A few observations after riding the Marathon Almotion HS603 with Aerothan tubes:
On pavement the HS603 (40-622) seems to have low rolling resistance and no handling quirks. The tread doesn't squirm or follow grooves or contours and hardly ever holds small stones or glass shards. I can hear a faint hum around 15 mph but nothing above or below that speed. Comfort isn't quite up to the level of a Rene Herse Endurance or a GravelKing slick but is still pretty good.
On hard dirt climbing traction is significantly better than any of the slicks I've ridden. I haven't noticed any cornering or off-camber traction issues but I haven't pushed it. I haven't ridden them on mud, sand, or snow.
I haven't used them long enough to judge tread wear or puncture protection but since the HS603 is an expensive touring tire I expect those to be good.
The Aerothan tubes are light, flexible, and easy to install. They stretch enough the tube is much smaller than the recommended tires so easy to install without pinching. Rolling resistance differences between different tubes are small, certainly below my ability to distinguish without instruments.
So far I've had one puncture, about 1 mm long. I haven't been able to find Schwalbe patches so I tried a Park glueless patch. Having heard about patch issues with Aerothas and having experienced those with Tubolitos I was quite careful. I patched the tube at home in a clean environment and pressed it firmly onto the tube by rolling a 24 mm socket over it while applying most of my weight. I let it sit for a day then inflated it outside of a tire and let it sit another day. After 10 days in the tire it lost 16% of its initial pressure, exactly the same as the unpatched tube in the other tire. I'd call that a success but I can't say how long it will hold up.
I've had such bad luck patching tubes that I've given up. I just toss them. If you can go 10 days and lose 16% it's good. If you are riding 40s, that's probably 35-40 or so psi? I ride mainly road with 25mm tires and 90-100 psi. My gravel is tubeless so 35-40 and and I haven't really tracked it, but lose maybe a couple psi per day? Tubeless seems like the way to go (for me) on fat tires. I still just write off the tubes on my road bike as part of the cost of participation. 🙂
In 10 days my rear tire dropped from 50 to 42 psi and the front from 45 to 38 psi. Those initial pressures were probably too high as the tires felt fine at 38/42 psi.
I also put Aerothan tubes in a pair of 32-622 GP5000s. Those lost 20% (from 54/60 psi) in 12 days which is about the same as the bigger tires.
