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.
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 2k figure was from a Michelin lithion 2, which was a decent for the price cheap (15 eur) 700x25 tire. It’s not an event tire. Mainly chosen for its relatively price and predictable performance (1 compound).
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.
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.
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 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.
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.
There's really no question. Cost of bike maintenance vs car maintenance. Societal cost of road wear due to a huge car vs a tiny bike. Burden on healthcare system, regulation and enforcement for dangerous driving habits. We all pay so much for cars, even when not driving one, when usually a bicycle is perfectly sufficient.
maintenance and road wear are clear winners for bikes being cheaper.
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.
I think bicycle calorie burn calculators are basically just nonsense. 600 calories is a ton to burn for a relatively short leisurely ride. Maybe 5x too much.
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.
I agree 600kcal is on the high side, but I don't think it's as far off as you think. Most estimates I've seen are between 300-500kcal per hour, depending on effort.
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.
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.
If we do this kind of calculus, it’s probably worth including the expected health costs of not exercising. Especially if your normal meal is a hamburger at McDonalds :-)
2000kcal of noodles costs like one Euro and fuels you for like five hours of cycling, 100km open road maybe. An average car burns 7l or 12€ of gas. But if you're concerned about calories, just buy an ebike.
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.