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Inner tubes... go big or go small? (lemmy.ca)

submitted 4 months ago by [email protected] to c/bikewrench

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I've got 32mm wide tires on my road/gravel bike. Currently looking at TPU tubes and I've got two options:

32-47mm
18-32mm

So, is it better to get one over the other, or will they both work equally well? Never used TPU tubes before, so I wouldn't even have a reference to compare these.

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[–] [email protected] 9 points 4 months ago* (last edited 4 months ago) (1 children)

I'm not a pro bike mechanic, but recently I had the same question for my 32 mm tires. And my conclusion after some cursory web searching was to go small, because a larger tube might fold upon itself when installing into the smallest compatible tire.

To be clear, both should be valid because 32 mm is within the advertised ranges. But IMO, the installation detail above would be the feather that tilts the scale towards going smaller. Unless, of course, you have other bikes that can use the same tubes in the larger range. If so, go larger.

I don't know much about TPU to know if that's significant to the tube sizing or not.

[–] [email protected] 1 points 4 months ago (1 children)

That's what makes sense to me, too. I do have wider gravel tires (40mm) for this bike that could use the wider tubes.

I'd rather not have a pinch flat, though, and going big seems like it would be more likely. At least, it seems that way in theory 😂

[–] [email protected] 1 points 4 months ago

All things considered, low air pressure is more likely to cause pinch flats than a tube fitted to a small-but-still-within-spec tire. So I'd go larger in your case. It also means you might consider investing in a suitable air gauge, if you don't already have one, so that checking air pressure regularly is a low-resistance activity.

Since you do have two bikes that can accept the same tubes, you can also view it as a reliability improvement: if either bike has a flat, you are more likely to have the spare tube on hand, meaning you can get back on the road quicker. So even if pinch flats become 0.0001% more likely, you're ready for it.

[–] suchwin 8 points 4 months ago (1 children)

I usually recommend people run the larger size tube. If it's not too big to install, then it will stretch less and be slightly more puncture resistant.

However, why are you getting into TPU? If it's for weight or rolling resistance, then definitely run the smaller tube.

I don't like using tubes on the end of their spectrum; just bc the box says it'll fit, doesn't mean it always will. Surely there's another brand of tubes with a better size range? That's my best answer tbh.

(Are tpu extra stretchy? 18-32 is a crazy range by butyl standards)

[–] [email protected] 2 points 4 months ago (1 children)

However, why are you getting into TPU? If it’s for weight or rolling resistance, then definitely run the smaller tube.

Apparently, they offer much lower rolling resistance, much lower weight, are way more compact (on bike repair kit), and should be more durable, too.

Surely there’s another brand of tubes with a better size range? That’s my best answer tbh.

I'll keep looking, but apparently this particular brand of (rather inexpensive) tubes are extremely popular and came recommended by someone in a riding group I was in.

[–] suchwin 1 points 4 months ago

Based off all that, I'd run the 18-32. Besides, assuming you're not buying in bulk, and you're not doing rural bike-packing, then getting a flat or other mechanical won't be too catastrophic or costly. Try em out a lil, and report back on how you like them :)