| Author | Message | ||
     Gemini |
i personaly wouldn't put as much worry as to the color of the rotor after riding as i would the function of the brake when riding. if you have a brake fade problem, don't come up with an idea and rule everything else out. if you rule every thing else out as a possible cause, you then become fearful of being wrong. great inventors welcome being wrong. thomas edison didn't fail, he found a thousand things that didn't work, or something like that. the bikes we buy are great bikes from the show room are great bikes. but remember, they are not full on race bikes. our bikes are more like a srt-8 challanger in comparison to a nascar ride. sure, the srt-8 is bad @$$, has killer brakes and more power than what is needed on the street, but still can't compete in the real race circuit. with that comparison being made, at short tracks such as martinville, nascar often puts cameras in the wheel wells to show off the glowing red rotors. in my initial thoughts, glowing red shows a major heat problem. but it's not. the teams work with what they have and make changes to work in the enviorment and complications of racing. they uses pads, rotors, calipers, fluid, master cyl and other bits with an understanding that the rotor is gonna get hot. i think the best approach to brake fade is look at the picture as a whole and how each peace adds a little to the condition. fluid boiling point, rotor material, pad matereial, pad thickness, pad backing plate thickness and material, caliper size, material of caliper and my goodness the list goes on forever. if the brake fade is caused by boiling fluid and not by off gasing of the pads, i would look at changing to a different brake fluid, a caliper that is more prone to shedding heat etc. but wait, how about a different type of pad that gives a good "bite" when at race pace but produces less off gasing. less off gasing then leads to less brake pressure needed, less heat. lower temp in fluid. this agument can go back and forth forever. both right and both wrong. aftermarket rotors out there that are wave cut, drilled and who knows what else. when taking it to that race level, it's a matter of finding the right combination for you. is part of the problem in the system the rider? if the rider can't change style, weight, habbits, technique, modify other parts. i don't mind being disagreeded with or wrong. i am not claiming to know what you need to change because i don't know every little detail about the situation nor to i understand enough about all of the physics involved or the dynamics of the substances used. we know of a guy that started out trying to make a bike and found out some of his thoughts were wrong. he regrouped and tried again. learned from mistakes and tried other new things, learning stuff along the way. because of that, most of us own atleast one of the bikes that shares his name sake. in fact, some of us own a few of them.  as for finger pointing, egos, "your wrong", appologies and such, seems kinda juveniel to me. i'm right you're wrong, you're right i'm wrong. does it really mean that much to hear that? | ||
| Lawineer |
Lawineer, >>> 1. Where do you think heat from the brake fluid goes? We were talking about the brake rotor, not the fluid. Not following your point. >>> 2. The cooling from brake fluid (to the AIR) is effectively constant between the two designs, except that the dual rotor design might again have a slight advantage for having two sets of lines, more fluid, etc. See above. Then I’m not sure what your original point was- I must be misunderstanding your previous gripe about convection. 3. Do you know what convective cooling is? Yes. Scored a 92 on my FE test. My professor, J. P. Holman, wrote the leading heat transfer text of the day, and Heat Transfer was one of my all time favorite undergraduate engineering courses of study. For senior design I wrote a lengthy fortran program for Texas Instruments that simulated convection heat transfer for computer chips. >>> Because that's pretty much how the brake is cooling itself to the air. "Cooling itself"? You mean "being cooled"? There is no "pretty much" to it. If there is heat being transferred from brake disk to air, which there obviously is, then it is only by convection. No, there is radiation, which YOU called me out on a page earlier. Apparently the negligible heat transfer through radiation is enough to call me out, so I’m just being precise with my wording. Not precise enough though, because I got called out for saying “cooling itself”  SOME heat is being transferred to the air molecules/ molecules in the air via radiant heat transfer. >>>Convection, conduction and radiation. Those are the 3 basic heat transfer methods. Those are the only mechanisms of heat transfer. Again, I’m just covering my bases before someone you call me out and says “ZOMG! IT COULD BE TRANSFERRED TO MECHANICAL WORK!!!!” If you’re going to cut my posts apart like a lawyer, I’m going to start writing like a lawyer. Convection and conduction are pretty much the same thing, except conduction is more solid-to-solid heat transfer. Same formula applies (in essence, the coefficients have different names). And the coefficients for convection are infinitely more complex, less accurate, and are subject to a myriad of constraints and pre-qualifications in order to be valid. Convection heat transfer is a science in its own right, vastly more complex. The mechanics of fluids including