Results 1 to 10 of 10
  1. #1
    MTB Addict
    Reputation:
    Join Date
    Jun 2007
    Posts
    631

    New question here. Giant Yukon Brakes

    I've got a 2006 Giant Yukon with Hayes GX-2 brakes (160mm discs). I'm looking to possibly upgrade to a set of Avid BB7s. Does anyone know what the largest size discs I can put on this bike are? (Bike is entirely stock right now) I would love to go to 185mm on both discs. My front almost never gets hot (only on one hill), but if I drag my rear lightly down a long hill, it gets hot, and once it does, it gets very loud and vibrates a lot. I ride mostly on road, the brakes have never gotten hot in the light off-roading I have done.

    Suggestions, as well as recommendations for brake levers to pair them with will be appreciated.

  2. #2
    mtbr member
    Reputation:
    Join Date
    Jul 2003
    Posts
    6,671

    You problem is not the rotor size....

    but you braking technique. The rear brake shouldn't be the only brake used on a downhill run to control you speed. Both brakes should be employed. Most of you braking power is in the front brake, this is due to weight shift while braking. The reason the rear is heating up so much is that it is the only one in use, and is the only one slowing you. With both brakes lightly applied it is much more efficient as both brakes are doing the work and the one that has the most effect (the front) is in operation so the load is shared.

    A good way to learn proper technique is when you start the run, apply the rear brake first just enough to keep the rear end stable, then apply the front brake with just enough force to control your speed. Apply the brakes only when you need to slow down for a turn or an obstical etc. If you need to apply the brakes firmly to slow down faster, get off the seat and move your weight back to unweight the front wheel a bit to prevent endos. As you get more comfortable with it, you'll be applying both brakes at the same time without even thinking about it. Any rotor brake combo, no matter who makes it or what size rotor is used, will heat up and make noise if used the way you describe.

    Anyway, I would recommend that you check with your fork manufacturer and with Giant. The max rotor size the fork is rated for will determine how big you can go. Usually you can go bigger on a hardtail frame in the rear without any problems, but it's always better to check and make sure. I would also suggest (if the fork will handle it) going with a 185mm rotor in the front and sticking with a 160mm in the rear. This combination with proper technique will give you plenty of stopping power. I'm 230lbs and ride a 29lb trail bike quite agressively. I'm using BB7's with the 185 front and 160 rear and have no problems with heat build up on the down hills. I used to run a 185 in the back as well, but found that it was just to easy to lock it up and skid it all over the trails. Not a good thing as it increases errosion and tears up the trail. That's besides if you only heat up the rear on that one run you actually doing okay and you'd likely totaly eliminate the problem by learning proper technique.

    So, what for are you running, the brand and model can be looked up to find out how big you can go with the rotor.

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

  3. #3
    MTB Addict
    Reputation:
    Join Date
    Jun 2007
    Posts
    631
    I was thinking maybe dual 185mm rotors, and even when I use both brakes, the rear heats up much more than the front, because it gets worse airflow for cooling. Looking at the bike and from some other research, the 185mm will fit. Also, I'm light (about 115 lbs). I never overheat offroad, but when trying to maintain speed (20-25 mph) down a long, steep hill (1/2 mile or more) on road, where I would otherwise be going 30+ mph, after a while, the rear gets hot. The front gets enough airflow to stay cool, except on one hill, where I have to stop at the bottom, where it occasionally gets hot. Also, the bike is about 32-35 lbs.

    EDIT: I am also wondering ifI can re-use my existing brake cables, or if I will need new ones.

    Also, other than the weight penalty, which I don't care about, are there any problems with having a slightly larger than needed rotor, as long as it fits on the bike?
    Last edited by comptiger5000; 01-25-2008 at 09:06 AM.

  4. #4
    AKA Dr.Nob
    Reputation: gumbymark's Avatar
    Join Date
    May 2007
    Posts
    887
    Stop dragging the back brake. If you need to slow down on a hill use the front brake for a few seconds to control speed.

    Better advice would be to grow a pair. I hit 50 mph in the wet on the mtb last weekend.
    Not that all teenagers are evil mind, just most of them.

  5. #5
    MTB Addict
    Reputation:
    Join Date
    Jun 2007
    Posts
    631
    Hills around here aren't that steep, haven't found one that'll get the bike over 35 (with pedaling, about 30 without). Also, with traffic on road, it's not always safe to go that fast. Some roads around here are pretty narrow. Offroad, however, it's not as much of an issue, so the brakes don't get hot. I'm probably upgrading to BB7s, so basically, my question at this point is is it going to hurt anything to go to 185/185 rotors? If not, being that it's an extra $4 per brake, I don't see any point in not doing it.

