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#1
Old 07-02-2018, 05:45 PM
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Why do motorcycles stop slower and follow further behind than cars?

Lately, on my daily commute, whenever I end up behind a motorcycle, they not only leave a noticeably larger gap in front of them (than I would in a car), they also slow down much more gradually and over a longer distance. This isn't just accident or timing, because when a traffic signal changes, they will accelerate slower, to restore that oddly large gap. I've seen them even slow to a crawl (like 18-wheelers will do) and snake back and forth across a lane to avoid coming to a complete stop.

I know almost nothing about motorbikes, only that they are much more agile than cars, and the lack of protection greatly magnifies the damage from any accident/spill.
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#2
Old 07-02-2018, 05:52 PM
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Quote:
Originally Posted by dstarfire View Post
...the lack of protection greatly magnifies the damage from any accident/spill.
This. Most (careful) motorcyclists will leave room in front when in traffic to make up for the car drivers (cagers, as they are known) lack of stopping distance.

Also, motorcycles don't have anti-lock brakes (as a general rule).
#3
Old 07-02-2018, 05:53 PM
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Because they are conscious of such dangers, they are driving more cautiously. Everyone would do well to keep larger gaps even in cars.
#4
Old 07-02-2018, 05:56 PM
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Quote:
Originally Posted by dstarfire View Post
Lately, on my daily commute, whenever I end up behind a motorcycle, they not only leave a noticeably larger gap in front of them (than I would in a car), they also slow down much more gradually and over a longer distance. This isn't just accident or timing, because when a traffic signal changes, they will accelerate slower, to restore that oddly large gap. I've seen them even slow to a crawl (like 18-wheelers will do) and snake back and forth across a lane to avoid coming to a complete stop.

I know almost nothing about motorbikes, only that they are much more agile than cars, and the lack of protection greatly magnifies the damage from any accident/spill.
Here are a few.

1) less surface area for breaking means that modern cars with ABS can stop faster
2) The personal costs of following too close on a motorcyclist are far higher than the average person in a car would suffer during an accident.
3 ) By increasing following distance you also increase the following distance of cars behind you, providing them with more time to react so they are less likely to pin you between the two cars if they fail to stop.
4) In general people tend to overestimate their abilities and follow way to close anyway, which is why there are so many accidents are rear endings.
5) it is fun, and useful to try to go as slow as possible as it builds muscle memory and improves riding skills.
#5
Old 07-02-2018, 06:06 PM
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To add context to this, 28% - 40% of crashes are rear-end collisions according to the NHTSA.

As a vulnerable road user, taking steps to reduce what amounts to a huge percentage of risk is highly prudent.
#6
Old 07-02-2018, 06:09 PM
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Quote:
Originally Posted by rat avatar View Post
3 ) By increasing following distance you also increase the following distance of cars behind you, providing them with more time to react so they are less likely to pin you between the two cars if they fail to stop.
This is a big one. A motorcyclist canít control the following distance of a car behind them. All they can do, if they feel the car behind is too close, is to increase their own following distance so they can slow more gradually themselves and avoid being rear ended.
#7
Old 07-02-2018, 06:09 PM
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Stopping a motorbike very quickly is more dangerous than stopping a car very quickly because it's far less stable. All the more so if the bike doesn't have ABS.

In many cases, a motorbike will require a greater distance to stop from the same speed. A car will have twice as many brakes and several times as much rubber on the road.

As you note, the lack of protection greatly magnifies the damage from any accident. If a bike runs into the back of a car even at low relative speed it probably won't go well for the rider.

So it's prudent for a motorcyclist to leave a larger gap.
#8
Old 07-02-2018, 06:17 PM
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Because they don't want to die?

Most drivers in America are shitty drivers, though it wasn't always this way. The ubiquitous combination of texting and driving makes city traffic a death-trap, which is why I sold my motorcycle a long time ago.
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Last edited by Lamoral; 07-02-2018 at 06:18 PM.
#9
Old 07-02-2018, 06:25 PM
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Originally Posted by Lamoral View Post
Because they don't want to die?

Most drivers in America are shitty drivers, though it wasn't always this way.
yes it was.
#10
Old 07-02-2018, 06:40 PM
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I will add another reason that is partially related to the others and something I observed repeatedly over the weekend. Those little potholes on a highway (I'm looking a you I-5 and I-90 near seattle) that your car sails over with just a bunch of noise can wreak havoc for someone on two wheels- same with other road debris. Having an extra second of lead time after the car in front "uncovers" such an obstacle to pick a better line on the road can mean a lot as far as safety goes.
#11
Old 07-02-2018, 06:57 PM
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Quote:
Originally Posted by dstarfire View Post
I've seen them even slow to a crawl (like 18-wheelers will do) and snake back and forth across a lane to avoid coming to a complete stop.
That's simply to avoid putting their feet down and then having to take off again from 0. You'll see it even more in situations where they'd have to do it over and over, like a 3 or 4 cars in front of them at a stop sign.
And it's not like it's a big deal to take off from zero, at least part of it is for fun.

When I took my MSF class having to come to a rolling stop and then taking off again is taught and practiced. Even on the final test/exam, you have to go as slow as possible for some set length. In motorcycle rodeos one of the things is to see how slow you can go.
For the record, they weren't telling us to roll through stop signs, it's just an exercise in using the throttle and brake and handling the bike. Like a regular bike, it handles differently when going very slow than it does at just about any speed over a few mph.

