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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]

#71

Post by jackvalentine »

newsclues wrote: post #68
doubled112 wrote: post #63

Earlier quoted context omitted.

I have done thousands of KMs of riding.

Cool, I've done thousands in a month. Do thousands every year. 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.

I’ll back him up - I do thousands of kilometres a month and log component changes when they happen!

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.

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

#72

Post by snozolli »

JohnFen wrote: post #64
snozolli wrote: post #41

Earlier quoted context omitted.

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 t…

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.

I have to replace the shoes on my rear brakes about 10 times more often than my front brakes.

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.

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

#73

Post by wiml »

soperj wrote: post #52
michaelteter wrote: post #21

Earlier quoted context omitted.

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…

So same thing as spinning on black ice in a car.

Same instructions, different reason. In a skid, your tires have lost traction and are no longer pointing in the direction they're moving. You steer into the skid to return to the usual "static friction" regime instead of the "dynamic friction" state of the skid. Only once your tires are gripping the road again do you have much ability to control your direction.

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

#74

Post by toast0 »

toast0 wrote: post #67
matsemann wrote: post #65

Earlier quoted context omitted.

Thousands are dying directly from car usage ("accidents"). A lot more indirectly from being sedentary, and lots of shortened life spans due to the pollution. 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.

There were apparently 454 non-traffic bicycle deaths in 2020[1], compared to 38,824 traffic deaths reported by NHTSA in 2020 [2]. I don't feel like bicycles are doing 1% of the trips in the US, even though they're more than 1% of the deaths. I feel like non-traffic death eliminates car vs bike deaths, but captures the basic idea that bicycles are more immediately risky. All sorts of terrain issues that are minor for…

Found some data on person trips by transportation mode [1] and person miles by transportation mode [2]. Based on that, about 75% of miles are done with car/truck/suv/van, and 0.2% with bicycles; but trips are more balanced, 80% by car/truck/suv/van and 1% by bike.

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

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

#75

Post by adrianN »

wiredfool wrote: post #12
adrianN wrote: post #8

Earlier quoted context omitted.

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.

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 2…

My Schwalbe Marathon Plus last around 20k. That's about five years for me.

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

#76

Post by adrianN »

faeyanpiraat wrote: post #14
adrianN wrote: post #8

Earlier quoted context omitted.

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.

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…

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.

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

#77

Post by pharmakom »

faeyanpiraat wrote: post #14
adrianN wrote: post #8

Earlier quoted context omitted.

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.

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…

You should still need to exercise if you drive.

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

#78

Post by pharmakom »

doubled112 wrote: post #29
newsclues wrote: post #28

Earlier quoted context omitted.

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.

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.

Agree that front brake is more important.

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

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

#79

Post by xtiansimon »

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…

Well, that explains why I did an endo riding my bike down the ramp of a Ryder box truck when my tire hit the edge of the ramp—fortunately I was wearing my wool beanie. It was Burning Man, 1998. Seemed like a good idea at the time

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

#80

Post by samstave »

sritchie wrote: post #47
itronitron wrote: post #45

Earlier quoted context omitted.

Do the same steering physics apply to riding a bicycle on rollers? That's so much more difficult I wouldn't be surprised if the fundamental steering behavior is changed somehow.

Iirc what makes rollers so tough is that the contact patch is much shorter on the roller than on the road, so the wheel turns more easily. Your reactions need to be that much quicker. 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!

This is one of the challenges of riding on such a thin (narrow) line (like a plank - or even just the painted line on the side of the road) is so difficult.

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.

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