We are not looking at fade, multiple stops, etc. Best run on stock brake components v. BBK. This is just for argument's sake, I have zero reason to run one whatsoever on my car.

Also, are there ANY (other than cosmetic) advantages of cross-drilled rotors over blanks? Again, I'll be running blanks until the cows come home, so feel free to take either side without worry of changing my plans or affecting any of my choices, as they just aren't relevant to me.

No. No.

I was 99% sure that was the answer. I tried Googling to find some technical responses/explanations to my questions, but I mostly found advertisements.

Stopping distance is mostly about the ambient conditions like temperature, road contamination and condition and the biggie - tires. You stop faster with sticky tires on a clean, not too hot or cold road. Add water, sand, snow, bald or hard tires and it goes to hell.

After all that you get into how well all 4 tires get used to do the stopping.

So at a second level of importance you get into pad friction, brake balance/bias, weight transfer, CG height, etc. Not to mention driving style, ABS interventions, etc.

All else being equal, tire adhesion is the limiting factor.

Drilled rotors like Zimmerman's have no function at all.

In professional racing 2 piece drilled discs are used to save up on unsprung weight. If you run 380 or 400mm discs with a low airgap drilling them full of holes saves a little weight.

BBK's dont STOP the car faster, they slow it down faster.

Measuring 70-0 means nothing. Measure from 140>80.

BBK's dont STOP the car faster, they slow it down faster.

Measuring 70-0 means nothing. Measure from 140>80.

I don't get it.

Three primary advantages of BBK's:
1) Greater thermal mass so they don't get as hot. Cooler pads generally last longer.
2) Fixed caliper design reduces/eliminates pad taper due to caliper flex of floating caliper.
3) Easier to swap pads

I don't get it.

At speeds where the stock brakes won't lock up and engage ABS is where a BBK will shine. Proper BBK's are more effecient at converting kinetic energy into thermal energy so they will slow the car down faster (repeatedly) at speed, and that is why they are typically preferred for track/race use where you never actually bring the car to a complete stop like you do on the street.

Don't forget increased braking torque because of the leverage on a rotational mass farther from the hub.

Three primary advantages of BBK's:
1) Greater thermal mass so they don't get as hot. Cooler pads generally last longer.
2) Fixed caliper design reduces/eliminates pad taper due to caliper flex of floating caliper.
3) Easier to swap pads

Well said. I'm waiting until these 3 factors are worth dumping another $2500-4000 into this car.

Three primary advantages of BBK's:
1) Greater thermal mass so they don't get as hot. Cooler pads generally last longer.
2) Fixed caliper design reduces/eliminates pad taper due to caliper flex of floating caliper.
3) Easier to swap pads

Couple of other things which involve the human factor
a) less pedal efforts
b) easier to modulate

So in that respect one could argue that the BBK will stop better since it involves a human being driving the car not a physics equation. ;-)

And I agree with whomever said the drilled rotors = less mass. My Brembos were lighter than my StopTechs because of the cross drilled (cast holes really) rotors.

Carlos.

At speeds where the stock brakes won't lock up and engage ABS is where a BBK will shine.

:confused

Correct me if I'm wrong. When the brakes "lock-up" is primarily a function of the different coefficient of friction between "kinetic" (when rubber slipping past road surface) and "static" (when rubber not slipping past road surface). That coefficient of friction doesn't change based on what sort of brakes you have, and it doesn't really change based on the speed you're carrying?

This is all from rudimentary physics in high school, so please correct me if I'm wrong.

Couple of other things which involve the human factor
a) less pedal efforts
b) easier to modulate

So in that respect one could argue that the BBK will stop better since it involves a human being driving the car not a physics equation. ;-)

And I agree with whomever said the drilled rotors = less mass. My Brembos were lighter than my StopTechs because of the cross drilled (cast holes really) rotors.

Carlos.


Are those the Brembo's that now adorn my car???:D

Gotta say Carlos, that was a great upgrade for my car. I absolutely love the Brembo 332mm's with an otherwise stock setup! Just wish I could get rid of the pedal travel on the stock MC.

Gotta say Carlos, that was a great upgrade for my car. I absolutely love the Brembo 332mm's with an otherwise stock setup! Just wish I could get rid of the pedal travel on the stock MC.
Sleeve the calipers down and get smaller pistons. Otherwise find a larger MC to bolt up, or you'll have to go to dual MCs.
BBK's dont STOP the car faster, they slow it down faster.

Measuring 70-0 means nothing. Measure from 140>80.
BBKs don't stop any better than stock brakes, nor do they slow the car down any better at high speeds. Problem is usually operator related - sometimes you just have to push that pedal in the middle harder. If your stock brake size is overheating in a race/track event, then you can modify your driving style and increase cooling to help to a certain extent. Pad materials are getting better all the time, so sticking with your tried-and-true compounds from the 90s may not be in your best interest.

Oh and I forgot to mention that rotors LOVE to crack between drilled or cast holes alike. Especially rotors that were never meant to have holes in them in the first place. The thermal stress is just too much, and pad technology does not require gas slotting or drilled rotors like they used to.

Went from tracking with the stock braking system to a 4 wheel BBK.