And just to reiterate what everyone else has been saying, you really don't want to stop to fast if it's at all avoidable. Locking up either your front or rear wheel can be bad, for different reasons.
#12
Old 07-02-2018, 07:37 PM
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Quote:
Originally Posted by dstarfire View Post
Lately, on my daily commute, whenever I end up behind a motorcycle, they not only leave a noticeably larger gap in front of them (than I would in a car), they also slow down much more gradually and over a longer distance. This isn't just accident or timing, because when a traffic signal changes, they will accelerate slower, to restore that oddly large gap. I've seen them even slow to a crawl (like 18-wheelers will do) and snake back and forth across a lane to avoid coming to a complete stop.

I know almost nothing about motorbikes, only that they are much more agile than cars, and the lack of protection greatly magnifies the damage from any accident/spill.
As one of the people on said motorcycles

Its so that
A) We dont get crushed between you and the car in front when you dont stop
then we at least have a change of an out.

B) So you notice we are actually stopping, because many drivers can not see a motorcycle right in front of them (or so they claim)

Also if you are not speeding on your bike, unlike cars, many times you wont even need to use the brakes hardly to stop, which on a bike can extend the life of costly little tires. A tire that would cost 40 bucks on a car costs 100 bucks for a motorcycle
And lots of braking and acceleration shortens their life a good deal, much much less life than the tire on a car which may run 40k 50k miles

Snaking back and forth is useless, just bored or lazy i guess and dont want to put their foot down.
#13
Old 07-02-2018, 07:47 PM
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A large gap also gives you a place to accelerate into when the car in front of you creeps up to speed and you want a little more stability on take off without appearing to hold up traffic or getting to close the the car infront.

I snake around mostly for the reason Weisshund mentions, bored and lazy. Sometimes road grooves jostle me some. Sometimes to use the rest of my tires more, it's really flat here so most roads are really straight and flat .
#14
Old 07-02-2018, 08:10 PM
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Quote:
Originally Posted by dstarfire View Post
I've seen them even slow to a crawl (like 18-wheelers will do) and snake back and forth across a lane to avoid coming to a complete stop.
It's for much the same reason -- it takes both of them longer to stop in an emergency. Trucks have a whole lot of weight behind them, an motorcycles have only 2 wheels on the pavement, unlike the 4 in cars (and cars usually have fancy ABS braking). Also, cycles are much less stable -- stop too fast, especially with more weight in front, and the cycle will flip up, and toss the driver onto the pavement, or in front of another vehicle.
#15
Old 07-02-2018, 08:14 PM
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Motorcycles generally take much more distance to stop than cars in the real world, and emergency braking from high speed is really hard and dangerous. Do it wrong, and it's easy to lose control.

For example, the most effective braking is on the front tire, because braking throws your weight and the weight of the bike over the front tire giving it more grip. But braking with the front tire alone can easily cause you to lose control of the bike. So you get taught that in emergency braking you start with the front, then add the back brake. But in a panic, it's hard to coordinate like that. So most people hit the foot brake for the back wheel first. At slow speed, that's more controllable. At high speed, again having the weight of you and the bike thrown forward you can unload the back tire, which will then break free and throw you into a slide. Therefore, it's hard for people to attain theoretical braking distances on a bike (which even theoretically stops longer than a car).

One time I came close to an accident on my bike, I was on the freeway. I left a large gap in front of me, which a clueless driver in the other lane then squeezed into, then hit his brakes because the car in front of him did and he had no space to carefully slow down. I tried all my best emergency braking manoevers, and still wound up sideways on the bike at about 50 mph. I just barely kept it under control and managed to stop maybe five feet from the other guy's bumper with my heart racing madly. One minute I was commuting along safely, and suddenly I was a hair's breadth from dropping my bike at 50 mph on a crowded freeway. Just because some asshole couldn't be bothered to think about what he was doing, or wasn't paying attention.

After that, I learned to be even more cautious on the road. I never passed anyone unless I was sure they knew I was there. I got into the habit of looking at the other drivers before I passed to make sure they weren't texting, or adjusting the radio, or arguing with someone else in the car. And let me tell you, once you start doing that it gets very scary. A high percentage of drivers just don't have their heads in the game, for many reasons. I once saw a woman with an iPad in the center of her steering wheel. She was watching a movie while driving.

Sometimes stuff like this makes you want to never take a motorbike on a public road again.
#16
Old 07-02-2018, 08:43 PM
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Like on a bicycle, hard braking can cause you to wipe out. Also, as mentioned potholes can cause a loss of control, but so can wet metal or painted lines (especially new thermoplastic), as well as loose gravel or sand. Those innocuous manhole covers, bridge expansion joints, stop lines, lane arrows, or a spilled bag of aquarium stones can easily cause a wipeout on a bike, whether motorized or not, whereas in a car it might only cause the briefest skid if anything at all.
#17
Old 07-02-2018, 09:03 PM
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Sam Stone, I was with you, until this:
“I never passed anyone unless I was sure they knew I was there.”
It’s impossible to know what the driver knows. They can be looking right at you, and not see you. IMO, it’s better to ride as if I’m invisible. I’m constantly imaging what the worst action is that drivers could take, and trying to create escape routes.
#18
Old 07-02-2018, 09:58 PM
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Quote:
Originally Posted by Capn Carl View Post
Sam Stone, I was with you, until this:
ďI never passed anyone unless I was sure they knew I was there.Ē
Itís impossible to know what the driver knows. They can be looking right at you, and not see you. IMO, itís better to ride as if Iím invisible. Iím constantly imaging what the worst action is that drivers could take, and trying to create escape routes.
This. I like to predend everyone else on the road is actively attempting to murder me.
#19
Old 07-02-2018, 10:16 PM
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That wasn’t quite what I meant. I agree that you should assume you aren’t being seen, but I also look to make sure that the driver is at least paying attention to the road. I still pass carefully, but I won’t pass at all if I can see that the driver is distracted.

