Results 1 to 6 of 6
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jun 2013
    Posts
    5

    Rotor Size for 1999 GT XCR 5000 iDrive

    I am working on doing some upgrades to my mountain bike and I have come across a deal for a set of disc brakes with 203mm rotors. Is there any real concern that they would not clear the fork? This would be my first set of disc brakes on a bike, so I am not sure which way to go.

  2. #2
    Huckin' trails
    Reputation: David C's Avatar
    Join Date
    May 2011
    Posts
    6,119
    Your fork and frame should have IS disc brake tabs, which means you can fit any size rotor using the proper IS caliper adaptor to position the caliper properly.

    However, this is a XC race bike and 203mm rotors would offer too harsh of a bite, turning a simple tap on the lever into a brutal braking effect. Basically it's gonna feel like an on/off brake setup, without any modulation to allow you to lightly shred some speed or control efficient braking in loose conditions.

    I run my XCR's with 160f/140r and BB7 mechanical calipers and I have plenty of power, but also better control over the bike by being able to control my speed and keep the bike balanced on technical sections by not over-throwing my body weight over the bars when grabbing the brakes.

    If the brakes are decent, you can always get them and then order smaller rotors and adaptors.
    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
    mtbr member
    Reputation:
    Join Date
    Jun 2013
    Posts
    5
    Thank you for the reply.

    Does me being 6'8", 240 lbs have any affect on what size rotors I should get? The 160f/140r combination sounds good to me, but I just wanted to make sure it is enough for a man my size. I don't see anything as far as specs for that type of thing, so any help along those lines is appreciated.

  4. #4
    Huckin' trails
    Reputation: David C's Avatar
    Join Date
    May 2011
    Posts
    6,119

    Rotor Size for 1999 GT XCR 5000 iDrive

    Hem, I'm about half your weight and a head shorter, so I can't say how much you will affect the braking, but since you'll out weight the bike momentum itself by far with your own body weight, well a lot more than I would, I think the concern would be more about the braking power your caliper can deliver and how much heat build up the rotors can sustain before you experience brake fading.

    The size of the rotor is gonna affect the harshness of the bite and the heat dissipation capacity a lot more than just the braking power. I think that if you're gonna be riding a bit aggressive, then a 160/140 combo with decent hydro brakes will not be able to handle the heat build-up. The power will be there though.

    So I think you might actually want to go 180/160 and learn how to brake (i.e. front for power, rear for control) and to move your body weight along with the flow of the trail to minimize braking need, then also to mostly use the brakes as a on/off instead of constantly on long descents.

    But still, this is XC riding and not AM, so you shouldn't be constantly on the brakes, at least not as if you were mostly going down hills with frequent braking.

    Others with on-hand experience about being your size and using different rotor sizes could shim in and give you real-trail advises of their own learnings and experimenting.

    All I can say is you should go hydro, no matter what rotor size. The new Shimano SLX and XT are getting A+ reviews here and the IceTech pads seems to be more than just marketing hype regarding heat dissipation. For myself, I've yet to ride them.

    But don't go any bigger than 180 on your GT.
    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
    Huckin' trails
    Reputation: David C's Avatar
    Join Date
    May 2011
    Posts
    6,119

    Rotor Size for 1999 GT XCR 5000 iDrive

    Btw, here's how my setup looks-like. Being lightweight has the advantage of being able to ride hardcore on light-weight stuff

    Rotor Size for 1999 GT XCR 5000 iDrive-imageuploadedbytapatalk1373845761.029020.jpg

    160 Avid HS1 front
    Rotor Size for 1999 GT XCR 5000 iDrive-imageuploadedbytapatalk1373845817.622220.jpg

    140 Magura Storm SL rear
    Rotor Size for 1999 GT XCR 5000 iDrive-imageuploadedbytapatalk1373845870.182501.jpg

    And here's some 203mm's one on my freeride bike. It's just too much but the look is killer.

    Rotor Size for 1999 GT XCR 5000 iDrive-imageuploadedbytapatalk1373846141.358128.jpg
    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!

  6. #6
    mtbr member
    Reputation: Berkley's Avatar
    Join Date
    May 2007
    Posts
    3,200
    Some forks are not rated for 203mm rotors. And some frames might not have clearance for a large rear rotor. Best to check before purchasing.

Similar Threads

  1. xt or slx and what rotor size?
    By SKPhoto816 in forum Brake Time
    Replies: 11
    Last Post: 4 Weeks Ago, 09:02 AM
  2. What rotor size do I need?
    By dboneslick in forum Brake Time
    Replies: 9
    Last Post: 05-11-2013, 07:13 PM
  3. Rotor size?
    By ArcticCat500 in forum Brake Time
    Replies: 9
    Last Post: 11-21-2011, 06:01 AM
  4. rotor size?!??
    By -eddie. in forum Brake Time
    Replies: 9
    Last Post: 11-01-2011, 05:59 AM
  5. 2007 iDrive 4 - Rear Rotor Size?
    By hardwarz in forum GT
    Replies: 7
    Last Post: 05-16-2011, 03:29 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •