Brake rotor sizes?- Mtbr.com
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  1. #1
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    Brake rotor sizes?

    How do I know what size will fit my Kona Unit? It's (Hubs) all stock. Do all rotor sizes fit? Is there simply a diference in braking power due to a larger braking surface? I'm going with Avid Mechanical. Thanks for your time!

  2. #2
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    Quote Originally Posted by vladamir
    How do I know what size will fit my Kona Unit? It's (Hubs) all stock. Do all rotor sizes fit? Is there simply a diference in braking power due to a larger braking surface? I'm going with Avid Mechanical. Thanks for your time!
    How do I know what size will fit my Kona Unit?
    Any size rotor will most likely fit on the front. Avid (and many other companies) design their calipers all the same and make IS adapters for whatever rotor size you want. (160mm, 185mm, 203mm, front or rear). You get the same caliper whether you buy the 160mm kit or the 185mm kit, they just come with different sized rotors and adapters. If you have a Manitou fork on your bike, I believe you still have to contact Avid and have them send you an adapter made for 74mm post mounts if you use a rotor bigger than 160mm. The main limitation for rotor size is fork manufacturers' warranties and the space in your frame. Many fork manufacturers state that rotors bigger than a certain size void the warranty (i.e. Fox allows no bigger than 180mm). Your non-driveside chainstay may not have enough space for a larger rotor (I have this issue on my bike, there is absolutely no space for a rotor bigger than 160mm, not even 165mm! It's tight!). Most people choose to put a bigger rotor on the front and a smaller rotor on the back anyways, because somewhere around 65-70% of your braking power comes from the front brake.

    Do all rotor sizes fit? Is there simply a difference in braking power due to a larger braking surface?
    Larger rotors do give you more braking "power" due to the fact that they have a bigger radius (larger amount of torque). They require less hand effort for a given amount of braking "power" exerted on the wheel. Avid actually has percentage figures on their website. It somewhere around 13% increase for a 185mm rotor and 24% or something for the 203. The larger surface area also keeps the system running cooler, so on prolonged downhills you're less likely to experience brake fade. Evaluate how much of your riding is downhill and how much you weigh to make this decision.

    As far as bolting the brakes right up to your ride, you need to make sure the hubs on your wheels are disc compatible. If the have a ring of six threaded holes on the non-drive side, you are good to go. Additionally, you will need new housing and cables (discs need longer cables than vee's). If you don't have wheels that are disc compatible, the cheapest route is usually to buy a new wheelset and sell the old one. Many on-line retailers sell them for cheap. All modern brake rotors/hubs use the industry standard 44mm bolt pattern.
    -Ryan

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