Last edited by Sam Stone; 07-02-2018 at 10:17 PM.
#20
Old 07-02-2018, 10:28 PM
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Quote:
Originally Posted by rat avatar View Post
Here are a few.

1) less surface area for breaking means that modern cars with ABS can stop faster
This is a common misconception. Static friction is, to a first approximation, independent of surface area. Besides, itís not friction between the front wheel and tire that limits motorcycle braking; itís pitchover. If friction were the limiting factor, pitchover (an endo) wouldnít be possible.

Cars can stop faster than motorcycles mostly because they canít pitch over. Rear-engined carsómostly the Porsche 911óbrake so well because they have a strong rearward weight bias. A long, low motorcycle with similar weight distribution to a 911 would brake nearly as well.
#21
Old 07-02-2018, 11:24 PM
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Originally Posted by jz78817 View Post
yes it was.
No, it wasn't this bad before. I started driving in 2001. Since then I have noticed in the past, like, 8 years, drivers in the main become far more sloppy and distracted and, worst of all, slow. I can't believe how goddamned slow so many drivers are off the line when the light turns green. I routinely get trapped between two red lights because some wanker up ahead waits three seconds before accelerating to 20-odd miles per hour (holding up the entire line of cars) because he or she was on their phone instead of paying attention to the traffic signals.
#22
Old 07-03-2018, 02:03 AM
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Quote:
Originally Posted by EdelweissPirate View Post
This is a common misconception. Static friction is, to a first approximation, independent of surface area. Besides, it’s not friction between the front wheel and tire that limits motorcycle braking; it’s pitchover. If friction were the limiting factor, pitchover (an endo) wouldn’t be possible.

Cars can stop faster than motorcycles mostly because they can’t pitch over. Rear-engined cars—mostly the Porsche 911—brake so well because they have a strong rearward weight bias. A long, low motorcycle with similar weight distribution to a 911 would brake nearly as well.
I do agree with most of what you said, or the intent.

Related to front tire lockup, it is far more possible that people would expect. Here is an example.

https://youtube.com/watch?v=tdiTrpPkh_I

Related to friction and area, and related to the fact that the bike in that video was a GS, with hybrid tires (and no endo)

You are referencing the classical physics Amonton’s paradox, where friction does not relate to area. Note that this does not apply in the case of stick and slip as in the shear forces generated at the tread–road interface are typically modeled as springs similar to bristles that cause the slip, and not static friction. Remember that a tire is a bending balloon and not a static surface.

As an example.

https://pdfs.semanticscholar.org/359...ca394dcebc.pdf

While there are factors like material choices and construction impacts this, my understanding it is typically carcass deformation that results in the initial skittering.

While the construction and the shape of a motorcycle and a car tire differ greatly, having a wider contact patch provides more "virtual springs" to spread this shear stress and greater weight to stop does impact this.

But the materials are quite similar, and Amontons' 2nd law as it doesn't account for the deformation that results form the shear force or the "true contact patch" but only the "apparent contact patch".

Here is another link that demonstrates the complexity in modeling this.

http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

Note that Amonton’s paradox has been resolved, as that classical model accounted for the apparent contact surface and not the actual or effective contact area.

Quote:
Friction also plays a major role in understanding earthquakes. Measurements of the contact surface of rocks [1] show that the friction force is proportional to true contact area, finally resolving Amonton’s paradox.


For more information you can search for "Bowden and Tabor" and their papers from the 1950s.

Unfortunately, unless you are a graduate student, work in the field, or obsessively read papers there would be no reasonable way run across this updated information with the intentional hard split between classical physics and modern physics in the educational system.

But thanks for the correction.

Last edited by rat avatar; 07-03-2018 at 02:08 AM.
#23
Old 07-03-2018, 04:18 AM
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Quote:
Originally Posted by rat avatar View Post
I do agree with most of what you said, or the intent.
Cool! I happen to agree with pretty much everything you wrote.

I should point out that I specified static friction and included the phrase "to a first approximation" on purpose, as I didn't want to get bogged down in excessive detail.

You're definitely more up to speed on the resolution of Amontons' paradox than I am, and I appreciate your extended response. I happen to be in a position to appreciate all of the complexity involved in modeling friction in tires. Like, eerily so.

Quote:
Originally Posted by rat avatar View Post
Unfortunately, unless you are a graduate student, work in the field, or obsessively read papers there would be no reasonable way run across this updated information with the intentional hard split between classical physics and modern physics in the educational system.
Funny you should mention those things. I was a grad student in engineering physics about fifteen years ago; my coursework included a graduate-level vehicle dynamics class and I did some research in a nanotribology lab, though that's neither here nor there.

It happens that I do "work in the field," as you put it, as long as the field is mechanical engineering. Mostly, I do finite element analysis of nonlinear structures, including, occasionally, hyperelastic/viscoelastic ones similar to tires (I haven't modeled tires, though, because I don't specialize in them; tire modeling is a career unto itself).

Quote:
Originally Posted by rat avatar View Post
But thanks for the correction.
I'm getting more than a whiff of snark here...am I imagining that?