boundary layer thickness profiles, turbulence, free versus forced convection, edge effects, separation of flow are just a few of the issues involved. Conduction heat transfer is simple. Q=kAT/x where Q is the heat flow rate k is the conductivity of the solid material through which heat is being conducted. A is the cross-sectional area of the solid material through with heat is being conducted T is the difference in temperature from one fast to the other of the solid material through which heat is being conducted. x is the length of the material through which heat is being conducted. Convection, not so much... Q=hAT That little "h" is a real pandora's box for anything but the most simplistic convective heat transfer situation. WTF does this have to do with anything? I said in my first post I simplified some not so simplified heat transfer. Convection is effectively conduction through a fluid. Yeah, the name of the coefficient changes. If you read my post, you’ll see I wrote “properties.” Yes, the field of heat transfer is far more complicated than what I summarized it in. Why is anything I said wrong? You fan boys keep dodging the issue- you have less thermal mass and less surface area. You’re going to have more heat issues, even if you dig deeper into the basic formulas. "The convective cooling airflow environment inside an automotive wheel is vastly different from that of a motorcycle front brake." >>> Yes, it is. What's your point? That exactly as Court stated in response to your claim of automotive brake expertise, "Some of the best practice and principles in auto brakes don't translate well to 2 wheeled vehicles." Why? Because the convective cooling environment is vastly different. You have less airflow? Wonderful. Doesn’t change a thing. Still the same formula. The coefficient changes. >>> You posted up some completely irrelevant picture of kinematics. Actually those are free body diagrams which illustrate the balance of forces in equilibrium; statics, not kinematics. If you want to call a pitched over bike, moving forward with rotating wheels “static,” I suppose. I’m a lawyer at work. I have no desire to be one with you. >>> In the end, the heat transfer in a car rotor and motorcycle rotor are the same exact physics Yes, physics is the same all over the planet Earth, no matter the subject, no matter the situation. Can you please find a new tune? Seriously, are you trolling me? Because you guys are the ones saying the physics isn’t the same. >>> using the same exact formula. Very doubtful that anyone is using a simplistic formula to characterize the highly transient heat transfer and widly varying fluid mechanics applicable to a motorcycle front brake. the values are dynamic, but it’s still the same shit. At the end of the day, less surface area results in less heat transfer. Your attempts to baffle with bullshit are disappointing. >>> Some of the numbers you plug in will be different, but that's neither here nor there... Unless you are trying to engineer an efficient motorcycle brake system, instead of an automobile brake system. Who is engineering a braking system? Last I checked, we were dancing around the obvious, trying to show that more surface area results in more heat transfer (or, if you’re on the fan-boy side, dodging the issue). >>> and it certainly has NOTHING to do with the image you posted. The image I posted pertains to the post in which it was presented, which had little to do with the details of any heat transfer analysis. Not sure why you are focusing on it. As stated above, the images are free body diagrams illustrating the balance of forces acting on the lower fork leg and brake caliper/bracket assembly. The image of the guy on the motorcycle, not your CAD… er MS Paint Imagineering. (Message edited by Lawineer on January 18, 2011) | ||
| Lawineer |
>>> Relatively minor design changes? You mean a totally different hardware mounting kit design and a completely different rotor? Yes, that'd be minor. Can't tell the difference from 20 feet away, same caliper, same rotor just thicker with added fin details. Yeah, from an engineering perspective, I'd call that minor. ----------------------------------- Very technical analysis there. If you can't tell the difference from 20 feet, it's not major. Solid. That's a pretty major change, dude. 5-6mm is 20% and a fin is a pretty significant addition. It's not like they changed the cross-drilling pattern a fraction of an inch or something. ---------------------------------- >>>>Major would be having to alter the basic configuration, change diameter, swept area of pads, different caliper or the like. --------------------------------- Only if you're grasping at straws. ----------- Just wondering, what would you consider minor? According to your comments, about every new Japanese repli-racer includes a major brake system redesign. Nah, they just refine it, change some connection hardware, not much too it. ----------- polishing the circumference of the rotor, changing the layout of the holes a bit, etc. -------------- The loads and primary specs stay the same. ------------- Well, yeah. Loads are rider dependent. Rotor thickness is a pretty damn important specification and it changed by 20%. They added a whole feature (fins). It's pretty significant. Just let it go. It's okay. | ||
| Jdugger |
> Just let it go. It's okay. To Blake's credit, he did. | ||
| Gemini |
lol. i was typing when the "let it go" was happening | ||
