+1 for the gearing. My R56 pulls like crazy with the 15" wheels. I can put a 225/45/15 tire that weights less than the 215/40/17 that I have. Lighter wheels and tires along with the difference in gearing go a long way towards changing how the car feels.
I was there also in an R56 Justa, modded with R56S rotors and Hawk HP+ pads front and back. Absolutely no brake issues for me. So what's the difference? R53 vs R56 S, the R53 exhaust manifold is on the back of the engine, the intercooler is on the top of the engine. For the R56, the exhaust manifold and turbocharger is on the front of the engine, and the intercooler is on the front and generally below the radiator and A/C heat exchanger. Point being that the R56S has a lot of heat being generated in front of the brake calipers, where the R53 had similar devices behind the front axle. Since btwdrivers car is lowered more than my car, and has significant heat sources ahead of the front axle that my car and R53s don't than the cure for this is probably ducting and shielding to keep the heat out of the wheel wells.
At least it was a test, a true data point, not just conjecture. :cornut: And the reduced gearing is a big plus for '03 MINI. At almost all tracks other guys are using a higher gear than I am. At ECR I use 3rd and 4th, even with the 15s. Most other MINIs are using 5th for a bit. Also, smaller diameter rotors/wheels/tires have less rotational inertia. As far as ducts in general I am skeptical. I don't know enough to do the physics but big rotors and calipers/pads and the wheels are a whole lot denser and heavier than air. Brakes dissipate an enormous amount of energy. It would take a lot of air to have a large affect. I'd love to see the math. I keep thinking of the guy that claims throwing ice in the pool helps - yea, if you throw a couple tons in. Alan
I tend to agree with you, re: the amount of air that would be necessary to significantly affect the cooling of your brakes. I am trying to find some hard data on that right now. I also know that virtually every race team on the planet uses brake ducts and they can't all be wrong. Just out of curiosity, do you have any ideas as to why I was having brake problems and you were not? I will grant you, you have a lot more track experience than I do.... it just seems like it has to be more than just that.
Do you take any stock in what SK8BRD said about the airflow? It seems to make some sense to me. Also, follow Alan sometime, you can tell from behind he's smooth. Goes deeper into corners before using the brakes and is back off them quick. The only way I can keep up is cause I have a little more HP and can pull back up down the straights. ECR I can hang with him, MSR, he walks away.
I am the first person to give Alan credit for is driving ability. He is super smooth and very fast. My lap times were right between Scott's and Alan's, so I can't think I was doing anything super wrong. What Sk8BRD is saying seems to make sense. I also think that the front air dam on my car is lower than Alan's, it almost looks like there are two pieces of the air dam the would channel air away from the front brakes. Take a look at the shot that I "borrowed" from Hart Photography: (The car is all the way loaded up on the right side, normally there is about 1 1/2 inches of ground clearance under the air dam).
I hear ya on the experiment, and yes you guys did collect some data. I realize that this is difficult, just pointing out that the experiment performed was not exactly controlled whereby there was only one variable, being the one under study. I know it is very difficult to eliminate all of the other variables. While it is fine to be skeptical about brake ducts, this experiment was not conclusive, and so ducts should not be dismissed based on this data. As far as gearing goes, I understand the intent, just not sure that my car needs a gearing change. Maybe I would feel different if I ran some 15s as a trial. Maybe if I had more experience, I could appreciate the 15s more, I dunno. Maybe I don't know where to shop, but Discount only had one tire, and Tirerack only had 4 tires in the 225/45-15 size, and they were not exacly cheap.
I'd have someone check the master cylinder. I'd also take a look around for any shielding issues. I also agree Mike may be on to something. You could be boiling fluid in a poorly placed line. There probably should NOT be any heat shielding above the turbo - I bet its there solely to save the paint on the bonnet. And yes, I absolutely agree that ducts improve the situation. I'm just saying they are in the 1% category. Kinda like heim joints vs. polyurethane bushings. Alan
Hey Track Junkies out there, is this the consensus on the effectiveness of brake ducts? The 1% range is significantly less than would be intuitive to me, but I am no expert. Alan, given your skills on the track your opinion is much valued, but are you purposefully exaggerating here, or just hate ducts, or just shootin' from the hip, or what? And you can't count that previously mentioned uncontrolled experiment.:nonod:
I can say that on my Cooper track mule (which is far from stock @ ~142 whp and is lighter than most @ 2650 w/me in it) the OEM brake system with 'track' pads and ducts still overheated in Texas Summer heat. Any other time of the year, it was fine. Swapping in our BDM took care of the situation... permanently. Being that my car is more of a momentum car, though, I definitely don't use the brakes as much as the higher hp MINIs and tend to carry more speed into and through the corners. IMHO, all MINIs are momentum cars, though, and I think a lot of people are really, really hard on their brakes - harder than they need to be, in fact, as they overdrive their cars to the max. I think it's just a matter of learning hard, smooth, progressive braking, using the tires to scrub speed in corners if necessary but maintaining throttle, and then tipping in the throttle judiciously when exiting - in other words, smooth inputs, aka Technique #1. This is the opposite of Technique #2, which is to hold the 'Go' pedal down until the very last second, STAND on the brakes at threshold praying you bleed off enough speed, then making the corner while coasting, and then standing on the throttle again - in other words, BIG, jerky inputs. Technique #1 will be faster than #2 almost all the time - unless there is a big hp differential. Then again, when Technique #2 cooks your brakes, the guy using Technique #1 will pass you... FWIW, every race car I have ever seen have some kind of brake ducting... Cooler IS better, in general. I think Alan's 1% category are for those eeking out every last little bit of potential in their cars and can actually use it - e.g. 1% of track junkies could actually USE brake ducts. Unless, of course, you're killing brakes at the track and putting yourself in potentially dangerous situations - then, brake ducts are a good measure of insurance.
