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The track of a bicycle back tire [pdf]

tlakoba.w3.uvm.edu

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Re: The track of a bicycle back tire [pdf]

#31

Post by newaccount74 »

matsemann wrote: post #17
faeyanpiraat wrote: post #14

Earlier quoted context omitted.

I've just done a back-of-the-envelope calculation about fuel costs, and the extra food you have to eat if you are cycling vs the fuel cost for the car for the same distance is in the same ballpark. 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 c…

How are you calculating that? 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.

https://biketips.com/calories-burned-biking/ says I burn ~600kcal to ride 20km.

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!

Re: The track of a bicycle back tire [pdf]

#32

Post by lonelygirl15a »

newsclues wrote: post #28
Someone wrote: post #2

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 : “It is common for a front tire to outlast a rear tire by as much as three to one. Rear…

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.

As a bicyclist, I use my front brake vastly more than the rear.

https://www.sheldonbrown.com/brakturn.html

Re: The track of a bicycle back tire [pdf]

#33

Post by mc32 »

matsemann wrote: post #6

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…

There are people who can ride bikes on rails. I would not be able to do that. It seems impossible, but I guess they are able to minimize the amplitude of deviation from straight to such a low value they can correct tiny deviations with shifting their weight and manoeuvering the front wheel.

Re: The track of a bicycle back tire [pdf]

#34

Post by matsemann »

newaccount74 wrote: post #31
matsemann wrote: post #17

Earlier quoted context omitted.

How are you calculating that? 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.

https://biketips.com/calories-burned-biking/ says I burn ~600kcal to ride 20km. 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 me…

What if the added calorie need comes from rapeseed oil or something really cheap? :D

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.

Re: The track of a bicycle back tire [pdf]

#35

Post by matsemann »

fluoridation wrote: post #24
Moru wrote: post #18

Earlier quoted context omitted.

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 :-)

How does that work? I don't see any way that just turning the bars would imprint forward momentum.

By "pumping" it's quite easy: 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.

Re: The track of a bicycle back tire [pdf]

#36

Post by matsemann »

fluoridation wrote: post #25
InCityDreams wrote: post #5

Earlier quoted context omitted.

At €70 a pop, my tyres get rotated front to back, as required. Back wears out much faster.

You're not actually saving anything in the long term, though. 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 hav…

True. What you do have is a more consistent / good front tire, which is important for handling curves in wet weather. So still worth doing, instead of riding with a front tire on its last 20% of life.

Re: The track of a bicycle back tire [pdf]

#37

Post by uoaei »

adrianN wrote: post #8
InCityDreams wrote: post #5

Earlier quoted context omitted.

At €70 a pop, my tyres get rotated front to back, as required. Back wears out much faster.

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.

And if you can do your own maintenance, and buy used frames and parts, you can probably say 2 OoM difference. You'd spend more on the calories that fuel your commute than on the bike and accessories.

Re: The track of a bicycle back tire [pdf]

#38

Post by uoaei »

newaccount74 wrote: post #31
matsemann wrote: post #17

Earlier quoted context omitted.

How are you calculating that? 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.

https://biketips.com/calories-burned-biking/ says I burn ~600kcal to ride 20km. 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 me…

The costs of sitting idly every time you travel, compared to doing some low-impact cardio over the same distance, for trips shorter than about 3 miles, definitely adds up over the years.

The results looks absurd because the math is ignoring a lot of real-world considerations.

Re: The track of a bicycle back tire [pdf]

#39

Post by fluoridation »

matsemann wrote: post #36
fluoridation wrote: post #25

Earlier quoted context omitted.

You're not actually saving anything in the long term, though. 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 hav…

True. What you do have is a more consistent / good front tire, which is important for handling curves in wet weather. So still worth doing, instead of riding with a front tire on its last 20% of life.

IME as long as the tire is not flat there's no difference in handling between a new and a worn front tire, at least on asphalt.

Re: The track of a bicycle back tire [pdf]

#40

Post by CE02 »

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.
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