
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hello,

thread revival

I was wondering is there is a specific reason why the e36 M3 Alcon fitment rotors are bigger in the rear (328mm) than the front (325mm). I was also wondering why these rotors are smaller than some of the competition (AP makes 330mm rotors for the front)? Is it only because of the race class restrictions or is there another reason UUC decided to produce 325mm instead of 330mm for the 4 piston?

Thanks,

PS. Pardon me if my question sounds naive.
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Old 06-09-2010, 04:16 PM   #57
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It's the same for all 3 series by the looks of it...I always have seen larger in the front (since the weight of the car shifts forward)...

I dunno?????
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Old 06-10-2010, 07:32 AM   #58
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i can try to answer that question..

the rotors used in this bbk are taken from the e46 m3 parts bin which has a 325 mm front diameter and 328 mm rear diameter. i suppose the reason behind it is because it is a common size to source and there is also a floating rotor option in the same size and thickness.. given the size of the caliper, it will work best with a certain rotor/pad thickness. the reason for the m3's larger rear diameter? i have heard from several people that the e46 m3 has a higher rear brake bias than the non m3's so i suppose bmw made the brakes larger diameter to help with the extra heat.

it looks like the alcon kits use the 325mm front and 328mm rear rotors on all their e36 and non m3 e46 kits.. i must say, the kit looks awesome.
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Old 06-10-2010, 08:50 AM   #59
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i have heard from several people that the e46 m3 has a higher rear brake bias than the non m3's so i suppose bmw made the brakes larger diameter to help with the extra heat.

it looks like the alcon kits use the 325mm front and 328mm rear rotors on all their e36 and non m3 e46 kits.. i must say, the kit looks awesome.
Thanks for the explenation... it def. make sense for the E46 M3...

but does the rear bias on the E46 M3 also explain the size choice for the e36 M3? Correct me if I a wrong... from what I understand the E36 M3 mostly need bigger rotors and calipers in the front because of heat issues (mostly on track), and that is why I am still wondering how this kit stacks up against a AP Racing 4pot with 330mm front rotors?
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Old 06-10-2010, 10:34 AM   #60
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Thanks for the explenation... it def. make sense for the E46 M3...

but does the rear bias on the E46 M3 also explain the size choice for the e36 M3? Correct me if I a wrong... from what I understand the E36 M3 mostly need bigger rotors and calipers in the front because of heat issues (mostly on track), and that is why I am still wondering how this kit stacks up against a AP Racing 4pot with 330mm front rotors?
I'll put one thing quite simply; all of our Alcon-based kits have the correct bias for whichever car we are offering them for. Rotor size is not the only factor that determines bias; brake torque (and then the comparison of front:rear brake torque) of a particular brake package is determined by a calculation using multiple factors including pad height, piston size, pad , blp, and rotor diameter.

In a nutshell, don't worry about it - if there's one thing you can be sure of, the UUC engineering on these systems is very, very thorough.

Now, as to why the E46 M3 has bigger rear rotors... it's not a question of brake bias. It has to do with DSC (Dynamic Stability Control) and traction control. This system actuates the rear brakes to control wheelspin, so the components are larger than previous 3-series to retain component longevity, affected by their more frequent use.
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