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  1. #1
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    Problems with 8" rotor and standard quick release hubs?

    I have an '04 Marz MX Pro (120mm) and have been running quick release hubs with my XT disc brakes. I am swapping up to an 8 inch rotor in front. Will I have any problems with this? I know Fox does not like when people do this, but I have not hear from Marz... I ride mostly cross country with some (quite a few) steep, rocky descents. I don't do drops or jumps. The main reason I like the idea of 8 inchers is that I do quite a few descents that are about 10 miles, and fairly steep for a good portion of it. The rotors get HOT, and I have noticed a little bit of fade. Thanks for any insight.

  2. #2
    DSR
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    I had an 8" Hayes rotor on an older model (2001) Marzo Z1 with a standard QR. Heard the same thing about 8" rotors and std QR, but never had any real problems other than just having trouble keeping them rub-free for more than a ride or two. But I had that problem both front and back. I'm now just switching over to a QR20 fork and Avid 8" discs just to mix things up and because I like the concept of Avid's adjustability. Not a real definitive answer, but at least one relative problem-free user of Marzo QR and 8" brakes. Others probably have more insight. S

  3. #3
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    Quote Originally Posted by CalPolyClimber
    I have an '04 Marz MX Pro (120mm) and have been running quick release hubs with my XT disc brakes. I am swapping up to an 8 inch rotor in front. Will I have any problems with this? I know Fox does not like when people do this, but I have not hear from Marz... I ride mostly cross country with some (quite a few) steep, rocky descents. I don't do drops or jumps. The main reason I like the idea of 8 inchers is that I do quite a few descents that are about 10 miles, and fairly steep for a good portion of it. The rotors get HOT, and I have noticed a little bit of fade. Thanks for any insight.
    I recently purchased some avids from cambria. I went in myself and the guy working said that the 183's are the biggest I could use. There must be some type of problem since 203 cost more and you would think thats what they would want to sell.
    P.S. go to poly slo? When and where do you ride? Always lookin for a good riding partner.

  4. #4
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    Yeah, I go to Poly. I ride mostly up on the grade. Morning Glory, Pick and Shovel, Shooters, all that. I usually start down at Poly and head up the canyon and climb Shooters, then ride down morning glory or pick and shovel. I also ride Madonna alot when I don't have much time. As far as when, its pretty much whenever. I am out of class by 1 every day, and I don't have a job right now, so I ride about 3 or 4 days a week. Are you involved with the Wheelmen club? I've been meaning to check that out.

  5. #5
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    Quote Originally Posted by CalPolyClimber
    The rotors get HOT, and I have noticed a little bit of fade.
    How about the so-called 7" rotors (185mm)? I see someone else mentioned that is as big as Cambria recommended. 185mm rotors have about 33% more surface area than 160mm rotors, so they should be able to handle a lot more heat without fading. That may be a good middle ground.

    The reasoning behind not using 8" (203 or 205mm) rotors applies to all forks with vertical drop outs. There are some forks showing up with drop outs at about a 45 angle that are "approved" for 8" use. When the brakes are applied, the entire wheel wants to rotate around the brake pads. This rotational force is trying to pull the axle out of the quick release, and an 8" rotor is capable of applying enough force to actually do it. So while Fox recommends against it, it's not a bad idea to avoid it on all vertical drop out forks. This does not apply to the rear because the caliper is positioned differently and is not trying to pry the wheel straight out of the drop out.

  6. #6
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    I was actually researching the question of what rotor sizes are okay on what forks like a year ago.

    Fox was the only vendor I found that okayed larger than 6" rotors on the std qr forks, and only 7" then ( e.g.: 180 / 183 / 185 mm ).

    Using a larger rotor on the fork unilaterally voided the warranty. I had specifically checked Fox, Zoke, Manitou & Rock Shox, but not any others as they were out the realm of what I was interested in or available to me.

    I DID run a 7" rotor on a zoke mx comp for about 9 months, and the fork did end up having a problem on both dropouts where the rearward "tongue" of the dropout started to crack off the fork. No idea if it was the rotor, or the 3000 miles of Texas rocks that did it in though.

  7. #7
    Chillin the Most
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    Here this may help http://www.pinkbike.com/modules/news...leview&id=1870

    SRAM has received a number of inquiries lately regarding RockShox fork and disc brake rotor sizes. Following is a list of all RockShox fork platforms and the maximum recommended disc brake rotor size.

    Fork Platform Maximum Recommended Rotor Size
    GPS 165mm
    Judy 165mm
    Pilot 165mm
    SID 165mm
    Duke 210mm
    Psylo 210mm
    Boxxer 210mm

    SRAM tests the structural integrity of all RockShox forks to that of the 210mm disc brake rotor size. However, other factors, including fork stiffness, bushing design, and intended use are considered when determining maximum rotor size.

    Psylo's and Duke's, both QR forks, can carry an 8" rotor. FYI, been using an 8" rotor on my Psylo for 2 years now and never an issue.

  8. #8
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    avid 185's

    i switched up to the 185's from the 160's last season, and the difference was unbelievable. fox says anything bigger than 180 voids the warranty, citing that you risk shearing the caliper mount off the fork leg. the way i see it, it's really only actually 2.5mm difference, as the 5mm is the diameter, and the caliper moves according to the radius.
    anyway, the 185's are supreme and they do require more attention in terms or being careful not to bend them on stuff when leaning the bike against things etc.

    good luck.
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  9. #9
    just along for the ride
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    If you have the time I ride Morro Bay, Montanna d'oro, looking to be sloppy the coming week so great time to test some of my new fugly full fenders, free samples for locals, PM me

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