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Metaldude
| | Posted on Tuesday, November 24, 2009 - 01:17 pm: | 
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This thread is very interesting because it seems to be an example of the "law of unintended consequences". At the heart of the problem is the fact that Buell has the largest diameter rotor on pretty much any bike in the world. This has some sort of characteristic that makes it prone to "gunking". My guess would be that its increased diameter equals four or five times the surface area compared to other bikes (any math majors out there?) Therefore, when you apply your brakes and you're gliding to a stop, the pad will hit any given spot four times less than a non-Buell and we miss out on the normal "sanding" action of the pad. Our rotors simply won't have the pad pass over a give spot as often. However, we will have just as many full stops as another bike. So the times when you hold your brake at a stop light or hill and a bit of the pad melts off, that gunk won't get sanded down the next time you glide to a stop. Conversely, it may even accumulate more gunk as the pad is passing over it.
I'm not sure exactly what the mechanism of the problem is, but I betcha it is caused by the fact we have such a big rotor. Maybe the only way around it (save changing the brakes completely) would be to change riding habits and constantly maintain the rotor surface with sandpaper. |
Sayitaintso
| | Posted on Tuesday, November 24, 2009 - 01:34 pm: |
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Just going to give my experience here. I bought my 06 in Feb of this year with about 6k miles and the front brakes pulsed kinda bad. I told myself that I would replace the pads when I got the time but would just put up with the pulsing until then.
Well, being the king of procrastination I never did replace the pads. Now I can't tell you exactly when it happened (probably happened slowly over this summer) but in August I noticed that the pulsing was gone.
Since I bought the Uly I put somewhere around 6k miles on the bike. This kinda leads me to believe that its riding style that causes the pulsing. But I have no idea what I do differently than anyone else that would cause the pulsing to go away. |
Crempel
| | Posted on Tuesday, November 24, 2009 - 02:39 pm: |
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If I calculate the circumference of the rotor (buell is 375 mm diameter) and compare it to your average sportbike (320 mm diameter) , the circumference/swept area is about 72% for a single disc, but since most have 2, bikes with "normal" brakes would have just under 150% of the swept area. Again, not an exact calculation. I don't know how this affects your theory, but my question still is the same. Why have I never even heard of any other bikes having this type of issue? I would also be curious to know if anyone who has replaced their rotor with one of the aftermarket or wave type has ever had an occurrence with one of those rotors? |
Froggy
| | Posted on Tuesday, November 24, 2009 - 03:30 pm: |
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quote: Why have I never even heard of any other bikes having this type of issue?
Because other bikes don't have floating rotors.
quote: Why have I never even heard of any other bikes having this type of issue?
I got a ZTL2 caliper, brake line, Nissin master cylinder, Lyndal gold pads, wave rotor. So, the only part of my setup that is stock, is the wheel and rotor springs. Yes, I have gotten a slight pulsing, but ONLY after doing a long series of stoppies. Stock setup would be the same. The 100% stock setups on my 1125R and CR have been trouble free too. |
Buellerxt
| | Posted on Tuesday, November 24, 2009 - 07:27 pm: |
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Why Froggy? Why do you think your brakes have been trouble free while others have had h*ll, and you doing those show off stoppies? lol By the way, Kudos Man! |
Froggy
| | Posted on Tuesday, November 24, 2009 - 07:37 pm: |
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Because I don't hold my front brake when stopped. Hence, why I started to get the slight pulsing only after doing the ton of stoppies. Part of the problem is the rotor surface getting gunked up, other part is the springs. Cleaning the springs can make a huge difference if that is the cause of your issue. |
Pkforbes87
| | Posted on Tuesday, November 24, 2009 - 07:47 pm: |
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"I got a ZTL2 caliper, brake line, Nissin master cylinder, Lyndal gold pads, wave rotor."
I would be on my face so fast with that setup..
The day I brought my XT home, I asked myself why Buell didn't upgrade the Uly's front brakes along with every other 1200cc model. After just one panic stop I know the reason why! |
Froggy
| | Posted on Tuesday, November 24, 2009 - 07:57 pm: |
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quote:I would be on my face so fast with that setup..
