Changing rotor size?- Mtbr.com
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  1. #1
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    Changing rotor size?

    Hey,
    I have a 2010 Giant Yukon. It comes with a 160 mm rotor. Now I am changing out the fork so I'll be putting on a 8" rotor up front and I was wondering if it would be possible to do the same at the rear, or will the mounts be different? If so is there an adapter that will allow me to do that?

    Thanks

  2. #2
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    On a somewhat separate note here in playing Devil's advocate - are you really sure you want the same size rotor out back as front? I think a sizable # of people here would likely give you the opinion that the majority of your braking power should be front with the larger rotor with less applied in the rear on a somewhat smaller one to avoid lockup.

    IMHO I've found this to be true with my 203/160 setup which seems to work well on the descents in the PA mountains . . .

  3. #3
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    Larger rotor on the rear equals easier rear wheel lockup. Something you don't want.

    I used to run 180mm rotors F/R, but was having trouble with a little too much rear wheel lock up. I dropped it down to a 160mm rotor on the rear. Solved my rear wheel lockup issues.

  4. #4
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    Yeah, I've got bigger front rotors vs rear on all my bikes, except for DJ. 203/180 on the DH, 203/160 on one trail bike, 180/160 on the other, and 160/160 on the DJ.

  5. #5
    NWS
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    I run 203/160 and like it.

  6. #6
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    The adaptors are available, but, like other posters have said, rear wheel lockup will become an issue. Also, if you are looking for more braking power, BB7s or even Hydraulics would be a better bet. On an entry level hardtail for trail riding, 203mm rotors are overkill. Better brakes would be a better bet than larger rotors with BB5s in my opinion. Perhaps even just better levers and cables. Levers can make a significant difference in feel and power with any mechanical brake...
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  7. #7
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    Ooooops... I also run 200mm front / 160mm rear. Just ordered a new pair of brakes 200mm front / 185 mm rear, only because it was cheaper than going 160mm rear. Well, if I get the rear lock up problem arising, I'll go back to 160mm.

  8. #8
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    Or, train yourself to feel when your rear wheel is locking up, and control your brakes accordingly to prevent such lock-up. It is not difficult to learn and will make you a better and more controlled rider.
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  9. #9
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    I just upgraded my front rotor and brake today. I'm now running 185mm BB7/160mm BB5.

    Always felt I needed a little more up front, but also think I could get away with v-brakes in the back if I were so inclined. Rear brakes just don't add much stopping power, and if I do much more than feather mine, it locks up quite easily.
    Quote Originally Posted by jrabikerepair
    Or, train yourself to feel when your rear wheel is locking up, and control your brakes accordingly to prevent such lock-up. It is not difficult to learn and will make you a better and more controlled rider.
    Absolutely, but if you can lock up your rear with a smaller/weaker brake, what's the point in having a larger/stronger one?

  10. #10
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    Tires and grip can have a huge effect on braking. If you have a tire with poor grip, you can lock it up with cantilevers. If you have a tire with good grip (for the terrain), you need more braking power simply because it is more difficult for the tire to lose traction.
    Plus, rear brakes do add a significant amount of control to your bike... Go on a ride using only your front brake, and you will see what I mean. Its all about rider control...
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  11. #11
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    Quote Originally Posted by jrabikerepair
    Plus, rear brakes do add a significant amount of control to your bike... Go on a ride using only your front brake, and you will see what I mean. Its all about rider control...
    Yeeeeeah, man, you've kind of wandered off the reservation.

    No one here is saying rear brakes aren't necessary. However, the consensus seems to be that it's not necessary to have a rear brake as large and powerful as a front brake.

  12. #12
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    The OP inquired about a rear brake upgrade, so that is what I am discussing. You mentioned that the rear brake doesn't add much stopping power, and I was stating that it, in fact, does affect both stopping power and control in a big way. The front does have a big impact on stopping power, but the rear brake is crucial for control when braking...
    I am also stating the fact that having the correct tires for the terrain improves grip, therefore increasing the need for a good rear brake.
    If you are locking up the rear brake really easily, you may need to improve your riding style and/or tire choice for the terrain.
    Your components are only as good as the part that transmits the power to the terrain...your tires...
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  13. #13
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    Quote Originally Posted by jrabikerepair
    You mentioned that the rear brake doesn't add much stopping power
    And I stand by that. It's rather elementary: the steeper the slope, the less weight on the back tire, the easier it will lock up, and the less influence it will have on the bike overall.
    Quote Originally Posted by jrabikerepair
    and I was stating that it, in fact, does affect both stopping power and control in a big way.
    Sure, the rear brake affects stopping power and control. Nobody has stated or is arguing otherwise, so I'm not sure why you keep harping on this. Nobody here advised the OP to get rid of his rear brake. The consensus is merely suggesting he doesn't need to upgrade it to the same size and power of his front brake.
    Quote Originally Posted by jrabikerepair
    I am also stating the fact that having the correct tires for the terrain improves grip, therefore increasing the need for a good rear brake. If you are locking up the rear brake really easily, you may need to improve your riding style and/or tire choice for the terrain.
    And what most everyone else in this thread is saying is that you don't need as large and powerful a rear brake and rotor as you do for the front. Are you actually denying this? Is that why you are ignoring what is written and instead lecturing on what you wish had been written? Is that also why you assume anyone who disagrees with you doesn't know how to ride and/or isn't running tires with good traction? Do you need a hug?


  14. #14
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    So you say the rear brake isn't influentual, then you say it is and argue against your first point. You are arguing against yourself...
    I am helping the OP decide whether or not it is necessary to upgrade to a 203mm rotor in the rear of an entry level hardtail with Avid BB5s. Like I said, it is overkill, and you are making it more difficult than it needs to be. The other posters mentioned rear wheel lockup, and I mentioned a tire choice alteration that does help with lockup (google: traction) by increasing traction as well as braking power, making the bike slow down more quickly.
    I am not denying the claim that you need as much power in the rear as you do in the front. But you asked why one would need a stronger brake in the rear, and I mentioned that with more traction comes more required braking power to break it loose. Just stating facts here, not trying to start a flaming war, and no, I get plenty of hugs from my wife, thank you.
    Plus, if you need more braking power in the front, but seem to lock up the rear by "feathering", you DO need to work on riding style and/or tire selection...
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  15. #15
    NWS
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    JRA: If you look hard enough for something to argue about, you'll find it, whether or not it's actually there.

  16. #16
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    Whatever bro, my original comment was that it is overkill to put 8" rotors on a Giant Yukon. I stated it is overkill, and gave suggestions on how to get the best braking power. Stating facts, nothing else. Not looking for an argument, just trying to help here. Sorry, bad attempt at trying to educate a bunch of know-it-all college students on how to make the best of their hobby... Jerk
    Finished giving advice on this particular topic...
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  17. #17
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    Quote Originally Posted by jrabikerepair
    So you say the rear brake isn't influentual, then you say it is and argue against your first point.
    Except that's not what I stated or implied.
    Quote Originally Posted by jrabikerepair
    But you asked why one would need a stronger brake in the rear
    I was being rhetorical: "if you can lock up your rear with a smaller/weaker brake, what's the point in having a larger/stronger one?"

    Translation: there's no point in upgrading to a more powerful rear brake/larger rotor if the existing setup gets the job done.

    But maybe the OP doesn't feel his 160mm setup does enough. It's all a matter of style and taste. /shrug

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