The track of a bicycle back tire [pdf]
tlakoba.w3.uvm.edu
tlakoba.w3.uvm.edu
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.
I had a winter of long roller rides (3.5 hours was the longest) and by the time I hit the road again I could ride on the white line with no effort. I think the dynamics are the same, just higher stakes on the rollers!
The thing is that in order keep a srtraight line on a very narrow path, you need much finer motor control of your arms, a good 'feel' for your bike, some good components, and the ability to remember to be able to look farther in front of the bike, but keep your awareness of where you are steering based on your inputs to the bike, but not looking down.
If you want to be impressed by one of the best in the world at steering difficult scary /r/sweatypalms courses:
https://www.youtube.com/channel/UC9kOkY1nYc0uADWRiRH64Rw
Watch the "do a wheeelie" vid on his YT home -- doing a wheelie on a train-rail, and jumping to the other train-rail without losing your wheelie or momentum - but all his vids are mind blowing.
[1]: https://www.youtube.com/watch?v=jGEkmDRsq_M
Edit - also OP, very cool thesis work!
Also, I skimmed the following to help my understanding; others may find it useful too: https://www.cyclingtips.com/2018/11/the-geometry-of-bike-han...
The handlebars aren't really used to steer the bike, the way most people think of steering. What they do is shift the bicycle further away from under the rider, which then, due to the bicycles naturally self-stabilising, steer to upright itself.
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:
“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.”
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.
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.
The tandem and wider tires are not the cheap ones though, they’re Rene Hearse, roughly 90eur or so. I’d say they’re worth it, but they are about the same price as my last car tires.
So if we also assume that during the lifetime of the vehicle the cost of fuel you'll burn will be in the same ballpark as the cost of the vehicle, then the total cost of riding the bike will only be around 50% of using a car.
Normally, one assume about 24% efficiency in human pedaling, so that 1kJ of energy going forward = 1 kcal consumed.
Now, fuel cost is anyways a small part of owning a car. My 1k bike + food has lasted me years, while that's less than a newer car loses in value each month.
600kcal is ~200g of bread + 20g of butter. Bread costs about 5€/kg, butter costs 2€ / 250g so 600kcal is roughly 1,25€.
My car uses about 6l gasoline per 100km, current price is ~1,60€ per liter, so 20km need 1,90€ of gasoline.
So if I just eat cheap food riding a bike is cheaper.
If I eat at McDonalds, then 600kcal is a hamburger with medium fries, which costs ~4,50€. Then taking the car is cheaper.
This is quite surprising!
But I think there's some factors at play here. One is that if I didn't commute to work, I would have to work out some other way to get my daily movement in. So it's not necessarily that I eat more just to bike. I just use that energy to move myself to work instead of on a treadmill going no where.
Another interesting factor is what about electrical bikes? The amount of kWh needed to move a small person vs multiple tonnes of car should make it a huge win.
The results looks absurd because the math is ignoring a lot of real-world considerations.
Edit: Source: https://assets.publishing.service.gov.uk/government/uploads/...
It is a more complex equation than that..
Probably the hardest variable to quantify is the risk of injury/death.
While I agree it could be better if everyone used bikes, but in the current reality if I choose to ride my bycicle, I'm going to share the road with 2000Kg metal boxes which are sometimes driven by distracted drivers, and I'm not willing to take that risk.
So even if I combine all the costs associated with both options, and bikes are cheaper objectively, it will still be more expensive for me.
Healthcare burden, I'm not so sure. Even with the massive difference in usage, street car tracks in Seattle cause a lot more healthcare burden to bikers (and pedestrians) than car drivers. There's certainly a benefit from exercise, but bicycling also has more exposure to injury during use, and not all of them are superficial injuries. Add in things like poor form inducing nerve injuries and it looks even worse.
So it's not even comparable. It's probably multiple orders of magnitude better on a societal level to be biking. Even better if we got rid of the cars causing the cyclists to be killed.
All sorts of terrain issues that are minor for a car are dangerous for a bicycle, especially at higher speeds. Where I live, it's very hilly, so it's hard to go anywhere on a bike without hitting speeds of at least 25 mph at some point on the journey. Mechanical issues, unexpected objects in the road, or errors in piloting at that speed will result in an injury for sure.
[1] https://injuryfacts.nsc.org/home-and-community/safety-topics...
[2] https://www.nhtsa.gov/press-releases/2020-traffic-crash-data...
So I think the fatality rate per trip is probably about the same for bike vs car/etc; but the rate per mile for bikes is significantly higher. It'd be interesting to look at comparable rates from say the Netherlands or another country where bicycling is better positioned.
[1] https://nhts.ornl.gov/person-trips [2] https://nhts.ornl.gov/person-miles
I have an older garmin that has told me I have burned 9000 calories in a weekend, and uh, I didn’t. No evidence for that, but I simply don’t believe it. Bicycle tourists would have to have wild food intake to sustain that for weeks.
It depends a lot on the bike and on the route. On a road bike going down a straight, flat road wearing lycra 20km/h is zero effort. On a city bike loaded with groceries going through urban environment with a bunch of traffic lights 20km/h average is quite an effort.
Let's say you start with brand new tires on both wheels. Let's further suppose that you completely wear out your rear tire in 1 year and your front tire in 4 years. If on the first anniversary you rotate and place the new tire in front, you'll need to repeat the procedure after 9 months, and then every 9 months after that. On the 4th anniversary you'll have bought 5 tires: on the 12th, 21st, 30th, 39th, and 48th months. If you simply replace each tire as it wears out without any rotation, on the 4th year you'll have bought 5 tires, 1 to replace the front tire once and 4 to replace the rear tire 4 times.
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.
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.
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.
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.
But then, if I'm not going very fast, I only use my rear brake. That might explain it.
That just means that you brake with your rear the most. I'm talking about maximizing braking potential.
I've been riding motorcycles for decades and it's drilled into you to practice panic stops regularly, which habituates the transition from 50:50 braking to 90+% front brake. I don't think many cyclists do this exercise, but they'd probably benefit from it.
I have literally seen people flip over their handle bars by solely using their front brake going downhill.
But if your bike doesn't have two brakes as you have stated, it doesn't matter how many KMs you ride, because you are not getting that experience to inform you.
My rear brake pads last about 5000km before they need a change, my front brake pads last about 3500km.
It would appear by observation of the consumables that the front brakes do the most work. This is in-line with my expectations from the experience riding the bike and established knowledge about how weight transfer works in vehicle braking - there is a reason cars always have bigger discs on the front and some cheap hatches still have drums on the rear.
However, I like to have both (and suggest you do too!) because:
1. Brakes can fail
2. In slippery and inconsistent conditions, locking up the rear is preferable to the front
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.
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.