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  1. #1
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    Cool-blue Rhythm 160 vs. 203mm rotors?

    I have a 29'er that came stock with avid BB5 160mm disc brakes. They're starting to suck, so I've decided to upgrade to BB7's for now to have a better system without moving up to hydraulic yet. I'm a big guy (6'3" 240) so I want all the stopping power I can get, so I'm considering the 203mm rotors. Is there any disadvantage to going up to the larger rotor size? I realized I'm a little more likely to smack one of them on a rock, but other than that, do they bend easier under braking heat or anything I should consider before buying? Thanks!

    MTBiker483

  2. #2
    I am a pathetic rider...
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    just make sure that your frame and fork can handle the extra loads that a 203mm rotor can dish out, and once you have those established, you will be fine.
    Save the Earth, Ride a Cyclist

  3. #3
    just along for the ride
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    Get some semi metallic pads before you jump the shark to larger rotors,resin pads are not made for clydes, have fun!

  4. #4
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    Quote Originally Posted by b4 stealth
    just make sure that your frame and fork can handle the extra loads that a 203mm rotor can dish out, and once you have those established, you will be fine.
    Ah good point I hadn't thought of that... If you (or anyone who reads this?) could help me figure that out - mucho appreciation!

    It's a 2008 Specialized Rockhopper Comp Disc 29er... 203mm rotors safe for me? (6'3" 240lbs)

    Thanks!

    MTBiker483

  5. #5
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    I don't think you will need 203mm rotors. I'm 6'2" 200 lbs and I run the 185 rotors and have more than enough braking power.

  6. #6
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    Does moving up in rotor size have any influence on modulation?

  7. #7
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    maybe just try a 200 on the front, then if you decide it is unnecessary you can swap back to the 160 from your bb5, or 180mm all around would be nice too.

  8. #8
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    i'm 230lbs and use avid sintered pads. I have bikes running bb7s and J5's, and a couple extra rotors lying around.
    160/160 is scary on half my trails
    185/160 is good on 90% of my trails
    203/160 never fades
    203/185 tends to lock up the rear wheel kinda easily.

    you can run up to a 210mm rotor on the tora.

    The larger size doesn't affect modulation, but the increase in power can feel like worse modulation. That's why i prefer the 160 in the back, and wouldn't mind something even larger than 203 in the front. I've never hit one with a rock, but if my skewer is loose it is more obvious with the larger rotor. They're ever so slightly thicker. i never really have any trouble with it being out of true, the 203 is now on my bike with the J5's, and i never ever have to touch those brakes.
    .

  9. #9
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    "you can run up to a 210mm rotor on the tora."

    STOP! Yes you can run up to a 210mm rotor on the Tora. However the 08 Rockhopper Comp Disc 29er is speced with a Dart 3! The Dart 3 is only rated to a 160mm rotor. Anything larger IS NOT RECOMMENDED! If you are using the stock fork don't put a 203 rotor on it! You could probably get away with a 185mm rotor depending on how you ride and the terrain that you ride. But even that is not recommended so do so at your own risk. The problem with going to a bigger rotor on fork that is not rated for it is the increased lever moment that the larger rotor has, i.e. more power. This imparts a twisting force to the fork when the brake is applied. The larger the rotor the harder it twists due to the greater braking force. This torque can cause QR's to come loose, break axels, cause stanchion tubes to come loose from the crown over time, etc. I had an old Manitou Black 100mm fork that was rated for 185mm rotors. However when used with one the twist that it imparted to the fork actually caused the bike to torque steerer when the brake was applied firmly. When holding the bike on a straight line and applying the brake it would actually cause the bike to vear to the left. Not dramatically but enough to be noticeable, and the twisting of the fork was visible as well. The fork got retired and relegated to a commuter bike with a 160mm rotor set up.

    So I'd deffinately steer clear of mounting a larger rotor than a 160 on that fork, esspecially at your weight. I know the feeling, I'm 225lbs geared myself and much prefer a 185mm front/160mm rear set up for off road. But the combination of our heavier body weight and the lack of ridgidity of some forks make it a risky proposition if the fork is not rated for the larger rotor. And even then it sometimes doesn't work out well as in the case of the Black that I mentioned earlier. Us bigger guys have to be careful.

    Good Dirt
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  10. #10
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    Quote Originally Posted by Squash
    "you can run up to a 210mm rotor on the tora."

