Answer: Watch a few Ballet videos on youtube, and duplicate the Grand Jette manoever.
Bear with me on this...
at around 15 seconds. Notice the dancer seems to hang in the air for a second.
So the body doesn't need to move up as much as the bike does, but the bike is blocked by the rider's body.
Here's a method:
- Approach the obstacle at decent speed and straight on, in a place with runout room on either side and a landing zone beyond.
- at a distance of 4 seconds from the obstacle, stop pedalling and level the cranks.
- immediately lower yourself on the bike. Chest and head should be down and backside should be off the seat.
- about 0.5-1 seconds before the obstacle, push your bike down into the road using even pressure between your arms and legs. Net effect is your body will rise up but with a flattish posture. Your Center of Mass is now taking on a parabolic arc.
- right at the edge of the obstacle your body should be moving upwards, and your bike is relatively unweighted. Right now you need to lift your toes and rotate your wrists to lift the bike. Your center of mass will continue in its parabolic arc, but your body will fly level for a bit. It should feel like pulling the bike up into your torso.
- the pothole or obstacle should be passing clean under you right now.
- Landing time - you can simply ride the bike onto the ground like an aeroplane hitting a runway, or you can reverse the step5 process and lower the bike smoothly, which looks better and is safer.
- resume pedalling and ride on.
Personally I find step 3 works better if my hands are on the drops rather than the hoods, but you may not have time for that.
Step 5 might be all you need to do to get over many obstacles. This is called Unweighting the bike and it will only be exerting ~10-20 kilos of pressure on the ground compared to your full mass+bike mass.
Step 5 is a lot easier with clips or clipless pedals. With flats you're going to have to try and push the bike down so the tyre springs you up somehow. (this is a gap in my knowledge.)
Step 7 can be a bad time if you're not going fast enough. Horizontal distance is a result of how high you jumped, and how fast you're going. That's all. If you're coming down short, you need to avoid smashing a rim into the corner of a pothole cos that risks punch flats, cuts, and a dinged rim, assuming you stay on the bike!
So back to ballet - you're maintaining the arc of your center of mass over the jump by sacrificing head/body height in favour of lifting the bike.
Practice idea - find a large open flat concrete area with no traffic, and lay out some lines with pavement chalk. Try and jump them, and the chalk should show exactly how far you got. Practice.