[S4to335]

Ok..I musta been under a rock..when did these come out? $1563?

[leftcoastman]

1) Doesn't fit the 335.
2) It's just the 135 brake setup...in all its 338mm glory.

[Craig@SupremePower]

This is the only kit i've seen but not available yet for the 335's...

http://www.e90post.com/forums/showthread.php?t=158305

[kinan_sleiman2006]

it" doesnt fit bw 335i my friend..any way thx for that post

[E92Fan]

Originally Posted by leftcoastman

1) Doesn't fit the 335.
2) It's just the 135 brake setup...in all its 338mm glory.

Actually, it does fit a 335... and yes, whilst the discs are smaller (BBK = 338 x 26mm | standard = 348 x 30mm), the greater efficiency of the caliper, plus the increased heat dissipation of the new rotor, actually gives better outright braking performance, with much less fade after repeated braking and a more progressive pedal feel.

However, the standard pads supplied with the BMW BBK are rubbish - they are OEM spec Jurid 310 pads, stamped with the Brembo name, but are the same pads you used to get as OEM on an E60 545i, for example. Must change to something like a Pagid 422 pad or Ferodo DS2500, then you'll have a very good braking setup for not much money.

The Jurid pads survived only 18 laps of the Nurburgring last weekend, before starting to break up. Have Carbo race pads on at the moment which are amazing, but groan and squeak like a bitch when driving in traffic. Will be changing back to Pagid 422 road pads next week.

[uberschnell]

Originally Posted by E92Fan

Actually, it does fit a 335... and yes, whilst the discs are smaller (BBK = 338 x 26mm | standard = 348 x 30mm), the greater efficiency of the caliper, plus the increased heat dissipation of the new rotor,

How does this rotor increase heat dissipation when it's both smaller and thinner?

Also, one of the biggest benefits to braking power from a BBK is the increased torque provided by a larger diameter rotor.

[E92Fan]

Originally Posted by Magna3

How does this rotor increase heat dissipation when it's both smaller and thinner?

Also, one of the biggest benefits to braking power from a BBK is the increased torque provided by a larger diameter rotor.

A) It's drilled

B) The increased torque does not necessarily come from a larger diameter rotor, given that the rotor itself is not exerting any frictional force. The frictional force comes from the caliper pressure, and also from the brake pad material. If the rotor is larger in diameter, and therefore the pads are located further out to the edges, then the greater rotational circumference will lead to greater torque, all other things being equal.

The BMW BBK kit, whilst not the be all and end all of brake kits (and far from it), does have the benefit of having a more efficient and effective caliper over standard. And from a practical and objective viewpoint, my car equipped with the BMW BBK stops in a shorter distance from 70mph than it did with the original OEM brakes. Whilst this is of course a benefit, the biggest advantage in my eyes is the issue of repeatability - I can do more stops from 70mph with the BBK without fade, than I can with the standard OEM brakes.

As an aside, which would you rather have?? An OEM brake setup using 348x30mm discs, standard single pot calipers, standard Jurid/Textar pads.... OR, a 6pot AP Racing caliper set, on 328x26mm discs, with decent pads... I know which option I'd rather use when driving around the Nurburgring

[uberschnell]

Originally Posted by E92Fan

A) It's drilled

B) The increased torque does not necessarily come from a larger diameter rotor, given that the rotor itself is not exerting any frictional force. The frictional force comes from the caliper pressure, and also from the brake pad material. If the rotor is larger in diameter, and therefore the pads are located further out to the edges, then the greater rotational circumference will lead to greater torque, all other things being equal.

The BMW BBK kit, whilst not the be all and end all of brake kits (and far from it), does have the benefit of having a more efficient and effective caliper over standard. And from a practical and objective viewpoint, my car equipped with the BMW BBK stops in a shorter distance from 70mph than it did with the original OEM brakes. Whilst this is of course a benefit, the biggest advantage in my eyes is the issue of repeatability - I can do more stops from 70mph with the BBK without fade, than I can with the standard OEM brakes.

As an aside, which would you rather have?? An OEM brake setup using 348x30mm discs, standard single pot calipers, standard Jurid/Textar pads.... OR, a 6pot AP Racing caliper set, on 328x26mm discs, with decent pads... I know which option I'd rather use when driving around the Nurburgring

Simply upgrading the pads on the oem set up would mitigate much of the advantage of the BMW BBK .

Also, technically it would be a SBK for the 335 (Small Brake Kit)

Also, I'd go for a 355mm kit over the options mentioned above.

