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  1. #1
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    140mm rear too small?

    I'm in the process of helping a friend upgrade her brakes. She wants to go with Hope Mini X2 pro's. Rider is 125lb +/-. Bike is a 28lb 5.5 full suspension. She doesn't do much cross country stuff, mostly loose rocky tech and hills(not downhill, mild up and down).

    Question, if she chooses a 160mm x2 pro front with a 140mm rear, will she be underpowered?

    Thanks.

    jeff

  2. #2
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    If she's not giving it much to do, then a 140mm should be fine. It's fairly straightforward to boost up to a 160mm if she finds that she needs a little more.
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  3. #3
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    Doesn't take much to get a rear tire to break traction. 140mm for the rear is more than enough.
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  4. #4
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    Quote Originally Posted by az1jeff
    140mm rear too small?
    Nope
    I also don't think that 160mm would be too much tho if the modulation is good (just for more options IMO)
    Honestly... ahh I give up

  5. #5
    cbx
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    I am 175 on a 22.5lb hardtail and running a 140 in the rear...seems fine to me. Most of your braking is up front anyways.

  6. #6
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    Quote Originally Posted by SteveUK
    It's fairly straightforward to boost up to a 160mm .
    . . plus the added expense of the additional 160 rotor + adapter to an already pricey set. Hence why I'm asking prior to making the buy. .

    Thanks for the input.

    jeff

  7. #7
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    ". . plus the added expense of the additional 160 rotor + adapter to an already pricey set. Hence why I'm asking prior to making the buy."

    I said that it was straightforward, not that it was inexpensive. You don't just have to throw the 'old' rotor away, you know? You'll get good money for it on eBay, especially if it's barely used. The best (only?) way to find out if a 140mm is enough for somebody in particular is for that somebody to try it for themselves. With 'preference' components, we generally have to pay to learn which suits us best.
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  8. #8
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    Quote Originally Posted by Kyle2834
    Doesn't take much to get a rear tire to break traction. 140mm for the rear is more than enough.
    Not on a 29er it ain't (155lb rider,normal xc stuff,used one for 6 months)
    '11 Origin 8 700CX
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  9. #9
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    140 is fine, but 160 is tried and tested. What is the motivation for 140 over 160? You will drop a few grams; you don't *need* 160, but it is the safe bet. Either way, hopes are good units...

    *shrug*

  10. #10
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    I've understood that the small Hopes are very nice but not excessively powerful. How many grams are you saving 160mm vs. 140mm? Does it matter?

  11. #11
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    Quote Originally Posted by longhaultrucker
    Not on a 29er it ain't (155lb rider,normal xc stuff,used one for 6 months)
    180lb rider on a 29er who switched to 140mm rotor in the rear on my 29"er bikes for this season. So far, it's been plenty of brake for the rear (which surprised me coming from 185mm's and 180mm's in the rear). I guess it all depends on the rider, the terrain, the brakes and individual needs.

    I would think, going back to the OP's wife who weighs only 125 lbs, the 140mm in the rear would be find and dandy. As others have said, the only way to find out is give it a try.

    BB

  12. #12
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    Quote Originally Posted by SteveUK
    "[I.[/I]"

    I said that it was straightforward, not that it was inexpensive. You don't just have to throw the 'old' rotor away, you know? You'll get good money for it on eBay, especially if it's barely used. The best (only?) way to find out if a 140mm is enough for somebody in particular is for that somebody to try it for themselves. With 'preference' components, we generally have to pay to learn which suits us best.
    So your advice is to spend a bunch a money, hope for the best, then spend more money if it doesn't work out?

    If it's a used rotor, you're not going to get much for it if it sells at all. Smarter to to do some diligence and get the right part in the first place, than to simply "hope" (no pun intended ) for the best and potentially making an already large ticket purchase more expensive.

