I think that it's a combination of caster (forward fork) and steerer tube angle (rake angle)
I had a Raleigh 10-speed in the 80's that had a Very similar geometry to the bike
@Marcela posted,..
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My Raleigh was very similar to this, including the foot straps,..
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I could easily ride it no-hands.
I bought a used Harrow mountain bike about 25 years ago that sucked to ride no-hands.
It was all twitchy because of that stupid "Quick Steer" crap.
About 10 years ago I decided to "fix" the quick steer problem by raking out my steerer tube.
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I wanted to cut the steerer tube off, then weld it back on at a more appropriate angle, but I suck at welding.
So I cut the down tube, torched the top tube, and sledgehammered the top tube to rake it out,..
View attachment 213316
Then I reconnected the down tube with aluminum tubing bolted in place.
(That was a Harrow frame that already had a bent top tube. I just bent it more.)
So that's how much I Don't like today's geometry.
And why I put downhill forks on my ebike.