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  1. #1
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    Comments on 140mm rotor

    Hello everyone,

    I would like to ask you guys, if you prefer a 140mm rotor as your rear brake. Would I benefit during training and racing or would I be in trouble while bombing downhill?

    Thanks,

    Doc
    [SIZE="4"]07 IBEX Asta Expert X9 "La Bonita"
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  2. #2
    AZ
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    For a xc ride I prefer 140 mm . If I plan on alot of d.h. I want as much brake as I can get .So , not a real answer , horses for courses .

  3. #3
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    Depends on your weight, riding style, and riding location. 140's are fine as long as you know how to properly break, and are not morbidly obese.

  4. #4
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    FIne

    I've been running one for 3 years on my 26" bikes. I have used the Hope Floating rotor, XTR CL, and Avid cleansweep all with good luck. I can lock up the wheel long before I feel like I'm running out of power, and my brakes have never heated enough to notice. I live in the land of big descents (I have a 3,000 footer near my house)

    The weight savings aren't enough, that I would go out of my way to do it...but it's what I have and it works.
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  5. #5
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    Quote Originally Posted by ::DYSLEXIC::
    Depends on your weight, riding style, and riding location. 140's are fine as long as you know how to properly break, and are not morbidly obese.
    I weigh 180lbs (used to be 165 a year ago, so I am trying to get back to this weight), and I would say that I have pretty good skills, I always keep my line, and I just rip them trails hehe, definitely love the sport. Have won a few races. Oh, btw I ride on the Sonoran Desert near the Tucson area. My descents are not that crazy, pretty fast and technical though with rock gardens, sand, and lots of cactii
    [SIZE="4"]07 IBEX Asta Expert X9 "La Bonita"
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  6. #6
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    Quote Originally Posted by used2Bhard
    I've been running one for 3 years on my 26" bikes. I have used the Hope Floating rotor, XTR CL, and Avid cleansweep all with good luck. I can lock up the wheel long before I feel like I'm running out of power, and my brakes have never heated enough to notice. I live in the land of big descents (I have a 3,000 footer near my house)

    The weight savings aren't enough, that I would go out of my way to do it...but it's what I have and it works.
    Yeah , I am doing some research trying to pick the right set of brakes. My juicies are ready to kick the bucket after 3 years of great service, and I definitely want something much lighter and not as noisy haha...I think I will shoot for the Hope Mini X2 pro 160fr/140back. I have been asking around about making this change because I wish to know what to expect from such setup.
    [SIZE="4"]07 IBEX Asta Expert X9 "La Bonita"
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  7. #7
    LMN
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    I have used 4inch rotors for a while.

    On a hardtail I prefer a 4-inch rotor. No suspension, low grip tires, and XC geometry mean that there is very little rear wheel grip under braking. Reducing brake power helps with modulation. On a bigger bike with more rear wheel grip I like a 6 inch rotor.

    With 4-inch rotors I have never had a problem with brake fade. My experience is the front brake over heats long before the rear one does.

  8. #8
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    Technically a 140mm rotor would be a 5.5" rotor, a 125mm rotor would be 5" and you'd have to get all the way down to 100mm for a 4" rotor. I'm just sayin'....

    I rode a hardtail with a 140mm rear XTR last summer and found that it felt under braked, it was hard to get enough modulation between just dragging the brake and getting it close to lock up, but I'm about 195 pounds. I find a 160mm rear provides enough range of modulation without getting a hand cramp or bending a brake lever. YMMV
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  9. #9
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    I have been using a 140 rotor for over a year on my 4" bike and I love it. It will instantly lock up if I want it to, but it provides much more modulation than the 160 it replaced. I have not been afraid of it being inadequate on any ride I've been on yet. I weigh a little less than 160 though, I would imagine the heavier you get, the less effective the rotor would be.

  10. #10
    LMN
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    Quote Originally Posted by rockyuphill
    Technically a 140mm rotor would be a 5.5" rotor, a 125mm rotor would be 5" and you'd have to get all the way down to 100mm for a 4" rotor. I'm just sayin'....

    Details, details, details...

  11. #11
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    Go for it. A year ago I was 215 and riding a Cannondale HT. I was using a 140mm rear rotor and never experienced any desire to go bigger. Like was mentioned before, you will still be able to lock it up if need be, and with good brakes you won't over heat much.

  12. #12
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    I'm a Virgo, it goes with the territory.
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  13. #13
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    I ran a 140 briefly, but went bigger, it was definitely a difference between my 160.
    The weight advantage is not that big, unless you are counting every gram stick with the 160.

  14. #14
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    What about a 140 with a 29er ht? Mainly flat, some short hills. I am pretty good at controlling my brakes and only in panic situations do i ever lock'em up. I'm about 175lbs, trying to be 165.
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  15. #15
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    140mm works everywhere but long steep downhills. I've found that even my 160s have always lost a bit of performance to heat as the grade gets to be around 18%-22% (steep!) for over a quarter mile. If I didn't ride these particular trails occasionally, I'd run a 140mm. I weigh around 160 lb.

    I find that I actually use the rear brake more on the long steep techy downhills as using the mainly the front to constantly check speed makes the bike unstable. The front and rear generally fade about the same time. My general rule of thumb is that if I'm anearobic in my 22-34 gear to climb it and struggle for traction, I'll at least need a 160mm rotor to descend it.

    I have NEVER ridden a race course that requires anything bigger than a 140mm. And if the grades are not steep AND long enough to make heatsoak an issue on the trails you ride, 140mm is all you need.
    Last edited by brentos; 11-06-2009 at 07:54 AM.
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  16. #16
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    I bought a 140 to replace my 160 but after weighing the 2 (including adaptor) the difference was only grams, so I didn't bother.
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  17. #17
    LMN
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    Quote Originally Posted by JoshS
    What about a 140 with a 29er ht? Mainly flat, some short hills. I am pretty good at controlling my brakes and only in panic situations do i ever lock'em up. I'm about 175lbs, trying to be 165.
    Give it a try. Most of people I know on 29ers find they have to run a bit larger rotor. But around here the descents are quite long and brake heat can be a factor.

  18. #18
    LMN
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    Quote Originally Posted by rockyuphill
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  19. #19
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    Quote Originally Posted by LMN
    Give it a try. Most of people I know on 29ers find they have to run a bit larger rotor. But around here the descents are quite long and brake heat can be a factor.
    we Just don't really have any discents where I live and those that are are short enough for only a speed check at the bottom. i have 2 160's right now, and someone wants one of my 160's to finish their build. i can either keep a 160 out back and get a 185 up front or run a 140 out back and a 160 front. normally i run a 180/160 for panic situations, since most trails i ride are 2-way, but it's usually the race tires that truly limit braking.
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