shelbyfv

Some guys swing that way. It's OK even if we don't understand.

Koyote

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jadmt

https://media.tenor.co/05DZPfIwsLQAA...enuVs47izU6eVc

tiger1964 

So, does Park Tool sell something to measure pavement roughness?

...and I guess I could stop at various points of a ride to adjust psi to road condition...

Russ Roth

You realize that based on the chart you posted, your comments here are total BS? The only time they run the tires below 60psi is on the drum, the rest of the data points start at 60psi and your estimate for lower pressures is an extrapolation of what you think the result would be based on the curve. The reason they probably didn't go lower for any other surface is something well understood by those of us who started racing on narrow tires; pinch flats suck and walking is slower. Again, my reply to you was that when it came to 20 and 23c tires, dropping down to low pressures would result in pinch flats, this is real world experience. Your "proof" is specifically for 25c tires, even the testers don't go below 60psi, and the optimal pressure for a 25c tire over the surfaces I generally ride is a solid 100psi, not some ridiculously low pressure. Not that I think smd4 has the right idea with his 140psi, personally I think that's nuts, but arguing an equal extreme in the other direction won't get you any further and ignoring the tire size he says he pumps up to that ignores the way these data points change with tire width.

elcruxio

I see you also decided to use the incorrect meaning of the word fast in this context. That's a cheap shot and you know it. We're not writing scientific papers here so common language is allowed. That's also a particularly low blow because you're besserwissering someone who isn't a native speaker.

Also on that vein, the need for different pressures for different weights is something I thought was obvious. As in, obvious enought that I shouldn't need to constantly in every message emphasize that. Of course the break point depends on the weight! It also depends on the tire, width, surface, and had you read the articles that were linked by me and others, rider body fat!

Come on!

Also the only way to accurately tell your particular break point for any particular tire and road combination is to use the Chung method yourself. Most of us have no time for that, but luckily there are pressure calculators which give a pretty good approximation of the correct pressure for any given condition. Personally I've found the Silca calculator to be fairly accurate. At least I notice pretty quickly if I go above the recommendated pressure.

If you read up on the Chung method you can evaluate the error. Especially in the Silca test they did a lot of runs which would with the Chung method render potential error to pretty small amounts. Also the Chung method is probably the only accurate way find the break point of any given rider as it does take the rider into the equation. That's the problem with drums as they do not include the rider.


That's a good point and if you have a bike that doesn't fit wider, you ride what you have to ride. However if you're on the market for a new bike there's very little reason to buy a bike that has severely limited tire space, UNLESS you're extremely lightweight and/or know that the bike will only be ridden on extremely smooth surfaces.

It's not the wrong conclusion. It is A conclusion. You can make different ones.

Here's the thing. For some reason when people disagree on these forums they suddenly become very stupid (not you, others on this topic). What I mean by that is that when a variable or a data point is given, people lose the ability to consider things around said data point and will only argument based on that particular data point. That was the case here. A 25mm tire fares badly on rough surfaces so the diehards suddenly feel that you either must swap tire pressures constantly or some other silly thing.

The correct way of interpreting said data point would have been to do what people have always done. Set the tire pressure to suit what they want it to suit. If your ride consists of 90 % smooth tarmac and 10 % of gravel use the tarmac pressure. If it's the other way around do the opposite.

What I was aiming to do is to make a point to smd4 in a somewhat abrasive and pointed manner as he seems to have an extremely high resistance against logical and well mannered argumentation. And also facts. But the point was, that there are better ways to set your tire pressure than pumping them to 140psi. Finding and using the break point will make the ride both faster and more comfortable. However smd4 has in multiple topics stated that he does not care about speed, so I'm not sure why he bothers harking on topics which relate to speed...

Using your legs is viable but only for short sections. That's something you'd usually consider when setting tire pressures for the ride.

Now that is an interesting topic. Because if you need to use pressures that are above the break point for the majority of the ride to avoid pinch flats, that just tells me your rig is not optimal for the course. That can happen and frequently does. However if it's a regular ride one does often, it might warrant for getting a more optimized bicycle for said course.

I can't recall ever having pinch flatted. Back in the day I used high tire pressures and when I learned about this new fangled stuff about break points I just decided to Eff it. At my weight I need something wide enough to give me reserve for the really nasty occasions. Hence, I ride 40mm tires now. Also because we have a lot of gravel. I don't see a downside. If I decide to build me a set of aero wheels I may need to use 28mm with those.
And to dispel any hybrid bike zingers, those 40mm Terra Speeds are only 5 watts slower than the fastest tubular on the market (drum testing, break point watts unknown). For me that's a rounding error.

elcruxio

You missed the point entirely. The point was to emphasize that it is as bad to use 140psi as it is to use 60psi. Both are slow. It is best to use a tire pressure near the break point, which in the case of the test behind said graph was around 110 psi +-10psi.

