10 ms·

The track of a bicycle back tire [pdf]

60 points by Phithagoras 4y ago

Someone 4y ago
FTA: Can we verify the folklore that on a long bike trip the back-tire wear is less than that of the front tire? I’ve never heard that folklore. I thought ‘everybody’ knew back-tires wear out a lot faster because the load on them is higher and because they’re the one being powered. https://www.sheldonbrown.com/tire-rotation.html https://www.sheldonbrown.com/tire-rotation.html: “It is common for a front tire to outlast a rear tire by as much as three to one. Rear tires have more weight on them, and also have to deal with drive forces.”
- leoedin 4y ago
  Yeah - that just seemed completely wrong based on my experience. I've commuted by bike for years, and my back tyre is always the first to go.
  - matsemann 4y ago
    Same. Also same on my road bike, which I bike in a very different manner (not as much stop&go, short turns etc). And I even do most of my breaking using the lever connected to the front tire.
- navane 4y ago
  From my experience, front tires only wear of age, not use. Backtires experience (frictional) shear forces, pushing along the earth. This erodes the surface.
  - michaelteter 4y ago
    And from those glorious big fishtailing skids we do as kids...
    - giraffe_lady 4y ago
      never stopped being fun this is why fixed gears are still a thriving niche
      - convolvatron 4y ago
        I picked up riding again after .. 40 years and a car braked in front of me and I did a perfect skid stop without even thinking. we are really amazing things.
  - c0nsumer 4y ago
    Cornering and braking does wear the front tire, and it is more notable when mountain biking where cornering tends to be more forceful and the tire knobs concentrate forces on more noticeable parts of the tire.
  - OffensiveIdiom 4y ago
    This has been my experience as well. The back tire gets worn down and the front tire lasts until the rubber starts cracking from age.
- InCityDreams 4y ago
  At €70 a pop, my tyres get rotated front to back, as required. Back wears out much faster.
  - adrianN 4y ago
    70€ for 15k kilometers or so is really cheap. It's incredible how cheap cycling is per kilometer. At least an order of magnitude cheaper than driving.
    - wiredfool 4y ago
      15K is an overestimate for most bike tires. It might be accurate for ultra hard commuter ones, but my experience is more like 2k miles for a rear (at 700x25c, single racing bike) and 5k for the front. At that point, the rear is a pretty square shape, with thin tread in the center, and starts to have some interesting handling issues. Wider, more supple tires might do better than that, the 26x2.2 rear on my tandem is 2k miles in, and probably has another 50% of its life left. Tandems are kind of noted for eating tires due to the loads on them.
      - ljf 4y ago
        I was about to agree then I did my own maths. I used to use GatorSkins - as they are perfect for London cycling. I used to commute 29 miles a day, 5 days a week, plus complete a 60ish mile ride on weekends - so times that by 47 weeks (5 weeks leave where I wasn't commuting) gives 9,635 miles. My gatorskins easily lasted a year, usually more - in fact I still have one of my London tires on my good bike, 7 years later (as the front tire) (I no longer cycle commute and only ride for leisure now.) So I think those miles really are possible on a good tire. I used to use cheapo tires but ended up changing them 3 or 4 times a year and burning through inner-tubes.
      - _Wintermute 4y ago
        2k miles is only 2 months for someone doing decent mileage, but even pros don't train on thin racing tyres.
- Moru 4y ago
  It depends on how you use the bike. When I was a kid I used to turn the front wheel left/right to go forward instead of using the pedals. This ofcourse wore out the front tire realy fast :-)
  - fluoridation 4y ago
    How does that work? I don't see any way that just turning the bars would imprint forward momentum.
    - matsemann 4y ago
      By "pumping" it's quite easy: https://www.youtube.com/watch?v=5tVlAlZ9wfM https://www.youtube.com/watch?v=5tVlAlZ9wfM You can to some extent do it without that much motion as well. Basically, you're "falling" to one side and getting momentum, and then you "save" the fall by twisting back getting the bike under you, and that instead puts the momentum forward.
      - anthomtb 4y ago
        I would like to add that you are not just "turning the handlebars" - you need to apply a lot of force to get the forward action to take place. Pumping is fun skill, easy to get the hang of with a little dedicated practice, and a prerequisite for BMX racing or any advanced MTB riding. Its also extremely inefficient for forward motion. You don't see any TDF guys using pump motion unless they're saving a crash.
    - Moru 4y ago
      It was 40 years ago, what I remember it works but not very good. As they say lower down, you need more movement to actually get any sort of speed forward. It was just something I liked doing while waiting for someone to show up.
- newsclues 4y ago
  Rear tires do must of your braking. If you hit the front break too hard/fast, you flip over the front tire, hit the rear brake hard/fast and you burn rubber/lose traction.
  - lonelygirl15a 4y ago
