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  1. #1
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    Interesting observation. Roundagon vs Cleansweep G2

    I had my bike on a trail that went 35 miles with a 7,000 foot drop and got to really try the brakes out for the first time.

    I have BB7s front and rear with a 203mm roundagon up front and a 185mm cleansweep in the rear. I have to admit I was wrong on my theory.

    First test, I got up to 30mph and braked somewhat gently and steadily until stopped on a 13% grade. I stopped in a marked off distance every time. My observations were the cleensweep although smaller didn't get as hot as the roundagon but it was close. I was stopping by dragging the brakes the whole time. These stops were at the limit of being able to touch them without burning myself instantly.


    Then I tried going faster but applying the brakes, letting off, applying again, letting off, until I was stopped. I did the same number of applications for each brake and this is where the real difference was. The cleansweep was pretty warm. The roundagon burned me pretty bad.

    I've always assumed that since the roundagon had more mass, it would take longer to heat up. This may still be true but the cleansweep cools so much quicker, in the real world it's going to run cooler under any normal condition.

    Regardless, they stopped me at 250lbs over and over from 30+mph without fail.

  2. #2
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    Not really a fair/valid test. The rear brake doesn't do as much "work" as the front because of weight shift on the bike as you're going downhill, and that your weight shifts forward when you're stopping anyway.

  3. #3
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    Quote Originally Posted by Monte
    Not really a fair/valid test. The rear brake doesn't do as much "work" as the front because of weight shift on the bike as you're going downhill, and that your weight shifts forward when you're stopping anyway.

    Re-read the test. I stopped in the same distance every time. Weight and traction makes no difference because I never approached the limits of traction. Each brake does the same work stopping the same weight from the same speed in the same distance.

  4. #4
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    My opinion: too many variables in the test. Front vs rear brake, rotors of different sizes. But that's beside the point. I think if you accounted for those and tested a roundagon vs a clean sweep of the same size under the same conditions, you would get the same result. My understanding is that clean sweep rotors come with hydraulic systems precisely because they're designed to cool faster and not overheat the brake fluid; mechanicals do not suffer that problem, hence being able to keep costs down with a less intricately machined rotor.
    Quote Originally Posted by JonathanGennick View Post
    I am a poser. But forums.poser.com doesn't seem to exist, so I come here instead.

  5. #5
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    Quote Originally Posted by Slow Eddie
    My opinion: too many variables in the test. Front vs rear brake, rotors of different sizes. But that's beside the point. I think if you accounted for those and tested a roundagon vs a clean sweep of the same size under the same conditions, you would get the same result. My understanding is that clean sweep rotors come with hydraulic systems precisely because they're designed to cool faster and not overheat the brake fluid; mechanicals do not suffer that problem, hence being able to keep costs down with a less intricately machined rotor.
    Don't forget that Avid also sells the BB7 for about half the price of their cheapest hydraulic brake (Juicy 3). Even if the Cleansweep did help the BB7 perform better as well, Avid probably doesn't want to raise the price of the BB7 more to include the better rotor. People will only pay so much for a mechanical disc brake

    Actually, didn't the BB7 used to come with Cleansweep rotors a few years ago? EDIT: yep, they did

  6. #6
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    You need ABS on your brakes.

  7. #7
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    Quote Originally Posted by Slow Eddie
    My opinion: too many variables in the test. Front vs rear brake, rotors of different sizes. But that's beside the point. I think if you accounted for those and tested a roundagon vs a clean sweep of the same size under the same conditions, you would get the same result. My understanding is that clean sweep rotors come with hydraulic systems precisely because they're designed to cool faster and not overheat the brake fluid; mechanicals do not suffer that problem, hence being able to keep costs down with a less intricately machined rotor.

    Don't forget, I was testing a smaller cleansweep against a larger roundagon and the cleansweep still stayed cooler. I think that's pretty conclusive being that the cleansweep was at a disadvantage but came out on top.

    I wish you guys would get off the front vs rear. I was stopping in the same measured distance for both brakes. Same g-force. Front vs rear does not matter in this case.

  8. #8
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    Most scientific test ever.

    JK it really isn't.
    Bike good, work bad.

  9. #9
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    Quote Originally Posted by Clutchman83
    Most scientific test ever.

    JK it really isn't.
    ...but come on, we need posts like this so we could laugh at someone

  10. #10
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    This experiment is very scientific. Factors that make it very scientific and controlled are:
    1. Using very reliable gauge to measure temperature - hand
    2. Test sample is very comparable - 203mm vs 185mm
    3. Using precision equipment to apply same force - hand again - abeit different sides
    4. Test very similar conditions - both mount on a bike - only one in front where front wheel has practically unlimited traction
    5. Test bias - test was NOT blinded so tester conducted test w/ prejudices

    See? Very scientific experiment. Might I mention that there was an experiment by Sir Robert Bennett Bean that found 100% correspondence that black people's brains were smaller than white people's. Only when Franklin Mall in the US tried to duplicate results but using a blinded study found 0% correspondence whatsoever.

  11. #11
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    "1. Using very reliable gauge to measure temperature - hand"

    Level 1: Meh
    Level 2: Ow.
    Level 3: Oooow!
    Level 4: Owwa!!
    Level 5: !*%?!
    Level 6: Aaargh!!!

    Looks perfectly scientific to me.