Granted, 140psi is unlikely to result in pinch flats, but it is more likely to result in loss of traction when cornering, loss of control on rough sections, increased punctures due to penetrations etc.

As I mentioned earlier in my reply to cycco, the need to vary pressures with a particular tire, width, rider weight etc. is such an obvious self explanatory thing, that I didn't really see the need to emphasize it separately. I see now that I may have been wrong. Perhaps in the future I'll need to mention in every post that gravity is a thing and that is causing all kinds of effects you need to prepare for. And to remind people that they need to breathe during rides. And not to ride bikes underwater. You see where I'm going with this?

elcruxio

So why are you so obsessed by telling everyone your tires aren't slow? Correction, high rolling resistance. It's you the tires are making slow.
You love being slow and bouncy. I can respect that.

What I can't respect however is that you come in every topic regarding speed and start behaving just like this. Your way is the best and when someone points out that's not great for speed, comfort or some other reason, you turn to the "BUT I LIKES IT!" -fallacy.

It's a waste of space. You never contribute. You're useless here.

shelbyfv

And yet, Finland has been crowned (for a record 6th time) the happiest nation in the world....

Russ Roth

And there's where your over generalization fails and makes your argument pointless, because there are tires at which it isn't as bad to use 140psi as it is to use 60 and you're not getting it. You're working off 25c tires and going up from there, but plenty of people still ride 23c and I would suspect, for a few more years there will still be more modern road bikes that can't take wide tires and will have to run 23c. I just sold my 2015 road bike that with velocity a23 rims couldn't fit a 25c without tire rub. And the difference between 60psi and 140psi is so little that I would bet that a similar testing of 23c would have no difference and maybe even go the other direction. But you're so set on being right that you're willing to wipe away all variables to be correct and base everything on a test of a size that isn't even being discussed by those you are trying to correct. So yes, for generic rider A on a 25c tire you're correct, yay and congrats, now stop trying to tell someone who isn't generic rider A, and who isn't using a 25c tire, and probably isn't using modern width rims, that they're over inflating because you have no basis for making a broad, generalized statement.

Now, if you want to argue something valid, should I make my daughter's tires 140psi on the basis of that chart since the surface of the velodrome is smoother than fresh blacktop being smooth and finished concrete and therefore closer to the surface of the drum?

smd4

You seem upset, having to resort to ad hominem attacks. I'm sorry you feel that way. Your command of the English language is exemplary. I admit I had to look up "besserwissering." So I'm not going to let you use your status as ESL as a crutch.

So I think you are being highly disingenuous when you say I'm "constantly obsessed by telling everyone [my] tires aren't slow." I certainly don't come in on every topic regarding speed--because, as you've noted, I don't care about speed. In case you aren't clear on it, the topic of this discussion isn't speed--it's inflation pressure. Go ahead if you don't believe me: read the title and the first post.

All of which begs the question: Why are you so obsessed with speed? Is that really all there is to cycling for you--just...being able to go from place to place as quickly as possible? Seems you might be missing out on the wider world of what riding a bike can be.

I'm really not into "speed," your conclusions to the contrary notwithstanding. I don't race; I don't ride in group rides where I'd need to keep up; I ride the local roads solo, or on the MUPs (known as "greenways" down here) with family. I go exactly the speeds I like to go. I don't feel exhausted at the end of rides, or feel like I got "beat up" by the road. Why for you is the end-all, be-all of cycling "going fast?"

Oh, and enjoying the ride I get isn't a fallacy, as much as you may wish it to be. I know--you don't have any way to argue or refute that point, and I suppose it's frustrating. Again, I'm sorry.

Kontact

The data shows that the pressure vs rolling resistance plot is a trough, with the lowest rolling resistance being between low and high pressure. There is one of those charts for every tire size - including 23c. That doesn't mean anything other than riding well above or below that pressure is stupid.

Do you understand?