| Boogiman1981 |
so what about a ceramic coating on the parts of the caliper that are exposed to the heat(ie the inner portion where the rotor is) the same for the pistons and let it rip? keeps more of the heat out of the fluid there by reducing or even eliminating the fade issue? | ||
| Gemini |
boogiman, so glad you have that idea. might work. if the fluid is the issue and you can keep the heat out of the fluid, then it would help. but you then have removed some of the heat sink from the rotor/pads. could the ceramic cause too much heat to be retained in the pads? to the point of seperating the friction material from the backing plate? don't get me wrong, i think it is neat idea and can very well help. it is just perfect timing to show how a change for the better may have adverse effects in the other parts of the picture resulting in a much worse fate. | ||
| Court |
>>>>so what about a ceramic coating on the parts of the caliper that are exposed to the heat Didn't some sharp young kid once make laminated rotors? :-) | ||
| Boogiman1981 |
Gemini Court I had the same thoughts but because in my mind at least where and how i am thinking of applying the coating it would reject the heat keeping the loss of heat sink area to a minimum concern. the pad separation thing is one of the bigger issues i am concerned with perhaps a sintered pad would be the solution, handy they are already available. i don't know how they are bonded to the backing plate though... again this is another example of the tradeoffs i guess as this wouldn't be an ideal solution for most of us but may be for those that need/want more than the stock system has. disclaimer: i am not an engineer but i play one on badweb lol | ||
| Jdugger |
The current state-of-the-art collection of parts for the ZTL2 system do a couple of things to help heat dissipation. First, the Erik Buell Racing rotor mounting kit helps the rotor sink more of the braking heat into the wheel itself. This is the reason for the copper washer between the wheel and the rotor, and why the top hat bushing holds the washer flush against the bearing edge of the wheel and the rotor, with pressure from the Belleville washer on the outside holding the rotor against the wheel. Second, both of the buell race pad options feature a "fat back" extra-thick backing plate on the pad itself. As stated way earlier in the thread, slowing a given weight a given amount of speed generates a given amount of heat. The question is "what to do with that heat?" From my standpoint, as long as the system's temperature stays below the boiling point of the fluid, all is OK. That seems to be the weak link in the system. So, finding ways to avoid heat transfer into the fluid is paramount. | ||
| Boogiman1981 |
i do wonder(again not an engineer) if perhaps turning the spokes at a slight angle would have been an option. thinking fan blade type effect. more air=lower temps? maybe an alternate race only wheel? | ||
| Jdugger |
Interesting idea, though I don't understand the implications of doing something like that, including the steering inputs such a "fan" might inadvertently cause. I'll say this: The ZTL2 system, after fluid, master cyl, race brake pad, rotor, and mounting hardware upgrades works pretty well, at least at my skill level. So, after roughly replacing the entire brake system, I like it a lot I am unable to make the system fade now, post upgrade, unlike the stock system which I can make fade at will. I've also noticed that with the new finned rotor and upgrades, I'm not getting as much color in the rotors as I was with the stock system, which implies there's less heat retention in the system. I don't have a way of measuring fluid temp to know how close I am to requiring my next upgrade, which I must suspect is the ZTL 2.5 caliper. That's the only thing left to replace on my race bike. God Bless RBF600. | ||
| Boogiman1981 |
JD that was something i wondered about too esp at higher speed so maybe just a twist at the top? i dunno just throwing ideas out there as they pop into my head. i've actually followed this thread from the beginning it's been interesting. | ||
| Jdugger |
> i've actually followed this thread from the beginning it's been interesting. Ain't that the truth. | ||
| Dannybuell |
Court - I like everyone here. Gemini - spot on. An SRT-8 is not a NASCAR is a great analogy. I am no racer. A racers experience is the sum of so many variables that I will never understand, this may be a bit off the wall. The Erik Buell Racing ECM idle air control defaults at 'dieseling 2 stroke'. With those settings and throttle off I would grab the brakes heading into a turn and nothing would happen. I was braking against the engine, the engine was winning. Engine RPM didn't matter I was braking against the engine. My primary response to this situation would be to pull in the clutch and regain control. What IAC settings do the racers mentioned in this thread use? | ||
| Blake |
>>> The question is "what to do with that heat?" I could use some about now. Someday, we'll be able to store that energy in a tiny module for use on corner exist. Danny, Something is wrong with your front brake. The engine should be helping you brake, not hindering. | ||
| Dannybuell |
The stock ecm IAC gives the bike full engine decelleration, it does not get in the way of braking. In my opinion the ebr default IAC gets in the way of braking. The motor diesels, like leaving the throttle on. Braking against a dieseling engine has to stress the system more. ebr will change the default IAC to almost stock which is close enough to restore engine braking. | ||
