Move the rear axle forward and the chair becomes dramatically easier to push and dramatically easier to tip over backwards.

Move it back and it is stable and it is exhausting.

It is a dial between effort and safety and it is set, individually, for one person, by somebody who knows what they are doing, usually across two or three appointments.

The chair we bought had the axle in the factory position, which is set as far back as it goes, because a display model has to be safe for a stranger to sit in.

Which means that the very expensive, very good, very light rigid frame my son sold a guitar for was configured to be about as hard to push as her old one.