DAMHIK
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Weekendwarrior
| | Posted on Tuesday, November 24, 2009 - 08:53 pm: |
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-------------------------------------------------- ------------------------------
quote:
Why have I never even heard of any other bikes having this type of issue?
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Because other bikes don't have floating rotors.
But yes, they do. I won't go so far as to say ALL Jap/Euro bikes have floating front rotors, but I can't think of any that don't. H/Ds are some of the only non-floating front rotors I've seen.
I can't complain though, 17k miles and new Lyndalls leave me with little or no pulse at the lever. |
Froggy
| | Posted on Tuesday, November 24, 2009 - 08:57 pm: |
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Interesting, I need to do more research then.  |
Crempel
| | Posted on Wednesday, November 25, 2009 - 12:43 pm: |
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I agree with Weekendwarrior. Most all Jap/Euro bikes have floating rotors. In fact floating rotors are supposed to cure this type of problem. I have sanded and sanded and sanded to no avail. No amount of sanding has produces ANY improvement, not even temporarily. I swear this is a metallurgical issue. There is a slippery spot. I wonder if when I remove the current rotor if I could find someone who could test it to see if there are any anomalies. I think before I deep-fry my turkey tomorrow, I will swap the rotors and see what happens. I guess I better do that early before I get into the sauce (I don't mean cranberry). |
Portero72
| | Posted on Wednesday, November 25, 2009 - 02:07 pm: |
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I don't hold my front brake at stops, either, and I'm about to get the 4th disc installed on my 09, all in less than 18k. On the SECOND disc(the first went about 7k till the pulsing became dangerous), I rode home and immediately put in Lyndalls. 3500 miles later, the pulse was back in a big way. 3rd disc, I went back to stock pads for feel and disc longevity reasons(7k is better than 3500 miles). I'm not a hooligan, so I doubt seriously that riding style is the culprit. There seems to be no obvious pattern to front brake pulsing. |
Glen
| | Posted on Wednesday, November 25, 2009 - 02:38 pm: |
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My Uly started pulsing a bit early this year, i figured that i had clamped the hot pads to the rotor at a light or somthing.
rode the front brake for a bit on the freeway and it eliminated my pulse. |
Crempel
| | Posted on Wednesday, November 25, 2009 - 05:13 pm: |
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Now thats an idea I hadn't thought of. I will try on the way home today. Like Portero, l don't ride like a hooligan. Mostly commuting. I sure hope this doesn't become a recurring trend. |
Jammin_joules
| | Posted on Wednesday, November 25, 2009 - 05:26 pm: |
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I know my parts manager has found some options for brake material pads and matching rotors that are supposedly what Danny Eslick switched to early in the season that solved his brake fade issue resulting in him starting to win races.
Don't ask how I know this.
James at High Country Buell
303.833.6777 |
Froggy
| | Posted on Wednesday, November 25, 2009 - 05:44 pm: |
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About the floating rotor thing, I did some research, and I should of used a different term. Not sure what the term would be, but the way the front rotor is mounted is with little springs to keep it in place. If your springs clog up with brake dust, the won't spring correctly, and it can make the rotor feel like its warped. |
Crempel
| | Posted on Wednesday, November 25, 2009 - 05:49 pm: |
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I periodically tap my rotor at the mounting points with a mallet to see if there is movement. I imagine that if they smack back and forth that they are free? |
Etennuly
| | Posted on Wednesday, November 25, 2009 - 07:42 pm: |
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The springs actually keep it from rattling loosely around on it's slider blocks. It does not move much at all. |
Slipknot
| | Posted on Thursday, November 26, 2009 - 11:28 am: |
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This is theory, but I think I have this correct: the larger diameter disc is traveling a longer distance, per revolution, than a smaller disc. SO the pads are grabbing a "faster" moving surface. Recall speed is distance traveled per unit of time. So it gets hotter. And then sitting at a stop after a long hard braking will help deposit material on the disc, giving the pulse.
Back to the physics of the speed. Airplane propellers, when made of wood, would shatter at the tips as they approached the speed of sound, so aluminum came into use. The tips had to travel at a faster speed to rotate around the axis.
