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  1. #1
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    Front Disc Brake Size poll for 29ers... 160mm or 185mm?

    Previous owner built mine with 160mm front and rear. I fade the front seemingly every ride on single track downhill. At first I though I'd be ok. I'm only 160 lbs w/ no gear and figured my downhill speed wouldn't be that fast on a SS, sure enough... sigh I think I need a 185. Modulation should be a bit better too right?

  2. #2
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    Tell you the truth I have never had any issues with 160mm on SS or FS geared and I weigh 205lbs. Since you mentioned it had a previous owner, you might want to check your brake pads.

  3. #3
    RLK
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    I second the recommendation to check the pads. My husband is heavier than the OP and uses 160 mm rotors all around without any trouble.

    What brakes are you using?

  4. #4
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    Pads are all good. I've even deglazed them and rebedded them. no noise and excellent performance in all conditions and situations except for rockin' gravity sections towards the bottom. they recover in seconds at the bottom so maybe I'm just being anal... These are just normal SW Pa trails. Avid Juicy 5's.

  5. #5
    Fall guy
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    My felt 9 came with 160mm rotors and Juicy 5's. They stopped me just fine, (150lbs dripping wet) but I prefer they weren't enough bite for my taste.

    I put a 185 on there and I like the feel a lot better. But I don't have many long descents to tell you if there's any problem fading.

  6. #6
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    180 lbs and I run 185mm up front. This is a great setup for me with long descents. 160mm stopped me OK but the bite is much better on 185mm

  7. #7
    meatier showers
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    203mm rotors on the front of all my bikes. I'm 200#. Lots of extended downhill singletrack around here. The larger (largest) rotor allows me to use less hand pressure at the lever plus they cool better so there's no fade.

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  8. #8
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    Strongly consider changing brake pads to factory pads. I'm 140lbs running Formula (The One) 180 front 160 rear. The pads are about $20/pair therefore I cheaped out and bought pads on ebay 5 pairs for $20. Didn't notice any problems until a 7 mile steep downhill descent. Fade after 300 yards and very difficult to stop using all my finger to grab brake levers. I had a very slow descent because I had to stop and let the rotors cool every 300-400 yards. Replaced cheap pads with factory pads. I rode the same mountain 2 weeks later braking with one finger and no fade.

  9. #9
    Schipperkes are cool.
    Reputation: banks's Avatar
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    Shimano 200mm Front
    Magura 180mm Front
    Avid BB7 160 Galfer Gothic rotor
    Quote Originally Posted by mikesee
    Better suited to non-aggressive 125# gals named Russell.

  10. #10
    Got a suspension fork
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    185 fronts on the BB7's and 160 fronts on the hydraulics.
    ONE SHOX, ONE GEAR, LOTS of FUN! www.TrailFu.com My Rides

  11. #11
    openwound
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    185mm on the front for me on all of my bikes except the DH rig, and that gets a 200/205. As Sparticus mentioned, the larger rotor means less effort at the lever. I could get by with 160's but why..? Mine go to 11.

  12. #12
    meatier showers
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    Quote Originally Posted by crvt427
    Strongly consider changing brake pads to factory pads. I'm 140lbs running Formula (The One) 180 front 160 rear. The pads are about $20/pair therefore I cheaped out and bought pads on ebay 5 pairs for $20. Didn't notice any problems until a 7 mile steep downhill descent. Fade after 300 yards and very difficult to stop using all my finger to grab brake levers. I had a very slow descent because I had to stop and let the rotors cool every 300-400 yards. Replaced cheap pads with factory pads. I rode the same mountain 2 weeks later braking with one finger and no fade.
    IME sintered metallic pads are the only way to go. Organic pads blow. Especially in wet conditions.

    --sParty
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    Quote Originally Posted by riverrat
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  13. #13
    WNC Native
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    Prefer 185's up front at 220lbs geared!
    "I ride to clear my head, my head is clearer when I'm riding SS. Therefore, I choose to ride SS."~ Fullrange Drew

  14. #14
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    I too have the 185 up front....I really feel like 29er bikes should come stock with 185's simply because there is so much more rotational mass to stop with the larger wheel....it only makes sense IMO!!

  15. #15
    meatier showers
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    Quote Originally Posted by bmxking45
    I too have the 185 up front....I really feel like 29er bikes should come stock with 185's simply because there is so much more rotational mass to stop with the larger wheel....it only makes sense IMO!!
    Actually it's more than just increased rotational mass. It's increased leverage. Since the distance from hub to outside of tire (radius) is longer, the leverage acting against the brake is greater. It would take a more powerful brake to achieve the same amount of stopping force with a 29" wheel even if that wheel somehow weighed the same as a 26" wheel.

    This is why, if you could outfit a skateboard wheel with disc brakes, a 2" rotor would offer adequate stopping power.

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    Quote Originally Posted by riverrat
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  16. #16
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    Quote Originally Posted by Sparticus
    IME sintered metallic pads are the only way to go. Organic pads blow. Especially in wet conditions.

    --sParty
    the pads that came on my bb7's are friggin incredible. I have 4 long hard years on them and they're still going. i think they are sintered metallic.
    I have been considering changing the brakes out for something with a little more modulation though. Now that i ride my cross bike 90% of the time, i nearly kill myself everytime i grab a fistfull of lever on my mtb. I can hardly keep from locking them up for the first 30 minutes. The only other option is throwing a set of disks on my cross bike, but i really think the cantis are part of the fun.

  17. #17
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    I got a 203 on my Monocog! Hell yeah!

    but I have no idea why

  18. #18
    psycho cyclo addict
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    I'm 190# and have 185's up front and 160's in the rear on both of my hydro braked 3x9's (Avid Juicy 7 and Avid Elixr-CR). A few places I ride have long descents where if you aren't braking consistently toward the bottom (before turns), it could be REALLY UGLY. I've thought about 160 mm up front lately but may leave things well enough alone.

  19. #19
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    Quote Originally Posted by nmanchin
    Pads are all good. I've even deglazed them and rebedded them. no noise and excellent performance in all conditions and situations except for rockin' gravity sections towards the bottom. they recover in seconds at the bottom so maybe I'm just being anal... These are just normal SW Pa trails. Avid Juicy 5's.
    This doesn't sound right to me. On the rare occasion my brakes fade, the whole fluid/disc/caliper system is so hot it takes quite a while to cool.

  20. #20
    meatier showers
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    Quote Originally Posted by edubfromktown
    I'm 190# and have 185's up front and 160's in the rear on both of my hydro braked 3x9's (Avid Juicy 7 and Avid Elixr-CR). A few places I ride have long descents where if you aren't braking consistently toward the bottom (before turns), it could be REALLY UGLY. I've thought about 160 mm up front lately but may leave things well enough alone.
    Not sure exactly what you're saying here. Sounds like you're saying that good brakes are necessary where you ride and you wouldn't want fade to be a factor, but you're considering moving from a larger rotor (185mm) to a smaller rotor (160mm) on the front. Is this right? If so, why would you consider changing?

    Maybe I'm missing something (probably).

    --sParty
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    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

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