Definitely do NOT want to inflate TPU tubes much outside of the tire as the material is inelastic - once it stretches, it’s not going back to the original size.
I’m wondering about your slow leak - how little pressure did you get to before pumping it back up? To date, the one time I got a major flat riding with a TPU tube was due to a gash in the tire from a fairly large piece of glass that would have killed any tube or tubeless tire (fortunately I had some duct tape in my seatpack to boot the tire and a spare butyl tube that I could limp back home at ~30 psi without severly pushing the boot through the gash in the tire) Upon examining the gashed TPU tube, I noticed it was not only cut where the gash in the tire was, but there were at least half a dozen snake bite-like punctures which must have happened with the sudden loss of pressure and me essentially riding on the rim for a good 20-30 feet to slow down and stop.
Chiming in. I’ve used latex for years for my road bike (rim brakes). The air loss is no big deal; Just a quick pump up before each ride.
I’ve been using TPU and latex for my gravel bike. Latex for the 30-35c tires I run for winter training and TPU for 40c+. I buy the inexpensive TPU tubes from a large online seller. They are decent quality and when you do have a flat it’s no big deal if it’s not repairable.
I run a mix of rim/disc and TPU and butyl on my road wheels. TPU/butyl/tubeless off-road - the only combo I’ve never tried is road tubeless.
I haven’t had any more issues with TPU than butyl (both road/gravel), other than for the first year I used them when TPU had plastic instead of metal valves. If I had to compare I’d say they flat slightly less? That’s a guess though - I don’t keep records.
I find myself buying TPU for spares rather than butyl though so I guess I’ve crossed over. I do always carry a butyl spare and patch kit. For longer road rides +1 TPU - mostly because of the small size; for gravel rides I usually have a bag so +1 butyl (and for longer gravel plugs/reamer.)
I’ve read quite a lot of threads about TPU in various places and there seems to be consensus of sorts that the metal valve stem is more reliable than the plastic. If you’re buying RideNows from AliExpress then you want the packets with the holographic logo for metal valves.
At the moment I’m running butyl front and rear and then carry a butyl patch kit and a TPU spare, that way if my spare fails I can just take the faff of the patch kit and hopefully still get home.
I’ve had great experience with RideNow TPU tubes in several wheel sizes. Latex has marginally better compliance, but won’t hold air for days on end. Most of my bikes are on TPU.
Really wish more TPU tubes had full-metal valves: I don’t trust the mostly-metal-still-some-plastic valves with electric inflators.
I use both latex (Vittoria) and TPU (RideNow). I find the latex has a longer lifespan; RideNow will just one day be done. It’s not catastrophic; they tend to spontaneously develop a slow leak that I’ll notice before a ride when it’s completely flat. The latex seem to last forever. Also, when latex tubes are done, they’ll biodegrade, and TPUs won’t.
Vittoria now makes a 30-38 latex tube which I’ve been using with no problems in 32mm gp5000. I do need to use valve extenders for deep rims but that’s not an issue for me.
Full time TPU user here after leaving the mess and bother of tubeless behind. I’ve had issues from time to time, but no more so than with other tube types and have had the same pair of rideon tubes in my wheels for 5,000, miles or so. No issues. Latex is great, but not worth the extra faffing about, IMHO.
Riding in the UK, all weathers I use Rene Herse tyres. 15 years ago I rode them tubeless but the extra light casings I prefer proved rather porous to the Stans sealant I was using. Several years followed using Dugast natural latex tubes and valve extenders with my Stans Avlon carbon rims. Topping up before every ready was acceptable as the ride quality was superb.
Dugast natural latex tubes have proved hard to find recently so having carried first a Tubolito and later some pink Ride Now TPUs as spares I thought I’d try them. The Ride Now proved inconsistent and if punctured hard to repair. Failure around the valve area happened a couple of times. So I went back to latex but this time Vittoria pink ones. Ride feel was good but they lost air at different rates compared to the Dugast ones making me question their quality.
Meanwhile Rene Herse and Silca started selling their own clear TPU tubes with full metal stems that were made in Germany (by a company called Eclipse I believe).
Eclipse sell thin lightweight TPUs they call Ultra and slightly thicker ones that they call Gravel. I’ve a couple of weeks riding on them now and ride feel is as per the latex. However, not having to top them up with air all the time is fantastic.