| Jdugger |
> What IAC settings do the racers mentioned in this thread use? Danny, My preference is a bike that exhibits essentially no drag at all when off throttle. I achieve this with a combination of a generous IAC setting and a slipper clutch. Everyone is different in their preferences, but my suspicion is you aren't using the brakes very hard and you are letting engine drag slow you down more than braking. These bikes will slow from more than 120 mph to zero in less than 300 ft. I do it all the time as a braking drill/practice. | ||
| D_adams |
My personal experience has been good for the most part. Street use, I've never had brake fade. I've done stoppies with it, so they definitely work. On the track with the stock setup, I got a chance to find out what brake fade really means. It was certainly a wakeup call coming into turn 1 a little too hot at BHF and overshooting the apex a bit. Hitting 140+ (pretty sure I saw 145 on the speedo once, never looked again after that) on the front straight was fun though. Next time, the cluster will get taped over. I guess tech missed it, so did I. My point is, I overshot the turn because it just simply wouldn't slow down enough, even though I used the same brake points and was doing roughly the same speed, I think it was the 4th session of the day. I called it quits after making 2 mistakes like that. I will blame it on judgement errors and fatigue, rather than the brake system, but it was definitely losing it's stopping power. I should have pulled off after the first time, but I guess it was just too much fun so I kept going for another lap or two. | ||
| Dannybuell |
Jdugger - your suspicions are fairly correct. I don't use the braking system as much as many. The fact is that for me the ebr ecm default IAC has the engine making power that defeats the brake system. I can only imagine that oh S*&^ ! moment, the brakes completely on and fade. Over the years there have been times when my speed and the turn were not well matched. I have slammed on the brakes with aggressive downshifting. The brakes alone were not enough to slow me, the engine helped slow me down. | ||
| Lawineer |
>>>>Over the years there have been times when my speed and the turn were not well matched. I have slammed on the brakes with aggressive downshifting. The brakes alone were not enough to slow me, the engine helped slow me down. Due to fade or not enough braking power? If it's due to a lack of braking power, unless you're going REALLY fast, use more front brake and don't use engine braking to stop you.... ever. | ||
| Dannybuell |
THX guys | ||
| Fdl3 |
I am in a testy mood. I suppose this is somewhat normal now that I have read every page in this discussion.  But, alas, I guess it's the "engineer wannabe" and/or "racer wannabe" in me that sucks me into reading such lengthy posts as these! I suppose, since I am neither (an engineer or racer), I find these posts sadisticly *fascinating*!  Anywho... Jdugger, Something jumped out at me like a glaring neon sign at 3am after a long night out. This observation of mine contributes nothing to this discussion, and for Pete's sake is NOT a personal attack. I just find it humorous that nobody else has mentioned it...or answered your question. For "cross-examination"  , I refer to this previous post of yours: Brake Rotor Color In this post, you provide three images showing the front brake rotors for: 1) one of Ty Howard's KTM race bikes; 2) one of Geoff May's Buell race bikes; 3) one of your Buell race bikes. Your point in posting the pictures was to correlate brake rotor color with temperature. Specifically, certain brake rotor colors indicate the temperature that must have been exerted on the rotor in order to produce the colors. From this, you assert the Buell ZTL brake system must have a greater heat problem because the color of the Buell rotors indicate higher temperatures (as compared to the brake rotors of another brake system). Not that you are asserting this is the *only* evidence, but this is an extremely weak argument. While heat can be a contributing factor to color, it is not the *only* factor. There are just too many other variables at play to conclude the Buell ZTL brake system suffers above-average heat issues based on brake rotor colors. I would submit the greatest of these variable is the user. And this brings me to my observation... You conclude by asking the question "Why are [Ty Howard's] rotors not colored at all"? Could the answer be because he uses his brakes LESS?! After all, even you claim Ty is: 1) the fastest rider in CMRA; 2) has 15 various track records; 3) consistently 13 seconds per lap faster than you at ECR. IMHO, spend more time on the THROTTLE and less time on the BRAKES! Doing so will most certainly tax your braking system LESS. At least, this is what I have read by other racers on the Internet. Don't you see the humor...nay, the unadulterated irony?! All this engineering and racing bantering comes down to how often and with what amount of force a user exercises one's brakes! I mean, how can you *ever* measure that?! Brilliant I tell you. Definitely makes for long, verbose discourses...in a forum...on the Internet...where nobody is wrong! And it kills time, too...! I think I have braking issues with post replies. No worries, I'm currently seeing a counselor... | ||
