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      09-20-2012, 06:00 PM   #1
aleckzandr
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Question To BBK, or not to BBK, that is the question

I've melted both the left and right stock front brake piston dust boots. I don't notice anything yet... but it's getting disconcerting. Other than pad dust, it's pretty clean in the front calipers as we don't see much rain in Colorado. I am running Pagid Yellows pads at the track. Do BBKs have the same issue, or is it time to simply get a dedicated car? ("Not to BBK" for this car would give me a nice chunk of change to start with a 944, for example.) With the extra disc area of BBKs, I assume the temps stay lower and thus less chance of stuff melting. I'd love to hear your opinion. Cheers.
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      09-20-2012, 08:26 PM   #2
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The total heat generated will be the same no matter what size brakes you use, but as you notice, the larger and better designed rotors will radiate the heat away more effectively.

The properly designed calipers will also reject far more heat keeping the pistons and therefore piston seals cooler. The seals will also be more robust, preventing such a problem.

So yes, this won't be a problem with a proper BBK.
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      09-20-2012, 11:26 PM   #3
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However, the answer to your question isn't that straightforward. If you are at the point where considering a dedicated car is an option, that may be the better route in the long run. Lighter car will be less $$ on brakes, tires, etc in the long run.
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      09-21-2012, 09:38 PM   #4
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Have you done any upgrades to the duct work to increase direction of airflow on the rotors? Higher temp fluid?
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      09-27-2012, 05:44 PM   #5
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Quote:
Originally Posted by aleckzandr View Post
I've melted both the left and right stock front brake piston dust boots. I don't notice anything yet... but it's getting disconcerting. Other than pad dust, it's pretty clean in the front calipers as we don't see much rain in Colorado. I am running Pagid Yellows pads at the track. Do BBKs have the same issue, or is it time to simply get a dedicated car? ("Not to BBK" for this car would give me a nice chunk of change to start with a 944, for example.) With the extra disc area of BBKs, I assume the temps stay lower and thus less chance of stuff melting. I'd love to hear your opinion. Cheers.
We have track extensively with our 335i back in the days and with the BBK upgrade you will not see the same issues as the OE brakes. BBK will run much cooler, not to mention repeated stops without fade with proper pads.
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      10-08-2012, 02:21 PM   #6
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Quote:
Originally Posted by aleckzandr View Post
I've melted both the left and right stock front brake piston dust boots. I don't notice anything yet... but it's getting disconcerting. Other than pad dust, it's pretty clean in the front calipers as we don't see much rain in Colorado. I am running Pagid Yellows pads at the track. Do BBKs have the same issue, or is it time to simply get a dedicated car? ("Not to BBK" for this car would give me a nice chunk of change to start with a 944, for example.) With the extra disc area of BBKs, I assume the temps stay lower and thus less chance of stuff melting. I'd love to hear your opinion. Cheers.
Are you still running stock rotors? The BMW stock brakes are pretty large and the rotors are 345mm in front and most BBK are only 355mm if I recall correctly. I believe Brembo makes a 380mm rotor but not sure if it fist the E9x 335i or only the E9x M3. I would say that if you have beter 2 piece rotors that can dissipate heat better than the stock ones even at the stock 345mm size then you should be ok. This would be minimal investment (~$1500-$1800) compared to a full 4 corner BBK which would run you $6500-7500 depending on which one you get.

I am debating the same thing and decided to get better rotors and pads at the stock sizes. I bought the RB Performance rotors that replace the stock ones and will be running PFC 08 pads this weekend at the track. If this is not sufficient then I would buy the BBK.

By the way I have found that you pay a hefty price to buy the entire kit and can probably piece the parts you need for less than a full kit. You probably already have the SS lines (I'm asuming). I have found Stoptech calipers for the BBK at ~$1000 each and the 2 piece rotors at ~$450 each. That makes the price about $5800 for the 4 corners vs $6800 from **********s.com. Add pads since usually the pads that come with these kits are not ones I would consider to use for the track. Just something to think about.

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      10-08-2012, 03:58 PM   #7
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BBK's can be had for much less when you can find a good "street price".
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      10-08-2012, 05:46 PM   #8
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Quote:
Originally Posted by HP Autowerks View Post
BBK's can be had for much less when you can find a good "street price".
Hey Harold I just got the PFC 08 in today. I cant wait to try them out.

Harold maybe you know the answer to this,...I understand that some people only do the front BBK and leave the stock calipers. Would this upset the natural brake bias that BMW has engineered? I would think so. If that is the case is it possible to use the FRONT calipers in the rear with the 345mm BBK rotor size? Since the front is 345mm and the BBK rears are 345mm why couldnt I upgrade just the front calipers until I am ready to do the rears? This way I use the front stock calipers AND rotors as the rear set until I am ready to shell out another $2000 or so on the rear set. Is this doable? Thanks.
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      10-09-2012, 09:44 AM   #9
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Alex, have you ever used an infrared temp. scanner on your rotors after you have tracked them? I was hitting upwards of 500F in the pits after a session a couple weekends ago, but I have no clue what is considered hot.

2-piece rotors may be at least worth a shot to help shed some of the heat and transfer less of it back to the caliper.
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      10-09-2012, 11:51 AM   #10
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Originally Posted by raceyBMW View Post
Alex, have you ever used an infrared temp. scanner on your rotors after you have tracked them? I was hitting upwards of 500F in the pits after a session a couple weekends ago, but I have no clue what is considered hot.

