Context: My "fast bike" is just a gravel bike with Conti Ultra Sport III (32mm wide) tires, and I do not train for speed, but endurance (total amateur, never been in a bike race, and don't plan to).
I put RideNow TPU tubes (36g version) in the tires a few days ago after hearing on and on about how good TPU tubes are.
I never had an issue with butyl tubes, and collectively, they've been trouble free on three bikes with a combined mileage of 15,000 km+ , so I've been pretty apprehensive about changing them.
The last three rides have been on TPU for about 150km. I've been riding in the same areas I usually do (strava says some segments have been ridden by me over 60 times).
My efforts have NOT been all out, and I'm not even trying to be fast (i.e. not getting aero as often as I could), so I come home quite fresh.
Over those 150km, I've recorded dozens of personal bests, including the first ride out with them, which had some nasty headwind.
I'm comparing my speeds with my previous bests, and they are something like 5km/h - 10km/h faster. This is with a ton of extra weight on my bike: metal bottles x 2 or 3, dashcam, headlight, bike computer, heavy-ass toolkit (butyl tube + hand pump + electric pump + multitool + extras...), frame bag, top tube bag, two "snack bags" hanging off the handlebars, and snacks.
Two days ago, I actually maxed out my gears at a cadence of 100 on the flats (over 50 km/h).
I'm speechless.
If this is the kind of difference that TPU tubes make, I honestly can't imagine what race tires would do. No wonder the pros are able to go so fast!
Is this the typical TPU experience?
No experience with TPU.
They should only have significant effect during acceleration and deceleration. Once the wheel is spinning, whatever mass it is has stored the energy needed to spin it up so the mass doesn't affect the energy needed to keep it spinnig. Air drag tries to slow it down but that only acts on the outside of the tire which hasn't changed.
Acceleration takes a lot of energy and weight reduction in the wheels is very noticeable. I've no idea what the savings are in watts, but perhaps the energy saved during acceleration leaves more available for cruising? I don't know if you're saving enough for an extra 5-10kph at cruising speed, given that air drag grows exponentially. 5-10kph on top of 30kph is a lot, and on top of 40 - exponentially more.
Which leads me to the psychological boost. You're high on an upgrade and you push like a mf. We've all experienced the power boost you get evrery time you click the lever of a new high end shifter!
Probably a combination of those.
Post in time with reliability observations. How much top up they need in comparison to butyl, etc.
Tires fitted with TPU tubes supposedly have measurably lower rolling resistance, something to do with how the tire and tube interact when the tire is deforming under compression
Huh, and that can reduce energy even while cruising then?
Yep
https://www.bicyclerollingresistance.com/specials/tpu-inner-tubes