| Fdl3 |
Lawineer, For the love of all that's sacred... Please, PLEASE, learn to use the text formatting code for quoting! Syntax: \quote{Your text} Example: \quote{This guy is nuts!}
Alternatively, some people like to quote text in blue. Syntax: \blue{Your text} Example: \blue{This guy is beyond nuts!!} This guy is beyond nuts!! | ||
| Jdugger |
> You conclude by asking the question "Why are [Ty Howard's] rotors not colored at all"? > Could the answer be because he uses his brakes LESS?! This is a keen observation, it just happens to make an incorrect assumption. If you take a lesson with Ty, he will tell you the faster you ride, the more time you spend on the brakes. In talking with Ty, I was shocked to discover our apex speeds were far less apart than I would have imagined. In other words, at the slowest point in the corner, we weren't that far off each other in speed. What makes Ty so much faster is really two things: 1. How much sooner he can use full throttle, and how much more time in the straight (and initial speed) he has accelerating at WOT. He has it mashed way sooner and way longer than I. and 2. How long he's able to hold WOT, because he can brake so much harder than I can (slow down faster) and deeper into the corner, meaning he carries that average high speed much longer. So, in every way, Ty is using MORE brakes, not less. | ||
| Jdugger |
> Jdugger - your suspicions are fairly correct. I don't use the braking system as much as many. > The fact is that for me the ebr ecm default IAC has the engine making power that defeats the brake system. I disagree, but for someone not used to the sensation of really mashing on the front brake, I'm sympathetic to the position. What I can recommend is you do some full stop drills. Start at 40mph and incrementally work up as you get used to the sensations of the front diving. Try to bring the bike to a full stop in less than 200 ft. When you get up around 100mph - 0 in that range, you are going to start dealing with the rear wheel coming up a bit. Learn to modulate the front brake under pressure so that you optimize braking (rear wheel skipping along), but minimize vehicle instability (rear wheel not keeping you straight). After you master that, the next drill is to do the same thing, but strive to not have the forks "bounce" as you come to a full stop. In other words, you "trail off" the brake as you are stopping so the motorcycle is fully settled, but also stopped, and ready for the next rider input. With practice, you should be able to stop in similar distances as a panic braking exercise, but of course have the motorcycle ready for something else, not still bouncing in recovery. After that, do the same exercise, but have your stop point be the apex of a corner, so you have to turn in while doing all that braking. > I can only imagine that oh S*&^ ! moment, the brakes > completely on and fade. Are your rotors colored? Whether FDl3 is right about the coloring indicator or not (I'm sure he is), I've still never seen a fast Buell track rider without at least some gold and usually pink red and blue in the rotors. So, if your rotors aren't getting colored from use, I'd say for now you have absolutely nothing to worry about. The great thing about the braking drills I mentioned is you are going to be doing them so that if the system does fade, you just keep going and it's no big deal. What you will learn is how amazingly well these bikes will stop when asked in the right way. And, if you get some fade, you can go down the path I recommended earlier. | ||
| Blake |
Always install nice thick new brake pads before taking to the track. Ensuring the system is well-bled, no air bubbles, no sponginess is vital too. | ||
| Blake |
Jim's suggestion for learning hard and smooth braking is excellent. It's not even a bad idea to start even slower in a parking lot. One you get a feel for how hard you can brake just before the rear tire comes off the ground, you'll be sooo much more confident in panic stop situations. I had my 70+ year old father do this on his S3. It was a revelation to him, a man who'd been riding motorcycles for over 40 years. | ||
| Blake |
JD, I too think there may be more to it than the brake system configuration. The amount of energy that must be transferred into brake heat is proportional to the speed of the bike squared. So if Ty is hitting higher top speed and slowing to the same apex speed, he's having to put more heat into his brakes. The greater mass and greater caliper mass of his bike certainly helps, but I'd be surprised if his brake rotors aren't getting to about the same temperature as yours. It sure would be interesting to know for sure. You about the same size as skinny ol' Ty? Would be interesting if he could do some laps on your bike to where he was dialed in and comfortable. | ||
| Jdugger |
> You about the same size as skinny ol' Ty? Don't I wish. But, I'm not drastically heavier. I'm 165 before gear. I think we could get to a reasonably educated guess by looking at a wide cross section of race bikes vs. a collection of Buells. In just walking around the CMRA paddock, you won't find lots and lots of dual disc bikes with the deep, rich coloring you see on my rotors. The other thing that's worth considering is that the alloys used on the KTM don't color the same. Still, color or not, I'm relatively confident in my assertion the ZTL2 system is relatively more heat prone than a dual disc system. |
