The (abridged) story of the Texas Speedwerks BDM brake kit

Discussion in 'Brakes' started by Mike, May 17, 2009.

  1. Mike

    Mike New Member

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    #1 Mike, May 17, 2009
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    As some of you know, Texas Speedwerks (TSW) is serious about creating and testing solid, track-tested products. I'd like to take a little time to tell you the story of the TSW big brake kit: where the idea came from to create it, how we developed it, and how we tested it.

    To begin, let's get in the way-back machine and return to 2004...


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    Figure 1: My MINI Cooper S back in 2004

    Ah, my 2003 MCS. In 2004, I allowed myself to enter the MINI in autocross competition, after holding off for a year or so. I just didn't want to spoil such a new car. To my delight, the MINI turned out to be a sturdy beast indeed. Notice here that the brakes are completely stock, except for some performance brake pads.



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    Figure 2: Stock brake setup

    I autocrossed the MINI a lot, and I also went to some track events. I had previously driven racecars off and on for about fifteen years at that point, so I was already up to speed on the track.


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    Figure 3: Rut Roh

    At the track, I began to find the limits of the stock brakes. I tried progressively more aggressive brake pads, but the pads would quickly wear down, and I would experience brake fade after about twenty minutes on track.


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    Figure 4: Facepalm

    Finally, something bad happened. Heading into a tight left-hand corner after a really fast, on-camber sweeper at Texas World Speedway, I applied the brakes, and the brake compound on one of the front pads sheared off of the backing plate. I managed to keep the car on the track through the left-hand turn, but the car was out of shape for the next right-hander just after. I managed to minimize the damage to the car by keeping the car from spinning into the wall, but I clouted a tire barrier with the left front.


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    Figure 5: Wierdest brake duct ever

    After the car was repaired, I looked into adding brake ducts to the car. This led me to do several simple experiments to determine how the ducts would be routed, and from where they could get some airflow. I fabricated several inlet ducts, and also tried the usual hole for the driving light. At the time, I decided that a proper duct would require the driving light hole to be cut and opened up. Otherwise, the airflow (as measured by the tube running into the cabin here) would be too low to make enough of a difference. And at the time, the idea of cutting up the MINI's face was just too much to bear!


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    Figure 6: Fresh tires, same old brakes

    So, for the next autocross season, I decided to step up to R-compound tires, in this case the Kumho V710. I thought that the slower speeds of autocross would allow me to stay with the stock brakes. If I did go back to the track, I would just take it easy. Riiiiiight.


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    Figure 7: Oh snap

    One autocross day, and the front rotors were toast. In Figure 7, you can see big stress cracks along the surface of the rotors. That was (finally!) the last straw. So I went and designed the TSW kit, right?


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    Figure 8: Wilwood 11.75" brake kit

    Wrong. Wilwood sells a brake kit that fits under 15" wheels. It includes 0.81" wide disks. I bought that and used it to good effect at the autocross in 2006. The disks were still getting hot, but at least they lasted for one season.


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    Figure 9: Back to brake ducts

    I continued to upgrade the suspension to the point that the brakes were starting to need new pads and disks every two or three events, which was getting pretty expensive. And then I got a new job and moved to the Mojave desert in California.

    As you can imagine, it's hot out here. The nearest track facility is Willow Springs, and the first track I went to was the Streets of Willow. "The Streets" appears everywhere, from Autoweek to Top Gear, mainly because it is fairly close to Los Angeles, it is devilishly difficult to master, and it is relatively cheap to rent.

    The Streets of Willow has it all. Off camber, on camber, elevation changes, sweepers, tight turns, evil pavement, good pavement, transitions, curbing, sandy corners, and HEAT. I signed up for a two day event, and at the end of the first day, I had trashed my rotors and eaten through a new set of racing pads. The brakes faded after ten minutes on the track, and when the pedal touched the floor, I said "uncle" and backed off.

