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  1. #1
    GMF
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    140mm rotor on the front?

    I've researched this a little, and am finding conflicting answers...

    Q: Can you put a 140mm disk rotor on an IS mount fork?

    Additional information - i am trying to pimp out my kid's 20" wheeled hotrock, and there is a disk mount on the fork. I have an avid BB7 caliper lying around, and can build him a wheel, no problem. I just want to put the smallest rotor on there to make it proportional for his bike size.

    Thanks for any help,
    -Damon

  2. #2
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    Quote Originally Posted by GMF View Post
    I've researched this a little, and am finding conflicting answers...

    Q: Can you put a 140mm disk rotor on an IS mount fork?

    Additional information - i am trying to pimp out my kid's 20" wheeled hotrock, and there is a disk mount on the fork. I have an avid BB7 caliper lying around, and can build him a wheel, no problem. I just want to put the smallest rotor on there to make it proportional for his bike size.

    Thanks for any help,
    -Damon
    You can buy a G2 rotor in 140mm version. Now you will have to find a adaptor for the Avid CPS for front IS mount in 140mm.

    Try eBay or your LBS may be able to order the rotor and adaptor.

    I guess you already have the CPS hardware with your caliper ? If not, you will need to order it too. You can get it in steel, stainless steel or titanium.

    David
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  3. #3
    GMF
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    Thanks for the reply,

    Yeah, i have the CPS adapter hardware, but i'm having trouble finding a front 140mm adapter. It isn't on the SRAM website, and my google-fu is failing me. I guess the adapter is the piece i am missing. Would you (or anyone else) know where a 140 *front* adapter might be found?

    It looks like i just need to faff around with the bike a bit more and try fitting things up again (despite lacking a 140 rotor for now)

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    Quote Originally Posted by GMF View Post
    Thanks for the reply,

    Yeah, i have the CPS adapter hardware, but i'm having trouble finding a front 140mm adapter. It isn't on the SRAM website, and my google-fu is failing me. I guess the adapter is the piece i am missing. Would you (or anyone else) know where a 140 *front* adapter might be found?

    It looks like i just need to faff around with the bike a bit more and try fitting things up again (despite lacking a 140 rotor for now)
    I was fooling around Avid/SRAM website today and I only saw 140mm rotor to be use in rear. But not spec to be used in front too... You might be able to fool around a 160mm adaptor for front IS and manage to cut 10mm off the caliper's mounting side. Remember you have to remove only 10mm, as it's only one half of the disc diameter that is affected.

    David
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  5. #5
    GMF
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    Well, that is almost 1/2 and inch, and i don't think there is that much meat in either the caliper body or the adapter. Now i'm not even sure if the caliper would even clear the fork leg if it was fitting a 140 rotor...

    Well, maybe someone has some direct experience with this...(?)

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    Quote Originally Posted by GMF View Post
    Well, that is almost 1/2 and inch, and i don't think there is that much meat in either the caliper body or the adapter. Now i'm not even sure if the caliper would even clear the fork leg if it was fitting a 140 rotor...

    Well, maybe someone has some direct experience with this...(?)
    Sorry, I only have experience with badass 203mm rotors...

    David
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  7. #7
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    Quote Originally Posted by David C View Post
    Sorry, I only have experience with badass 203mm rotors...

    David
    And thinking about that... 180 or even 203mm rotors would look very sick on a 20" wheel... A bit like big disc on motorcycles...



    David
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  8. #8
    GMF
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    Quote Originally Posted by David C View Post
    And thinking about that... 180 or even 203mm rotors would look very sick on a 20" wheel... A bit like big disc on motorcycles...



    David
    Yeah, but at a certain point i'll just stick with the super big disks that are already on there - the super badass 1275mm rims

    I just want to be able to give him some modulation and control so he doesn't flip over the bars in a panic stop - little dude is just 6 :-)

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    Quote Originally Posted by GMF View Post
    Yeah, but at a certain point i'll just stick with the super big disks that are already on there - the super badass 1275mm rims

    I just want to be able to give him some modulation and control so he doesn't flip over the bars in a panic stop - little dude is just 6 :-)
    Yeah, I know...

    Well try to go to your LBS and see if there's any adaptor that exists...

    Or then use 160mm.

    I wish I had disc brakes on my bike as a kid

    David
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  10. #10
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    Quote Originally Posted by David C View Post

    I wish I had disc brakes on my bike as a kid

    David
    When I was a kid I just pedaled backwards to stop

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    I never heard of a 140 on the front, and I'm not surprised that you are having problems finding an adapter.
    I would just put a 160 up front. It isn't going to make that big of a difference vs 140. Modulation should be fine. If its not, you can then start worrying about cutting down adapters and all that jive, but I'm quite certain the 160 will be fine.
    Get some organic pads if you want less bite.

    If he's only 6, would a back brake be enough?

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    Quote Originally Posted by dundundata View Post
    When I was a kid I just pedaled backwards to stop
    Me too... But now it won't work anymore on my bikes, so I need a better way to stop me from kissing that tree...

    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  13. #13
    GMF
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    Quote Originally Posted by smilinsteve View Post
    .... I'm quite certain the 160 will be fine.
    Get some organic pads if you want less bite.

    If he's only 6, would a back brake be enough?
    Well, he's been riding for almost 3 years now and does better with hand brakes. This is also his first geared bike (the 6sp rear freewheel won't be on there for much longer, either...).

    In all honesty, the disk brake thing is more for me than for him. V brakes will clearly work just fine, but well... What's a dad going to do?

    I just want to pimp his ride so he can have a ton of fun when we start hitting the trails.

    And thanks for the input on the brakes. The more I think about it, the more likely I am to stick with just a 160 rotor, but I likes to tinkah. :-)

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    When I changed from 140 to 160 in the rear, I hardly noticed a difference.

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    If it's got too much stopping power you can always squirt a little wd-40 on the pads.

    I doubt he'd ever get it hot enough to burn it off, and it should still have decent stopping performance with such light weight on a tiny wheel.

    Just a thought.

    -Eric

  16. #16
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    Unfortunately no one that I know of makes a 140mm front adapter. This is due to what you have already noted, clearance on an IS mount fork. I could possibly be done on a post mount fork as long as the diameter of the lowers wasn't too great. But most modern post mount forks with stanchions larger than 28mm would have a lower leg diameter that would interfere with the caliper.

    If it were me, I'd hold off on the disc brake for a while. I mean after all he's 6, does he really ride at a level where disc brakes are needed. Yeah I know, dad wants to pimp his ride. But I think he'll have just as much fun on the trails with dad, with or without disc brakes.

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

  17. #17
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    I have never owned BB7's but I heard the modulation is pretty good on them. Just because a brake is strong doesn't mean its hard to modulate.

  18. #18
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    Quote Originally Posted by GMF View Post
    I've researched this a little, and am finding conflicting answers...

    Q: Can you put a 140mm disk rotor on an IS mount fork?

    Additional information - i am trying to pimp out my kid's 20" wheeled hotrock, and there is a disk mount on the fork. I have an avid BB7 caliper lying around, and can build him a wheel, no problem. I just want to put the smallest rotor on there to make it proportional for his bike size.

    Thanks for any help,
    -Damon
    No, not possible to use a 140mm rotor on a production fork.

    But it is very easy to de-tune a BB7 to suit your kid's needs.
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