    STOP! Yes you can run up to a 210mm rotor on the Tora. However the 08 Rockhopper Comp Disc 29er is speced with a Dart 3! The Dart 3 is only rated to a 160mm rotor. Anything larger IS NOT RECOMMENDED! If you are using the stock fork don't put a 203 rotor on it! You could probably get away with a 185mm rotor depending on how you ride and the terrain that you ride. But even that is not recommended so do so at your own risk. The problem with going to a bigger rotor on fork that is not rated for it is the increased lever moment that the larger rotor has, i.e. more power. This imparts a twisting force to the fork when the brake is applied. The larger the rotor the harder it twists due to the greater braking force. This torque can cause QR's to come loose, break axels, cause stanchion tubes to come loose from the crown over time, etc. I had an old Manitou Black 100mm fork that was rated for 185mm rotors. However when used with one the twist that it imparted to the fork actually caused the bike to torque steerer when the brake was applied firmly. When holding the bike on a straight line and applying the brake it would actually cause the bike to vear to the left. Not dramatically but enough to be noticeable, and the twisting of the fork was visible as well. The fork got retired and relegated to a commuter bike with a 160mm rotor set up.

    So I'd deffinately steer clear of mounting a larger rotor than a 160 on that fork, esspecially at your weight. I know the feeling, I'm 225lbs geared myself and much prefer a 185mm front/160mm rear set up for off road. But the combination of our heavier body weight and the lack of ridgidity of some forks make it a risky proposition if the fork is not rated for the larger rotor. And even then it sometimes doesn't work out well as in the case of the Black that I mentioned earlier. Us bigger guys have to be careful.

    Good Dirt


    specialized website says:

    2008 Rockhopper Comp Disc 29
    "RockShox Tora 318 SL fork, for 29" wheel, 80mm travel, Mag lower, Solo air spring, alloy steerer, 32mm Cro-Mo stanchions, rebound adjust w/ lockout and preload adjust"
    .

  11. #11
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    Quote Originally Posted by scottzg
    specialized website says:

    2008 Rockhopper Comp Disc 29
    "RockShox Tora 318 SL fork, for 29" wheel, 80mm travel, Mag lower, Solo air spring, alloy steerer, 32mm Cro-Mo stanchions, rebound adjust w/ lockout and preload adjust"
    To confirm this -- yes, it does have the Tora 318 SL. It's a 2008...I think the Dart may be on the 2009 model.

  12. #12
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    Quote Originally Posted by scottzg
    i'm 230lbs and use avid sintered pads. I have bikes running bb7s and J5's, and a couple extra rotors lying around.
    160/160 is scary on half my trails
    185/160 is good on 90% of my trails
    203/160 never fades
    203/185 tends to lock up the rear wheel kinda easily.
    im 30lbs lighter, and still 100% agree.. 203 is never too much!

    i just start to fade the rear after a a few miles of continuous downhill.. but thats kinda to be expected, and it never fades enough to cause concern.

    alligator rotors are under 20 bucks at pricepoint.. good cheap way to jump up to 203's.

  13. #13
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    Quote Originally Posted by MTBiker483
    To confirm this -- yes, it does have the Tora 318 SL. It's a 2008...I think the Dart may be on the 2009 model.
    My Bad I was indeed looking at the 09 spec! Since it is indeed the Tora for 08 I retract my previous post!

    The Tora will take a 203, actually up to 210mm, though I don't know where you'd find one that size.

    Anyway, my oppologies, and go nuts with it. At your weight and considering it's a 29er, the 203 would be the way to go for sure.

    But as a side note: Yes I have seen incorrect information posted on Bikepedia. Not often but occasioanlly.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  14. #14
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    I have a 2009 Rockhopper with the Dart 3 and have done the BB5 160mm to BB7 203 swap, even with my light weight (130lbs before my pack) the fork is like a limp noodle. I have already started to save for an upgraded fork. The braking power is amazing but if i were to be looking to make the upgrade again i would go with a 185mm rotor on a mid level hydraulic. I just got my first set of hydraulic brakes and love them to death ( juicy 3s on a bad boy) so i would say just bite the bullet and go hydraulic.

    Not to jack your thread but what would be a good fork to upgrade to?

  15. #15
    willtsmith_nwi
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    185/160 ...

    I'm 280# and this is plenty. I only use one finger to brake. I cannot easily lock the front put you really should't do this anyway.

    The back is still easy to lock up. Though, I don't want to spend the $$$ to convert 3 wheels to 140mm rotors.

  16. #16
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    "Not to jack your thread but what would be a good fork to upgrade to?"

    Depends on what you are willing to spend. But the Rock Shox Reba 29er and the Fox F29er are two of the best. The Fox carries a pretty hefty price tag though. And of course you already know that the Tora is available in a 29er version.

    Good Dirt
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  17. #17
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    I'm 6'4", 240 and run 185/160 BB7s with stock pads. VERY steep hills here (St. Thomas), and have no issues or lack of braking power with one finger. You can go bigger on the rotor but, as you mentioned in the OP, your risk of damage increases the bigger you go. Just my $.02...

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