You are correct a well bled system has no air in it. However if you look at the image below you can see that when the lever is in the released position the brake line is open to the reservoir. With hard braking the line pressure can exceed 2000 psi. With a second actuated lever in the system there is no way that the reservoir/badder container can hold that kind of pressure. And with the air chamber on the vent side of the badder all the air would have to be expelled before any pressure was built up in the line.
With the vent in the system the reservoir is only designed to hold the fluid at no pressure. If you look close you should see the vent hole in the body of the lever on any hydraulic system.
Simply adding a Y in the system with two normal brake levers will not work. If it did there would be no reason for the SHIMANO GRX - Hydraulic Disc Sub Brake Lever
As JimT says, the GRX sub-brake levers do exactly what you want – I put these on my gravel bike, albeit with drop-bar GRX brake-levers as the primary brake (which is what they are designed to work with) – having a set of these was the main reason I put Shimano parts on the gravel bike instead of SRAM. They work just fine, a bit of a pain to bleed, but they are pretty neat. I’d imagine they would work with a Shimano straight-bar lever too.
Anyway, there is a thread on here about them, which is probably best for this discussion:
It’s a marathon speed. When riding long distances, I am closer to 18-19 kph.
And a 36er allows even higher speeds. Currently I reach 27-28 max when sprinting with a top speed ever at 30,1 kph during at least 3 seconds. A 36er allows to keep speeds up to 30 kph for minutes. And if you add a schlumpf hub, you can keep more than 33 kph for more than an hour (if you are @toutestbon ).
Anyway, I would like to go a bit faster to finish the unicon marathon in less than 1h45 (=24 kph mean), but it might be really hard.
I ride a 3 mile loop around my neighborhood almost daily on my 29” Nimbus and have ridden up to 9 miles a couple times (with a lot of stops😄). Best I have done is a couple stops; either UPD or stops for traffic. Today was able to do it non- stop and was also able to conquer a steep hill that has been my nemesis.
Today, I changed the pedals location on my KH36 to the 127mm position for the first time and averaged 24km/hr on a 3.7km bike path loop. Not as scary as I thought… Now I really am looking forward to the Schumpf hub - coming soon I hope. To start with, I’ll probably not change gears on the move, and try to start in high gear with 150mm crank length.
In Sydney there is a dedicated bike lane around Centennial Park. 3,7km.
I did a lap with the usual setting at 150mm. I feel comfortable with this for the hilly commute to work - 14km - it was impractical (spinning pedals) in Centennial Park due to not having to stop for lights or ascend hills.
Hard to say. Each time out, I’m averaging longer distances, so I think the longer you ride, the more you can efficiently practice. I’m starting to find a comfortable rhythm, but it comes and goes during the ride.