    What use is a philosopher who doesn't hurt anybody's feelings? -
    Diogenes


  12. #12
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    Quote Originally Posted by Clutchman83
    Most scientific test ever.

    JK it really isn't.
    No ****. I must've forgotten my heat sensor for my mountain bike ride.

    The plain and simple of it is the stopping distances were measured and kept consistant for every test. So was the speed. It was nohwere near the limit of traction even for the rear so front/rear bias plays no role. The only thing lacking are acutal temp measurements. There was enough difference in temp to feel it with my fingers which is all the proof I need.

    Really, I know it makes you feel good to try and pick others apart but besides your useless comment, explain to me why this is not valid.

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    Come on guys, just go through some of the OP's post history if you want to have some real laughs at boneheaded observations and theories.

  14. #14
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    Quote Originally Posted by vk45de
    This experiment is very scientific. Factors that make it very scientific and controlled are:
    1. Using very reliable gauge to measure temperature - hand
    2. Test sample is very comparable - 203mm vs 185mm
    3. Using precision equipment to apply same force - hand again - abeit different sides
    4. Test very similar conditions - both mount on a bike - only one in front where front wheel has practically unlimited traction
    5. Test bias - test was NOT blinded so tester conducted test w/ prejudices

    See? Very scientific experiment. Might I mention that there was an experiment by Sir Robert Bennett Bean that found 100% correspondence that black people's brains were smaller than white people's. Only when Franklin Mall in the US tried to duplicate results but using a blinded study found 0% correspondence whatsoever.
    Are you people too stupid to read my entire post?

    1. There was enough difference to feel by hand. When one burns you and the other will allow you to leave your hand on for a few seconds, that's a difference.

    2. Once again I'll repeat myself. The 185 (cleansweep) was at a size disadvantage yet still ran cooler so this is even more evidence to support the superiority of the cleansweeps.

    3. What does force matter when I'm applying just the right amount to stop in a pre-measured distance from the exact same speed?

    4. Once again, repeating myself, the measured distance vs the speed resulted in a slow steady stop. Traction of either tire played no role. I stopped just as slowly with the front as I did with the rear.

    5. Predjudices? I had no idea what was going to happen and I really didn't care. What I wanted was my front and rear rotors to look the same so I needed to figure out whether to buy another roundagon or another cleansweep.

    Seriously, everyone in this thread is so caught up in their superiority complex that they end up looking like the stupid ones.

  15. #15
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    Quote Originally Posted by Jerk_Chicken
    Come on guys, just go through some of the OP's post history if you want to have some real laughs at boneheaded observations and theories.
    Ah the peanut gallery is alive and well. Last I remember I tore you a new *******.

  16. #16
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    i find that since my fingers are calloused from bike maintenance, i use my tongue to test the "heat" of a brake.

    i burned myself on the front rotor after a ride, but the back didn't burn as bad.

    clearly meaning the front one was less efficient.

    i tried to run my finger over the rotor while i was riding once, too, but then i went over the front bars for some reason. clearly my brakes are to blame.

  17. #17
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    Quote Originally Posted by BuickGN
    Seriously, everyone in this thread is so caught up in their superiority complex that they end up looking like the stupid ones.
    HA!

    This one's gonna be fun.
    Bike good, work bad.

  18. #18
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    Quote Originally Posted by BuickGN
    Ah the peanut gallery is alive and well. Last I remember I tore you a new *******.
    Must have been the Pabst Blue Ribbon talking.



    There's always the NASCAR mullet as well:



    Anyhow, just like your old posts. You resort to calling everyone else a-holes, when your post history kind of shows either a bit of trolling, or an unhealthy obsession, coupled with lack of understanding, of the operation of brakes.

  19. #19
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    Quote Originally Posted by eat_dirt
    i find that since my fingers are calloused from bike maintenance, i use my tongue to test the "heat" of a brake.

    i burned myself on the front rotor after a ride, but the back didn't burn as bad.

    clearly meaning the front one was less efficient.

    i tried to run my finger over the rotor while i was riding once, too, but then i went over the front bars for some reason. clearly my brakes are to blame.
    That's very intelligent. You can't intelligently pick apart anything so you make smart ass comments. Another one that's too stupid to realize he's stupid.

  20. #20
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    Quote Originally Posted by Jerk_Chicken
    Must have been the Pabst Blue Ribbon talking.



    There's always the NASCAR mullet as well:



    Anyhow, just like your old posts. You resort to calling everyone else a-holes, when your post history kind of shows either a bit of trolling, or an unhealthy obsession, coupled with lack of understanding, of the operation of brakes.
    As usual, nothing to contribute. You follow me around like a little ***** looking for attention. One day you'll get off my nuts but I suppose negative attention is better than no attention for someone like yourself.

  21. #21
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    I won't take "you're stupid" from the likes of you.
    Quote Originally Posted by BuickGN
    3. What does force matter when I'm applying just the right amount to stop in a pre-measured distance from the exact same speed?
    Exemplary case - yes it does. Did you know that if you apply more force towards the beginning of the stop, your brakes will be cooler when you do stop?

  22. #22
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    "Another one that's too stupid to realize he's stupid."

    That should be another one who's too stupid...