I guess I can see why someone like yourself might bristle at being told he held a common misconception about this subject, which is exactly what I told you. I didn't mean to offend you (if I did), but in my defense, I had no way to know what you knew based on what you wrote.

I could tell you were probably a motorcyclist (as am I) but on the other hand, you mis-spelled "braking," which didn't immediately suggest a serious interest in the relevant theory. I don't care about spelling or typos, but really, I had no straightforward way to intuit the depth of your knowledge here.

You had no way to intuit mine, either, except for maybe looking at my public profile. I don't fault you for not figuring it out; maybe you could cut me some slack too.

Or maybe you didn't intend to be snarky and I've misunderstood. Either way, I'm digging the ASME paper you posted. Thanks!





P.S. You're right, of course, that a nontrivial number of motorcycles on the road are limited in braking by friction, not pitchover. I concede that I was thinking of sportbikes and things like GP motorcycles, which aren't exactly prone to skidding their front wheels in straight-line braking. But that thought doesn't jibe with the OP's question or the post (by you) to which I initially responded.

Another reason I wrote what I did about pitchover because there's currently a slightly silly debate in the bicycle world about road bikes with disc brakes. It's common to hear people claim that, while mountain bikes are well suited for disc brakes, road bikes aren't because "the greater braking force would overwhelm the smaller road bike contact patch." Any decent road or mountain bike (save recumbents and tandems) is braking-limited by pitchover, not friction.

So I reflexively responded to something you didn't say and did so in an excessively narrow way. Sorry about that!
#24
Old 07-03-2018, 04:31 AM
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Quote:
Originally Posted by EdelweissPirate View Post
Cool! I happen to agree with pretty much everything you wrote.

I should point out that I specified static friction and included the phrase "to a first approximation" on purpose, as I didn't want to get bogged down in excessive detail.

You're definitely more up to speed on the resolution of Amontons' paradox than I am, and I appreciate your extended response. I happen to be in a position to appreciate all of the complexity involved in modeling friction in tires. Like, eerily so.



Funny you should mention those things. I was a grad student in engineering physics about fifteen years ago; my coursework included a graduate-level vehicle dynamics class and I did some research in a nanotribology lab, though that's neither here nor there.

It happens that I do "work in the field," as you put it, as long as the field is mechanical engineering. Mostly, I do finite element analysis of nonlinear structures, including, occasionally, hyperelastic/viscoelastic ones similar to tires (I haven't modeled tires, though, because I don't specialize in them; tire modeling is a career unto itself).



I'm getting more than a whiff of snark here...am I imagining that?

I guess I can see why someone like yourself might bristle at being told he held a common misconception about this subject, which is exactly what I told you. I didn't mean to offend you (if I did), but in my defense, I had no way to know what you knew based on what you wrote.

I could tell you were probably a motorcyclist (as am I) but on the other hand, you mis-spelled "braking," which didn't immediately suggest a serious interest in the relevant theory. I don't care about spelling or typos, but really, I had no straightforward way to intuit the depth of your knowledge here.

You had no way to intuit mine, either, except for maybe looking at my public profile. I don't fault you for not figuring it out; maybe you could cut me some slack too.

Or maybe you didn't intend to be snarky and I've misunderstood. Either way, I'm digging the ASME paper you posted. Thanks!





P.S. You're right, of course, that a nontrivial number of motorcycles on the road are limited in braking by friction, not pitchover. I concede that I was thinking of sportbikes and things like GP motorcycles, which aren't exactly prone to skidding their front wheels in straight-line braking. But that thought doesn't jibe with the OP's question or the post (by you) to which I initially responded.

Another reason I wrote what I did about pitchover because there's currently a slightly silly debate in the bicycle world about road bikes with disc brakes. It's common to hear people claim that, while mountain bikes are well suited for disc brakes, road bikes aren't because "the greater braking force would overwhelm the smaller road bike contact patch." Any decent road or mountain bike (save recumbents and tandems) is braking-limited by pitchover, not friction.

So I reflexively responded to something you didn't say and did so in an excessively narrow way. Sorry about that!
To be clear, no snark at all. I personally take finding out when I am in error a happy event as I learned something.

I don't know everything and no matter how much I do know it will always be eclipsed by what I don't know.

I apologize if it came across in that fashion, the only snark in that post was directed at myself, because I tend to read papers when others seem to have more healthy hobbies.

(I have two custom bicycles with disc brakes btw, but that is because I commute in the rain and don't like to wait for the pads to wipe the rim clear before they start to work)

Last edited by rat avatar; 07-03-2018 at 04:32 AM.
#25
Old 07-03-2018, 06:42 AM
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Quote:
Originally Posted by EdelweissPirate View Post
Besides, itís not friction between the front wheel and tire that limits motorcycle braking; itís pitchover. If friction were the limiting factor, pitchover (an endo) wouldnít be possible.
This depends very much on the bike. a 600-cc sportbike (i.e. relatively lightweight) with sport (i.e. grippy) tires and a short wheelbase (i.e. center of mass relatively high and close behind the front tire's contact patch) will be prone to pitchover.

Heavier bikes, longer wheelbases, and less grippy tires (i.e. touring or sport-touring) mean that front wheel lock-up is more likely to be the limiting factor.

I have a BMW R1200RT, which is more in the latter category. On clean, dry pavement, very hard braking engages the ABS on both wheels; the rear wheel gets very light, but I've never encountered a situation where I felt it becoming airborne.

