[nealric]

Makes sense. Someone above said otherwise.


I feel like I get a lot more flats when it’s wet. Lubing up the glass or drips of rain bumping glass shards into a nice upward point maybe. Maybe just my mind

Not sure if it's been scientifically tested, but most people report more flats at low tire pressure. The issue is that the tire will deform and allow small sharp objects like a shard of glass to lodge in the tire. Repeated revolutions can then force it through the tire into the tube. A high pressure tire wouldn't pick up the shard in the first place. You can also get pinch flats from low pressure, where the tire bottoms out on the rim after hitting an object or pothole.

 

[Lombard]

Can low pressure result in more flats? No.

Can high pressure result in more flats? No.

Can too low pressure result in more flats? Yes.

Can too high pressure result in more flats? Yes.

Just so we have everything in perspective.

 

[hummina shadeeba]

I’d think baring a pinch flat the softer the tire the better for avoiding flats. No?

 

[Lombard]

I’d think baring a pinch flat the softer the tire the better for avoiding flats. No?

It's not that simple. As I said, keep things in perspective. The best pressure is a range based on effective tire width and load.

Keep in mind that if you never hit any road hazards, you won't get any pinch flats even at lower than ideal pressures. However, you will still be deflecting that tire more than the 15% ideal where you will put more stress on the tire sidewalls.

 

[hummina shadeeba]

It's not that simple. As I said, keep things in perspective. The best pressure is a range based on effective tire width and load.

Keep in mind that if you never hit any road hazards, you won't get any pinch flats even at lower than ideal pressures. However, you will still be deflecting that tire more than the 15% ideal where you will put more stress on the tire sidewalls.

But talking about a puncture from something sharp alone you don’t think softer tires would do better? It just seems it should go one way or the other related to sharp things. Does a soft tire allow something to lodge in the tire and work it’s way to the tube or does the soft tire conform and not allow the sharp object to go through. Figured it be decided by now and some evidence one way or the other.

Of course everyone is a different weight and there’s different rubber formulas but I’d think there’d be some evidence of what hardness of tire is optimal for stopping glass getting through.

I don’t buy the idea a softer tire will allow glass to “stick”. Maybe it’s the case but I can’t find evidence. Dont see why glass would be any more likely to stick to the same rubber if less pressure applied. To me it seems as simple as u have a sharp thing and either the pressure to get through the tire or not and less tire pressure can alleviate some of the pushing force of the glass through the tire

 

[bilbo]

Makes sense. Someone above said otherwise.


I feel like I get a lot more flats when it’s wet. Lubing up the glass or drips of rain bumping glass shards into a nice upward point maybe. Maybe just my mind

I don't know if this is true, but I definitely remember the flats (and resulting repair) more if they happen when it's raining.

 

[Lombard]

I don't know if this is true, but I definitely remember the flats (and resulting repair) more if they happen when it's raining.

There is definitely some validity to this. Sharp objects stick to wet tires more easily than to dry tires.

As far as more vs less pressure, I maintain there will be no difference unless you go outside the correct range of pressure based on tire width and load weight.

FWIW, I generally ride about 3,000 miles per year and have less than one flat per year.

 

[hummina shadeeba]

The debate continues elsewhere and seems undecided still. https://bicycles.stackexchange.com/questions/10259/relationship-between-punctures-and-tube-pressure

Not that I think there’d be a substantial difference in how easily a tire will be breached depending on the pressure.. but I’d like to knowfor the sake of understanding physics.

I’m strongly betting on the softer (less air) tire being more able to avoid a puncture from a shard of glass. As I say it’s likely not much difference but ..

 

[Kerry Irons]

I don't know if this is true, but I definitely remember the flats (and resulting repair) more if they happen when it's raining.

I used to ride regularly on a rail trail that had been paved with "glassphalt" - they mixed crushed glass in the asphalt. Glass chips were about 1-2 mm and smaller. In dry weather, flats were not an issue. We really avoided the trail in wet weather because flats went from "essentially never" to "most every ride." Some argue that the wet conditions make the glass shards more "slippery" and therefore more able to penetrate the rubber. Whether that is the case is open to discussion, but for sure capillary action meant that for sure the little glass chips that were constantly coming out of the pavement stuck to the wet rubber. Issue was always greatest in the spring after a winter of freeze/thaw resulted in much increased glass chips on the trail You could hear them crunch in dry weather. There were so many complaints from riders that they eventually paved over the glassphalt, and the issue went away.

 

[D&MsDad]

Is the calculator really meant for commuting and riding around town?

No, you silly person!!

Obviously, it is meant to give us something new to argue about. The "Best chain lube/(Waahhh) No one waves back at me/What-bike-should-I-buy/Blah, blah, blah" threads are wearing out.

New-ish blood. (Although, admittedly, this "new" argument is just a variation on the very old, dead horse-ish "what's the best tire pressure" theme.)

I know - I'm mixing metaphors. Hey, at least I didn't use "break" for "brake". (IMHO, a bannable offense.)

 

[froze]

That calculator is wrong. I tried following it when I got my touring bike this last spring, and with the rider, load and bicycle it's a total of 250 pounds running on 700 x 45c tires, and the calculator says 38 and 39 psi (rounding up). But I had a problem, the bike shimmied like crazy, what the heck was going on, I noticed the sidewalls on the front tire flexing like crazy and these are stout tires, and the bike is made of steel large-diameter tubing, this thing shouldn't be shimming like that. So for kicks I stuck in 65 psi, the shimmy lessened but didn't go away and I noticed the sidewalls weren't flexing near as much, so I put in 75...the shimmy was gone. A 40 some odd pound error.

 

[hummina shadeeba]

i just shimmied for the first time on a bike no handed after dropping my tire pressure. i guess the softer tires will accentuate oscillations.