    What use is a philosopher who doesn't hurt anybody's feelings? -
    Diogenes


  23. #23
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    Quote Originally Posted by BuickGN
    That's very intelligent. You can't intelligently pick apart anything so you make smart ass comments. Another one that's too stupid to realize he's stupid.
    i just find your methodology hilarious.

    even if you took an IR temperature gun out there with you, i'd still laugh at you for comparing a front bb7 rotor with a back one, and of different size and specs for that matter--not even considering if you had the brakes adjusted properly.

    given the fact that i use a tiny rear bb7 brake rotor because anything bigger just tends to lock up the rear wheel (not a good thing), the cable slack, mechanical disadvantage, pad adjustment, pad wear, etc. are so random that if your funny little test were to mean anything, you'd have to try it under the same conditions with two similar FRONT rotors and use some kind of scientific (big word for book learnin) methodology to prove your ramblings.

    i use clean sweeps because i THINK they bite harder compared to roundagons.

    i have no proof for that.

    and neither do you in your assertions.

  24. #24
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    Quote Originally Posted by eat_dirt
    i just find your methodology hilarious.

    even if you took an IR temperature gun out there with you, i'd still laugh at you for comparing a front bb7 rotor with a back one, and of different size and specs for that matter--not even considering if you had the brakes adjusted properly.

    given the fact that i use a tiny rear bb7 brake rotor because anything bigger just tends to lock up the rear wheel (not a good thing), the cable slack, mechanical disadvantage, pad adjustment, pad wear, etc. are so random that if your funny little test were to mean anything, you'd have to try it under the same conditions with two similar FRONT rotors and use some kind of scientific (big word for book learnin) methodology to prove your ramblings.

    i use clean sweeps because i THINK they bite harder compared to roundagons.

    i have no proof for that.

    and neither do you in your assertions.
    But everything you cite doesn't matter. Explain to me why it matters if it's on the front or the rear when I'm no where close to the traction limits. I set a distance and speed that could be easily stopped with the rear brake with no locking.

    If I said the smaller rear is inferior because it gets hotter than the larger front, that would be dumb. But in fact the smaller rotor stayed cooler, that means something.

    And once again, get off this front vs rear thing. It makes no difference on these super easy stops. It only matters when the front braking exceeds the rear traction limits which did not happen in this case.

  25. #25
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    Quote Originally Posted by vk45de
    I won't take "you're stupid" from the likes of you.

    Exemplary case - yes it does. Did you know that if you apply more force towards the beginning of the stop, your brakes will be cooler when you do stop?
    Yes, and that's the first good argument in this thread. Thank you for that.

    I did my best to keep the stops linear. We're talking 10+ stops here, not just one and every time I had the same results.

    I understand this is not the most scientific test but I got the same results over and over again.

  26. #26
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    the smaller rotor is staying "cooler" because of cable tension, pad adjustment, your own "subjective" opinion of what it is cool and hot, the fact that it's not working as hard, the interaction of the different design with the pads, checking one rotor before the other, heat dissipation... too many variables. you might as well be comparing the heat of the cassette to the front rotor.

  27. #27
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    Quote Originally Posted by BuickGN
    But everything you cite doesn't matter. Explain to me why it matters if it's on the front or the rear when I'm no where close to the traction limits. I set a distance and speed that could be easily stopped with the rear brake with no locking.

    If I said the smaller rear is inferior because it gets hotter than the larger front, that would be dumb. But in fact the smaller rotor stayed cooler, that means something.

    And once again, get off this front vs rear thing. It makes no difference on these super easy stops. It only matters when the front braking exceeds the rear traction limits which did not happen in this case.
    The front brake is still doing more work even before you reach the limit of traction, because of weight transfer

  28. #28
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    Quote Originally Posted by boomn
    The front brake is still doing more work even before you reach the limit of traction, because of weight transfer
    No it's not. I can't believe this many people don't understand this. You could have 1,000lbs on the front and 100lbs on the rear and as long as you're not stopping harder with the front than the rear is capable of at it's traction limits you will not generate any extra heat.

    Total weight is what matters here, not weight on each tire.

  29. #29
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    Quote Originally Posted by BuickGN
    If I said the smaller rear is inferior because it gets hotter than the larger front, that would be dumb. But in fact the smaller rotor stayed cooler, that means something.

    And once again, get off this front vs rear thing. It makes no difference on these super easy stops. It only matters when the front braking exceeds the rear traction limits which did not happen in this case.
    You really need to evaluate your thought processes regarding this statement. You are disregarding tons of variables. If you want to be taken seriously you will realize you are wrong and your test is completely irrefutably un-scientific and dumb as hell.

    Are you 12 years old? Or did you drop out before science class in high school?

    It's got to be one or the other.
    Bike good, work bad.

  30. #30
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    Quote Originally Posted by BuickGN
    No it's not. I can't believe this many people don't understand this. You could have 1,000lbs on the front and 100lbs on the rear and as long as you're not stopping harder with the front than the rear is capable of at it's traction limits you will not generate any extra heat.

    Total weight is what matters here, not weight on each tire.
    WRONG! SO WRONG IT'S NOT EVEN FUNNY! STOP POSTING IMMEDIATELY!!!!
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  31. #31
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    Quote Originally Posted by Clutchman83
    WRONG! SO WRONG IT'S NOT EVEN FUNNY! STOP POSTING IMMEDIATELY!!!!

    Elaborate, please. So you're saying that at the same braking rate at the same speed, the rear will always run cooler? That weight that transfers to the front magically disappears and goes away? You've found a way to defy physics. That's awesome.

