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Thread: 9 inch rotors

  1. #1
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    9 inch rotors

    I was wondering if anyone has any experience with trying out 9 inch rotors?

    I'm starting a project 29er DH bike and thought it might be of some advantage.

    I've been running an 8 inch on my long travel fat bike with 29inch dia tires and older Saint brakes and it's working ok but at times having a larger rotor on the front might be a good thing. I have a 6 inch on the rear and my right finger gets sore having to pull so hard on the rear brake. I'm switching out to a 7 inch which should be ok for that bike but with even bigger tires on the full 29er and gravity oriented I'm thinking 8 on the rear and 9 on the front might be the ticket.

    There isn't much available and I need an adapter for a Dorado fork that I haven't been able to find so far and would want aluminum centers to save a bit of weight. Hope is probably the one to use although Formula did make one too.
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  2. #2
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    I used a 9" front and 8" rear in early fiddling with 29" DH.

    Truth is, had I started with a better brake I'd never have needed to go so big on the rotors. These days I use 8/7 with a simple 2-piston Hayes Prime brake.

    In short, if I were you, I'd borrow a few different brakes from friends before following through on the 9"er.

    Best of luck,

    MC

  3. #3
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    +1 If 8in isn't big enough it's not the rotor size you need to change. Have you seen the price on 9in rotors? Crazy
    www.quinnphoto.smugmug.com
    07 S-Works Enduro SL - Sold
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  4. #4
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    My 2011 Saints on one bike are a lot better than the first generation Saints on my fat bike and I've read some mechanical test results that show Saints are the strongest brakes on the market, plus modulation seems good and they can be had for pretty cheap.

    Btw ChainReaction has 9" and 8" Hope 6-pot aluminum center discs for $59.47 each, so not really that much money. Might still have to fab a bracket.

    Mike, How did you arrive at the Primes over the Saints? Lighter? Cheaper? More stopping power? 2 vs 4 piston?

  5. #5
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    The max recommended rotor diameter on every fork produced now is probably 8"
    Ocala Mountain Bike Association - www.omba.org

  6. #6
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    Quote Originally Posted by modifier View Post
    Mike, How did you arrive at the Primes over the Saints? Lighter? Cheaper? More stopping power? 2 vs 4 piston?
    I rode 'em both locally--that was enough.

    Saints had good power but little modulation--they seemed to be either on, or off, with no sweet spot in between.

    Primes had at least as much power, but a huge modulative sweet spot. Sold.

    Keep in mind that the friction material (aka pad compound) is at least as important as what's pushing the pads together. Starting with a fresh set of pads and rotors can be a shockingly effective solution. If your existing setup was properly burned in (or not, as the case usually is) by someone else, somewhere else, they may not be ideal for where you live and ride. There are SO many factors that go into what works, where. Relative humidity, amount of organic material in the soil, and soil moisture content play a BIG role in braking feel, power, and consistency. As well as what friction material is ideal.

    Try one new 8" rotor and a new set of pads. Give them a proper burnish after a clean install. If that seems to be a good improvement, then you're halfway there. If not, you're only out half the $$.

    Good luck,

    MC

  7. #7
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    Here was the front on my VP Free. Hope Mono 6ti with adapter so needed a 9in rotor. Used the Formula. This setup had so much power it was downright scary. Too much IMO.

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  8. #8
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    go all in and run dual 8''ers.

  9. #9
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    Good job!

    Quote Originally Posted by b-kul View Post
    go all in and run dual 8''ers.
    I would run 2 calipers on a 140mm rotor!

  10. #10
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    Like this?
    Attached Thumbnails Attached Thumbnails 9 inch rotors-36er9.jpg  


  11. #11
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    Quote Originally Posted by bquinn View Post
    Here was the front on my VP Free. Hope Mono 6ti with adapter so needed a 9in rotor. Used the Formula. This setup had so much power it was downright scary. Too much IMO.
    Looks cool and perhaps yes, too much power.

    I had an 8" rotor on a XC bike with a BB7 because it was what came with the brake at the sale price and the 8 was overkill, so I eventually switched out to a 7 inch and modulation was improved but still with plenty of stopping power.

    That is the only setup where modulation was ever a problem however and I find the Saints to have and easy touch with organic pads. Maybe that's just because I haven't tried any other current state of the art brakes.
    Last edited by modifier; 12-14-2011 at 10:56 AM.

  12. #12
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    Quote Originally Posted by modifier View Post
    Like this?
    yes

  13. #13
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    I will run a 9" Formula rotor front next season. Just need a little more braking going hot into a few turns.

  14. #14
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    Quote Originally Posted by sikocycles View Post
    I will run a 9" Formula rotor front next season. Just need a little more braking going hot into a few turns.
    Let me know how it works out.

    You happy with the Formula brakes?

    What are you doing for a 9" adapter for the Dorado?

    So you liking you PBJ? Anything custom about it other than the paint?

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