This may not be the actual problem with the Buell disc because the speeds may not be that much different comparing the diameters of the "usual" brake disc to the perimeter disc but it is interesting to through this out there and keep the ball rolling. Perhaps Dr. Greg would like to comment. |
Rwcfrank
| | Posted on Thursday, November 26, 2009 - 01:32 pm: |
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FYI bent wheel equals bent rotor.... |
Dr_greg
| | Posted on Thursday, November 26, 2009 - 03:38 pm: |
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quote:Perhaps Dr. Greg would like to comment.
Hmm, at a given angular velocity (rpm of wheel) the velocity of any point on the wheel (or brake disc) is directly proportional to its distance from the axle (center of rotation). So if the Uly disc is twice the radius of a typical disc its periphery is moving twice as fast.
Don't know much about the velocity affecting friction, but I agree that it could be an issue.
By rights, Coulomb friction (the kind we're talking about here) is independent of velocity. But realistically, it is dependent on MANY parameters, and is a very complicated (and difficult to model) phenomenon.
What we need here is a tribologist; they're the guys that are experts in interacting surfaces in relative motion (friction, lubrication, etc.) Unfortunately we don't have on in the M.E. Department at UNM (used to, but he left).
--Doc |
Crempel
| | Posted on Friday, November 27, 2009 - 07:16 pm: |
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OK. Got out the tools yesterday and was going to have at replacing the rotor. The mounting bolts for the rotor are #&%^#*$NG tight. One broken torx socket and two bruised knuckles later I was not happy. Today went and bought a decent set of torx sockets and popped the T40 onto my DeWalt 18V impact driver. It took nearly 10 seconds to have all six bolts out.. B E A utiful. I will this evening reinstall the wheel and see how it works. |
Etennuly
| | Posted on Friday, November 27, 2009 - 11:45 pm: |
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Oh yeah, it will be difficult to remove the bolts unless you have a proper driven impact tool, air, A/C electric, or battery powered.
If you are not putting a new set of pads on, because you have nearly new from trying to fix it, remember to clean the used pads with 'brake cleaner' then sand them a bit with 80 or 100 grit paper to give them a 'new' surface to start with. |
Crempel
| | Posted on Monday, November 30, 2009 - 04:40 pm: |
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HAPPY HAPPY JOY JOY. All is well once again with the brakes. I had become so accustomed to the pulsing that it actually now feels strange to stop so smoothly. I will try my best to get used to it. If at first the dealer doesn't succeed, do it your damn self. I guess now we shall see how long it lasts.  |
Etennuly
| | Posted on Monday, November 30, 2009 - 07:31 pm: |
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If at first the dealer doesn't succeed, do it your damn self.
Now you are starting to understand your Buell and BadWeB!
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Crempel
| | Posted on Monday, November 30, 2009 - 07:46 pm: |
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BTW. Visited a friend today who used to be a Buell/HD dealer and saw some of his vintage collection. OMG. Ariel Square Four, Vincent Rapide, Indians X 4, etc. WOW. All runners and ridden on a regular basis. |
Panhead_dan
| | Posted on Monday, November 30, 2009 - 09:56 pm: |
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Don't discard those rotors folks. Unless measurable warp is detected or they are thinner than minimum spec.
I suspect the reason we are so confused about this very real problem is because it is actually two or more problems. Contaminated pads is something to think about. Clean and resurface your rotor all you want. If the pads sucked before, they will suck again.
Stock vs aftermarket pads. I'm starting to think the stock pads suck and they are expensive. I installed some SBC HH(?) sintered pads, cleaned my rotor with brakeclean and all is good for like 6 months now.
Then there is the spring thing. These parts have to be clean and able to work as designed.
I would love to have a box full of the rotors people have chucked trying to fix this issue. |
Metaldude
| | Posted on Monday, November 30, 2009 - 11:39 pm: |
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Crempel, great to hear things are finally working for you! Let us know if you can see anything goofy with the old rotor now that you have gotten to the root of the problem. Maybe us a sheet of glass to test for warping. Can't think of a test to see if there's a "shiny" spot on it. Maybe running an old brake pad over it?
I love the old bikes, I'm so jealous that you got to check out the dealer's collection! |
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