  32. #32
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    Quote Originally Posted by eat_dirt
    the smaller rotor is staying "cooler" because of cable tension, pad adjustment, your own "subjective" opinion of what it is cool and hot, the fact that it's not working as hard, the interaction of the different design with the pads, checking one rotor before the other, heat dissipation... too many variables. you might as well be comparing the heat of the cassette to the front rotor.

    That's one very large ASSumption.

    They're both working equally as hard.

    Same pad material.

    Subjective, maybe, but one burns instantly while the other does not, that's pretty conclusive.

  33. #33
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    Quote Originally Posted by BuickGN
    That's one very large ASSumption.

    They're both working equally as hard.

    Same pad material.

    Subjective, maybe, but one burns instantly while the other does not, that's pretty conclusive.
    you clearly don't understand how your bike works. or elementary jr. high physics.

  34. #34
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    Quote Originally Posted by eat_dirt
    you clearly don't understand how your bike works. or elementary jr. high physics.

    A reading comprehension class wouldn't hurt you.

    I was not touching one brake and then the other. I was doing a run, touching the rotor and then doing the exact same run and touching the other rotor. Not one and then the other so that one has time to cool before the other.

  35. #35
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    Quote Originally Posted by BuickGN
    A reading comprehension class wouldn't hurt you.

    I was not touching one brake and then the other. I was doing a run, touching the rotor and then doing the exact same run and touching the other rotor. Not one and then the other so that one has time to cool before the other.

    Wait.

    Are you trying to say that you're testing one brake at a time on these runs?

    Not that it changes much of what has been said to this point, but if that's the case, I don't think that was made very clear in the first post. If so, I think you are justified in your argument that the front or rear brake works equally hard, when it is the only brake applied. If both brakes are being used simultaneously, the general consensus withing the cycling (and moto/auto) community is that the front brakes "do more" than the rear brakes when coming to a complete stop.
    Quote Originally Posted by JonathanGennick View Post
    I am a poser. But forums.poser.com doesn't seem to exist, so I come here instead.

  36. #36
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    Quote Originally Posted by BuickGN
    Elaborate, please. So you're saying that at the same braking rate at the same speed, the rear will always run cooler? That weight that transfers to the front magically disappears and goes away? You've found a way to defy physics. That's awesome.
    There is no way you can quantitatively say this with the variables you are working with. I'll spell it out for you.

    1 - Your fingers are not an accurate device with which to measure force. Others have already told you this but you keep choosing to ignore it.

    2 - You have different size rotors which exact different torques on the wheel even if you were using the exact same force (which you are not, I guarantee you) you would need to be able to take this into consideration. Others have already told you this but you keep choosing to ignore it. This doesn't even matter because you are using your fingers as force sensors AND temp sensors, which is totally stupid.

    3 - You aren't taking into consideration you're pad composition or level of use. You cannot be certain the pads are at the same level of wear, or even if they are of the same type. Organic or metallic? New or not? This doesn't even matter because you are using your fingers as force sensors AND temp sensors, which is totally stupid.

    4 - Cable and housing condition, are the cables new or stretched out? Is the rear cable stretching more than the front because it's longer? This doesn't even matter because you are using your fingers as force sensors AND temp sensors, which is totally stupid.

    5 - Brake lever setting. Are you certain the front and rear are set the same? The avid levers have an adjuster for the leverage it exacts on the caliper so you can set it to be stronger or weaker. This doesn't even matter because you are using your fingers as force sensors AND temp sensors, which is totally stupid.

    5 - Brake caliper alignment. Are you certain both front and rear brakes are aligned properly, not dragging the calipers, not off center/bending/warping the rotor when you apply the brakes. This doesn't even matter because you are using your fingers as force sensors AND temp sensors, which is totally stupid.

    There's more, but I'm wasting too much time typing this.
    Bike good, work bad.

  37. #37
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    Quote Originally Posted by Slow Eddie
    Wait.

    Are you trying to say that you're testing one brake at a time on these runs?

    Not that it changes much of what has been said to this point, but if that's the case, I don't think that was made very clear in the first post. If so, I think you are justified in your argument that the front or rear brake works equally hard, when it is the only brake applied. If both brakes are being used simultaneously, the general consensus withing the cycling (and moto/auto) community is that the front brakes "do more" than the rear brakes when coming to a complete stop.
    I should've made that more clear. Now I understand how I sounded like an idiot.

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    Fantastic thread. Hope we can do it again, fellas.

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    Quote Originally Posted by eat_dirt
    the smaller rotor is staying "cooler" because of cable tension, pad adjustment, your own "subjective" opinion of what it is cool and hot, the fact that it's not working as hard, the interaction of the different design with the pads, checking one rotor before the other, heat dissipation... too many variables. you might as well be comparing the heat of the cassette to the front rotor.
    This makes sense if you thought I was using both brakes at the same time. I should've been more clear in the beginning.

  40. #40
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    Blood, guts, carnage!

    Damn!...I looked at this thread...noticed JC was driving the locomotive...and sure enough in a very short time....
    Attached Images Attached Images

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    Dude, you even got mullets. What else could you ask for?

    ...and hell, I knew enough to let the loco steer itself. Even went food shopping, and sure as hell, it went straight into a neighboring town.