    That night, in desperation, I removed the driving lights, opened up the holes, and fabbed up brake ducts.


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    Figure 10: Finished brake duct

    The brake ducts helped: the brakes faded after 16 minutes, and the pedal never quite touched the floor. But by Sunday night, the new rotors were cracked and gouged, and I had eaten through all of my brake pads.


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    Figure 11: Heat-soaked brakes

    Worse, the brake hat had turned a funny color from the heat, and so had the caliper. I think I've heard this song before, and it ended with a bang - a sort of MINI-meets-wall bang.

    But what could I do? There were no other brake kits available to address this problem that would allow me to use the 15 inch wheels I loved so much. Ah, now we get to the point of all of this.


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    Figure 12: Wider is better

    With the 15 inch wheels, I could not go to a larger diameter rotor. But to be honest, a slightly larger rotor diameter wouldn't net enough of a performance gain. What I needed was a wider rotor.

    When a car decelerates into a turn, the kinetic energy of the car is converted into heat energy by the brakes. The brake rotors then transfer this heat to the air around the rotors. There are two things going on here. First, when the brakes are applied, the rate at which heat is generated in the rotors is much higher than the rate at which the heat is carried away by the air. This is true for any vehicle brake system at maximum braking force, from a bicycle up to a Formula 1 car. This means that the brake rotors will heat up. For a given energy input, the increase in the average temperature of the rotor depends directly on the mass of the rotor. Therefore, a more massive rotor will store more heat per unit temperature (that is, it has a higher heat capacity) than a ligher weight rotor.

    Conversely, a lightweight rotor will run hotter. A higher difference in temperature between the rotor and the air will increases the heat transfer rate, but the brake system has a maximum tolerable time-temperature curve (which I exceeded when I stripped off a pad face and hit the wall on stock brakes). That is, the life of a brake system is determined in large part by the area under the time-temperature curve. In other words, really hot brakes die really quickly.

    The other half of the picture is the rate at which the rotor transfers heat to the air. As the car leaves the corner, the brakes are relaxed, and the rotors continue to transfer heat to the air. The amount of air flowing past (and through) the rotor makes a big difference, of course, but it still takes time for the rotors to cool. This works well as long as there is enough time for the brakes to cool before the next turn. If not, the brakes will get progressively hotter with each lap, until the rotor temperature reaches a point where the heat transfer to the air equals the heat input per lap - or the brakes fade away and the driver backs off.

    I said before that I needed a wider rotor. While a larger diameter rotor (say, 12.2" instead of 11.75") does give slightly more area for heat transfer, and slightly more mass for heat storage, the difference is minimal. However, moving from a .81" wide rotor to a 1.25" rotor gives a HUGE difference in heat transfer area within the cooling passages of the rotor, AND it greatly increases the heat capacity of the rotor, all without greatly increasing the moment of inertia of the rotor.

    In other words, the brakes stay much cooler, the components have a much longer life, and the car accelerates the same as it did before (minus an immeasurably small amount).

    But, will it all fit together?


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    Figure 13: Calipers out, fingers crossed

    At this point I needed to mock up the new brake kit to see if it would clear both the wheel and the suspension. The "hub" is little more than some metal scraps I pulled out of my toolbox, and some spacers I whipped up for the occation.


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    Figure 14: Air brackets

    The caliper is then put in place, and air pressure is applied to clamp it (and the pads) to the disk. A little cajoling of the caliper is needed, and a lot of judgement is also needed so that the resulting "air bracket" can be converted into a real mounting bracket.


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    Figure 15: Eureka!

    After a lot of furrowed brows, I managed to fit everything together. All I needed was actual hardware.


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    Figure 16: Prototyping

    I made a pair of these brackets on the milling machine, and they worked perfectly the first time. I cleaned up the design a bit for the production run, but the geometry worked out the first time (that's always nice).


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    Figure 17: Done (whew!)

