What sized brake discs?

xcracer
xcracer Posts: 298
edited November 2007 in MTB buying advice
I'm upgrading my Spesh Rockhopper from v-brakes as its now getting a bit too soggy and muddy for them out in the forest! I'm thinking of either some Avid Juicy 5's or Shimano LX's or XT's or whatever Shimanos I can get a good deal on.

My question is though; which size discs do I need?

I believe that the bigger the disc the more the braking power. Is that right?

I ride mostly cross-country and some singletrack with occasional steep rooty downhill sections. I presume the small ones (160mm) are just for light cross country stuff and road use and the larger ones (203mm) are for downhill? Yes? So maybe I need the mid-sized one?

Can anyone shed any light on this?

Also, if anyone does have any comments on which make and/or model to go for then let me know.

Thanks in advance.

Comments

  • gthang
    gthang Posts: 293
    Well most bikes that are not used for downhill have 185mm on the front and 160mm on the back. Front break does most of the work so is normally bigger then the back.
    My Bike
  • nicklouse
    nicklouse Posts: 50,675
    i would sugest 160 160 for all general XC type stuff.

    i am 100kg and use 160 160, but if you have some long long decents that require lost of braking EG the alps then 180 would be a better bet.
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  • Quirky
    Quirky Posts: 123
    I'm looking to upgrade my brakes too, I was looking at avid juicy 7's with 203mm discs as I thought the bigger the disc the more stopping power, so is it a bad idea to go for the biggest discs?

    edited to mention the the most I ever do is the red/black route at glentress
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  • Sir HC
    Sir HC Posts: 20,148
    Check your fork and frame manuals, the manufacturers give a maximum size you can run.
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  • fireheed
    fireheed Posts: 55
    180mm would be a nice size tha would work well. Plus most forks can cope with 180mm rotors these days.
  • dombo6
    dombo6 Posts: 582
    I ride similar stuff to you, and weigh 66kg, probably 70 fully kitted, and have Hope Mono Mini 160/140 combo. these have served well for enduros, racing, and general xc. remember you only need to scrub off a bit of speed, it's rarely necessary to bring yourself from 40+ mph to a dead stop.
  • gthang
    gthang Posts: 293
    Dombo6 wrote:
    I it's rarely necessary to bring yourself from 40+ mph to a dead stop.

    Everyone should have savings in the bank for the rainy day, I believe the same theory applies to breaks.
    My Bike
  • Splasher
    Splasher Posts: 1,528
    A well bled, non-contaminated 160mm hydro brake can easily lock the wheels of a mountain bike so no more brake force is required. And riding UK trail centres like Glentress will not give your brakes any temperature issues.

    Larger rotors just add unsprung rotational mass (the worst you can add) to the bike. I reckon 160/160 is the way to go for you.
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  • supersonic
    supersonic Posts: 82,708
    ^^ absolutely. You get better modulation with smaller rotors too (generally).
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  • dombo6
    dombo6 Posts: 582
    Pick your line, look far ahead at where you want to go, not at what you might hit.
  • The Big Cheese
    The Big Cheese Posts: 8,651
    I weight ~85 kilos and I am ~6ft

    Race bike: 160mm front and rear

    AM rig: 160mm front and rear

    FR: 203mm fr (only because forks demand it as minimum) and 185mm rear.

    To be honest 185mm is too much for me but got a deal on the Avid Codes so went with it.

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