Bicycle Rolling Resistance: Tire Rolling Resistance Tests and More

Also on 2 wheels going fast around corners doesn't only involve grip but confidence. This is partly personal/psychological and partly based on feedback from the tire that comes on how the carcass of the tire deform while you are leaning the bike. It could be that a tire with more grip doesn't give you as much confidence as a tire with less grip on which you are closing in much closer to the limit.

Off the road the grip is so dependent on surface that it is even more difficult. There are tire for dry, mud or mixed surfaces and what you will encounter on the trail might be somewhere in between all of these.

Not quite. You can air down narrower road tires for this. The difference is that a wider tire (i.e a tire with more volume) is going to be more efficient at lower psi, because of a wider contact patch that ends up spreading the load out more and deflecting the tread less.

This effect definitely is pronounced for gravel riding when you have to run pressures lower than 60 psi, and a wider tire is better. However for on road riding, even on rough roads, a narrower tire is going to usually be better, because you gain the aerodynamic advantage, even if you run at lower psi. If you can sustain above 20 mph, running a 28c tire vs a 38c will save you 20 watts, which is noticeable.

>Then bytul vs latex vs tpu tubes.

This matters extremely little for most people. Maybe like 4 watts at most. For racing, when you are optimizing everything, its worth it, but generally tubes matter way less then tire selection. That being said, there really isn't any reason not to run TPU tubes because they are a lot more pliable and puncture resistant.

Generally asking bike industry to do actual engineering is an impossible task, but for optimal design there is no reason why even road bikes should not have suspension that doesn't rely on tire compliance. You can do carbon leaf springs with very small dampers. The best we get is suspension stems and seatposts, which suck because you still have all that unsprung mass of the entire bike bouncing around.

You don't have to be on the Pro Tour to benefit from aero gains with narrower tires. Even moderately fit people usually can sustain 15 mph on flat, at which point aero gains start to matter. Even more for hilly terrain where you can easily pick up over 20 mph on descents. The wider tires roll more efficient at lower psi (when you have to air down for comfort). But roughness of pavement road usually doesn't require less than 60 psi, and above 60 psi the rolling resistance of wider tires is about the same as narrower tires, but watt savings from aero can be significant.

I got a gravel bike to replace my old road bike because everyone was raving about it, and I absolutely hated riding it. Sure, at slow recreational speeds, it was more comfortable, but when getting places, it just didn't roll as well down hills, making me having to pedal more over extended times to get uphill.

Now I ride an aero road bike with TT bars, with 28c tires, and even when running them at 60-70 psi for rough pavement, the aero gains from the narrower wheels are significant, as I can pick up speeds over 30 mph on some descents which carry me way further uphill.

The only tests which BRR does which are likely applicable to mountain bike tires mounted to mountain bikes ridden on trails are the puncture tests, as you're likely to find sharp objects even on trails. Maybe the wet grip tests matter, if you often encounter wet large rock that you ride on.