[uberschnell]

Pretty good explanation of the advantages of a larger diameter rotor:

Well sports cars and race bikes typically have much bigger discs or rotors than your average family saloon car. The reason again is to do with heat and friction. A bigger rotor has more material in it so it can absorb more heat. More material also means a larger surface area, which as well as meaning more area for the pads to generate friction with, also translates to better heat dissipation. On top of that, the larger rotors mean that the brake pads make contact further away from the axle of rotation. This provides a larger mechanical advantage to resist the turning of the rotor itself. To best illustrate how this works, imagine a spinning steel disc on a pivot in front of you. If you clamped your thumbs either side of the disc close to the middle, your thumbs would heat up very quickly and you'd need to push pretty hard to generate the friction required to slow the disc down. Now imagine doing the same thing but clamping your thumbs together close to the outer rim of the disc. The disc will stop spinning much more quickly and your thumbs won't get as hot. That, in a nutshell explains the whole principle behind why bigger rotors = better stopping power.

http://www.about-brakes.com/strona-2...ed-rotors.html

[E92Fan]

Originally Posted by Magna3

Pretty good explanation of the advantages of a larger diameter rotor:

Well sports cars and race bikes typically have much bigger discs or rotors than your average family saloon car. The reason again is to do with heat and friction. A bigger rotor has more material in it so it can absorb more heat. More material also means a larger surface area, which as well as meaning more area for the pads to generate friction with, also translates to better heat dissipation. On top of that, the larger rotors mean that the brake pads make contact further away from the axle of rotation. This provides a larger mechanical advantage to resist the turning of the rotor itself. To best illustrate how this works, imagine a spinning steel disc on a pivot in front of you. If you clamped your thumbs either side of the disc close to the middle, your thumbs would heat up very quickly and you'd need to push pretty hard to generate the friction required to slow the disc down. Now imagine doing the same thing but clamping your thumbs together close to the outer rim of the disc. The disc will stop spinning much more quickly and your thumbs won't get as hot. That, in a nutshell explains the whole principle behind why bigger rotors = better stopping power.

http://www.about-brakes.com/strona-2...ed-rotors.html

I agree totally with the above information - having a larger rotor does give better braking performance in all areas, if the rest of the equipment remains the same.

However my point with the BMW BBK is that the rest of the equipment is not the same - the 6pot calipers accommodate a much larger pad surface area, and in themselves dissipate heat better than the standard single pot caliper the 335i comes with as standard.

So therefore, whilst the BMW BBK is not necessarily designed for the 335i, and uses a smaller disc than normal, its overall performance is still better, because all the equipment has changed, not just the rotor.

[E92Fan]

Originally Posted by Magna3

Also, I'd go for a 355mm kit over the options mentioned above.

So would I - I'd even try to squeeze a 380mm setup behind the wheels if I could, but that's not the point I was making...

[scollins]

Originally Posted by E92Fan

A) It's drilled

Drilled rotors are a gimmick really. Drilled rotors are far more likely to crack than solid rotors, especially when worked hard on a track. Drilling the rotors doesn't increase air flow through the rotor (the holes are 90 degrees to the rotation after all), and just reduces some of the mass available as a heat sink. The best option is a slotted 2 piece rotor. The SBK rotor is still a single piece rotor.

A reference: http://www.marcusfitzhugh.com/CLK/DIY/brakecdrill.html

B) The increased torque does not necessarily come from a larger diameter rotor, given that the rotor itself is not exerting any frictional force. The frictional force comes from the caliper pressure, and also from the brake pad material. If the rotor is larger in diameter, and therefore the pads are located further out to the edges, then the greater rotational circumference will lead to greater torque, all other things being equal.

You forgot pad surface area, as this will play a role as well. I've been trying to find the specs on the stock 335i pads vs. the 135i pads (identical to the SBK pads). This is all I can find:

Stock 335i pads measure: (Textar T4165 or Jurid 422)
155.1mm (width 1), 156.3mm (width 2)
68.4mm (height 1), 66.5mm (height 2)
20.3mm thick

Stock 135i pads measure: (Jurid 310)
86.9mm width
76.2mm height
17.1mm thick

*According to Textar's website: http://www.textar.com/content/view/25/46/lang,eu/

Looks to me like the stock 335i pads are significantly larger in surface area.

The BMW BBK kit, whilst not the be all and end all of brake kits (and far from it), does have the benefit of having a more efficient and effective caliper over standard. And from a practical and objective viewpoint, my car equipped with the BMW BBK stops in a shorter distance from 70mph than it did with the original OEM brakes. Whilst this is of course a benefit, the biggest advantage in my eyes is the issue of repeatability - I can do more stops from 70mph with the BBK without fade, than I can with the standard OEM brakes.

Did you actually do before and after tests (measured stopping distances, etc.), or is this just conjecture on your part? I've read a thread here from another member who did the conversion to the SBK, and he indicated that his braking performance decreased. It was specific to stopping distances and not fade resistance.

Car & Driver recently did a massive test on braking performance, including the 335i. It can be found here: The Power to Stop Tech Stuff.