Thanks for the expert's view Scott. So, for the case of BTWDriver, he obviously needs brake ducts as he is running out of options. In general though, brake ducts would not be the first thing to do, in fact closer to the last thing to try in an attempt to get every last bit of cooling. Is that a fair assessment of what you stated above?
Scott, while I think I can definitely improve my braking. I have a really hard time chocking the issues with my brake fluid boiling to "you just need to drive better". I also don't think there are that many people tracking R56's with 15" wheels and the BDM. There are enough differences between the R53 and R56 that they can't be used as direct comparisons.
Does brake bias factor into any of these issues? A heavier car will make the brakes do more work, and if the rears aren't keeping up with the BBK in the front, the front brakes will do much more work. Are you guys all running the same race pad in the rear?
That is an interesting question..... I am running Carbotech XP8's in the rear on stock rotors. The front pads are the Raybestos ST-43's, which is almost definitely a more aggressive pad. I wonder if I could be getting brake fade in the rear and not noticing it, that would put additional load on the front pads. The rear end does not feel especially squirmy when braking, but not sure if that really means anything or not.
I wasn't specifically referring to you or your driving style - there are a lot of people that tend to over-drive with all the various inputs you have from behind the wheel. It was a general comment, as I have never been on the track with you (yet - ). I do think your issue has to do with lack of airflow and running 15's - not to mention 100+ degree ambient temps.
Could be - we recommend running Porterfield R4's in the rear with ST-43's in the front for the track. This setup has always worked for us, although there are others out there that have commented they can't modulate the ST-43's (shrug, never had that issue). The reason we like the R4's in the rear is that they work great with the ST-43's in the front for the track or the R4-S pads for the street. There are some others running other brands of pads in the BDM kit and in the rear, based on what they like and trial and error (e.g. ryephile, IIRC). All we know if what works for us and YMMV... I'm not familiar with the Carbotech line, so that could also be part of btw's issue... You do want similar pad profiles in the front and rear at the track. If you have a significant difference in the profile (e.g. coefficient of friction vs. temp), you could overwork one end of the car (almost always the front). If you had too much rear bias, you'd definitely notice that under threshold braking...
Had another track day with the BDM this past weekend at autobahn. Minimal fade toward the end of the day, it holds up unbelievably well. Rotors still look fantastic, pads are down a bit but looks like I can probably get one more full track day out of them. I may end up ducting, I run fifteens, but it's probably overkill. I have xp10's on the rear, and I'll probably try the Porterfield's next. I may switch back to my xp8's--I think the 10's may be a bit much, the rears really aren't heating up enough for them... I probably drive a bit too much like driver #1 in Scott's comparison, but trying to become more like driver #2. But the BDM gives some added insurance as I'm learning--it's the one thing on the car I absolutely don't worry about. Before, the brakes were a major headache, and source of concern....
I did a twisty mountain run a couple weeks ago, and on the way down, I boiled the fluids on my new MDM kit. Might have been 'cause I was still getting the kinks (and remaining air) out, but I think it's cause I still have Carbotech Bobcat pads on the rear and R4-S pads on the front. I don't think the rears did enough work - no air came out of the rears when I bled the system.
I just haven't had any brake issues after installing the BDM. For me, its the nut behind the wheel that needs the most attention. I'm working on staying relaxed and back in the seat. Brian definitely has some major issue. Like I said before I think Mike may be on to something with the R56 engine configuration. The exhaust is in front of the front brakes and turbos trap a lot of heat. I'd work harder at getting the heat out the top - remove heat shield from top of turbo and have a reverse hood scoop that pulls air out. I'd even try removing the hood for a DE day if Rick would let me. Just to validate the concept. I'd be adding ducts too. What he went through at ECR was no fun. Alan