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    It's interesting observation indeed. What is most interesting that peoples keeps arguing even after clarifying on the test condition (one brake at a time), meaning they are just arguing for the arguing sake

    I'm lazy to look up the history of the OP to see if other posts carry proper argumentation, but this thread great example of how to read internet responses. Whole page of garbage with single proper counterargument

    But hey, all good. Nice entertainment for few minutes (Yes, I'm really bored)
    I used to run tubes like you are, but then I got thorn in my wheel.

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    Am I arguing now?!!

    Quote Originally Posted by Stalk
    It's interesting observation indeed. What is most interesting that peoples keeps arguing even after clarifying on the test condition (one brake at a time), meaning they are just arguing for the arguing sake
    Actually, the thread almost instantly died when that was finally made clear about 5 posts ago

  44. #44
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    Frictional force is the coefficient of friction times the normal force. Normal force can be determined by mass, gravity, and the angle. If there is less weight over the rear wheel, there is less normal force, therefore less frictional force. This means that less force is required to exceed the frictional force. In other words... it takes less power to break traction. Weight is also transferred forward while braking... note the weight transfer in a car. In a straight line, slam on the brakes. The front end will dive down. Or... Romp on the gas... the rear end will squat and the front end will rise.

    Suspension design and setup (both front and rear) will also affect the ability to maintain contact with the ground.

    I run a 140mm rotor in the rear, and it still stays much cooler than my 160 front, or even a 203mm fromt.

    This is hardly a scientific test by any means.

    Put the rotor on a brake dyno. Have the dyno spin at a specific speed and with a specific amount of torque. Apply the same amount of pressure for the same amount of time for each rotor. Measure the temperature.

    Though you may have stopped in the same distance, or even used the same number of applications of brake... the force applied to the rotor can vary. The front rotor being larger will have a larger moment arm. So less force is probably applied over a longer duration.

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    No you don't ... or do you? (I'm confused )

    But why no one is discussing if having cooler rotor is actually good or bad (OP assumes it's good)?
    Since stopping is only achieved by braking and initial kinetic energy the same, braking should transform it to the same amount of heat. If one rotor is cooler its either cooling faster (that would be good thing) or it's just taking less heat and more heat goes into pads/caliper. For mechanicals it may not be an issue, but for hydro I would like to heat rotor instead of caliper for less chances of brake fade.
    So, since rotors made from same material and cooler rotor actually smaller (less area) so it can't cool-off any faster (true term would be dissipate large amount of energy over same period of time) , so it's indeed causing more heat transferred to the pads/calipers. So roundagon seems a winner for hydraulics.

    I warned that I'm bored
    I used to run tubes like you are, but then I got thorn in my wheel.

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    Or it could be that some energy is converted to energy other than heat... like sound.

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    Quote Originally Posted by XSL_WiLL

    I run a 140mm rotor in the rear, and it still stays much cooler than my 160 front, or even a 203mm fromt..
    Of course it will because you *can* apply much more force to the front brake. I was stopping in the same distance at the same speed with either rotor so that point is null and void.


    Quote Originally Posted by XSL_WiLL
    Though you may have stopped in the same distance, or even used the same number of applications of brake... the force applied to the rotor can vary. The front rotor being larger will have a larger moment arm. So less force is probably applied over a longer duration.
    You're right but that's not the topic. What I was interested in is the temps in a real life braking situation, not using the exact same clamping force on each rotor which would result in different braking force since they are different sizes. Forget using the exact same psi from each caliper, what matters is stopping with exactly the same g-force over the same distance at the same speed and then comparing temps.

  48. #48
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    Actually the caliper can apply no more force regardless of whether it is front or rear. But doesn't your statement also make your claim null and void? Given that you are running a smaller rotor in the rear.

    It's simply not a fair comparison when using two different sized rotors on different ends of the bike. With the larger rotor, the pads don't have to bite as hard. This means less pressure needs to be applied to the rotor.

    My proposed experiment was to use one of each rotor in the same size.

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    Quote Originally Posted by XSL_WiLL
    Or it could be that some energy is converted to energy other than heat... like sound.
    That would be interesting Given OP can burn finger with energy off one rotor, that's would contribute to a lot of sound. "Dune" fans rejoice, sonic gun is closer to reality then we thought.
    I used to run tubes like you are, but then I got thorn in my wheel.

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    Quote Originally Posted by Stalk
    No you don't ... or do you? (I'm confused )

    But why no one is discussing if having cooler rotor is actually good or bad (OP assumes it's good)?
    Since stopping is only achieved by braking and initial kinetic energy the same, braking should transform it to the same amount of heat. If one rotor is cooler its either cooling faster (that would be good thing) or it's just taking less heat and more heat goes into pads/caliper. For mechanicals it may not be an issue, but for hydro I would like to heat rotor instead of caliper for less chances of brake fade.
    So, since rotors made from same material and cooler rotor actually smaller (less area) so it can't cool-off any faster (true term would be dissipate large amount of energy over same period of time) , so it's indeed causing more heat transferred to the pads/calipers. So roundagon seems a winner for hydraulics.

    I warned that I'm bored
    LOL. Now you're just arguing for argument's sake. A cool rotor is always a good thing. Even if a large portion of heat is going into the pads, a cooler rotor can keep pad temps under control.