As for why I ride the way I do:
Quote:
Originally Posted by dstarfire
they not only leave a noticeably larger gap in front of them (than I
would in a car),
If someone is tailgating me, I'm going to leave a very long gap in front of me so that I can stop gradually enough to avoid having my tailgater hit me. Even if nobody is tailgating me, I'm going to leave a long enough gap so that I can stop without much drama if the guy in front of me slams on his brakes. I also want lots of warning in case the car in front of me rolls over an object that could take me down. A 2x4 laying in the road won't make a car crash, but it might make a bike crash; I'd rather go around something like that than over it. (this is part of why smart riders ride in the wheel tracks instead of the center of a lane: the wheel tracks are less likely to have problematic debris in them.)

Quote:
Originally Posted by dstarfire
I've seen them even slow to a crawl (like 18-wheelers will do) and snake back and forth across a lane to avoid coming to a complete stop.
If you're talking about stop-and-go traffic jams, there are two reasons:

#1: your clutch hand gets tired of repeatedly pulling the lever (and holding it while stopped). Same goes for a trucker's left foot.

#2: at very low speeds (less than first gear, i.e. clutch pulled in), it's a bit of a self-challenge to see how slowly you can ride without having to put your feet down. Basically a way to pass the time under an otherwise boring riding condition.

Here's a question for you: are you leaving a large enough following gap when you're driving your car? Depending on who you talk to, the recommendation is 3-5 seconds. On the bike, since crash outcomes are worse, I'm going to tend toward the latter.
#26
Old 07-03-2018, 08:23 AM
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Regarding comments upthread about weaving back and forth in the lane, when you weave you cover a greater distance than when traveling in a straight line. Bikes that are geared tall have a hard time creeping with slow traffic without slipping the clutch excessively. I do this routinely right up to the point where I turn around and go another route. Or lanesplit!
#27
Old 07-03-2018, 09:32 AM
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One other thing that I haven't seen mentioned yet: There are still a fair number of air-cooled motorcycles on the road (fewer and fewer in the US, as EPA regulations make it more difficult to meet pollution limits with an air-cooled motor). Sitting still in traffic severely limits the cooling ability of the fins on the outside of the cylinders, causing the bike to heat up. This can result in overheating. Sometimes, if traffic is stalled for extended periods, you may see bikers pull off the road and stop, or start filtering in-between cars. While filtering is also often done out of impatience with traffic, I believe it was originally intended to provide bikes with a way to keep air moving across their engines.

In second (or third) to the posters above, it's also about trying to prevent getting pancaked by a read-ender and it's kind of a fun skills challenge to try not to put your feet down. When we ride in groups and hit traffic, there is often a spontaneous "slow-roll" contest.
#28
Old 07-05-2018, 01:33 PM
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Originally Posted by rat avatar View Post
(I have two custom bicycles with disc brakes btw, but that is because I commute in the rain and don't like to wait for the pads to wipe the rim clear before they start to work)
Hold on. It sounds like you're saying most bikes have the same nearly-useless style of brakes as their pedal-powered siblings!!

I know the first motorbikes where just regular bicycles with an engine attached, but that was DECADES ago. But, surely, they've added some sophistication since then.
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#29
Old 07-05-2018, 01:56 PM
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Originally Posted by dstarfire View Post
Hold on. It sounds like you're saying most bikes have the same nearly-useless style of brakes as their pedal-powered siblings!!

I know the first motorbikes where just regular bicycles with an engine attached, but that was DECADES ago. But, surely, they've added some sophistication since then.
That was an off topic thread, and was only related to the post I was responding to, where the subject of disc brakes was mentioned.

With Bicycles there are two serious issues with rim brakes if you ride in the wet daily.

1) Soft rubber pads collect road grit, and this grit wears away at your breaking surface in an accelerated fashion.

2) Due to lower pressures, softer materials, and higher speeds rim breaks need to wipe a layer of water before they become effective where disc breaks have.
a) more pressure
b) great distance from major water sources
c) stiffer materials
This results in about half a lane of distance difference in stopping in my non-scientific tests. People buy road bicycles pretty much based on what the bike racers use, irrespective of if it is better for them or not. While they have been working on getting disc brakes on road race bikes there is a problem about unequal breaking in large groups and potential dangers of discs working like a bacon slicer. This is changing right now in this time of history. (Note it also allows for wider tires which are more energy efficient BTW)

https://bicycling.com/bikes-gear...o-racing-2018/

But on the subject of motorcycles, yes I use to commute on vintage motorcycles. 1967 Triumph Thunderbird and a 1969 Moto Guzzi Ambassador to be specific, for years. I gave up all of those bikes and even more modern ones for a bike with a slipper clutch, traction control, modern suspension and ABS. Those vintage bike's brakes were marginal at best even with upgrades to modern materials.

Things have improved in the motorcycle world, but unfortunately they have improved more for automobiles. ABS and Traction Control can be far more aggressive on a 4 wheeled car even ignoring contact patch area etc... simply because they can mediate the lockup of two wheels per end, and can risk on wheel sliding for a greater time than would be allowed for in a motorcycle.

Last edited by rat avatar; 07-05-2018 at 01:58 PM.
#30
Old 07-05-2018, 02:23 PM
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Quote:
Originally Posted by Machine Elf View Post
All right. I'm impressed.

Quote:
Originally Posted by BrianDime View Post
Sitting still in traffic severely limits the cooling ability of the fins on the outside of the cylinders, causing the bike to heat up. This can result in overheating.
Motorcycles are also required to have their headlights on at all times. Basically, for any bike built since the 1970s or later, if the key is in the "on" position, the light is on. We can't turn the light off without shutting the bike off. Many motorcycles don't put out enough charge when they are sitting still or crawling in stop-and-go traffic, so aside from overheating, you can also end up with a dead battery.