    All of this effort finally resulted in a true prototype, which I promptly took back to the Streets of Willow, and also to Buttonwillow a few times. After many track days, I'm still on the original rotors AND pads! The difference in pad life is astonishing.

    So, here ends the story of the TSW BDM brake kit. It was a fun trip down memory lane for me, as I had forgotten just how long it can take to follow through on a project when pesky things like day jobs and cross-country household moves get in the way!












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  2. mini_racer

    mini_racer Well-Known Member

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    Thanks for the background on the TSW BBK Mike. So, where are the brake ducts? With this kit do you recommend not to have ducts? just not needed?

    Isn't more cooling always better?
     
  3. Mike

    Mike New Member

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    The duct is hidden in the last picture just by chance. Ducts can only help the brake cooling. I don't think these brakes need ducts, but why take them off, you know?

    Some may point out that the ducts could funnel road rocks to your brakes, and this is true. If that is a worry, then some coarse expanded metal will screen out the big stuff.
     
  4. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    Very cool post, Doc. :Thumbsup:
     
  5. Longboard

    Longboard New Member

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    Really nice write up Mike. I now what it's like to have a big project or two.

    When i was looking for new brakes your kit was one of three on my list. I finally ended up with a StopTeck BBK mostly because I got them used real cheap. If I tracked or auto X my car at all you would have been the kit for me.

    Congrats on making one hell of kit.

    Longboard
     
  6. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    If it came in red I'd have it already... :p

    Darn Texas guys and their gunmetal fetish.
     
  7. Mike

    Mike New Member

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    Mmmmmm... :arf: gunmetal.
     
  8. cct1

    cct1 Well-Known Member
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    Mine is going on as soon as it gets here (as well as KW V2's and R-comps; figure a brake upgrade is in order too); can't wait to give it a go--I have the Wilwood 11.75/0.81, and I'm just plain tired of going through rotors (3 sets last summer) and pads.

    I don't have air ducts on yet--gonna try them without, might put in the Way ducts as a project this winter depending on how things go. I don't think the Way ducts are quite as good as what Mike has on his car--Mike is shooting air directly into the hub, but with the BDM I'm thinking it would be enough if I need a little more. But maybe the BDM will be just fine without.

    And props to Mike for all the help w/r to suggestions for setting my car up!
     
  9. BlimeyCabrio

    BlimeyCabrio Oscar Goldman of MINIs
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    You know, I had never recall hearing anyone report on rotor and pad life with this setup before this thread. It must run radically cooler than the OEM setup to have that kind of rotor and pad life.... which is a good thing. Hmmmmmmm..... given how much I roast my brakes and wheels on the Dragon and at the track, I'm seriously thinking this may be my next big mod...

    And since they run so cool, my caliper paint will last a long time when I paint them red. :D
     
  10. Bimmer Lite

    Bimmer Lite New Member

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    #10 Bimmer Lite, May 19, 2009
    Last edited: May 19, 2009
    Loved reading about this; thanks for posting!

    I've been through the wilwood rotor game and installed the Way ducts this off season. First track day was Friday at Lime Rock and the rotors and pads are still fine. I made a concerted effort to have a real cool-down lap, and I drove around the paddock for 5 minutes before parking. Once I parked, I moved the car a couple of times to get the pad on a different part of the rotor.

    All that said, I don't kill brakes like Dr. Mike does according to the pics above - I'm not fast enough!

    So which 15 inch rims do these brakes fit under?

    - Marc
     
  11. cct1

    cct1 Well-Known Member
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    Team Dynamics. I already had one set, bought another strictly for the track.

    They won't fit the Kosei's I had before; template doesn't quite clear. Which is a shame because I really, really liked the Kosei's, they are so light. They are shaped oddly on the inside though--kind of like a funnel, which I really never noticed before I put the template to them.
     
  12. Nathan

    Nathan Founder

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    Please post pictures and the specs in your Wheel Rack to share with all....

