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Discussion Starter · #1 ·
Silly question but I thought y'all might be entertained.

Getting There: Reader hit by a 'track' bike asks if they're legal

By LARRY LANGE
P-I REPORTER

Question: A reader who identified himself only as Jon had a reason for wanting to know about brake requirements for "track" bikes, sometimes used by bicycle messengers.

"I was struck at low speed by a downtown Seattle bicycle messenger in a crosswalk. ... No one was hurt, and the incident ended in some not-so-nice words being exchanged between us. He was unable to stop for his red light in time as I walked out into the crosswalk. I noticed that this cyclist was riding a 'track' bike, which had no brakes. I then started noticing that a large percentage of downtown messengers were riding such bikes. Is this actually legal? It seems to me that this puts people at risk, especially in downtown traffic."

Answer: Seattle traffic management director Katherine Casseday said the city requires that all bicycles "be equipped with a brake which will enable the operator to make the braked wheels skid on dry, level pavement." The type of braking mechanism, however, isn't specified in the code.

Track bikes are fixed-gear bikes where braking is activated by resisting the rotation of the cranks with the rider's legs instead of using the hands to squeeze a lever that compresses braking pads onto a wheel's rim. Casseday said track bikes are able to skid on dry, level pavement and are legal.

"Bicyclists riding on a city street are subject to all the duties applicable to a driver of a vehicle," Casseday said. "Bicyclists are required to obey all traffic control devices and can be ticketed for traffic violations. Safety is dependent on compliance and attentiveness of all users of the street system."
 

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rcnute said:
Silly question but I thought y'all might be entertained.

Getting There: Reader hit by a 'track' bike asks if they're legal

By LARRY LANGE
P-I REPORTER

Question: A reader who identified himself only as Jon had a reason for wanting to know about brake requirements for "track" bikes, sometimes used by bicycle messengers.

"I was struck at low speed by a downtown Seattle bicycle messenger in a crosswalk. ... No one was hurt, and the incident ended in some not-so-nice words being exchanged between us. He was unable to stop for his red light in time as I walked out into the crosswalk. I noticed that this cyclist was riding a 'track' bike, which had no brakes. I then started noticing that a large percentage of downtown messengers were riding such bikes. Is this actually legal? It seems to me that this puts people at risk, especially in downtown traffic."

Answer: Seattle traffic management director Katherine Casseday said the city requires that all bicycles "be equipped with a brake which will enable the operator to make the braked wheels skid on dry, level pavement." The type of braking mechanism, however, isn't specified in the code.

Track bikes are fixed-gear bikes where braking is activated by resisting the rotation of the cranks with the rider's legs instead of using the hands to squeeze a lever that compresses braking pads onto a wheel's rim. Casseday said track bikes are able to skid on dry, level pavement and are legal.

"Bicyclists riding on a city street are subject to all the duties applicable to a driver of a vehicle," Casseday said. "Bicyclists are required to obey all traffic control devices and can be ticketed for traffic violations. Safety is dependent on compliance and attentiveness of all users of the street system."

No, fixed gear is not the issue. The lack of brakes is the point of contention. A fixed gear can be equipped with brakes.
 

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I deliver on a college campus on a regular geared road bike with good brakes, but a co-worker riding fixed on a steamroller without breaks can definitely lock his rear wheel with his legs on flat level dry pavement. So maybe the guy that hit you was just a wuss that should get some breaks or some legs, but definitely one or the other.

As a bike delivery guy I definitely have to ask if you were looking when you stepped out though. Even if you're legally right, Isn't it reasonable to expect that the rider had been in your field of view for no less than 5-10 seconds? You had more time to react than he did, if it went how it normally does for me when I hit people who had been standing still for 5-10 seconds as i watched them, then as I get 5 feet from them going 20-22 mph they just take that one step in front of me. I have never hit someone hard enough to knock them off step though, only a brush usually, but that happens about once an hour all day when its crowded.

I know when I'm working I am always at about 400% alertness which can't be expected of podestrians just getting from A to B, but it amazes me how people on the streets and sidewalks act like zombies sometimes and just walk around looking at their toes.

So yea that kid should definitely have control of his bike, and if it was me and I hit you to the point of one of us losing step, I would have stopped, apologised, fealt like an idiot, and retought my riding strategies.
 

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Discussion Starter · #4 ·
No. According to the power-that-be cited in the article the "fixed" nature of the drivetrain is the brake. I think most fixed-gear riders are better bike handlers than the vast majority of riders with brakes.
 

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It's still irresponsible to ride a bicycle with no way to brake the front wheel. We all know from experience how much shorter you can stop when braking at the limit of traction with the front wheel than with the back wheel. That's just how the physics works.
 

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Discussion Starter · #6 ·
Hey, I use a front brake. :)
 

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Different laws for different states.

I believe to be legal in our state you must have a front brake, the legs can be considered the back brake on a fixed.