Quote:
Originally Posted by BrianDime View Post
In second (or third) to the posters above, it's also about trying to prevent getting pancaked by a read-ender and it's kind of a fun skills challenge to try not to put your feet down.
Same for me. I don't want to get pancaked, and I like the challenge of trying not to put my foot down.

I have two bikes, a fairly lightweight Honda that takes off like a bat out of hell and stops on a dime, and a much heavier Harley that definitely does not stop on a dime. I can probably stop the Honda in close to the same distance as a car can stop, but definitely not the Harley. Even with the Honda, though, I'm not going to risk it. If the rear wheel locks it's not that big of a deal, but if the front wheel locks, you absolutely have to react very quickly or you're going to be sucking pavement.

Neither of my bikes has ABS.
#31
Old 07-05-2018, 03:11 PM
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Quote:
Originally Posted by dstarfire View Post
Hold on. It sounds like you're saying most bikes have the same nearly-useless style of brakes as their pedal-powered siblings!!

I know the first motorbikes where just regular bicycles with an engine attached, but that was DECADES ago. But, surely, they've added some sophistication since then.
motorcycles had mechanical drum brakes for a fairly long time, then like cars switched to hydraulic discs up front first. later many switched to hydraulic rear discs, but some (typically Japanese cruisers) still employ mechanical rear drum brakes.
#32
Old 07-05-2018, 03:35 PM
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Originally Posted by engineer_comp_geek View Post
All right. I'm impressed.
What keeps a bike upright is a surprisingly complicated question but a fascinating one.

I get the OP is on about motorcycles and not bicycles but the same physics principles apply (I would think) to any two-wheel contraption when it comes to its balance.

(Someone provided that link to me here some time back when I asked about keeping bikes upright...I looked a bit but did not find it again to give proper thanks for the source here.)

Last edited by Whack-a-Mole; 07-05-2018 at 03:37 PM.
#33
Old 07-05-2018, 10:01 PM
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An additional reason I followed further behind cars was because you never know what you are going to find on the road. (This is a variation on the previous comment about potholes). If a tin can or a piece of wood or an oil slick appears on the road, I can only see it after the car has passed over it, and I have a very short time to change my position. If I am in a car, I don't worry much: other cars have already tested the obstacle, and the worst it's going to do is damage the car.

I rode much further back in the wet: if I hit something on the road, the car behind me would be unable to stop in the wet, and was going to drive right over me. In the dry, I would mostly worry about the car in front of me stopping suddenly: I have to assume that the car in front was completely unaware of me (and wouldn't care much anyway), as frequently demonstrated.

I stopped riding around 1990. I'm surprised at the consensus that "cars stop faster than bikes". If that's the case now, the stopping distance calculators and documentation on the web haven't yet caught up with reality. An additional reason I could stop faster than a car was because I rode with my hand on the brake. It used to be that car drivers drove with the brake foot on the accelerator, and had to move it across to brake, which, particularly at high speed added a big step to their braking distance (even when trained and motivated). On most cars, that still the case.

Last edited by Melbourne; 07-05-2018 at 10:03 PM.
#34
Old 07-06-2018, 12:43 AM
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Quote:
Originally Posted by Melbourne View Post
I'm surprised at the consensus that "cars stop faster than bikes".
Yeah, me too. My RZ stops so hard, my eyeballs hurt.
#35
Old 07-06-2018, 02:09 AM
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Originally Posted by Melbourne View Post
I'm surprised at the consensus that "cars stop faster than bikes".
I don't know that it's really a consensus. It seems to be a hotly debated topic on the internet.

IIRC, the Motorcycle Safety Foundation does say this in their basic rider's course.

I have seen a test of a car and a motorcycle, both with ABS. The motorcycle had the shorter stopping distance at both lower speeds and at highway speeds. My memory is a bit fuzzy but I think the two speeds they tested were something like 30 mph and 60 mph.

To be fair, it was one bike and one car. There are all kinds of different bikes out there with all kinds of different stopping distances, and the same goes for cars.

I can add the two more data points that I already posted upthread. My late 90s Honda Nighthawk stops in about the same distance as a car, and my Harley (also late 90s) doesn't. Neither bike has ABS.
#36
Old 07-06-2018, 07:25 AM
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Quote:
Originally Posted by Melbourne View Post
I stopped riding around 1990. I'm surprised at the consensus that "cars stop faster than bikes".
IIRC, ABS first debuted on a motorcycle in the early 1990s; it's becoming more common, but only in a relative sense; I think most bikes on the road still don't have it. Motorcycle tires do tend to be grippier than car tires, so if you have a very experienced rider, on smooth, clean, dry pavement, in a non-panic situation, he may be able to exceed what a car can do, even if the car has ABS.

That's a very rare set of circumstances. Most of the time the pavement isn't perfectly smooth/clean/dry, or the rider hasn't practiced emergency stopping techniques, doesn't know the limits of his machine, or has outright panicked. If he's thinking clearly, he's probably going to underbrake the front (where most of your stopping power is) and skid the back; if he's in a panic, he'll probably lock up both wheels and fall over (or go over the bars if it's a grippy sportbike).

So I think the assertion that cars can stop faster than bikes is, on average, true: take an average driver in an average car, and put him next to an average rider on an average bike, and the driver will have a shorter stopping distance than the rider.
#37
Old 07-06-2018, 08:57 AM
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Quote:
Originally Posted by engineer_comp_geek View Post
I don't know that it's really a consensus. It seems to be a hotly debated topic on the internet.