    Thanks
     
  13. cct1

    cct1 Well-Known Member
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    Will do, once everything is put together...
     
  14. Alan

    Alan Active Member

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    I cracked a rotor after about 10 DE weekends and 3 sets of Raybestos pads. Rotor showed no wear - none. It could probably be made of a slightly softer metal to better handle heat cycling. No ducts.

    We did a heat paint test at Eagles Canyon - the local brake killer track - and ducts made no difference. Of course heat paint is accurate to within several hundred degrees F. Both BDM rotors got as hot as the rear rotors. I think it was 1200 or 1300 F, but don't hold me to that. It was right in the middle of the range for the Raybestos pads.

    Alan
     
  15. Alan

    Alan Active Member

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    I run Team Dynamics Pro Race 1.0s 15X7 -40 offset. There is enough clearance for several sheets of paper.

    I know that 1.2s will not fit over the BDM on an R56.

    Alan
     
  16. Nathan

    Nathan Founder

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    It was closer to 1450F. The color we saw corresponds to 800C on the chart.

    Alan, keep in mind that you are probably not as hard on the brakes as I am. You carry more corner speed and I get down the straights faster meaning to tiptoe around the corner like I do more speed needs to be scrubbed off. So maybe the ducts did help.

    I still have this Genesis Technology kit and will probably never ever use it all. I'd be willing to share for the cost of shipping. We can then all share our brake temps. Send me a note if you want to use it.
     
  17. cct1

    cct1 Well-Known Member
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    #17 cct1, May 19, 2009
    Last edited: May 19, 2009

    It's supposed to on a R53 with +35 offset...If it doesn't, I'm hosed.

    **Update: Just because you got me all hot and bothered, I put a template up on the TD 1.2's and other than having to be careful with the wheel weights it looks like it should clear just fine.
     
  18. Vernon29RW

    Vernon29RW New Member

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    do the outlaw calipers have dust booted pistons? I love the idea of the big fat rotor but doesn't non booted pistons not work well with the winters up here in the northeast?
     
  19. paulsminis

    paulsminis New Member

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    I have run non booted pistons in Ohio for years, both on my classic Minis and on R53s and now R56s. All it takes is a bit of maintenance. I take the calipers off in late Fall and again in early Spring and using an old tooth brush, I scrub them down with brake cleaner, paying special attention to the protruding pistons. I have used Wilwood booted calipers and proceeded to melt the boots on the track, so I will only use non-booted calipers on cars that do track days.

    Dr. Mike, your explanation of pad disintegration at the track was very interesting to me. I had a similar fate with the same brake kit at Gingerman. Unfortunately, the car did not survive, but both my instructor and I walked away basically unhurt. Since I never got possession of the wreck, I was not able to do a post-mortem, but I did examine the brakes and both outer pads were missing their lining.....so now I am fairly sure I know exactly what happened.

    I now use a similar kit with Outlaw calipers and 1.22 inch disks and the stopping power is awesome.

    Paul
     
  20. cct1

    cct1 Well-Known Member
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    Alan, you were right. The 1.2's don't clear, as I just found out. I had the 1.0's, not the 1.2's on the car, ordered 1.2's for the track, and they don't clear.

    Guess I'll run my 1.0's with all-seasons monday and slip and slide (Looks like it's going to thunderstorm so maybe it won't be all bad), and see if I can get some Pro Race 1.0's. Although now that I remember, the ones that I bought were like the last set I could track down...

    Anyone know where I might be able to find a set of 15x7 TD's Pro Race 1.0's? Looks like its a special order from england, have to see if there are any old sets around at some of the vendors I guess.

    If not, looks like I'll be going to a sixteen inch rim, as there don't appear to be any other 15's that fit....Damn...May have a very nice brand new set of TD 1.2's with Nitto 01's never used going for sale soon. Double damn....
     

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