    The cooler rotor does not mean it's transferring more heat into the pads. It can mean it's cooling more during it's rotation where it's not between the pads which is what I think is happening. It is an interesting point you bring up though.

    Of course the mechanicals can suffer from pad fade just as easily as hydros. It may be a little harder to boil the fluid though.

    My original theory was that the roundagons with their extra mass would take longer to heat up and I figured heat dissipation between the two would be a wash. It looks like the additional surface area with the cutouts in the cleansweep do make a difference.

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    OP, why don't you swap the rotors and repeat the test - and then come back with the results?
    Honestly... ahh I give up

  52. #52
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    Hydros have fluid that heat can be transferred into. In theory, a well designed hydro brake should resist fade better than a mechanical.

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    Quote Originally Posted by XSL_WiLL
    Actually the caliper can apply no more force regardless of whether it is front or rear. But doesn't your statement also make your claim null and void? Given that you are running a smaller rotor in the rear.

    It's simply not a fair comparison when using two different sized rotors on different ends of the bike. With the larger rotor, the pads don't have to bite as hard. This means less pressure needs to be applied to the rotor.

    My proposed experiment was to use one of each rotor in the same size.
    It's not fair which is why I was so surprised that the smaller rotor ran cooler.

    I'm sure you guys will look forward to "Part II" in a few weeks when I have a chance to run teh 203mm cleansweep up front lol.

  54. #54
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    Quote Originally Posted by XSL_WiLL
    Hydros have fluid that heat can be transferred into. In theory, a well designed hydro brake should resist fade better than a mechanical.
    Good point, I've never looked into the inner workings of the mechanical to see the heat path after it soaks the piston. I know that the calipers on mine do get pretty hot so there is some transfer but I'm sure it's less than a comprable hydro.

    Do they make finned calipers for the bike hydros like they make on high end car brakes?

  55. #55
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    Quote Originally Posted by highdelll
    OP, why don't you swap the rotors and repeat the test - and then come back with the results?
    hd...that's pure genius...and you did it one sentence.

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    Quote Originally Posted by TNC
    hd...that's pure genius...and you did it one sentence.
    seems reasonable to me
    Honestly... ahh I give up

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    Quote Originally Posted by highdelll
    seems reasonable to me
    Me too. Unfortunately I don't care that much, to swap the front and rear and then install the new cleansweep.... Unless I run 203mm all around..... kidding.

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    Nevermind
    Last edited by Lbsigman; 04-28-2009 at 11:12 PM.

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    BuickGN if you do swap rotors (front to rear &rear to front) you have to swap calipers .
    or get new brake pads. since the pads as they are now with all that testing are set into the rotors. they are worn together kind of like a lock and key.
    next time

    [QUOTE=spazzy] Might as well sell your bikes, E-riding is much more productive.

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    Instead of swapping rotors and pads/calipers.
    You could redo your experiment this time riding backwards.
    lol

    But just for argument sake weight shift does still factor in.
    Even if you are only braking front or rear on at a time and you're not at the traction limit.
    Because when only braking with the front most of the weight is behind the front axle.
    And when you brake with only the rear most of the weight is in front of the rear axle.
    Still causing the weight to shift to the front. Even though the rear brake is doing all the work
    next time

    [QUOTE=spazzy] Might as well sell your bikes, E-riding is much more productive.

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    Folks still confusing this discussion with front vs. rear.
    What OP is stating is following: You got rotor A and rotor B.
    For individual sample (test run) only 1 rotor was used.
    During run, same mass (rider+ bike) was stopped from same initial speed over same period of time and over the same distance. Hence each run same amount of kinetic energy were dissipated.
    Rotor/brake location is irrelevant since total amount of energy converted into heat/sound/vibration is constant.

    OP run multiple tests to average result and hence reduce the error of measurement (even if it's just tactile measurement As the matter of fact it's a valid test in the silicon industry)

    However like I mentioned this test doesn't qualify "cooler" rotor as better rotor. In this particular case smaller rotor obviously "stores" less thermal energy and hence cools faster. Best rotor would have high thermal capacity but would show attributes of accelerated heat dissipation (Hope vented rotor for example, or latest Magura rotor that uses spider as fan to accelerate the air flow around rotor).
    I used to run tubes like you are, but then I got thorn in my wheel.

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    A cool rotor is always a good thing.
    Even in braking systems where the friction material requires a certain temp to work better, or reach its stated friction coefficient? I'm sure most everyone has driven a car or ridden a bike where the brakes grab even harder after getting some heat in them.

  63. #63
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    Quote Originally Posted by WTF-IDK
    BuickGN if you do swap rotors (front to rear &rear to front) you have to swap calipers .
    or get new brake pads. since the pads as they are now with all that testing are set into the rotors. they are worn together kind of like a lock and key.

    Definately. In fact I thought mine were broken in long before this test but I have better braking power now that I've abused them.

    Next time I'll have an IR heat gun. I thought about running the bike on a treadmill for consistency's sake but quite honestly I think better consistency can be had with stopping over a measured distance at a given speed. Reason being as long as I stop somewhat linear over the distance, results should be repeatable but on the treadmill I would be guessing on the lever pressure.

    I will also measure caliper temps to put to rest the cooler rotor might possibly equal a hotter pad.

    I'll start with the bike as is. Then swap the front and rears. Next, install my (on order) 203mm cleansweep on the front and compare to the other two.

