this post was submitted on 23 Sep 2023
53 points (86.3% liked)

No Stupid Questions

35925 readers
2111 users here now

No such thing. Ask away!

!nostupidquestions is a community dedicated to being helpful and answering each others' questions on various topics.

The rules for posting and commenting, besides the rules defined here for lemmy.world, are as follows:

Rules (interactive)


Rule 1- All posts must be legitimate questions. All post titles must include a question.

All posts must be legitimate questions, and all post titles must include a question. Questions that are joke or trolling questions, memes, song lyrics as title, etc. are not allowed here. See Rule 6 for all exceptions.



Rule 2- Your question subject cannot be illegal or NSFW material.

Your question subject cannot be illegal or NSFW material. You will be warned first, banned second.



Rule 3- Do not seek mental, medical and professional help here.

Do not seek mental, medical and professional help here. Breaking this rule will not get you or your post removed, but it will put you at risk, and possibly in danger.



Rule 4- No self promotion or upvote-farming of any kind.

That's it.



Rule 5- No baiting or sealioning or promoting an agenda.

Questions which, instead of being of an innocuous nature, are specifically intended (based on reports and in the opinion of our crack moderation team) to bait users into ideological wars on charged political topics will be removed and the authors warned - or banned - depending on severity.



Rule 6- Regarding META posts and joke questions.

Provided it is about the community itself, you may post non-question posts using the [META] tag on your post title.

On fridays, you are allowed to post meme and troll questions, on the condition that it's in text format only, and conforms with our other rules. These posts MUST include the [NSQ Friday] tag in their title.

If you post a serious question on friday and are looking only for legitimate answers, then please include the [Serious] tag on your post. Irrelevant replies will then be removed by moderators.



Rule 7- You can't intentionally annoy, mock, or harass other members.

If you intentionally annoy, mock, harass, or discriminate against any individual member, you will be removed.

Likewise, if you are a member, sympathiser or a resemblant of a movement that is known to largely hate, mock, discriminate against, and/or want to take lives of a group of people, and you were provably vocal about your hate, then you will be banned on sight.



Rule 8- All comments should try to stay relevant to their parent content.



Rule 9- Reposts from other platforms are not allowed.

Let everyone have their own content.



Rule 10- Majority of bots aren't allowed to participate here.



Credits

Our breathtaking icon was bestowed upon us by @Cevilia!

The greatest banner of all time: by @TheOneWithTheHair!

founded 1 year ago
MODERATORS
 

Why there are no (to my knowledge) electric bikes with 700c tires? All the ones I’ve seen use fat tires, what is the reason behind that? Cc @[email protected]

you are viewing a single comment's thread
view the rest of the comments
[–] [email protected] 7 points 1 year ago* (last edited 1 year ago) (2 children)

No, since the contact face has constant size which is mostly dependent on the air pressure in the tire, for fat tires, the contact face is 'shorter' but 'wider' compared to a slim tire. Thus, as less rubber needs to be deformed in rolling direction creating an angular momentum, they have lower rolling resistance. However, at elevated speeds of 20 km/h (~15 mph) and above, the air resistance, where slim tires perform better, becomes more important. Thus, racing bikes have very slim tires under very high pressures (also inertia plays an important role here).

Source: https://www.schwalbe.com/en/rollwiderstand , e.g.

[–] [email protected] 11 points 1 year ago (1 children)

I think there is an important factor you are missing here — although I fully acknowledge I may be missing something; I’m no tire expert.

Per your source, fat tires have lower roller resistance than narrow tires at the same pressure. A quick search shows that 700cc tires are usually run around 100psi. Fat tires appear to run at or below 30psi. Fat tires generally provide a cushier ride because they deform, but that deformation expands the contact patch and ups the rolling resistance. Are there super high pressure fat tires? I’m guessing no, but maybe that’s something I’m just not aware of.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (1 children)

I mean my mountain bikes run at a reccomended 50-80PSI, my road bike 60-120

I can also get up to about 40mph downhill on both (which should be a good indicator of rolling resistance/air resistance as it takes out the pedaling part), so that leads me to believe (given the rolling resistance info) that the actual biggest factor which makes the road bike so much easier to ride is weight (and gear ratios, but that's not relevant to e-bikes)

[–] [email protected] 3 points 1 year ago

In this case presumably the MTB weighs more, which helps on downhills.

I think there's a whole literature out there on rolling resistance as it relates to tire size and pressure as a function of road quality


for really nice pavement/velodrome, skinny tires at high pressure win, but for rougher surfaces (e.g., chipseal or less than perfect pavement) lower pressures can be advantageous.

[–] [email protected] 2 points 1 year ago

Thanks for that read