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disc brakes, 160,180 combo

mak3mmak3m Posts: 1,469
edited March 2011 in MTB beginners
mate of mine has asked if i would have a look at his bike as its been sat in his garden under a rain cover for two years.

bit of rust on chain but saveable, just needs a clean and a lube

but i noticed his disc brakes, just basic cables shimano 8 speed vbrake levers, but he has a 180mm rotor on the front and a 160mm rotor on the back.

im a bit of a disc nub but is that the wrong way round??? surely you would need the greater stopping power on the back

he uses it on the road, with huge dh tyres :roll: , but i dont want him goiung over the bars, should i switch them round or am i just being newb and thats an okset up

Posts

  • Andy BAndy B Posts: 8,115
    you get much more stopping power from the front, so bigger rotor up front.
    2385861000_d125abe796_m.jpg
  • sniper68sniper68 Posts: 2,899
    Exactly the dame principal as a motorbike..large at the front.
  • mak3mmak3m Posts: 1,469
    aha told i was a nub

    :oops:
  • bennett_346bennett_346 Posts: 5,092
    out of curioscity what was your reasoning behind thinking the smaller should be at the front?
  • mak3mmak3m Posts: 1,469
    larger the rotor the more stopping power

    i thought on the bike you want more stopping power in the rear, as a tight pull on the front is going to send you over the bars

    so now im thinking going over the bars is ONLY down to poor technique rather than too much power
  • sniper68sniper68 Posts: 2,899
    mak3m wrote:
    larger the rotor the more stopping power

    i thought on the bike you want more stopping power in the rear, as a tight pull on the front is going to send you over the bars

    so now im thinking going over the bars is ONLY down to poor technique rather than too much power
    Look at motorbikes.Hypersports have two massive front discs with 6-pot callipers and a small rear.It's all down to progressive braking.In theory you can endo a motorbike but you don't as you brake progressively,the front fork will dive and the bike(motor or MTB) will come to an abrupt stop.
    Some people associate being able to skid the back wheel with power,again this is poor technique.If the back wheel is skidding you're not in control.You can lock the rear wheel just as easily with a 160mm rotor as you can with a 203mm.
    Even on very steep,rocky technical terrain I feather the front brake as well as using the rear.
    As with a motorcycle you should use both together with the front doing most of the work 8)
  • mak3mmak3m Posts: 1,469
    when i think about it yes thats how i brake with my v's feather both brakes and gradually increase the front to stop or slow right down.

    just seemed counter intuitive for some reason :mrgreen:
  • diydiy Posts: 6,680
    Under regular breaking your weight shifts to the front, which increases the contact area and the amount of braking force that can be applied before skidding. The opposite is true of the rear. The harder you brake the less grip you have on the rear. That is pretty much where the analogy of sports motorbikes ends.

    On an MTB you do still need decent rear brakes as you will use the rear for control when going over loose ground, where you can't risk a front wheel slide. Also heavy front breaking makes steering harder, so sometimes you bias to the rear to keep the front light.

    Most people typically use their rear brake more, but their front brake harder. i.e. front for stopping, rear for control.

    To stop as quickly as possible - use front, add back, then more front. The rear is much easier to lock up because there is no weight over it.

    Its not just motorbikes - its the same for cars too.
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