Road disks... 140mm vs 160mm rotors. And why? - Page 2
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  1. #26
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    Quote Originally Posted by cxwrench View Post
    You'll never give up, will you?
    save the rim brake.jpg
    Too old to ride plastic

  2. #27
    'brifter' is f'ing stupid
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    Quote Originally Posted by OldChipper View Post
    Sure I will! When the manufacturers stop creating more problems than they're solving. It started with the proliferation of BB standard - none of which are better in the long run that threaded - and continues with stooopid and un-needed road discs. If they would continue to make both rim and disc on high-end bikes, I'm OK. Just don't force inferior tech on me so they can make more $$$.
    Various bb standards are definitely not a new thing. Neither are different types of brakes. Everything else w/ brakes has settled on discs, why not bicycles?
    #promechaniclife

  3. #28
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    Quote Originally Posted by cxwrench View Post
    Various bb standards are definitely not a new thing. Neither are different types of brakes. Everything else w/ brakes has settled on discs, why not bicycles?
    Because there is a certain subset of cyclists who are fierce Luddites.

  4. #29
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    Bike frames and forks are structurally rated for a maximum disc rotor size. Best to not exceed the rated diameter, even if there seems to be clearance for a larger diameter.

  5. #30
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    Quote Originally Posted by 4slomo View Post
    Bike frames and forks are structurally rated for a maximum disc rotor size. Best to not exceed the rated diameter, even if there seems to be clearance for a larger diameter.
    What was the source of this information?

    At first glance I'd question this observation.

  6. #31
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    Check with your frame and fork manufacturer(s) for the maximum brake disc diameter they recommend.

    Quote Originally Posted by SwiftSolo View Post
    What was the source of this information?

    At first glance I'd question this observation.

  7. #32
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    Quote Originally Posted by SwiftSolo View Post
    What was the source of this information?

    At first glance I'd question this observation.
    think logically. As the disc diameter gets larger, the caliper also needs to be moved out away from the fork leg further thus creating a higher leverage at its point of attachment at to the fork leg. This causes at least a couple issues. One, caliper will have more movement, more flexy, and 2) easier for caliper to snap off from the fork leg. You don't just make one component bigger without taking into account of the stress it puts on the rest of the system.

  8. #33
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    Quote Originally Posted by aclinjury View Post
    think logically. As the disc diameter gets larger, the caliper also needs to be moved out away from the fork leg further thus creating a higher leverage at its point of attachment at to the fork leg. This causes at least a couple issues. One, caliper will have more movement, more flexy, and 2) easier for caliper to snap off from the fork leg. You don't just make one component bigger without taking into account of the stress it puts on the rest of the system.
    I don't think it's that simple.

    As we go to larger discs the amount of load transfer to the calipers is reduced. The total force possible is limited by tire contact patch friction. Because modern hydraulic disc brakes will easily overpower road bike tires, the caliper load question becomes one of leverage.

    The distance from the road surface to the fulcrum (the axle) remains fixed. The factor that changes is the distance from the fulcrum to the caliper. It increases, thereby reducing the possible load.

    Also, my newer disc brake bikes locate the caliper mounts on the compression side of affected members in such a manner that shear loads on fasteners and connections should be minimal.
    It is the 30 page safety manual on my Cannondale hi-mod that causes me to question the challenged premise. With the seemingly endless ways to kill oneself outlined, I don't recall any reference to changing disc size.

  9. #34
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    Just ordered a bike and the build is using a blend 140 & 160. I googled and saw this isn't unusual. Assume they know what they're doing and didn't question it.

  10. #35
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    Thumbs up

    Quote Originally Posted by aclinjury View Post
    Another reason to go 160mm front and 140mm rear is that the UCI is standarizing to these sizes. This will force manufacturers to concentrate their developements and offerings in these sizes.


    Ah... suddenly the mystery has been solved (Not sure how I missed reading this info when it was posted, but)...

    I've been considering downsizing my bike's stock 160mm rotors to 140mm rotors, largely to reduce the bike's chubby weight. I've had 140mm discs on previous bikes and didn't have an issue.

    In scouring the Interwebs, I noticed that pro bikes often had 140/140 as recently as 2019 and then all of the sudden, all of their bikes are 160/140 or 160/160. I also noticed that bikes like the Giant TCR Advanced Pro 0 came with 140/140 and then switch to 160 with the latest model. Knowing that the UCI has standardized on 160/140 answers my question on why the sudden change!

    I keep reading that for *normal* roadies that 140/140 should be fine, especially if using Shimano ICE-Tech rotors... which I am. I don't live near any mountains and don't usually use my brakes for much more than stopping at stop signs, so I'm pretty sure heat dissipation is a non-issue for my riding style.

    From 2019...



    From 2020...

    https://cyclingtips.com/2020/01/pro-bik ... part-four/


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