    As a bicyclist, I use my front brake vastly more than the rear. https://www.sheldonbrown.com/brakturn.html https://www.sheldonbrown.com/brakturn.html
  - doubled112 4y ago
    I don't even have a rear brake. Weight is transferred to the front on heavy braking, and if you have proper technique, you will not go over the bars. The front tire does all of the actual stopping.
    - snozolli 4y ago
      The rear brake is very important for initial braking, in order to transfer weight to the front, which allows harder braking without locking up the front tire. When you initially hit the brakes, your braking potential is split around 50:50. At absolute maximum potential braking force, your rear tire is near lifting, so it's around 100:0. That said, if you only have one brake, it's better to have it on the front than the rear.
      - JohnFen 4y ago
        Interesting. I have to replace the shoes on my rear brakes about 10 times more often than my front brakes. But then, if I'm not going very fast, I only use my rear brake. That might explain it.
        jackvalentine 4y ago
        Do you ‘ride the brake’ to control your speed a lot?
        4y ago
matsemann 4y ago
The math and physics and engineering behind bicycles is so cool. Such a "simple" device, but so many interesting things to dive into. I wrote my thesis on spoke patterns for the wheels [0]. Another cool thing is how the steering of a bicycle works. You don't really turn the way you want to, you actually turn the other way first to initiate so the bike moves from under you, and you then lean the other way to actually turn. This is why, if you're for instance biking close to a curb and want to get away from it, you really can't and it feels like the curb is "sucking" you closer and closer. Since it "feels" wrong to first turn towards it, but without doing that you actually can't get away from it. [0]: https://news.ycombinator.com/item?id=10410813 https://news.ycombinator.com/item?id=10410813
- sam_lowry_ 4y ago
  While cyclists learn to turn intuitively, motorcyclists have internalized this knowledge. The avoidance maneuver is part of motorcycle license tests in many countries.
- thunderrabbit 4y ago
  Wow! This explains the trouble I've had trying to ride with the end of my handlebar sliding along a smooth wall near the sidewalk. Thank you!
  - matsemann 4y ago
    I found this short video that very nicely describes what I tried to say with words: https://youtu.be/llRkf1fnNDM https://youtu.be/llRkf1fnNDM
  - giraffe_lady 4y ago
    Also about half the time when you hear about a cyclist dying because they "lost control of the bike" in traffic this is what happened. Car passes slow and too close to give you room to countersteer and you fall into and then under it.
- michaelteter 4y ago
  I have taught several kids to ride bikes. My instructions were very simple: ride, and if the bike starts tipping to one side, turn the handlebars that way. With humans, that's about all you need to say. You very quickly feel how the lean changes based on the steering input, so righting yourself becomes obvious. And when you inevitably overdo it and end up leaning the opposite way, you turn the bars that new direction. WOBBLE WOBble wobble straight.
toxik 4y ago
Where else would the department of theoretical physics engage itself in modeling bicycle tires than in the Netherlands?
- defrost 4y ago
  Somebody had to advance Feynman's work on spinning plates. How on earth science.uva.nl was inspired to pair up plates, add some thickness and a drive chain will likely remain a mystery for the ages.
mhandley 4y ago
I've probably been a computer scientist too long, but this feels like a problem that requires complicated maths or a very simple computer simulation. In this case they end up with equations that can (for the most part) only be solved numerically, so simulation seems just as effective. But then they deduce that in general the amplitude of the path of the rear tyre is always less than that of the front. And while we can demonstrate this with simulation, we can't prove it.
CE02 4y ago
As much as this may seem like merely an interesting dive into the subject of wear and tear, the broader world of bicycle geometry and design is fascinating. I used to race downhill and the tire path of the bike's design combined with how that path changes as the rig goes through its suspension travel is integral to feeling stable/planted. When you see some of the patents regarding modern bike design, especially in the world of suspension linkage, its mind boggling how much depth is put into these machines. All so I can go fast down a hill, fall on my ass, and get covered in mud.
O__________O 4y ago
TLDR: “We have shown that if the path of the front tire of a bicycle is specified, it is possible to derive the corresponding path of the back tire.” Possible I am wrong, but there is a critical assumption, that being: “With additional inspection, knowing that the tangent vectors from the back-tire point with fixed distance to the front-tire track, we can find which way the bicycle went.” As result, if the front and back tires do not maintain a fixed distance, prior research does not apply. Examples of factors that might produce minor variations include: suspension, untrue wheels, etc.
browsertasker 4y ago
[flagged]