    I posted her specifics in hopes that others faced with the same or similar situation would post up their experience to help with the decision to opt for the available 140 or wait for the 160.
    Last edited by az1jeff; 04-14-2009 at 11:21 AM.

  13. #13
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    Quote Originally Posted by perttime
    I've understood that the small Hopes are very nice but not excessively powerful. How many grams are you saving 160mm vs. 140mm? Does it matter?
    Not really about the weight, just the availability of the 140. She'd prefer the 160.

    jeff

  14. #14
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    Jeff, could you point out where I've said or inferred that anyone should "hope for the best"? I don't see how you can construe anything I've said as being so flippant.
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  15. #15
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    Sounds like the 140 will most likely be enough: she's relatively light and not doing anything too extreme. Plenty of big guys are doing fine with XC brakes and 160 rotors in the rear.

  16. #16
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    My apologies. I probably should have detailed the reason for the original question about the 140 vs. 160. It doesn't have to with the miniscule weight difference, but that it stems from availability.

    I personally have never used a 140 rear so I wanted to get some feedback from others who have before I just went and mounted up the 140 on someone elses bike. The terrain is rocky, loose and hilly, so I just wasn't too sure if the 140 would be a problem. Also, she's running a 160 rear now.

    Thanks again for all the input. Very helpful.

    jeff

  17. #17
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    Quote Originally Posted by az1jeff
    I'm in the process of helping a friend upgrade her brakes. She wants to go with Hope Mini X2 pro's. Rider is 125lb +/-. Bike is a 28lb 5.5 full suspension. She doesn't do much cross country stuff, mostly loose rocky tech and hills(not downhill, mild up and down).

    Question, if she chooses a 160mm x2 pro front with a 140mm rear, will she be underpowered?

    Thanks.

    jeff
    I'm 190 with gear and find that a 160 on the rear is plenty adequate for anything I ride on a 32 lb bike, including all the 2,000 - 4,000 foot descents I did living out west, and even a few lift service days. A 140 should be fine in the rear for a 125 lb rider.

  18. #18
    JmZ
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    Quote Originally Posted by kapusta
    I'm 190 with gear and find that a 160 on the rear is plenty adequate for anything I ride on a 32 lb bike, including all the 2,000 - 4,000 foot descents I did living out west, and even a few lift service days. A 140 should be fine in the rear for a 125 lb rider.
    Heck, I'm bit north of that, but live in areas a bit flatter than that. I've had no issues with a 25 pound bike and a 140 rear rotor.

    The ONLY I had issues was when I forgot to change pads on the brakes before a bike vacation, but that was user error and not the brakes fault.

    If I ever move to someplace with elevation I'd probably go 180/160, but that's more than a fair bit of difference between a 210lb guy and a 125lb rider.

    JmZ
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  19. #19
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    I'm 165lbs and ride all types of terrain in Arizona. My epic has a 140mm rear rotor and it's been fine. My caliper sprang a leak recently so I stuck a juicy ultimate with 160mm rotor on the rear, replacing the XTR with 140mm, while my brake was being repaired. I could tell the difference in stopping power. Could just be the brake system (Juicy Ultimate versus XTR), or it could the the rotor size, I don't know. The 140mm has been more than enough brake for me, but the 160mm does seem to have a little more stopping power. I can lock the rear tire with the 140 anywhere at any time. I don't know how much more power you need than that.
    "Confidence is the feeling you have before you fully understand the situation".

  20. #20
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    Riding conditions. I'm only 145lbs fully-geared.

    I currently run 160f / 140r. If my 180mm rotor was of the lighter variety, I'd stick it back on front in place of the 160.

    180f / 140r seems appropriate due to inherent traction limitations, but I don't have a way to test required force of pull on a lever to see if it balances the pull weight. Would be interesting to see. And for heavier riders, 203f / 160r. *shrug*

    And for a 120lb geared-up rider, a 160f / 120mm rear rotor, but I don't think that's an easy find.
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