this post was submitted on 20 Sep 2024
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Holy shit, 6.4 - 6.7 bar...
Is this even possible?
Road bicycles like the ones used in the Tour de France use pressures in the 120-140 psi range, but cars generally float around the 32 psi area.
Trucks often 60-100 though
Go to the truck stop and use the big rig hose. You'll get what you want 🤯
Yep, 60/80 PSI on my work truck, but the tires are 12-ply.
Probably less these days as it’s shown lower pressures and larger tires can improve performance.
Which type of performance? Surely not fuel economy/emissions?
Yes fuel economy. Energy expended per distance traveled or power needed to maintain a given speed. Just the fuel in this case is burned by your own body.
At world class levels, a few watts here and there will make a big difference by the end of a race.
Aah, gotcha. I had thought that
was in reference to this part at the end of the parent comment:
and I haven't seen anything to contradict all the previous literature on under-inflated automobile tires being worse for fuel economy.
Yeah it’s because the theory has been that high pressure decreases tire deformation and this is more efficient. This is where the wisdom of under inflated tires become less efficient. However lower pressure (like 80-90 psi) allows bicycle tires to absorb road imperfections and vibrations which actually ends up slightly more efficient. But if you go too low efficiency will be negatively affected.
Airplane tires actually have very high pressures to prevent hydroplaning, which is more important than ride quality or fuel efficiency for them.
Also planes have to land, and the impact on the tires is like hitting a pothole. You don't want the tires to touch rim at ~200 MPH on a many-million-dollar vehicle
Source?
All the studies I've read (and my experience) show that narrower tires and higher pressures improve economy. Less traction and less ride comfort are the tradeoffs, respectively.
GCN has a number of videos on this subject: https://youtu.be/jTZfrBVr5pQ?si=M5v6KP5ZZ9ZU5MXz
https://youtu.be/AK5KLvrzrb4?si=aMcYxYnWi9poZ8SA
And here is some technical data from SRAM: https://www.sram.com/globalassets/publicsites/cms-campaign-pages-not-story-pages/zipp/totalsystemeffeciency/pdf-downloads/tse-explained2.pdf
Basically new data includes vibration losses which get larger as pressure increases. There’s a sweet spot to balance between rolling resistance (which decreases with pressure) and vibration (which increases with pressure). So when you mention ride comfort as a trade off, it actually has a much larger effect than you might imagine.
Thanks for the videos and the PDF, but they are all bicycle related.
A car has a whole sophisticated subsystem dedicated for absorbing vibrations (the suspension), so I'm not sure the results can be applied there...
Oh I was only addressing this:
Fair enough
Suspension is great for smoothing out low frequency unevenness, but not so much for high frequencies, like something the size of gravel- a spring will ring like a bell.
That's why a suspension is much more than a spring.
Tops on my trucks is 44
Not in a car... But 10 or 12 ply truck/tractor/trailer tires can run around 90 psi
I just looked it up. It seems that normal car tires will explode at 115 - 145 psi.
In not really talking about possible, I am more talking real world running pressure.
I'm sure you can air up a car tire but at 90 psi it would be so rock hard that travel on it would be extremely uncomfortable. Also you would risk blowing it out whenever you went over a big enough bump. The tire volume inside would deform and cause a massive pressure spike.
Tractor trailer tires are made with more layers of rubber and steel belting so they can safely handle higher pressures.
Right, you would likely pop a tire on your friendly neighborhood pothole. Even if you were lucky and avoided all of that, the tires will bulge in the center, drastically reducing the contact patch with the ground and you'd have probably 15-35% traction compared to proper inflation.
Yeah you can definitely do it with car tires for a short time at least, that’s how you check for leaks (overpressure to like 80 psi and put it in a tub of water, look for the bubbles)
You do not need to overpressurize to find leaks. This is dangerous advice, as a tire blowing at even lower pressures can kill you. And there won't be any warning before it does.
Sorry buddy but you’re full of shit, this is standard practice at tire shops. The reason you overpressure is that a tire at rest may not lose air noticeably, you overpressure to mimic driving down the highway when the tire is bulging out more due to centrifugal forces.
80 psi for a few minutes is not really that dangerous, the tires blow up at 120+ psi.
I won't be as rude, but you are the one making a claim that exceeds both common sense and the warning on a typical car tire sidewall. A leak from a puncture area, bad bead seal, or tire failure point will show at normal inflation pressures with a water/soap test, as anyone in their backyard can attest to. You don't need to simulate flexing and stress for this, in fact pushing the tire to its limits with high pressure will absolutely find a failure of the tire structure very quickly, which was the point of my warning. Maybe you've never seen or heard a tire explode. It doesn't pop like a balloon.
I would question any shop doing this procedure from a manufacturer's recommendations and from OSHA standards.
Your tire shop is the kind that would inflate a split rim tractor tire without a tire cage.
It's [email protected] life - let him waste it how he wants! /s
Do NOT do this!
Don’t slash ‘em
Unless you want to end up in a watchpeopledie sub