60 points by Phithagoras 4y ago

FTA: Can we verify the folklore that on a long bike trip the back-tire wear is less than that of the front tire? I’ve never heard that folklore. I thought ‘everybody’ knew back-tires wear out a lot faster because the load on them is higher and because they’re the one being powered. https://www.sheldonbrown.com/tire-rotation.html https://www.sheldonbrown.com/tire-rotation.html: “It is common for a front tire to outlast a rear tire by as much as three to one. Rear tires have more weight on them, and also have to deal with drive forces.”

leoedin 4y ago
Yeah - that just seemed completely wrong based on my experience. I've commuted by bike for years, and my back tyre is always the first to go.
- matsemann 4y ago
  Same. Also same on my road bike, which I bike in a very different manner (not as much stop&go, short turns etc). And I even do most of my breaking using the lever connected to the front tire.
navane 4y ago
From my experience, front tires only wear of age, not use. Backtires experience (frictional) shear forces, pushing along the earth. This erodes the surface.
- michaelteter 4y ago
  And from those glorious big fishtailing skids we do as kids...
  - giraffe_lady 4y ago
    never stopped being fun this is why fixed gears are still a thriving niche
    - convolvatron 4y ago
      I picked up riding again after .. 40 years and a car braked in front of me and I did a perfect skid stop without even thinking. we are really amazing things.
- c0nsumer 4y ago
  Cornering and braking does wear the front tire, and it is more notable when mountain biking where cornering tends to be more forceful and the tire knobs concentrate forces on more noticeable parts of the tire.
- OffensiveIdiom 4y ago
  This has been my experience as well. The back tire gets worn down and the front tire lasts until the rubber starts cracking from age.
InCityDreams 4y ago
At €70 a pop, my tyres get rotated front to back, as required. Back wears out much faster.
- adrianN 4y ago
  70€ for 15k kilometers or so is really cheap. It's incredible how cheap cycling is per kilometer. At least an order of magnitude cheaper than driving.
  - wiredfool 4y ago
    15K is an overestimate for most bike tires. It might be accurate for ultra hard commuter ones, but my experience is more like 2k miles for a rear (at 700x25c, single racing bike) and 5k for the front. At that point, the rear is a pretty square shape, with thin tread in the center, and starts to have some interesting handling issues. Wider, more supple tires might do better than that, the 26x2.2 rear on my tandem is 2k miles in, and probably has another 50% of its life left. Tandems are kind of noted for eating tires due to the loads on them.
    - ljf 4y ago
      I was about to agree then I did my own maths. I used to use GatorSkins - as they are perfect for London cycling. I used to commute 29 miles a day, 5 days a week, plus complete a 60ish mile ride on weekends - so times that by 47 weeks (5 weeks leave where I wasn't commuting) gives 9,635 miles. My gatorskins easily lasted a year, usually more - in fact I still have one of my London tires on my good bike, 7 years later (as the front tire) (I no longer cycle commute and only ride for leisure now.) So I think those miles really are possible on a good tire. I used to use cheapo tires but ended up changing them 3 or 4 times a year and burning through inner-tubes.
    - _Wintermute 4y ago
      2k miles is only 2 months for someone doing decent mileage, but even pros don't train on thin racing tyres.
Moru 4y ago
It depends on how you use the bike. When I was a kid I used to turn the front wheel left/right to go forward instead of using the pedals. This ofcourse wore out the front tire realy fast :-)
- fluoridation 4y ago
  How does that work? I don't see any way that just turning the bars would imprint forward momentum.
  - matsemann 4y ago
    By "pumping" it's quite easy: https://www.youtube.com/watch?v=5tVlAlZ9wfM https://www.youtube.com/watch?v=5tVlAlZ9wfM You can to some extent do it without that much motion as well. Basically, you're "falling" to one side and getting momentum, and then you "save" the fall by twisting back getting the bike under you, and that instead puts the momentum forward.
    - anthomtb 4y ago
      I would like to add that you are not just "turning the handlebars" - you need to apply a lot of force to get the forward action to take place. Pumping is fun skill, easy to get the hang of with a little dedicated practice, and a prerequisite for BMX racing or any advanced MTB riding. Its also extremely inefficient for forward motion. You don't see any TDF guys using pump motion unless they're saving a crash.
  - Moru 4y ago
    It was 40 years ago, what I remember it works but not very good. As they say lower down, you need more movement to actually get any sort of speed forward. It was just something I liked doing while waiting for someone to show up.
newsclues 4y ago
Rear tires do must of your braking. If you hit the front break too hard/fast, you flip over the front tire, hit the rear brake hard/fast and you burn rubber/lose traction.
- lonelygirl15a 4y ago
  As a bicyclist, I use my front brake vastly more than the rear. https://www.sheldonbrown.com/brakturn.html https://www.sheldonbrown.com/brakturn.html
- doubled112 4y ago
  I don't even have a rear brake. Weight is transferred to the front on heavy braking, and if you have proper technique, you will not go over the bars. The front tire does all of the actual stopping.
  - snozolli 4y ago
    The rear brake is very important for initial braking, in order to transfer weight to the front, which allows harder braking without locking up the front tire. When you initially hit the brakes, your braking potential is split around 50:50. At absolute maximum potential braking force, your rear tire is near lifting, so it's around 100:0. That said, if you only have one brake, it's better to have it on the front than the rear.
    - JohnFen 4y ago
      Interesting. I have to replace the shoes on my rear brakes about 10 times more often than my front brakes. But then, if I'm not going very fast, I only use my rear brake. That might explain it.
      - jackvalentine 4y ago
        Do you ‘ride the brake’ to control your speed a lot?
      - 4y ago