IIRC, the Motorcycle Safety Foundation does say this in their basic rider's course.

I have seen a test of a car and a motorcycle, both with ABS. The motorcycle had the shorter stopping distance at both lower speeds and at highway speeds. My memory is a bit fuzzy but I think the two speeds they tested were something like 30 mph and 60 mph.

To be fair, it was one bike and one car. There are all kinds of different bikes out there with all kinds of different stopping distances, and the same goes for cars.

I can add the two more data points that I already posted upthread. My late 90s Honda Nighthawk stops in about the same distance as a car, and my Harley (also late 90s) doesn't. Neither bike has ABS.
both my bikes have ABS, but I've only ever triggered the rear ABS on my Dyna, during a class.
#38
Old 07-06-2018, 09:45 AM
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I'm scared when a motorcyclist is on the road near me, scared for their safety, and try to avoid being in front of one. I hope they are operating safely. I got this way because of the time a biker did not operate safely and got hurt.

I was accelerating from a stop at a light, my left turn signal on, because I was going to turn onto the left on-ramp to the highway just ahead. It was dusk and I had my lights on. In my rear-view mirror I saw the headlight approaching, accelerating through the green light but then not slowing down, though I was accelerating at a lower rate. It all happened in 2 seconds. I felt the impact of his wheel on my bumper like a kiss and saw the headlight topple sideways. The crashed motorcyclist was lying in the gutter, semiconscious, groaning in pain and bleeding from his head. There was no helmet. I called 911 and waited until the ambulance and police came and I gave a report. It was on a Friday night in Twinsburg, Ohio.

I was not at fault. He hadn't been paying attention where he was going. He chose to ride without a helmet and got his head bust up. Still, though it was over 30 years ago, I cautiously keep as much distance from motorcycles as I can.
#39
Old 07-06-2018, 10:18 AM
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To the posters on Amontons: I can't put my finger on what is paradoxical being discussed in Amontons' Laws discussed above. Rather than unduly stress the OP here, I have bumped
Did I just lie about Galileo to a fat kid on a sled?
which is essentially on that topic as much as this OP is, but I think at a level better suited to "whoah, huh?" posts, as opposed to those on first-order approximations and their alternatives.

Rather than x-post, I ask here my "" and if any help can be posted to that fat kid thread.
#40
Old 07-06-2018, 10:52 AM
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Quote:
Originally Posted by Melbourne View Post
I stopped riding around 1990. I'm surprised at the consensus that "cars stop faster than bikes". If that's the case now, the stopping distance calculators and documentation on the web haven't yet caught up with reality.
The online debates concern training and technology.
When I took lessons in 2002 they were teaching that motorcycle riders with track experience could stop in a shorter distance than cars.

However this was comparing riders who had been trained on how to blip their brakes to the verge of locking up, compared to a driver who was locking the brakes and skidding to a stop.

Since then ABS in cars has become the norm (although I don't believe it's mandatory in US or Canada) and cars so equipped on a flat surface will be stopping in a shorter distance than a motorcycle.
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#41
Old 07-06-2018, 03:40 PM
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Quote:
Originally Posted by Barbarian View Post
The online debates concern training and technology.
When I took lessons in 2002 they were teaching that motorcycle riders with track experience could stop in a shorter distance than cars.

Here is more information.

However this was comparing riders who had been trained on how to blip their brakes to the verge of locking up, compared to a driver who was locking the brakes and skidding to a stop.

Since then ABS in cars has become the norm (although I don't believe it's mandatory in US or Canada) and cars so equipped on a flat surface will be stopping in a shorter distance than a motorcycle.
That comparison was with older ABS systems and typical cars with GP bikes and riders in perfect conditions. To have a similar comparison consider a modern F1 car driver experiences up to ~4 Gs of deceleration during braking. Due to the higher CG, I doubt motorcycles will ever get to that level of performance. I know I couldn't do a handstand with 3 of me on my feet too. 1 G would be ~45 degrees but 4 G is closer to a handstand.

Modern ABS and traction control systems use fuzzy logic and other methods and more sensors to dramatically improve breaking. Now it is not uncommon for more advance cars to get close to 1 G of deceleration. It requires a lot of skill, and comfort with stopping while doing a wheelie to reach this point and is not practical for emergency stops in less than ideal conditions.

Here is a diagram that show how narrow the band is where a driver/rider can best ABS. What this does not capture is that due to the low margin of error and high costs of exceeding that limit most riders/drivers will not brake hard enough early enough to compete with these systems. In other words, even if the driver/rider is highly skilled they are more likely to utilize that optimal braking zone if they have ABS available if they misjudge.

https://imgur.com/a/DgbM8GV


ABS does under-perform in some conditions like ice but modern motorcycle ABS like KTM introduced about 5 years ago will do better than even the top riders in gravel.

Last edited by rat avatar; 07-06-2018 at 03:44 PM.
#42
Old 07-06-2018, 11:44 PM
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The bike I ride is a Kawasaki KLR 650. They have relatively poor braking performance.
#43
Old 07-07-2018, 11:35 AM
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Quote:
Originally Posted by rat avatar View Post
ABS does under-perform in some conditions like ice but modern motorcycle ABS like KTM introduced about 5 years ago will do better than even the top riders in gravel.
I can confirm from personal experience that motorcycle ABS underperforms on ice. In my case, it underperformed to the tune of about $200 worth of broken bits.