If stopping distances are reduced they are fairly negligable. Pedal firmness and feel is improved but that to me that is a minor perk. I spent the $$ on the BBK because I was tired of chewing up the stock-sized rotors and pads so quickly at the track.

Quite happy now with how much pad I have left after a recent weekend at Sebring. I can also swap the rear pads to the front now since my stoptech calipers are both the same (pistons are just difference).

In the long run it'll save me $$. Might pay for itself in a year... at least thats how I try to justify the initial costs :D

In the long run it'll save me $$. Might pay for itself in a year... at least thats how I try to justify the initial costs :D

Damn, you must you using gold plated pads and rotors to pay for the BBK in a year.

Couple of other things which involve the human factor
a) less pedal efforts
b) easier to modulate

So in that respect one could argue that the BBK will stop better since it involves a human being driving the car not a physics equation. ;-)

And I agree with whomever said the drilled rotors = less mass. My Brembos were lighter than my StopTechs because of the cross drilled (cast holes really) rotors.

Carlos.

Yes true, but cross drilled crack easier than slotted rotors. Slotted also add a bit more bite.

At speeds where the stock brakes won't lock up and engage ABS is where a BBK will shine. Proper BBK's are more effecient at converting kinetic energy into thermal energy so they will slow the car down faster (repeatedly) at speed, and that is why they are typically preferred for track/race use where you never actually bring the car to a complete stop like you do on the street.Note that the OP specifically excluded multiple stops or repeated braking. He asked about a single braking event, presumably with pad temps within their operating range.

We are not looking at fade, multiple stops, etc. Best run on stock brake components v. BBK. This is just for argument's sake, I have zero reason to run one whatsoever on my car.

.

I was watching some show on SPEED a couple years ago and they had installed a BBK on a RSX. They dyno'd before and after and actually lost a couple hp due to the rotational mass being further from the hub. I believe that's what they stated but like I said, it's been a couple years.

I have data from my car and BBK... both Cobalt SpecVR and XR2 pads w/ RA-1's. What kind of numbers are you looking for?

I have comparable data from one other e36 M3, my brakes worked a lot better than his:
http://forums.bimmerforums.com/forum/showthread.php?t=617785

To quote my previous analysis:



One thing I noticed, comparing Collin and Trevor's braking zones is that Trevor would brake earlier and longer than Collin. While many make the case that the stock M3 brake system (sans pads and fluid) is more than sufficient, I believe some timed was gained by Collin's upgraded brakes (stoptech 332mm front, Cobalt SpecVR pads). When Trevor reached his max speed of 97 mph on the straight between 6-7, Collin was travelling at 99 mph and only gained 1 more mph before he started braking. It also appears that Collin's 97 M3 has slightly better acceleration as Trevor had a slightly better exit from 6.

...

Trevor: (in Tim's car)
I think the #1 disadvantage this car had vs the other M3's is tires. While on good street tires, they didn't seem to have quite the grip of the Toyo RA-1's on both Collin and So's cars. Lateral acceleration was close, but not quite. The biggest gap on the friction circle, however, was deceleration g's. While Collin and So both consistently hit 1.2 g's in negative acceleration (braking), Trevor was more around .9 g's. I'm sure tires are a part of this, but braking system as a whole could be a contributing factor. I don't think Tim (owner of the car) really believes me but oh well, lol. Here are some friction circles from both Trevor and Collin, note how they are similar in the lateral and forward direction, but the top of the graph (deceleration) the peak just isn't there for Trevor. Yes, tires are a part... but if tires were that much of a disadvantage, the car would not have the same lateral grip either. (unless street tires handle lateral grip better than deceleration grip? I might learn something here)

http://i22.photobucket.com/albums/b327/Hornswoggler/Car%20pictures/Analysis/friction-circle-trevor.jpg
http://i22.photobucket.com/albums/b327/Hornswoggler/Car%20pictures/Analysis/friction-circle-collin.jpg

Start with tires, then consider brakes. We could always capture more data next season once Tim upgrades to RA-1's or similar. Fortunately we can make these kinds of fact-based decisions with the ability to capture and compare data. If this car could late brake like So's, there is a lot of time to be gained.

even the Tire Rack is saying not to use cross-drilled or slotted rotors on the track ...

http://www.tirerack.com/brakes/tech/techpage.jsp?techid=87

bruce

even the Tire Rack is saying not to use cross-drilled or slotted rotors on the track ...

http://www.tirerack.com/brakes/tech/techpage.jsp?techid=87

bruce

Slotted are the proper race rotors.

For a single stop, tires and brake pad compound make more of a difference on these cars. Having bigger rotors is useless if the brake torque cannot be put down to the pavement. If we were talking about Mustangs, my answer would be different.

why do you say that?
I would think that if Tire Rack even marginally thought they could push their slotted rotors for race track usage, they would jump at that opportunity... but they actively discourage the practice.
As someone mentioned earlier, new pad compounds don't outgas as much.
cheers,
bruce


Slotted are the proper race rotors.

Because the provide better bite than cross drilled and are more durable.
I should rephrase, that they are better than cross drilled for race applications.