matsemann 4y ago

The math and physics and engineering behind bicycles is so cool. Such a "simple" device, but so many interesting things to dive into. I wrote my thesis on spoke patterns for the wheels [0]. Another cool thing is how the steering of a bicycle works. You don't really turn the way you want to, you actually turn the other way first to initiate so the bike moves from under you, and you then lean the other way to actually turn. This is why, if you're for instance biking close to a curb and want to get away from it, you really can't and it feels like the curb is "sucking" you closer and closer. Since it "feels" wrong to first turn towards it, but without doing that you actually can't get away from it. [0]: https://news.ycombinator.com/item?id=10410813 https://news.ycombinator.com/item?id=10410813

sam_lowry_ 4y ago
While cyclists learn to turn intuitively, motorcyclists have internalized this knowledge. The avoidance maneuver is part of motorcycle license tests in many countries.
thunderrabbit 4y ago
Wow! This explains the trouble I've had trying to ride with the end of my handlebar sliding along a smooth wall near the sidewalk. Thank you!
- matsemann 4y ago
  I found this short video that very nicely describes what I tried to say with words: https://youtu.be/llRkf1fnNDM https://youtu.be/llRkf1fnNDM
- giraffe_lady 4y ago
  Also about half the time when you hear about a cyclist dying because they "lost control of the bike" in traffic this is what happened. Car passes slow and too close to give you room to countersteer and you fall into and then under it.
michaelteter 4y ago
I have taught several kids to ride bikes. My instructions were very simple: ride, and if the bike starts tipping to one side, turn the handlebars that way. With humans, that's about all you need to say. You very quickly feel how the lean changes based on the steering input, so righting yourself becomes obvious. And when you inevitably overdo it and end up leaning the opposite way, you turn the bars that new direction. WOBBLE WOBble wobble straight.

toxik 4y ago

Where else would the department of theoretical physics engage itself in modeling bicycle tires than in the Netherlands?

defrost 4y ago
Somebody had to advance Feynman's work on spinning plates. How on earth science.uva.nl was inspired to pair up plates, add some thickness and a drive chain will likely remain a mystery for the ages.

mhandley 4y ago

I've probably been a computer scientist too long, but this feels like a problem that requires complicated maths or a very simple computer simulation. In this case they end up with equations that can (for the most part) only be solved numerically, so simulation seems just as effective. But then they deduce that in general the amplitude of the path of the rear tyre is always less than that of the front. And while we can demonstrate this with simulation, we can't prove it.

CE02 4y ago

As much as this may seem like merely an interesting dive into the subject of wear and tear, the broader world of bicycle geometry and design is fascinating. I used to race downhill and the tire path of the bike's design combined with how that path changes as the rig goes through its suspension travel is integral to feeling stable/planted. When you see some of the patents regarding modern bike design, especially in the world of suspension linkage, its mind boggling how much depth is put into these machines. All so I can go fast down a hill, fall on my ass, and get covered in mud.

O__________O 4y ago

TLDR: “We have shown that if the path of the front tire of a bicycle is specified, it is possible to derive the corresponding path of the back tire.” Possible I am wrong, but there is a critical assumption, that being: “With additional inspection, knowing that the tangent vectors from the back-tire point with fixed distance to the front-tire track, we can find which way the bicycle went.” As result, if the front and back tires do not maintain a fixed distance, prior research does not apply. Examples of factors that might produce minor variations include: suspension, untrue wheels, etc.

browsertasker 4y ago

[flagged]