stargazer48

Walmart has inner tubes for my 20" folding bike with Schalbe max. 100PSI tire. Normally they're $5, but now are 1/2 off. My question is, do cheaper inner tubes hold the higher pressures, at least, for a couple of weeks and 100 to 200 miles of paved road riding?

squirtdad

YMMV but in my experience, innertubes are an area where you get what you pay for

soyabean

I'd rather put $5 towards a pint of beer, and patch the tyre of folding bike.

I can't take a folding bike seriously, so beer takes priority here.

Trakhak

Don't worry about those tubes. Most local bike shops - certainly all the shops I worked for over the years - buy inexpensive tubes in bulk to use for repairs. Manufacturers of inexpensive tubes don't want to have to take back whole production runs of tens of thousands of tubes, so their products tend to be as reliable as the more expensive tubes, if somewhat heavier.

In fact, whenever I've heard of a batch of tubes being bad, it's usually been Continental tubes or some other name brand. Anyway, regardless of the brand or cost of the tube, in most cases of a customer bringing a tube back, complaining that it failed, it turned out that the customer hadn't understood how to install the tube without damaging it.

Iride01 

What brand tubes at Walmart? I get Bell inner tubes there in the 700C size. They last every bit as good or even better than the Continental Tire inner tubes I've also bought. They are a little bit heavier than the Continental's. So I'm assuming they are thicker rubber. I don't get the puncture resistant Bell tubes that are much heavier.

If you are talking about the Slime inner tubes, I've never used them. Don't see any point in having sealant in my tubes since I don't get flats but every other year or so lately.

alcjphil

Inner tubes are not responsible for maintaining high pressure. They are confined in place by the rim and tire. In fact, the least reliable inner tubes I have ever used were quite expensive. They were lightweight Scwalbe inner tubes that I bought when the distributor I worked for at the time had lost Scwalbe as a client

mpetry912 

a problem I have seen is that the tubes were rolled up and into the boxes before fully cooled and developed a crease 180 degrees from the valve

that entire batch failed at that location

I had some very nice Michelin tubes that all failed right at the valve stem where it was vulcanized into the tube

I guess the point is if you find tubes you like, stick with them. especially if your tires are hard to repair / remount in the field when you don't have your bead jack.

/markp

soyabean

Walmart's Bell tubes appear much thicker and heavier than LBS premium tubes, I believe the reason for that is it will be tougher for same BSO's that were also purchased from same Walmart.

Chuck M 

I'm figuring on a folder, you likely aren't racing, touring or riding centuries. For that price I don't know that I would worry about a Walmart tube. I suspect it will be fine for the intended purpose. In fact I may look to see if they have them in 700s if I think about it.

stargazer48

Thanks for the comments.
For those who asked, the inner tube brand is Bike Shop selling either, one for $2.50 reduced from $4.96 or four for $7.50 reduced from $13.96. I believe a number of different sizes are available at those prices based on stock availability. The 700's have the same price. It looks like they only sell to Walmart.

stargazer48

That's why I mentioned that I have tires with a max of 100 PSI. I was concerned about the material and the valve perhaps not able to support a higher PSI.

SpedFast

I'd buy a bunch of them at that price. I've had bad luck with both higher priced name brands as well as bulk from China. It's the tire I won't skimp on.

jasoninohio

I just recently noticed the half-price tubes on walmart.com; I would imagine the 20 inch tubes should be decently durable as they will be aimed at kids bikes and BMX for the Walmart crowd

For the folks mentioning 700c I think the skinniest size they stock in the store brand is 700x25-34 with a 32mm valve stem

KerryIrons

Completely wrong. It is essentially the tube that determines the rate of pressure loss. The type and thickness of the rubber is what controls the diffusion of oxygen and nitrogen through the tube. And if you have poor seas on the tube valve, than can result in pressure loss. The tire contributes little to the equation.,

And to the OP, it is not miles ridden that determines pressure loss. It is time and the permeability of the tube.

SurferRosa

Going back to my oil field days, I would say it's the porosity, not permeability.

Iride01 

"maintain" might have been a poor choice of words, but the idea was that the tire is where most of the strength is required. I doubt that one could even inflate a tube to the correct pressure for riding without it being constrained by the tire and rim.

Do we have to nit-pick everything?

KerryIrons

Porosity is the mechanical structure of the material. Permeability is the measure of (in this case) gas diffusion through the tube. Something with high porosity might have high permeability, but if the surface of the material is "attractive" to the gas, then the permeability will be decreased even if the porosity is the same. This explains why CO2 diffuses more rapidly through butyl rubber than oxygen or nitrogen.

cyccommute 

Nope. Even from your oil field days. In oil fields, porosity is the ability of the rock to hold a fluid. Permeability is a measure of how fast the fluid moves through the rock. For a bicycle tube, porosity is the measure of how much gas would be held in the walls of the tube. Permeability is the measure of how fast the gas moves through the tube. Rubber doesn’t have a very high porosity, i.e. it doesn’t have many holes in it. But what holes it does have let the gas pass through fairly quickly…i.e. high permeability.

cyccommute 

The tire and rim are responsible for containing the pressure. The inner tube is responsible for maintaining the pressure. It’s the bladder that holds the pressure in place. If the tire were tubeless, the tire takes over that function.

Fick’s Law is what describes how gas diffuses across a membrane. It says

For bicycle tubes, that means that the thicker the tube, the slower the diffusion. Lightweight tubes are, by design, thinner so they decrease in pressure more rapidly. Higher pressures will also lose pressure faster than lower pressure systems.

Chuck M 

No. But that doesn't deter a lot of people.

PeabodyPK

I've always had good luck when picking up inner tubes from Walmart when on a bicycle tour, for 1/2 off I'd vote with the group that says "grab them".

t2p

recently observed this

on one bike switched to Schwalbe lightweight butyl tubes and they appear to lose air pressure a tad quicker than the standard Schwalbe butyl tubes

the Schwalbe Aerothan TPU tubes might retain air pressure as well or better than the Schwalbe lightweight butyl tubes (tough to make accurate comparison given our variables)

t2p

I’ve had both good and bad luck with inexpensive 20” tubes

the one bad luck :

replaced original tires on a late 60’s Stingray so I thought it would be a good idea to replace the original tubes - especially because the original tubes were just about fused to the rust covered rubber rim strips and rims

one of the new tubes failed quickly - blew apart at a seam (? can’t recall exactly) ... so back to the original rust covered tubes lol

cyccommute 

Thermoplastic polyurethane (TPU) is a very different class of materials than either natural (latex) or manmade rubber (polybutyldiene, aka “butyl”). Gas retention is very different as well. Even different polyurethanes may have different gas properties. I haven’t used any of the modern TPU tubes but I had a belly boat that I put a urethane tube in ages ago (more than 20). The tube was not elastic at all. Modern TPU tubes seem to be elastic and may be thermoplastic elastomers (TPE). Here’s a discussion of the differences.