Legality aside, 70 percent of your stopping power is in your front brake. Even if you start to skid by locking your rear tire up, your stopping distance is horrendous. You just can't stop very fast without a front brake. If someone doesn't believe this do a little test on a bike by going a set speed and stopping as quick as you can using both brakes and then rear brake only.


That in my opinion is not something you want to handicap yourself with while riding. Let's be honest, even with front and rear brakes on a road bike, it is not like you are stopping on a dime anyway, why double or triple your stopping distance?
 

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rcnute said:
Hey, I use a front brake. :)
I too use a front brake most of the time. I was riding in town a few years ago, nothing as crowded as seatle, but a city with traffic. I was riding down the street on the way home from my ride and very casualy this kid steps out from behind a huge SUV right in front of me, I just swerved around him and kept on going, but he said "watch it". I didn't reply, but wanted to educate him a little of looking both ways before crossing a street. Even if pedestrian have the right of way, they need to look before crossing a street.
 

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Anonymous said:
I have a front brake. :D
lol...i have one too. it sits in my garage with my tools. hehe. wait, i have two front brakes. the other one is on a geared bike. sorry for the mislead. hehe :)
 

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likeguymontag said:
It's still irresponsible to ride a bicycle with no way to brake the front wheel. We all know from experience how much shorter you can stop when braking at the limit of traction with the front wheel than with the back wheel. That's just how the physics works.
The standard that the official in the article quoted implied that in normal conditions, the rider just needs to be able to stop the bike--in general. Anything beyond that is included in what she said about the responsibility of the rider: "Safety is dependent on compliance and attentiveness of all users of the street system." A rider who isn't strong enough to stop his bike without brakes has the responsibility to equip the bike with a brake. Any accident involving the inability to stop when he should would be his fault, unless it's raining, or snowing, or a truck carrying ball bearings has had a terrible accident.
 

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OverStuffed said:
The standard that the official in the article quoted implied that in normal conditions, the rider just needs to be able to stop the bike--in general. Anything beyond that is included in what she said about the responsibility of the rider: "Safety is dependent on compliance and attentiveness of all users of the street system." A rider who isn't strong enough to stop his bike without brakes has the responsibility to equip the bike with a brake. Any accident involving the inability to stop when he should would be his fault, unless it's raining, or snowing, or a truck carrying ball bearings has had a terrible accident.
That seems like a reasonable standard. After thinking about it for a moment or two, it seems like that's also a practical standard from a legal standpoint - whether or not you're able to effectively stop your vehicle. That way it would be perfectly legal to ride brakeless - up until the moment you hit someone. Besides bicycle brakes, lots of other objects or actions are only legal depending on the context.
 

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I just don't get it ---

I like to ride fast.

I like to ride my fixie fast.

If I don't run a front brake, I can't stop as quickly. This means I can't ride as fast.

I run a brake.

If you don't wanna go over 20 kph, then, yeah, whatev, go brakeless.
 

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Some riders (not me) can stop from those speeds. I can't, you can't, we take the responsibility to equip the bike with a brake. It's just not that big a deal for the most part.
 

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mikbowyer said:
As a bike delivery guy I definitely have to ask if you were looking when you stepped out though. Even if you're legally right, Isn't it reasonable to expect that the rider had been in your field of view for no less than 5-10 seconds? You had more time to react than he did, if it went how it normally does for me when I hit people who had been standing still for 5-10 seconds as i watched them, then as I get 5 feet from them going 20-22 mph they just take that one step in front of me. I have never hit someone hard enough to knock them off step though, only a brush usually, but that happens about once an hour all day when its crowded.
From the article,
He was unable to stop for his red light in time as I walked out into the crosswalk.
The rider had several seconds of yellow light in which to prepare for the red light.
 

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likeguymontag said:
It's still irresponsible to ride a bicycle with no way to brake the front wheel. We all know from experience how much shorter you can stop when braking at the limit of traction with the front wheel than with the back wheel. That's just how the physics works.
It's true that on a conventional road or track bike the front wheel will provide a little bit more static friction than the back wheel. Of course, other frame designs, such as beach cruisers and recumbants, load the back wheel differently and on those the rear wheel can provide more braking force than the front.

The bigger factor is that regardless what frame geometry you use, two wheels with brakes have much more friction than one wheel with a brake whether it's the front or the rear. This means that any bike with brakes on both wheels will stop in around half the distance of one with only one brake. No matter how strong your legs are, a fixie without a front brake will take about twice as much distance to stop as a fixie with a front brake.

However, if you say that it's irresponsible to ride a bike without a front brake, you're banning all kids' bikes, beach cruisers, etc. that are equipped only with coaster brakes. I think that's going too far. The key is that the rider should understand his ride and operate it safely. If you're going to use only one brake, you should not ride as fast as someone with two brakes.
 

