BicycleCrazy

My tire size is 700c x 40mm. What size tubes do I need?

Thanks!

Bill Kapaun

This post will explain it-
https://www.bikeforums.net/bicycle-m...tube-help.html

Look for a tube sized 622-4?.
They will usually be listed to fit a range of sizes.
Look for one where the "40" is within the range ie- 622-35-45 for example. (or 37-47 or.....

You'll also need to pick your valve type. Schraeder or Presta.
The length of the valve may also be a consideration, depending on rim style.

cxwrench

Obviously one that covers the width of the tire you have. They will generally always be sized like: 700 x 28-38mm or something like that. As long as 40mm is in (or very close to) the range on the box you're good.

Hondo6

To the OP: for clarity, "700c" and "622" referred to above refer to the same tire size. The former is the old French designation for that tire size and is commonly used for tires/tubes of that size. 622 is the ETRTO/ISO bead seat diameter (BSD) for that tire size.

CliffordK

Tubes get bigger when inflated. So you can use a variety of tube sizes. Generally you won't want to go HUGE. But, as mentioned any tube around 700-40 or 622-40 will be fine.

It is my belief that going with as large of a tube as will work with the tire will favor getting slow leaks over fast leaks.

So, start with, say a 700-25 tube, and a tiny hole and the tire will go flat almost immediately.

On the other hand, go with a 700x40-45 tube, and you may have a chance to air up the tube and make it home.

Lombard

Huh? Provided you found the object that punctured your tire in the first place, a smaller tube, say one that is made for a 700c x 25 tire in a 700c x 40 tire will make it home fine. Granted a stretched tube will be more porous and lose air faster, but we're talking a difference of days, not hours. Hey, what do you think those expensive "ultra lite" tubes are? Think of a smaller tube as a poor man's ultra-lite tube.

urbanknight

I think the theory is a smaller tube would be stretched more, thus tearing more (and leaking faster) when punctured.

KerryIrons

Actually it's a hypothesis. A theory (like gravity or evolution) is pretty much a proven concept. At least in science.

Lombard

Or would be more likely to puncture in the first place.

urbanknight

Picky, picky, picky. But really, thanks, I should know that.

ShannonM

I switched from 700Cx20-25mm tubes to 28-32mm ones and had a substantial reduction in pinch flats. Daily commute over the same terrible roads, on the same 700Cx23 tires.

--Shannon

Hondo6

You mean like the theory that the universe is geocentric? Or the theory that light propagation was enabled by luminiferous aether? Or the theory of atoms being elementary particles and indivisible?

As I recall, all of of these were once accepted scientific theories - or, if you prefer, were considered to be "proven concepts". All were later proven false by experiment.

I believe a better definition of an accepted scientific theory is an explanation that (1) best explains all observations to date, and (2) which has not yet been contradicted by a repeatable experiment.

Science is always open to the possibility that there is a better explanation for our understanding of reality than current theory.

Lombard

How did you stuff those bigger tubes inside the tires? If you are regularly getting pinch flats, you either need to watch where you are going or use wider tires.

ShannonM

No need to stuff anything. They went on just fine. There's an insignificant weight penalty, but who cares?

As to your closing sentence, well... wider tires don't fit under the fenders, (that were on the bike when I bought it, and which I couldn't afford to replace,) and as to my assumed (by you) need to "watch where I'm going, a) I've been riding road bikes for 38 years now, so I figure I kinda know what I'm doing, and b) Eureka has some of the worst roads of any city in California, so yer gonna hit stuff no matter what.

--Shannon

Lombard

Yikes! If roads are indeed that bad there, I think I'd be riding a mountain bike! I think my joints would give out before I would get pinch flats! What size tires are you riding there?

I don't care about weight penalties.

grumpus

Or run the existing tyres at a higher pressure.

Lombard

Yikes! If you are running tire pressure correct for your tire width and weight and still getting pinch flats, increasing pressures would make for a horribly jarring ride.

grumpus

True, but who among us can solemnly swear that they always check and adjust tyre pressure before going out? And just a bit more air, for a bit less chance of pinching, might be worth the odd extra bump and rattle. You only need a millimetre less squish to avoid some flats.

Lombard

Road tubes made of butyl rubber lose about 10 PSI per week, so checking before each ride is silly unless you only ride once a week. If you are losing air faster than that, you either have a tiny puncture already or are using latex tubes.

I honestly can say that in the last 30K+ miles of riding, I have never had a pinch flat - ever. All my flats were due to an object I found that punctured the tube or from a faulty valve stem. Granted I have hit a couple of nasty unavoidable potholes that I was sure would flat me, but didn't.

zhoushenglin

Thank you, it also helps solving my problem.