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.
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)
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.
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 :)