Do Your Tires Lose Air?

[Autoworker]

I like to keep my tires inflated to the maximum at all times, for less rolling resistance. I find that with all five of my bikes, I have to top up the air about once a week, whether I've ridden it or not. My granddaughter has a Giatex with 16' wheels that is particularly bad in this respect.

Since all of them have inner tubes, I'm pretty sure it's the tubes that are "lossy". Does anyone else notice this?

Are some brands of tubes more "lossy" than others? Whenever I go to my LBS to buy an inner tube, I don't specify a particular brand, and I haven't noticed a selection of brands anyway. It seems that at the LBS, a tube is a tube is a tube.

Any comments or observations?

[trueno92]

go with schwalbe tubes, they are around $8 a piece. i think lower spec tubes (for lower spec tires ~ MAX 35-45) most likely their valves cannot hold higher.

then again, i have no idea, but since schwalbe make tires that can do 100 psi max in a 16" size, i figure their tubes are good for that.

[MnHillBilly]

It happens - I think it's more of just a natural zen reaction of the material with the environment vs. wear and tear. Example: I kept my folder in the trunk of my car over the winter in the cold, and it needed air when I eventually took it out to prep it for the season. Didn't ride it at all, and it had plenty of air in it when it was tucked away for the season. Air will leak and react to the air pressure around it in the environment no matter what happens to the tube itself.

The better quality the tube, obviously, the better it will respond. Don't have any particular "brands" to recommend as being better than others, but I'd trust the Bontrager tubes I get from my LBS to perform better in this regard than the Bell tubes I keep on hand from Wal-Mart in my emergency kit(s). Pricier, but Bontrager does nothing "but" tires, and Bell is sort of all-things-to-all-folks brand. LBS usually have their preferred brand that they use in their repairwork, and might carry a few more to satisy a niche customer, but Bontrager is all my preferred LBS carries, for example. Another franchise LBS only carries Specialized tubes. Same deal - Specialized would be a better bet than something off the Wal-Mart shelf - though when you're talking tubes to get you home after a flat - it's true that a tube is a tube is a tube, so Wal-Mart's not a bad choice for stashing in your seat bag.

[snafu21]

Slime them. What you loose in not being able to repair tubes, you gain in not having to pump 'em up every other day..

[jur]

Schwalbe tubes are significantly better for staying up longer. Like in 10x better.

[fmattheus]

The better quality the tube, obviously, the better it will respond.

It depends on the tube. Some tubes are made to be lighter weight. They will lose air quicker. Where other tubes are made to hold air in well and aren't as light weight. I could imagine that Specialised and Bontrager for example would make tubes more towards the light weight end, where Schwalbe would make them more durable.

[law4jba]

Tubes made from butyl rubber will always loose pressure. Butyl rubber has a small, non-zero constant of diffusion (don't remember the extact term) which governs the rate at which gas passes across a membrane. The higher the pressure and/or the thinner the tube, the faster the rate of gas diffusion through the tube.

Other materials have different rates of diffusion (e.g., latex etc). I'm not sure which has the lowest rate of diffusion.

If you haven't guessed, I'm a recovering chemist....

[vik]

I check my tire pressure and add some air every week. It isn't a big deal and I have yet to find a tube that didn't require some regular maintenance in that regard.

I also will adjust my air pressure depending on what I'm doing with the bike {terrain/load, ect..]

Keep in mind that max air pressure and lowest rolling resistance are not the same thing and in fact you may well be slower with higher pressure in your tires depending on the tire and the road surface.

[EvilV]

All tyres lose air. It's only a question of how much. The molecules go through the rubber. I once saw an electron microscope picture of tube rubber. It is full of tiny holes which get bigger when it is stretched. Air molecules get through them and make their way outside. It's because for some reason, we pump up the air so it's under pressure and hence, always trying to get out.

:)

[alhedges]

I think that all tubes lose air, and higher pressure tubes lose air faster. After a week of riding my 70 psi Schwalbes, they may have 65 psi in them. On the other hand, it seems like my 125 psi road bike's tires were down to 90-100 psi every other day. (Which may be something of an exaggeration, but it seems like I was *always* pumping those tires).

[snafu21]

I think that all tubes lose air, and higher pressure tubes lose air faster. After a week of riding my 70 psi Schwalbes, they may have 65 psi in them. On the other hand, it seems like my 125 psi road bike's tires were down to 90-100 psi every other day. (Which may be something of an exaggeration, but it seems like I was *always* pumping those tires).


Air today, gone tomorrow...


My father used to stuff his tyres with straw in WWII. He said it worked reasonably well until he came to a corner, whereupon said bicycle refused to go round it.