Also from experience: even with ABS, even with some racetrack braking experience, and even with a special customization that inhibits both endos and wheelies (it's called "obesity"), I still leave room when I think to do so, for a lot of the reasons that have already been mentioned. I'll add this, though. For some of us, there is a persistent, subliminal terror of stalling the engine when starting off from a stop. So you try to minimize how many stops that you make, and try to be sure that you get the clutch fully engaged after starting, which takes space. This may not be conscious, but it does happen.

There may also be a defect of scale involved. Your perspective on a bike is much different than it is in a car, and I would not be surprised if many riders were trying to transfer their idea of proper following distance from their car to a bike, and not quite getting it right because the perspective is different, and you don't have the hood of the car helping to scale distances out. I know that my own following distances get to be inexcusably tight after I've been commuting daily on the bike for a few weeks.
#44
Old 07-07-2018, 07:55 PM
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In the last ~20 years, I’ve seen 60-0 braking distances dropping for cars. They’ve stayed the same for bikes. 110 feet is very good for a bike, 125 is about average. High performance cars can now stop in under 100 feet.
#45
Old 07-07-2018, 08:45 PM
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Originally Posted by Capn Carl View Post
In the last ~20 years, Iíve seen 60-0 braking distances dropping for cars. Theyíve stayed the same for bikes. 110 feet is very good for a bike, 125 is about average. High performance cars can now stop in under 100 feet.
Well that's my 30-years-out-of-date experience explained, which is interesting. But you're comparing an average bike to a high performance car? What about typical cars on the road?

Quote:
Originally Posted by Barbarian View Post
.
Since then ABS in cars has become the norm (although I don't believe it's mandatory in US or Canada) and cars so equipped on a flat surface will be stopping in a shorter distance than a motorcycle.
---but remember that "distance it takes to stop a car" is not the same as stopping distance. How many drivers driving with their left foot resting over the brake pedal now?
#46
Old 07-08-2018, 11:18 AM
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Originally Posted by Capn Carl View Post
In the last ~20 years, Iíve seen 60-0 braking distances dropping for cars. Theyíve stayed the same for bikes. 110 feet is very good for a bike, 125 is about average. High performance cars can now stop in under 100 feet.
You're not comparing apples with apples. I stand by my assertion upthread:

Take an average driver in an average car, and put him next to an average rider on an average bike, and the driver will have a shorter stopping distance than the rider.
#47
Old 07-08-2018, 11:44 AM
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Quote:
Originally Posted by Melbourne View Post
Well that's my 30-years-out-of-date experience explained, which is interesting. But you're comparing an average bike to a high performance car? What about typical cars on the road?



---but remember that "distance it takes to stop a car" is not the same as stopping distance. How many drivers driving with their left foot resting over the brake pedal now?
Magazine braking tests results for average cars and average bikes are about the same, around 120 feet.

The thing about bikes is, the highest performance ones have the best brakes, but theyíre also short and relatively tall, so theyíre more apt to lift the rear tire when braking. So their brakes can handle multiple laps of hard braking without fading, but maximum deceleration is always limited by their geometry.

You have a good point about drivers not always having a foot poised above the brake pedal. On the other hand, how many motorcyclists can achieve, and hold at, max deceleration? It took me hours of track time to get comfortable with floating the rear wheel just above the asphalt. I know riders much more skilled than me who still canít do that, because it wasnít a priority. Iíll bet itís far beyond the braking skills of the average rider to match the 60-0 times achieved by magazine testers, who test braking regularly.
#48
Old 07-08-2018, 11:47 AM
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Quote:
Originally Posted by Machine Elf View Post
You're not comparing apples with apples. I stand by my assertion upthread:

Take an average driver in an average car, and put him next to an average rider on an average bike, and the driver will have a shorter stopping distance than the rider.
You can stand by your assertions all you want, and I’ll continue to agree with you.

When I said ‘they’ve stayed the same for bikes’, I meant that bike stopping distances haven’t improved much over the years, compared to the improvement that cars have shown.

Last edited by Capn Carl; 07-08-2018 at 11:51 AM.
#49
Old 07-08-2018, 07:23 PM
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The highly focused on a simple task average human reaction time is about .3 of a second. But that is assuming perfect attention to an expected event. For an alert driver there is an average latency of
around 1.3 seconds.

At 30mph you are going 44 feet per second. This means that 44 to 57 feet at 30 MPH will be covered before you even know you need to react. If the average car is 15 feet long this means that you will cover 3-4 average car lengths before you even know to start braking. If you are following behind a truck and cannot see the traffic in front of you this means that if they rear-end someone you will hit them before you even apply the brakes unless you are more than 60' from them.

This gets exponentially worse as speeds increase, but lets be honest, how many people give 3 seconds of distance at 30mph? This is 44 yards or pretty close to half the distance of a football field.

This is part of the reason multi-vehicle rear-end collisions are so common. While you may be able to react in the case of a co-slowing car, almost no one gives enough following distance to avoid an accident if someone in front of you rear ends someone without significant slowing.
#50
Old 07-10-2018, 11:31 AM
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Quote:
Originally Posted by Melbourne View Post
---but remember that "distance it takes to stop a car" is not the same as stopping distance. How many drivers driving with their left foot resting over the brake pedal now?
That's somewhat irrelevant though, innit? What started this discussion was why riders leave a long space in front of the car in front of them, and it's specifically so that they can stop before ramming that car.

If the driver behind them doesn't react in time, the driver's better technology *may* help, but that's entirely a second problem.
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