The specific results of the 335i are here: 335i brake tests.

It made it through 7 complete test cycles before they quit due to a brake warning light (possible brake pad sensor.) They indicated it "did very well in the tests." Too bad they didn't test a 135i at the same time.

As an aside, which would you rather have?? An OEM brake setup using 348x30mm discs, standard single pot calipers, standard Jurid/Textar pads.... OR, a 6pot AP Racing caliper set, on 328x26mm discs, with decent pads... I know which option I'd rather use when driving around the Nurburgring

They are not AP Racing calipers, they are BMW-branded Brembo calipers, which use Jurid 310 pads. So the stock pads that come with the SBK are no better than the stock pads that come with the 335i. I see that many aftermarket pad companies make a wide range of choices for the stock 335i brakes. So frankly, I'd take the stock 348x30 discs with good pads over the SBK's 328x26 discs with good pads.

Car and Driver lists the 70-0 stopping distance of the 335i Sedan at 157 feet, and the 70-0 stopping distance of the 135i Coupe also at 157 feet. Keep in mind the 135i Coupe is over 200 lbs lighter than the 335i Sedan. I know your argument has been over fade resistance, and not braking performance overall, but I still don't think the SBK option from BMW is a better choice than the stock brakes. I think it is more of the mentality that "6 pots HAVE got to be better than 1 pot brakes, even with smaller, lighter mass rotors." I just don't see the physics in it.

I think the bigger "bang for the buck" with the stock 335i brakes would be upgraded pads, stainless steel brake lines and a better fluid, like Motul RBF600.

[S4to335]

I dunno guys..I will stick with my 365mm Alcons.

[Mr. 5]

I agree about the drilled holes, but let's look at an example of the brakes that I replaced.
I added the 6 piston Rotoras that replaced my OEM 335 front brakes.

The first thing that I noticed was how the rotoras do not use the same width of the rotor that the OEM brakes use. Actually, I was pretty dissapointed because I was thinking that the surface area was more with the OEM brakes.
Umm, not even close.

I just went out to the grage and took a picture to compare my Rotora brakes with the OEM brakes. There is so much surface area with the rotoras.
I also did the math to get a pretty good estimate.

The rotora brake is easy to figure out since you can take the top dome part and add it to the bottom. Doing this makes the pad into a rectangle. Now it's an easy length times width equation.

For the OEM pad, I made this into a sector and forund the angle by using a protractor. I then found the area of the entire sector, and subtracted the bottom sector since this area is not a part of the pad. The smaller sector is the dotted lined part.

The final results:

Rotora Pads have 10.875 square inches of surface area.
The OEM pads have 6.87 square inches of surface area.

Now also notice that the more the pad wears, the more surface area that connects with the rotor because the edges are angled, but the same goes for both pads.


The OEM

Originally Posted by scollins

Drilled rotors are a gimmick really. Drilled rotors are far more likely to crack than solid rotors, especially when worked hard on a track. Drilling the rotors doesn't increase air flow through the rotor (the holes are 90 degrees to the rotation after all), and just reduces some of the mass available as a heat sink. The best option is a slotted 2 piece rotor. The SBK rotor is still a single piece rotor.

A reference: http://www.marcusfitzhugh.com/CLK/DIY/brakecdrill.html


You forgot pad surface area, as this will play a role as well. I've been trying to find the specs on the stock 335i pads vs. the 135i pads (identical to the SBK pads). This is all I can find:

Stock 335i pads measure: (Textar T4165 or Jurid 422)
155.1mm (width 1), 156.3mm (width 2)
68.4mm (height 1), 66.5mm (height 2)
20.3mm thick

Stock 135i pads measure: (Jurid 310)
86.9mm width
76.2mm height
17.1mm thick

*According to Textar's website: http://www.textar.com/content/view/25/46/lang,eu/

Looks to me like the stock 335i pads are significantly larger in surface area.



Did you actually do before and after tests (measured stopping distances, etc.), or is this just conjecture on your part? I've read a thread here from another member who did the conversion to the SBK, and he indicated that his braking performance decreased. It was specific to stopping distances and not fade resistance.

Car & Driver recently did a massive test on braking performance, including the 335i. It can be found here: The Power to Stop Tech Stuff.

The specific results of the 335i are here: 335i brake tests.

It made it through 7 complete test cycles before they quit due to a brake warning light (possible brake pad sensor.) They indicated it "did very well in the tests." Too bad they didn't test a 135i at the same time.



They are not AP Racing calipers, they are BMW-branded Brembo calipers, which use Jurid 310 pads. So the stock pads that come with the SBK are no better than the stock pads that come with the 335i. I see that many aftermarket pad companies make a wide range of choices for the stock 335i brakes. So frankly, I'd take the stock 348x30 discs with good pads over the SBK's 328x26 discs with good pads.