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Fredke said:
The bigger factor is that regardless what frame geometry you use, two wheels with brakes have much more friction than one wheel with a brake whether it's the front or the rear. This means that any bike with brakes on both wheels will stop in around half the distance of one with only one brake.
This is not correct. The front tire has more than enough traction for all the braking that is possible. A bicyle tire on clean drive pavement has a coefficient of friction (grip) of about 1. As a bicycle brakes (regardless of which wheel is braked) weight is shifted to the front wheel, increasing its traction. While braking in a straight line on clean dry pavement on most upright single bicycles, the rear wheel will lift off the ground and the bicycle will endo before the front wheel looses traction.

This can be demonstrated easily with a simple experiment. While riding on clean dry pavement on a bike with a front brake, squeeze the brake harder until either: 1) the front wheel skids; or 2) the rear wheel lifts off the ground. You'll find that the rear wheel lifts before the front wheel skids.


Fredke said:
No matter how strong your legs are, a fixie without a front brake will take about twice as much distance to stop as a fixie with a front brake.
This is true, but not for the reasons you state. As mentioned above, during braking, weight shift off the rear wheel and onto the front wheel. This decreases rear wheel traction. On a standard upright bicycle, the rear wheel will skid about 1/4 g of braking deceleration. However, since the front tire increases traction during braking, the limit of braking with the front brake is the point that the rear wheel starts to lift off the ground. This occurs at about 1/2 g braking deceleration (about twice the braking rate of rear wheel alone).

Because the traction/tipping limits, a bike with only a front brake can brake at about twice the rate as bike with only a rear brake.
 

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Mark McM said:
This is not correct. The front tire has more than enough traction for all the braking that is possible. A bicyle tire on clean drive pavement has a coefficient of friction (grip) of about 1. As a bicycle brakes (regardless of which wheel is braked) weight is shifted to the front wheel, increasing its traction. While braking in a straight line on clean dry pavement on most upright single bicycles, the rear wheel will lift off the ground and the bicycle will endo before the front wheel looses traction.
This would be correct if tire friction worked the way physics books describe it: frictional force = normal force times coefficient of friction. However, we know that's not correct for rubber tires. If it were, the rolling resistance and the braking friction would be independent of the tire width (normal force and coefficient of friction don't depend on the shape of the contact area), but in fact wide tires have both greater rolling resistance and greater braking friction.

Rubber exhibits not only Coulomb friction (the F = μN friction from Physics 100), but also viscoelastic and adhesive friction, which depend not only on normal force but also on the surface area of contact and the speed of rolling/sliding. There's a good discussion of the basics of rubber tire friction at http://www.insideracingtechnology.com/tirebkexerpt1.htm and there's an extensive literature on how the "coefficient of friction" between rubber tires and road surfaces is not constant, but depends on speed, load, contact area, etc.

Real-world friction is much more complicated than F = μN and more area of contact between rubber and road = more braking force even if the total normal force is constant. This means that front and rear braking will stop you a lot faster than front braking alone.
 

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Fredke said:
This would be correct if tire friction worked the way physics books describe it: frictional force = normal force times coefficient of friction. However, we know that's not correct for rubber tires. If it were, the rolling resistance and the braking friction would be independent of the tire width (normal force and coefficient of friction don't depend on the shape of the contact area), but in fact wide tires have both greater rolling resistance and greater braking friction.
I think you are missing the point. Tire traction is not the limitation on braking rate (see more below). Also, if you had done a little more research, you'd find that rolling resistance is not caused by the friction/adhesion with the road surface (it is instead caused by hysteresis losses in the rubber), and, all else being equal, wider tires have less rolling resistance, not more.

Fredke said:
Real-world friction is much more complicated than F = μN and more area of contact between rubber and road = more braking force even if the total normal force is constant. This means that front and rear braking will stop you a lot faster than front braking alone.
No, additional traction does no mean more braking force, because traction is not the limitation on braking force. Bicycles have relatively high centers of gravity compared to the length of their wheelbase. This means that a bicycle will tip over (endo) at relatively low g-forces (typcally 0.5-0.6 g). When applying the front brake only, a bike will endo before it runs out of traction on the front tire. The rear wheel lift-off point is the limiting of braking, not the traction limit of its tires.

The only way to get any meaningful braking with the rear wheel is if there is meaningful traction on the rear wheel, which in turn means that there is meaningful weight on the rear wheel. But if there is meaningful weight on the rear wheel, you are not close to the rear wheel lift-off point - and therefore not close to the maximum braking rate.

Vehicles with lower centers of gravity (automobiles, even tandem bicycles) can get meaningful braking from the rear wheel. But a single upright bicycle can not. The rear wheel lift-off limit on a bicycle is about 0.5-0.6 g, which is smaller than the traction coefficient of the tires (typically about 0.8-1.0).
 

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jaded bitter joy crusher
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OK, I see your point, but I think something's got to be missing because I have locked up both wheels on my roadie without endoing. When I have time, I'll work out a free-body diagram to see whether I can figure it out.
 
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