[bicyclridr4life]

I have to air all my tires up about once a month; no matter how much I use the bikes.

[Simple Simon]

Yes my tyres loose air - and yes its damn annoying !
A bi-weekly task I could do without ! (especially when all others in family dont seem to notice)
I Will try 'Schwalbe tubes' Thanks Jur, and maybe even 'slime' Thanks Snafu
Please keep more suggestions coming.... eg do some other gases permiate less through inner tube rubber ?

[CaptainSpalding]

I think it can also depend on where your tire size is relative to the size range of your tube. For example, suppose your tube is labeled 16x1.5-1.75. If you put that tube in a 16x1.75, when it is inflated, the wall thickness may be thinner than for the same tube in a 16x1.5" tire. My thought is that the tube's permeability is affected by how far it is stretched.

[snafu21]

Yes my tyres loose air - and yes its damn annoying !
A bi-weekly task I could do without ! (especially when all others in family dont seem to notice)
I Will try 'Schwalbe tubes' Thanks Jur, and maybe even 'slime' Thanks Snafu
Please keep more suggestions coming.... eg do some other gases permiate less through inner tube rubber ?

There are as many pro-Slime threads as there are anti. For me it works on my pootling bike. I don't use it on my road bike with skinny tyres.

There is another thread hereabouts which discusses why filling your tyres with CO2 is a never ending task - they go down again in three days.

It's the size of yer molecules, says one chap. Nay! sez another - rubber is porous to CO2.

Me, I slime my Big Apples on the D7, and use it on rough country lanes, off-road and gentle tracks.

I also have one of those 12 volt electric air pumps and a battery pack, so getting 110 psi into tyres is merely a matter of sitting back and waiting. But I don't carry it with me, natch.

Slime adds weight though! NO!!!!!!!!!!!!!!!!!!!

Run away now. :D


The race-car guys use nitrogen. "It don't expand and contract as much as air" says this month's edition of 'Top Gear'; a car magazine for people who have 'Motorsport' sign-written across the top of their economy sedan windscreens, and no girlfriend

Nitrogen is possibly cooler - in every sense - than CO2. You need lots of equipment to store it, you can freeze strange things with it - like daffodils - then shatter them with a hammer, and there is endless scope for pulling amusing pranks by dipping parts of your anatomy into liquid nitrogen and watching them turn black and fall off. It's said to be painless.

Air though, is handy stuff. You can get it most places, and pressurise it with hand operated equipment. Bicycle pumps - endlessly cool gadgets in themselves, can easily be converted into artillery capable of firing bits of chewed up paper or potato for many metres. In the event of an attempted bicycle-jacking, a large frame mounted bike pump can be used to beat off attackers, or merely poke out their eyes from a safe distance:

"Stand away from the bicycle NOW- I have Bicycle Pump, and it is loaded!"

(Foot operated pumps, you may not be surprised to hear can fire an air-gun pellet through a car windscreen. )

There are downsides: a weird law of physics makes the point that compressing air generates heat, a fact known to Chinese bicyclists since 3000 BC. As belabouring eco-cyclists rarely point out - a lot of the energy they put into pumping causes melting of the Polar ice-caps.

But compressed air and its retention in silly little circular tubes of latex is a satisfying hobby for many. When air leaks occur in inner tubes, they can be repaired with sticky patches and spit, or prevented altogether with the addition of fluorescent goo. Cyclists can waste days discussing tube materials and pump technology. How thrillingly satisfying all of this is. And yet, people still gripe about having to pump up their tyres.

No matter. In terms of practicality and cost, pressurised air is hard to beat. It's always on special offer, they're still making it, and just getting it into your tyres is a science lesson.

How it gets out, though, is a complete mystery, and should remain that way.

[CaptainSpalding]

No matter. In terms of practicality and cost, pressurised air is hard to beat. It's always on special offer, they're still making it, and just getting it into your tyres is a science lesson.

How it gets out, though, is a complete mystery, and should remain that way.
Everyone knows how it gets out. Every night, just after midnight, the bicycle gremlins come. Tiny things they are, but devilish. Have you ever set your bike up against the wall, sure it was secure, only to return later to find your bike on the ground? Bicycle gremlins. They push and pull on derailleurs, kick spokes until they bend, sprinkle sand on chains, and cast their squeeking spell upon the brakes. Then, to relax, they unscrew valve caps and puff away on innertube air. They love CO2 even more, and will suck an innertube dry in a day or so. Pure nitrogen holds little interest for them.

I never have to fill my tires, as I've taken the trouble to rub a little Tabasco sauce on the rim of the valve stem. The gremlins hate that. I fear, however, that in the long run I will suffer their vengeance. . .