Russ Roth

Right, and you've made no effort to show where that trough is on a 23 or 20c tire, nor that being on the high side of that trough is worse than being on the low side for those sizes, you've just made grandiose statements with no proof, now do you get it? For the tire sizes that were being discussed YOUR CHART IS MEANINGLESS AND HAS NO BASIS FOR COMPARISON BECAUSE TIRE SIZES MATTER TOO MUCH, which is why I can run my 2.25 mtb tire over roots at 30psi but can't make it down the block on my 23c tire at the same pressure. You're argument would be valid for a 25c tire based on that chart, but you jumped in on 20 and 23c tires and those numbers are going to change considerably. From memory, 90psi on an 20c was asking for a pinch flat, which is why people stopped using them, but even 70psi on a 23 is getting close to the point you will dent a rim on a crack in the pavement. Get it?

cyccommute 

Yes, it is obvious and that’s what I said. They needed to make those measurements or, if they did make them, they needed to report it. I did read the article. And it is body mass.

That’s not the way it works. The author of a paper should tell you their methodology and referring to another person’s method is perfectly legitimate. But the author of a paper should never tell the reader that they can measure the error of that author’s particular experiment by making the measurements themselves. That’s not how it works. The error in a particular set of measurements is particular to that set of measurements and need to be reported with the data. No one can exactly replicate anyone else’s exact results nor should they be asked to. Without that error information, the reader can’t evaluate if the measurement is valid or not. If, for example, the error is 0.5W, their measurement are valid. If the error in the measurement is 10W, not so much. But the way the graph is presented we, the audience, have no way of knowing if the measurement is valid.

I agree that it is a conclusion…it’s just the wrong one. Most people who do go to wider tires run them at even lower pressures. People with tubeless go to even lower pressures because they don’t pinch flat anymore but they do end up with dented rims.

I use my legs as suspension for entire rides. The mistake that most people make about bicycles is that they consider the saddle to be something that they actually sit on. It’s only there for support and, when properly used…i.e. by not putting your full weight on the saddle all the time… is not as uncomfortable as many people make it out to be. Tires, especially anything under about 40mm, doesn’t offer much in the way of suspension and comfort. It offers a little but it is only a “little” comfort.

I don’t know about you but “setting a tire pressure for the ride” would be very difficult for me in most cases because the surface of the ride varies widely over any given ride and changing pressure constantly would impede progress far more than Silica’s “impedance” would. We all use a pressure that is convenient and generally stick with that pressure independent of what we think we are going to ride on.

That “break point” in the graph isn’t anywhere near where I would expect anyone to experience a pinch flat with the exception of the rotomilled pavement. 115 psi (8 bar) is bumping up against the limit on most 25mm tires. That’s the max on the GP4000S used in the Silica paper. At this point, about all we are discussing is the music to play for the angels dance on the pin head.

I don’t pinch flat either because I use the proper pressure. The current fashion, however, is to run on pressures are low as possible…and sometimes less than possible…for “comfort”. Many people talk about running 32mm tires at 40 to 50 psi which, according to the Silca pressure calculator, is appropriate for a 120lb (54kg) rider/bike/gear combination. The people running that kind of pressure in my experience are not 100 lb (45kg) people. For my rider/bike/gear, Silca suggest around 66 psi for normal pavement. I find that a bit too low for my tastes and generally run about 15 psi above that.

Kontact

Grandiose?


So you are just upset that there isn't a chart for every tire size and loading?

I don't see that as necessary since we already have tire charts that show ideal preload pressure. So unless the example with the 25c tires is wildly different than the recommended pressure charts, you can pretty much presume that ideal pressure recommendation is at or just below the break point, since the impedance is caused by not have the necessary 15% droop.

Russ Roth

Guess I'm done with this. Enjoy mindlessly telling people that they're over inflating 23c tires.

Kontact

Right. Because physics changes when the tire gets 2mm smaller.

Very smart.

Bald Paul

I'm pretty sure the OP also torques bolts by the "tighten until it snaps, then back it off 1/2 turn" philosophy.

soyabean

Agreed.

It appears that the OP just makes up stuff.

Like they have in other BF threads here.

I'm quite sure they are just smiling happy at all the attention they are getting!

rc5781

I currently ride these:
https://www.walmart.com/ip/Kujo-Trib...0&from=/search

They have max psi 65 and I inflate to about 52 psi which is 80%. They're working fabulously for me.

I have a 2019 Honda Accord LX with max psi 51, which I inflate to about 40 psi which is a little less than 80% max psi. Door jam says 32 psi. I think car manufacturers are biased towards telling you to underinflate care tires because they want you to have a "smoother" ride. And from a previous question no, the most wear is on the front tire (because it's front wheel drive) and on the outer sides of the tire, not middle. I don't pay to rotate car tires. Just let the front ones wear down, then get a mobile installation via tirerack.com. Get the new tires installed to the rear and the rear older tires moved to the front for stability.

Bill Kapaun

It took 106 minutes for them to make my ignore list from the time of the 1st post in this thread.
Don't feed the Trolls.

smd4

I think that’s pretty far from the record, though. I myself believe I have 106 beat.