  6. #6
    ballbuster
    Reputation: pimpbot's Avatar
    Join Date
    Dec 2003
    Posts
    12,624

    It's not the airflow

    Quote Originally Posted by comptiger5000
    I was thinking maybe dual 185mm rotors, and even when I use both brakes, the rear heats up much more than the front, because it gets worse airflow for cooling. Looking at the bike and from some other research, the 185mm will fit. Also, I'm light (about 115 lbs). I never overheat offroad, but when trying to maintain speed (20-25 mph) down a long, steep hill (1/2 mile or more) on road, where I would otherwise be going 30+ mph, after a while, the rear gets hot. The front gets enough airflow to stay cool, except on one hill, where I have to stop at the bottom, where it occasionally gets hot. Also, the bike is about 32-35 lbs.

    EDIT: I am also wondering ifI can re-use my existing brake cables, or if I will need new ones.

    Also, other than the weight penalty, which I don't care about, are there any problems with having a slightly larger than needed rotor, as long as it fits on the bike?
    but yeah, get 185s if you like. i'm sure it will be fine. Take a look at your existing rotors. How close are they to hitting the chain stays? Can you fit another 7.5mm diameter in there?

    The downside of bigger rotors is that you loose modulation... that is, fine control over the brakes. You feel this most when doing tight downhill switchbacks and techy stuff. Bigger rotors make the brakes feel grabbier. Avids have poor modulation as it is. Let me put it this way. I'm 200#, run 160mm Hope Mono Mini brakes on my 29er, ride fast down steep stuff, and I don't overheat my rotors.

    Also, stop dragging your brakes. Try applying them, then letting go to cool off. Pulsing as they say in auto racing. The problem is the pad faces don't get much air if they are always pressed against the rotor. Letting them off for a second lets some air rush through there.

  7. #7
    MTB Addict
    Reputation:
    Join Date
    Jun 2007
    Posts
    631
    Ok, that makes sense. Even my stock Hayes GX-2 brakes (160/160) have decent modulation. Also, I'm thinking of the Avid BB7 Mechanical brakes, which get good reviews. Hydraulics are too expensive at this point. I figure that the modulation should be about the same or better than what I've got now, or would it be worse?

  8. #8
    C S
    C S is offline
    mtbr member
    Reputation: C S's Avatar
    Join Date
    Sep 2007
    Posts
    610
    Quote Originally Posted by comptiger5000
    Ok, that makes sense. Even my stock Hayes GX-2 brakes (160/160) have decent modulation. Also, I'm thinking of the Avid BB7 Mechanical brakes, which get good reviews. Hydraulics are too expensive at this point. I figure that the modulation should be about the same or better than what I've got now, or would it be worse?
    If your stock brakes are working fine, why change them? If you use them properly as the other posters described, they won't get so hot with the noise/vibration that comes with getting hot.

    If you insist on getting new brakes, don't completely write off hydros. You can get a set of Juicy 5s for a bit more than BB7s with levers and new brake cables.

  9. #9
    MTB Addict
    Reputation:
    Join Date
    Jun 2007
    Posts
    631
    Well, BB7s and levers are about $150 for the 185/185 setup, and the stock brakes are ok, but I feel that both based on experience and reviews, the BB7s would be better. Also, the stock brakes don't do well with very light braking (like on gravel). Furthermore, they could definitely have more power.

  10. #10
    AKA Dr.Nob
    Reputation: gumbymark's Avatar
    Join Date
    May 2007
    Posts
    887
    Quote Originally Posted by comptiger5000
    Hills around here aren't that steep, haven't found one that'll get the bike over 35 (with pedaling, about 30 without). Also, with traffic on road, it's not always safe to go that fast. Some roads around here are pretty narrow. Offroad, however, it's not as much of an issue, so the brakes don't get hot. I'm probably upgrading to BB7s, so basically, my question at this point is is it going to hurt anything to go to 185/185 rotors? If not, being that it's an extra $4 per brake, I don't see any point in not doing it.
    If the rotors fit do it. You wont hurt anything.

    But I do think that the problem is more of your riding technique. If your stuck behind a car on a long downhill and have to check your speed STAND UP, get your weight back and use your front brake to slow down.
    Not that all teenagers are evil mind, just most of them.

Posting Permissions

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