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As fixie-biking is really trendy at the moment, i often see fixie riders 'skidding' and stopping their bike by blocking their backwheel.

As this only works by shifting the riders weight to the front of the wheel i recently wondered if there is a physical limit (like weight) where this braking method will not work anymore because the pressure on the back wheel is still to big to skid?

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On a standard form-factor bicycle, on "normal" pavement, when the brakes are applied weight shifts to the front wheel and weight is removed from the rear wheel. The rear wheel will almost certainly skid if enough back pressure is applied. –  Daniel R Hicks Feb 18 at 17:04

3 Answers 3

up vote 10 down vote accepted

There are more factors involved. Gearing being a major one - it is much easier to skid on a 38x18 compared to a 50x14 which is more like a track ratio. Other major factors include road surface, rider strength, dry/wet, tyre width, tread pattern, rubber compound and inflation.

Indeed, as others have mentioned additional weight might actually make it easier to skid given increased momentum and pedal resistance provided they shift their weight appropriately.

I would say there is no practical upper limit for rider weight but gearing and tyre characteristics (a really fat slick tyre with a big contact patch on dry tarmac) could prevent it. Nevertheless, skidding the rear wheel is an ineffective way to slow or stop your bike even if it is good fun.

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Thanks a lot for this detailed answer! –  Obl Tobl Feb 19 at 6:24

I would assume that rider weight wouldn't prevent this as a heavier rider is going to have more momentum to maintain the skid. They are also going to be more able to hold the wheel stationary.

Any time the bike slows dramatically, the weight will be shifted forwards even further, so good grip on the rear wheel will then reduce leading to a skid.

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It takes a bit of getting used to but it's fairly easy to unweight the back wheel by shifting forward & locking out your rear foot. Just costs a lot in tyres if you do it too much! –  bearcomp99 Feb 18 at 11:20
    
Ok. Perhaps I should have included the comment that your weight is proportional to the unweighting the back wheel (allowing from the bike weight). As stated by James, the momentum / weight is also linked to the force required to lock out the wheel. Though weight does have a bearing, in reality the ability to stop is dictated by the skill of the rider to skid at a controlled rate in the given space. A lighter rider can alter their position to apply more weight to the back wheel, provided they have the strength to lock it out. –  bearcomp99 Feb 18 at 12:40

The accepted answer fails to point out that skidding is less effective at slowing the bike than not skidding. To stop a brakeless fixie quickly, the rider must shift their weight backwards as far as possible (to help prevent loss of traction, as weight moves forwards under braking), while resisting the pedals' rotation as hard as they can, without locking up the rear wheel. Rolling friction > sliding friction.

The heavier the rider, the more difficult it is to stop - there is more momentum to resist. Also, the longer the gearing, the less mechanical advantage your legs have to resist the pedals; again it is more difficult to stop.

However, with manageable gearing (i.e. NOT track ratios!), and good leg muscles and technique, the limiting factor becomes tyre adhesion. Where I live there are hills on which I can only stop with brand-new racing tyres. Worn tyres or harder compounds just give up and skid!

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