Using “ignore” is the BF equivalent of putting your hands over your ears and yelling “NA NA NA, I CAN’T HEAR YOU!”

elcruxio

You should probably read my post with the graphs with thought. I did and didn't find any of your implications.

However the silca article also had a previous test result made with 23mm tires. The break point was very near that of 25mm tires, which isn't surprising as there isn't a huge difference tire size or air volume.

elcruxio

[QUOTE=smd4;22899353]You seem upset, having to resort to ad hominem attacks. I'm sorry you feel that way. Your command of the English language is exemplary. I admit I had to look up "besserwissering." So I'm not going to let you use your status as ESL as a crutch.[/QUOTE]

Takes one to know one.

You should however consider going easy with me as I seem to have difficulty conveying the meanings of certain terms to some people.

Besserwissering is german btw.

You don't care about speed but you seem to care quite a bit that in your opinion wide tires are slow, disc brakes are slow, modern bine tech is slow etc. And when you're called out you sidestep to your "i like the ride" fallacy. It has become fairly predictable at this point.

Inflation pressure directly correlates with the speed you can maintain with a given energy, ie. speed. Also we're not supposed to be 100% constrained by the topic title. Discussing things would be difficult if we were.

Inflation pressure is free. If I can get a completely free performance boost that takes next to no effort, I'll take it even if I'm riding slowly. Makes cycling more fun when I'm not needlessly encumbered.

As to being obsessed with speed, well me using 40mm tires should have already told you I'm not all that obsessed. I don't even own a skinsuit. Or aero wheels. I might get an aero helmet though. One of the cool ones with a visor. But if I go hiking I don't just fill my pack with rocks because I can. Rolling resistance is the second biggest drag in cycling after aerodynamic drag and it's not insignificant. If I can make that resistance less with a few presses from a pressure gauge, I'll do it in a heartbeat.

My "obsession" with tire pressures (if you can call it that) comes from mountain biking where you see and feel the difference much more drastically, especially with a fatbike. The difference of 1psi can make or break riding a certain section.

Personally I enjoy the faster speeds, the wind in my hair, seeing my enemies driven before me, hearing the lamentation of their mechanics, that sort of thing. For me it is more fun to ride 30kph than 25kph for the same energy (the tires themselves don't allow that but I don't have the energy to calculate the difference).

Also too high pressures cause vibrations which are fatiguing and can cause injuries especially when you ride 1500+km per month.

Oh it's not believe me. I truly do not care if you shake your tooth fillings out (although it is a funny thought). But you invading every fun topic and spewing your retro grouch narrative how everything new is bad for everyone and only bikes ridden should be hand built cinellis does get a bit old.

elcruxio

It's body mass but in the other article not linked by me Josh Poertner discusses the effect of body composition and its damping effect. Apparently lean tissues have less damping effect than body fat, in which case body composition could have an effect on the break point.

It's really interesting stuff.

You're not wrong. But the article in question wasn't a scientific paper and this is an internet forum. All we do here is well educated guesses. I'm sure Poertner has the errors documented, but since he also does R&D for pro teams especially in the field of tire pressures I'm not sure he's inclined to publish too much of that info. In case the competing teams get an advantage.

Yeah I don't get that. Except when mountain biking but that's a special case. Road pressures should be optimized for efficiency which also means optimized for comfort as it turns out.

I think we misunderstood each other here. I meant that using your legs was to ride out the rough stuff out of the saddle. Sitting or perching on the saddle will always transfer vibration which leads to body damping. You can lighten your butt, but like riding out of the saddle that's only viable for a limited time.

But the level of perching and riding posture probably does have an effect just like body composition.

Changing pressures on a road ride isn't viable. I do it the fatbike but typically only twice per ride. It's more fun to ride to the trailhead with high pressures (15psi) and drop them to trail pressures the trailhead (6-7psi).

For road I usually take the paris-roubaix mentality so it's compromise between surfaces. A bit too soft for the shiniest new asphalt and a bit too hard for the roughest stuff I'll encounter. With 40mm tires the scale isn't wide anyways. For gravel it's always gravel pressures and no care for the asphalt sections.

That's true. All this was unfortunately brought forward by the 140psi crowd.


Yeah I don't get the low pressures on road. For me the break point pressure is comfortable enough because I just don't feel the road vibration. Going lower would be pointless and slower. Going higher would be pointless, slower and less comfortable.

it needs to be said that the silca calculator isn't infallible. No calculator is. It's a starting point. I add a bit extra to my rear tire and use the front value of the silca calculator most times.