    If you guys can come up with any other/better ideas for measuring the different style rotors' effectiveness, let me know. All I'm really interested in is proving once and for all that the cleansweep rejects heat faster than the roundagon and results in a cooler pad/caliper.

    Lastly, should I bother posting results for fear of another flame war?

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    Almost forgot, anyone wanting a 203mm roundagon, $5 will take it.

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    Hanging oneself with christmas lights will solve all brake issues.

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    i have a 203 roundagon up front and a 160mm hayes out back.. the front gets hotter because its a front brake.. same reason cars use bigger rotors up front.

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    Quote Originally Posted by Stalk
    Folks still confusing this discussion with front vs. rear.
    What OP is stating is following: You got rotor A and rotor B.
    For individual sample (test run) only 1 rotor was used.
    During run, same mass (rider+ bike) was stopped from same initial speed over same period of time and over the same distance. Hence each run same amount of kinetic energy were dissipated.
    Rotor/brake location is irrelevant since total amount of energy converted into heat/sound/vibration is constant.
    No the location is not irrelevant. The deceleration pattern is very important in determining which will end up cooler. By virtue that the front can take more force leads to more confidence in them and thus they may be used later into turns and the like. It doesn't help that the force applicator isn't the same (your left and right hand dexterity and strength are very different).

    Quote Originally Posted by stalk
    However like I mentioned this test doesn't qualify "cooler" rotor as better rotor. In this particular case smaller rotor obviously "stores" less thermal energy and hence cools faster.
    What his hand measures isn't energy, it's average random kinetic energy known to mortals as temperature. Like all averages, temperature is a total (energy) divided and the # of contributing elements (metal atom represented by their mass). Therefore a smaller rotor cools faster because it is at a higher temperature (energy/mass) to start with. Both rotor's temperatures will asymptote as they approach environment temperature but if all else is equal, the smaller rotor will be ever slightly hotter.

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    Anyone into calc, by the way?

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    Quote Originally Posted by tomsmoto
    i have a 203 roundagon up front and a 160mm hayes out back.. the front gets hotter because its a front brake.. same reason cars use bigger rotors up front.
    Did you read past the first post?

  70. #70
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    Quote Originally Posted by BuickGN
    Did you read past the first post?
    Did you read my last post?

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    Quote Originally Posted by vk45de
    No the location is not irrelevant. The deceleration pattern is very important in determining which will end up cooler. By virtue that the front can take more force leads to more confidence in them and thus they may be used later into turns and the like. It doesn't help that the force applicator isn't the same (your left and right hand dexterity and strength are very different).
    No one will argue that the front has the potential to run hotter and likely will in real life. Location is relevent since the front has more traction due to weight transfer and can be used harder. However, in my test I was using each brake far below the traction limits of the rear tire. The front tire's superior traction did not play a role therfore the location was irrelevent for this test.


    Quote Originally Posted by vk45de
    What his hand measures isn't energy, it's average random kinetic energy known to mortals as temperature. Like all averages, temperature is a total (energy) divided and the # of contributing elements (metal atom represented by their mass). Therefore a smaller rotor cools faster because it is at a higher temperature (energy/mass) to start with. Both rotor's temperatures will asymptote as they approach environment temperature but if all else is equal, the smaller rotor will be ever slightly hotter.
    Agreed.

  72. #72
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    However, in my test I was using each brake far below the traction limits of the rear tire.
    How were you able to evaluate that? What is the percentage of traction that is considered "max traction"?

    Also, is it possible the tire's angular velocity (coverted to linear) would not match the ground's velocity with respect to the bike?

  73. #73
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    Quote Originally Posted by BuickGN
    However, in my test I was using each brake far below the traction limits of the rear tire. The front tire's superior traction did not play a role therfore the location was irrelevent for this test.
    The traction limit of the rear is quite low especially on dirt, far below would be hardly braking at all.
    Quote Originally Posted by Jerk_Chicken
    Anyone into calc, by the way?
    Into calc? I think you're gonna get negatives all around. What kinda calc calculations have you got in mind?

  74. #74
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    Quote Originally Posted by Jerk_Chicken
    Anyone into calc, by the way?
    Psshh, what we need is good physics. Calc is just the tool

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    [QUOTE=vk45de]The traction limit of the rear is quite low especially on dirt, far below would be hardly braking at all.

    QUOTE]

    Are we nit picking? I chose a distance and speed that would not exceed the rear's traction limit. Far below may have been an exaggeration but you get the point.

  76. #76
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    I'm into talc


    I've said too much
    Honestly... ahh I give up

  77. #77
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    Quote Originally Posted by Jerk_Chicken
    Anyone into calc, by the way?
    Yup. Physics too. I'm a Geologist by study though so it's debatable how good I am at either though. I'm better with rocks and dirt ya know.

    Quote Originally Posted by vk45de
    Folks still confusing this discussion with front vs. rear.
    It doesn't matter because the test is flawed in the first place. Judging by your screen name it would appear the car guys are flocking together. I used to drool over running an RB25DET in my old '73 240Z. The VK45DE is a racing only motor right? I can't think of a production rig that has that, but I've been out of Nissans for a while.
    Bike good, work bad.

  78. #78
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    Quote Originally Posted by Clutchman83
    Yup. Physics too. I'm a Geologist by study though so it's debatable how good I am at either though. I'm better with rocks and dirt ya know.