2-piece rotors may be at least worth a shot to help shed some of the heat and transfer less of it back to the caliper.
Good chart on working (capacity) and optimal temp ranges for different pads, but you can get a feel for what pads can handle and how close you are to fading them.
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      10-09-2012, 12:16 PM   #11
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Quote:
Originally Posted by N54_Fan View Post
Hey Harold I just got the PFC 08 in today. I cant wait to try them out.

Harold maybe you know the answer to this,...I understand that some people only do the front BBK and leave the stock calipers. Would this upset the natural brake bias that BMW has engineered? I would think so. If that is the case is it possible to use the FRONT calipers in the rear with the 345mm BBK rotor size? Since the front is 345mm and the BBK rears are 345mm why couldnt I upgrade just the front calipers until I am ready to do the rears? This way I use the front stock calipers AND rotors as the rear set until I am ready to shell out another $2000 or so on the rear set. Is this doable? Thanks.
Do you mean upgrading the front to a proper BBK and leave the rear as is? This has been done many times and will not upset the balance of the car at all. Stoptech BBK engineers their BBK so the user can upgrade the fronts only.

Please PM me your current set-up so I can help you further.
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      10-09-2012, 01:10 PM   #12
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Quote:
Originally Posted by N54_Fan View Post
Hey Harold I just got the PFC 08 in today. I cant wait to try them out.

Harold maybe you know the answer to this,...I understand that some people only do the front BBK and leave the stock calipers. Would this upset the natural brake bias that BMW has engineered? I would think so. If that is the case is it possible to use the FRONT calipers in the rear with the 345mm BBK rotor size? Since the front is 345mm and the BBK rears are 345mm why couldnt I upgrade just the front calipers until I am ready to do the rears? This way I use the front stock calipers AND rotors as the rear set until I am ready to shell out another $2000 or so on the rear set. Is this doable? Thanks.
If you mean take the existing front OEM caliper and use it in the rear, the answer is a simple NO. First you would have to custom fabricate a bracket to fit the much larger caliper to the rear. Second, that rear caliper now will have significantly increased in size of piston and therefore completely f**k up your front/rear balance AND totally screw up your master cylinder to slave size ratio.

It won't work. The only reason(s) why most front only kit works, is that the overall surface area of the multiple pistons are no larger than the factory single piston size, so the brake proportioning remains the same while brake torque, heat capacity and dissipation has increased thus improving overall efficiency.
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      10-09-2012, 02:07 PM   #13
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Quote:
Originally Posted by The HACK View Post
If you mean take the existing front OEM caliper and use it in the rear, the answer is a simple NO. First you would have to custom fabricate a bracket to fit the much larger caliper to the rear. Second, that rear caliper now will have significantly increased in size of piston and therefore completely f**k up your front/rear balance AND totally screw up your master cylinder to slave size ratio.

It won't work. The only reason(s) why most front only kit works, is that the overall surface area of the multiple pistons are no larger than the factory single piston size, so the brake proportioning remains the same while brake torque, heat capacity and dissipation has increased thus improving overall efficiency.
Do you know what the single piston size is in the front of the 335i?

The stoptech 335i kit is 4x30mm, 2x36mm... unless the stock piston is ~70mm, then the stoptech caliper would have more piston area. If the front piston is 60mm, then stoptech has considerably more...
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      10-09-2012, 03:58 PM   #14
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Quote:
Originally Posted by The HACK View Post
If you mean take the existing front OEM caliper and use it in the rear, the answer is a simple NO. First you would have to custom fabricate a bracket to fit the much larger caliper to the rear. Second, that rear caliper now will have significantly increased in size of piston and therefore completely f**k up your front/rear balance AND totally screw up your master cylinder to slave size ratio.

It won't work. The only reason(s) why most front only kit works, is that the overall surface area of the multiple pistons are no larger than the factory single piston size, so the brake proportioning remains the same while brake torque, heat capacity and dissipation has increased thus improving overall efficiency.
Thanks. That is what I suspected. But I think you misunderstood one thing...although I think the answer will likely be the same. What I was getting at is to put on a BBK to the fronts (355mm or similar) with calipers and everything then move the stock front caliper to the rear with the 345 mm stock size front rotor. Most BBK sold for the rear are 345 mm rotors (same as stock fronts size) and designed to work with 355mm front rotors and stock master cylinder. This was why I was asking the question. I suspect the answer is the same because of the braket you mention but not sure why this situation would drastically upset the brake bias since the front is still larger than the rear and bias would remain "relatively" unchanged and in fact should be the same as BBK in front as well as rear.

Thanks
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      06-24-2014, 01:14 AM   #15
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Quote:
Originally Posted by DallasBoosted View Post
Do you know what the single piston size is in the front of the 335i?

The stoptech 335i kit is 4x30mm, 2x36mm... unless the stock piston is ~70mm, then the stoptech caliper would have more piston area. If the front piston is 60mm, then stoptech has considerably more...
Unless the StopTECH kit has 12 pistons, you are doing your math wrong.

The way to calculate the overall piston area on fixed caliper is to take the overall area on ONE SIDE only. I.E. You count only 3 pistons on the same side in a 6 piston set.

Don't ask me why. I don't know why. That's just how it is.
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