Car and Driver lists the 70-0 stopping distance of the 335i Sedan at 157 feet, and the 70-0 stopping distance of the 135i Coupe also at 157 feet. Keep in mind the 135i Coupe is over 200 lbs lighter than the 335i Sedan. I know your argument has been over fade resistance, and not braking performance overall, but I still don't think the SBK option from BMW is a better choice than the stock brakes. I think it is more of the mentality that "6 pots HAVE got to be better than 1 pot brakes, even with smaller, lighter mass rotors." I just don't see the physics in it.

I think the bigger "bang for the buck" with the stock 335i brakes would be upgraded pads, stainless steel brake lines and a better fluid, like Motul RBF600.

[scollins]

Originally Posted by Mr. 5

I agree about the drilled holes, but let's look at an example of the brakes that I replaced.
I added the 6 piston Rotoras that replaced my OEM 335 front brakes.

The first thing that I noticed was how the rotoras do not use the same width of the rotor that the OEM brakes use. Actually, I was pretty dissapointed because I was thinking that the surface area was more with the OEM brakes.
Umm, not even close.

The final results:

Rotora Pads have 10.875 square inches of surface area.
The OEM pads have 6.87 square inches of surface area.

Now also notice that the more the pad wears, the more surface area that connects with the rotor because the edges are angled, but the same goes for both pads.


The OEM

Yes, that is the Rotora and not the SBK pad though. Does the Rotora caliper use the same pad as the SBK? If so, then the SBK does have greater pad surface area.

I can't find any information on what pads the SBK uses, other than Jurid 310 pads. But when I try to find information on Jurid pads, I get a bunch of useless junk from Google.

[Mr. 5]

Originally Posted by scollins

Yes, that is the Rotora and not the SBK pad though. Does the Rotora caliper use the same pad as the SBK? If so, then the SBK does have greater pad surface area.

I can't find any information on what pads the SBK uses, other than Jurid 310 pads. But when I try to find information on Jurid pads, I get a bunch of useless junk from Google.

When you are saying SBK, do you mean the BMW perf kit?
I can't comment on that but I would imagine that they are much bigger than the OEM. Especially since they do use the full width of the rotor in addition to being big enough to cover the 3 pistons on the side.

I was just making an example of my surface area, and this topic made me compare the 2 sizes.
Although the feel is 10 times better, it looks like mathematicaly, I've made the right choice.

[scollins]

Originally Posted by Mr. 5

When you are saying SBK, do you mean the BMW perf kit?
I can't comment on that but I would imagine that they are much bigger than the OEM. Especially since they do use the full width of the rotor in addition to being big enough to cover the 3 pistons on the side.

I was just making an example of my surface area, and this topic made me compare the 2 sizes.
Although the feel is 10 times better, it looks like mathematicaly, I've made the right choice.

Yes, I'm being cheeky by calling the BMW Perf. Brake kit, with its smaller-diameter-than-a-stock-335i-rotor an "SBK", as in "Small Brake Kit."

It's always hard to get good details about specific pads, since almost everyone uses "stock" photos for everything. I find this true across all aftermarket parts actually. I don't think the KW V3 that we see in ad pictures around here look anything at all like the product that actually gets installed on the E9X.

[Mr. 5]

Here's another thing, the pad surface area is actually less then what I came up with since I forgot to deduct for the area that is missing for the pad sensor wire.

This is one of the cons for going with the Rotoras. I don't have a brake pad sensor anymore. It is currently twist tied to the strut.
I guess I just have to keep an eye on my brakes and do it the old fashioned way.

[S4to335]

Originally Posted by Mr. 5

Here's another thing, the pad surface area is actually less then what I came up with since I forgot to deduct for the area that is missing for the pad sensor wire.

This is one of the cons for going with the Rotoras. I don't have a brake pad sensor anymore. It is currently twist tied to the strut.
I guess I just have to keep an eye on my brakes and do it the old fashioned way.

That is SO hard to do..like the old days...remember?

[Mr. 5]

Originally Posted by S4to335

That is SO hard to do..like the old days...remember?

haha, yah, it's sooo hard to do but I'll get by.

[Ironring Racing]

Good comparison 5.

For me, I'm just hoping they bring out a 335i specific performance brake kit, 345 ir 355mm. Unless it's 3x the price of the 135 kit, it's still going to be a great deal for 6 piston (presumably) drilled and slotted brakes. Add RBF 600, better pads, and steel braided lines and you've got a nice system.

I just don't understand why BMW is so much cheaper than the aftermarket with his particular peice. They're not floating rotors, but I don't see that alone making that much of a price difference. I really can't see them releasing a low quality brake system, and if it's Brembo designed/made, it seems even less likely, so why is it so much cheaper?

[phattbam]

E92fan, did you get your rear Performance "bbk"s installed as well?