    It doesn't matter because the test is flawed in the first place. Judging by your screen name it would appear the car guys are flocking together. I used to drool over running an RB25DET in my old '73 240Z. The VK45DE is a racing only motor right? I can't think of a production rig that has that, but I've been out of Nissans for a while.
    Me too. Just like car guys flocking together!

    Now, what would be your take on introducing an idea of the linear velocity (converted from angular) being slower than the bike (with respect to the ground) speed?

  79. #79
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    Quote Originally Posted by BuickGN
    Are we nit picking? I chose a distance and speed that would not exceed the rear's traction limit. Far below may have been an exaggeration but you get the point.
    Low braking force means not much heat generated meaning you have to go a long way to heat it up to a detectable temperature. This in turns means that there is a lot of time for your brake force to change which alters the uniformality of the test. So call it nitpick, but when you have so much points that I can nitpick, your results become questionable.

    Quote Originally Posted by Clutchman83
    The VK45DE is a racing only motor right? I can't think of a production rig that has that, but I've been out of Nissans for a while.
    No, it is the current V8 in the Fuga and was in the FX45. BTW, it's an engine b/c it runs on petroleum.
    http://en.wikipedia.org/wiki/Nissan_VK_engine

  80. #80
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    Quote Originally Posted by highdelll
    I'm into talc


    I've said too much

  81. #81
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    Quote Originally Posted by vk45de
    Low braking force means not much heat generated meaning you have to go a long way to heat it up to a detectable temperature. This in turns means that there is a lot of time for your brake force to change which alters the uniformality of the test. So call it nitpick, but when you have so much points that I can nitpick, your results become questionable.
    No kidding but I did the tests multiple times and every time there was a pretty good difference in temp. I could understand if I did it once that maybe I stopped harder towards the beginning and backed off toward the end or vice versa. What are the odds I did it 10+ times in a row....

    You guys make it sound like I waited until the last second to hit the front brake and locked the rear so it produced no heat. Give me some credit here.

  82. #82
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    I think its time to push this up the ladder to the MYTHBUSTERS.

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    Quote Originally Posted by frdfandc
    I think its time to push this up the ladder to the MYTHBUSTERS.
    Not a bad idea...

  84. #84
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    Quote Originally Posted by Jerk_Chicken
    Now, what would be your take on introducing an idea of the linear velocity (converted from angular) being slower than the bike (with respect to the ground) speed?
    My physics is so rusty I'm gonna have to think about that for a minute!

    Quote Originally Posted by vk45de
    No, it is the current V8 in the Fuga and was in the FX45. BTW, it's an engine b/c it runs on petroleum.
    http://en.wikipedia.org/wiki/Nissan_VK_engine
    Engine and motor are interchangeable when discussing vehicles that employ petroleum as a fuel. Motor is a word that describes a device that has one or more moving parts to convert energy to motion. Engine requires more than one moving part and excludes electricity as a fuel.

    Not looking for a pissing contest but if you want to go there...
    Bike good, work bad.

  85. #85
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    Quote Originally Posted by Clutchman83
    ...Not looking for a pissing contest but if you want to go there...
    The audience chants "PISSING CONTEST!! - PISSING CONTEST!! - PISSING CONTEST!! - PISSING CONTEST!!"
    Honestly... ahh I give up

  86. #86
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    Quote Originally Posted by BuickGN
    You guys make it sound like I waited until the last second to hit the front brake and locked the rear so it produced no heat. Give me some credit here.
    Not at all. It's just when you're using such a low braking force, so that a little force variance becomes bigger. Remember that the difference in rotor surface area is small too.

  87. #87
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    Quote Originally Posted by vk45de
    Not at all. It's just when you're using such a low braking force, so that a little force variance becomes bigger. Remember that the difference in rotor surface area is small too.
    Point taken.

    I know this is far from scientific, just something I did for fun on the side of the road spur of the moment. It was because of your point that I quoted that I did it so many times to try and get different results. I'll try and think of a different method to elimitate that variable when my new rotor arrives.

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    Sorry guys, but BuickGN is right. While the test isn't perfectly scientific, it's decent. If you slow the bike down fairly evenly over a controlled distance several times with each brake (allowing the rotor to cool between runs and without skidding any tires) and average the results, it will give decent numbers. Physics says that if you stop from 10mph in 50 feet, regardless of which brake does the work, the same amount of energy is being converted to heat.

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    Quote Originally Posted by comptiger5000
    Sorry guys, but BuickGN is right. While the test isn't perfectly scientific, it's decent. If you slow the bike down fairly evenly over a controlled distance several times with each brake (allowing the rotor to cool between runs and without skidding any tires) and average the results, it will give decent numbers. Physics says that if you stop from 10mph in 50 feet, regardless of which brake does the work, the same amount of energy is being converted to heat.
    The bolded part is right. The outlets for the energy don't necessarily have to be in what is being isolated here.

    There's a lot more to this story that's being overlooked.

  90. #90
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    I'll give you $5 for that 203mm rotor if it's barely used.
    "It looks flexy"

  91. #91
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    Quote Originally Posted by vk45de

    No, it is the current V8 in the Fuga and was in the FX45. BTW, it's an engine b/c it runs on petroleum.
    Motor's can produce torque at zero RPM, engines cannot.
    Nobody cares...........

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