3 ms·

I did some measuring and thinking when I returned my bike to the bike room. I looked up some stuff, and .5g is where one typically goes over the handlebars. .

I did some measuring and thinking when I returned my bike to the bike room. I looked up some stuff, and .5g is where one typically goes over the handlebars. .3g is typical stopping speed for an average rider. Elite riders can achieve .7g by moving their butt way behind and below the seat. The front tire friction limit is around .8g with good dry conditions. My bike is way too small and I have the seat post about 1cm into the tube, and I’m also a bit top heavy. The wiki page on bike physics says rear wheel only braking gets about .25g. https://en.m.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics https://en.m.wikipedia.org/wiki/Bicycle_and_motorcycle_dynam... I measured my mountain bike, and the seat is 41” high, and 35” behind the front contact patch. This is terrible for braking, though not entirely out of line with some of the fancy road bikes in the bike room. I should probably get a different bike, as I am quite sure I go over the handle bars at about .3g rather than the more normal .5g. At any rate, I am not sure how one learns limit braking on a bike. Modern cars the computer does it for you if you just stomp the pedal and some cars even do it preemptively with collision avoidance.

sudosysgen 6y ago
One learns to avoid locking up the brakes by feel and experience. ABS is not necessary, though it is more reliable. For an extreme example, Formula 1 drivers or MotoGP drivers do not use ABS, and yet are able to brake at the very edge of possibility. Indeed, it is actually possible to brake ever so slightly more efficiently without ABS than with ABS using very slight wheel slip, and smoother braking allows for weight pre-loading going into a turn. https://www.nathanarose.com/blog/2017/10/4/braking-capabilities-of-motorcyclists-a-literature-review https://www.nathanarose.com/blog/2017/10/4/braking-capabilit... According to this study, braking using both wheels on modern motorcycles (And, by extension, modern bicycles as both have in the past decade standardized braking systems that operate at the limit of grip) achieved .75G +- .15G. This is without ABS, and the limit using perfect braking at higher speeds yielded deceleration rates greater than 1G. If the average, skilled rider is able to achieve .7G on modern bikes, this is not at all worse than cars where the average driver is assumed to brake at .4G. According to https://nacto.org/docs/usdg/vehicle_stopping_distance_and_time_upenn.pdf https://nacto.org/docs/usdg/vehicle_stopping_distance_and_ti... , a moderately skilled driver is assumed to be able to brake at about .5-.6G. This compares favorably. As for braking technique, it is about extracting as much braking force as possible from the rear tire, then attempting to lower one's center of gravity by leaning down and backwards. An absolutely crucial difference is that in a car, braking is very detrimental to turning, causing over-steer. This is not so on a bicycle or motorcycle, which contributes furthermore to safety, as most accidents are avoided via steering, then steering and braking, and then only braking. According to this, braking forces of up to 0.83G are possible on a normal bicycle, without suspension nor special positioning: http://www.industrializedcyclist.com/braking-pitchover.pdf http://www.industrializedcyclist.com/braking-pitchover.pdf
wffurr 6y ago
Apply both brakes. When the rear wheel starts to skid, you are near the limit of your braking ability with the front brake. https://www.sheldonbrown.com/brakturn.html#frontuse https://www.sheldonbrown.com/brakturn.html#frontuse It's really quite simple. And you learn it with cursory research about braking on bicycles. Really this ought to be taught in schools.

sudosysgen 6y ago

One learns to avoid locking up the brakes by feel and experience. ABS is not necessary, though it is more reliable. For an extreme example, Formula 1 drivers or MotoGP drivers do not use ABS, and yet are able to brake at the very edge of possibility. Indeed, it is actually possible to brake ever so slightly more efficiently without ABS than with ABS using very slight wheel slip, and smoother braking allows for weight pre-loading going into a turn. https://www.nathanarose.com/blog/2017/10/4/braking-capabilities-of-motorcyclists-a-literature-review https://www.nathanarose.com/blog/2017/10/4/braking-capabilit... According to this study, braking using both wheels on modern motorcycles (And, by extension, modern bicycles as both have in the past decade standardized braking systems that operate at the limit of grip) achieved .75G +- .15G. This is without ABS, and the limit using perfect braking at higher speeds yielded deceleration rates greater than 1G. If the average, skilled rider is able to achieve .7G on modern bikes, this is not at all worse than cars where the average driver is assumed to brake at .4G. According to https://nacto.org/docs/usdg/vehicle_stopping_distance_and_time_upenn.pdf https://nacto.org/docs/usdg/vehicle_stopping_distance_and_ti... , a moderately skilled driver is assumed to be able to brake at about .5-.6G. This compares favorably. As for braking technique, it is about extracting as much braking force as possible from the rear tire, then attempting to lower one's center of gravity by leaning down and backwards. An absolutely crucial difference is that in a car, braking is very detrimental to turning, causing over-steer. This is not so on a bicycle or motorcycle, which contributes furthermore to safety, as most accidents are avoided via steering, then steering and braking, and then only braking. According to this, braking forces of up to 0.83G are possible on a normal bicycle, without suspension nor special positioning: http://www.industrializedcyclist.com/braking-pitchover.pdf http://www.industrializedcyclist.com/braking-pitchover.pdf

wffurr 6y ago

Apply both brakes. When the rear wheel starts to skid, you are near the limit of your braking ability with the front brake. https://www.sheldonbrown.com/brakturn.html#frontuse https://www.sheldonbrown.com/brakturn.html#frontuse It's really quite simple. And you learn it with cursory research about braking on bicycles. Really this ought to be taught in schools.