Wallonthefloor

I have a room that is my stable of 5 bikes and some wheels. Its been months since I've rode due to injury and I have worked on my bikes. After all being pumped with air around the same time why are half of my wheels and tires completely flat and some still feel good to ride? Are certain tires/tubes leaking? they are all brand new and 700x23-28. What brand innertube does NOT leak?

alcjphil

The thickness and type of rubber used in the inner tube will affect how fast a tire goes flat. Lightweight latex inner tubes will lose a noticeable amount of air in a day or two. Thick butyl inner tubes will not lose air as fast. The wider the tire and the lower the working pressure needed, the slower the air loss. My mountain bike tires only need refilling after months of sitting idle while my road bike with 700 x 25 tires and latex inner tubes will be flat in a couple of weeks

dedhed

None.
https://www.velonews.com/gear/techni...-short-frames/


OK maybe this one.
https://www.stopaflat.co/

Iride01 

The butyl rubber inner tubes we use are thin and let air pass through them. You should be happy if they have enough pressure to ride after a week.

I top my tires off every other day when I'm riding regularly. You probably should too, or at least check them.

When bikes sit around for months and some tires eventually go flat altogether, then you can damage a tube just rolling them with flat tires. So I recommend you pick them up if you ever have to move them again with flat tires. Or pump them up before you move them.

KerryIrons

Not really. I use Michelin lightweight Airstop tubes and they lose about 10 psi per week. Well within the range of rideability. Butyl rubber was a big improvement over natural rubber because it held air so much better, but it is still permeable to oxygen and nitrogen. Thickness of the rubber is a significant factor in reducing permeability.

70sSanO

My recipe has been Michelin Airstop at the low side of the size range; i.e. 700x25 tires with a 25-32 tube.

A bit of a pain to get it to fit, but it seems to hold air quite well.

John

Iride01 

I'm on a road bike with 25mm tires. So my inflation pressures might be higher than yours. And to me, 10 lbs would be significant. I try to keep my tires within about 2 lbs psi of the desired inflation pressure.

If I let them drop to 10 psi less than what I normally keep I'd pinch flat for certain on some of the approaches to bridges where the asphalt of the road and concrete of the bridge are not at the same level.

I've noticed that the rate of PSI loss seems to taper off slowly as the pressure reduces. Which makes some since if one thinks about how holes in any fabric generally get bigger when stretched and smaller when not stretched.

veganbikes

Rubber is naturally porous. The only real way to stop leaks is to find a molecule that is larger than the holes in rubber which is kinda silly. The air is a good portion nitrogen so using pure nitrogen is an added cost and silliness. I would just pump once and a while. I typically find about once a week (give or take) is about right sometimes you might pump a little more often sometimes less often but check every ride. As others have said wider tires tend to need less pressure and potentially less fill ups. I find my 650bx2.4 Super Moto Xs don't tend to need air that often and I pump them less frequently and that is my daily driver, however it is a very thick rubber tire and I usually pump up to the higher end of the range and let it soften up a little over the week.

KerryIrons

I ride 25 mm tires as well. It is highly unlikely that your pressure gauge is accurate to 2 psi and a pinch flat is MUCH more likely a result of riding differences than a 2 psi difference in tire pressure. The tube is stretched the same regardless of pressure: it is constrained by the tire and so more pressure stretches it only as much as the tire stretches. The reason pressure loss rate decreases as the pressure decreases is simple physics: pressure is the driving force to push the air through the inner tube so as the pressure decreases, the driving force decreases.

KerryIrons

If you think about it, the nitrogen concentration in your tires increases naturally. You pump the tire up with air (79% nitrogen) and the oxygen diffuses through the tube faster than the nitrogen, so the concentration of nitrogen increases. You add more air and the process repeats. If you don't deflate the tire, the N2 concentration continues to increase. Sort of the opposite of when you charge a tube with CO2, which leaks out much faster than air. Best practice is to deflate the tire and fill back up with air so it doesn't go soft as fast.

Iride01 

Yes you are correct about the tube not stretching any more at a lower pressure than a higher pressure once it's filled out the space it is contained in. My stupid mistake in thinking that I haven't realized till you just pointed it out.

However my gauge just needs to be consistent in what it displays a particular pressure at. Whether it's off by 2 lbs or 10 psi or even more isn't as important to me because I ride by what I feel in my legs and the data generated on the rides I do when I'm wondering what if I used y amount of psi instead of x amount. Also by the road surface I'm riding. If I do ride chip seal roads or other roads where coarse aggregate is exposed, then I'll lower the psi in my tires for that ride. The only issue accuracy of the gauge would be a factor is if I used another gauge and didn't know any correction factor for it to compare to the gauge I use on my bicycle tires.

As for me keeping it within 2 lbs, that isn't for pinch flats. It's more just a personal preference and a little bit for eliminating PSI differences as a possible difference in the stats I collect every ride. The pinch flats are something that I would worry about if my tires were 10 psi lower in pressure. Despite my generally smooth asphalt here, I do hit some bumps along the way. Some of those particularly bad bumps are where the asphalt is almost 1½" lower than the concrete road surface of some bridges here. Not very much of a rounded edge either.

CliffordK

Tannus tires will never go flat. At least not the original ones.

If your tire is a little spongy after a few weeks or a month or two, it may be normal leaking out.

On the other hand, if it is completely flat, then it may be an actual puncture.

I tend to choose tubes that are the maximum size that will fit in the tire. So, if it is a 25mm tire, then choose 25-32mm tube. That way the sidewalls of the tube are stretched less. This may also give slower leaks that you may be able to limp to your destination.

In some cases, you might try a "thornproof" tube that may also leak slower.

KerryIrons

There are three elements to measurement: accuracy, precision, and reproducibility. You are right that as long as the pump reads the same pressure with the same number (reproducibility) then accuracy is not a serious issue. Precision is how many significant figures the gauge is reading. That said, your gauge is very unlikely to be reproducible or precise to 2 psi. And more to the point, if you look at the published data (see Bicycle Quarterly among others) you will clearly see that 2 psi is insignificant in terms of rolling resistance. Temperature, humidity, and what you had for your meal before riding will all have much more impact on your times and power output. Enjoy the control you feel with daily pressure checks, but don't kid yourself that 2 psi is meaningful.

Iride01 

I think you are the one attaching meaningfulness to them. Read what I said... And it might actually be three or more rides before I check sometimes if a squeeze with my fingers satisfies me. But I didn't want to put in every if, and or but to make my reply a novels worth of information.

We all have little things we do just to please ourselves. I'm sure you do little things that are not significant but you do them anyway because it's what you like to do. For me, this insignificant habit will ensure I don't leave the house with a tire pressure lower than desired. And since when I do check them with a gauge, it's not much more effort to pump them up to my desired pressure. Usually one or two strokes of the pump.

For me, 10 psi is a lot. Maybe it's not to you and that's okay. I can feel 10 psi of difference and 10 psi does start to show up in data. But not much, that still less than 1/2 mph on an 90 min ride for me. Maybe even just a 1/4 mph. And of course there are other possible factors since I can't do a blind test when I fill the tires. But when I do the same ride 12 times at one PSI, then twelve rides at another PSI, take the best six of each, then the lower PSI is always the slightly slower speed for of those rides. And also the ones where I felt more perceived effort, which is something else I keep track of for most of my rides..