Back a few degrees past vertical. Height set so the pan carries your thighs all the way to the knee. Close enough that you're not reaching for the wheel with your shoulders.

A driver with 34 years in said it flat under a cushion ad: "Adjust your seat so you're leaning back into the seat, not straight up or leaning forward. You will never have back problems if you do this." He's not wrong. If you haven't spent a full afternoon on this, do it before you spend a dollar on anything.

But watch the clock on it. Seat position is the variable right up until about hour six. After that it isn't - because moving the seat never changed what the bone at the base of your spine is carrying. It only changed the angle it carries it at.

Everybody knows this one. If you've been sitting on a folded wallet since the nineties, moving it is worth more than most things you can buy.

Here's the tell, though. A wallet causes an uneven problem - one hip riding higher, one side that aches, one boot wearing faster. If yours is dead centre, low, right at the tailbone, and it turns up around the same hour every single day, the wallet was never the thing.

It was just the cheapest thing to blame.

Air up, air down. Soft over the rough stuff, dumped for the yard. One driver's rig runs so well set up he told a comment thread he doesn't even use the airbag under the seat anymore.

The air ride is doing real work. It's the reason your spine is in better shape than a driver's was in 1985.

But look at what it manages: force arriving from underneath. It has nothing at all to do with the other thing - that sitting down puts your entire upper body onto a bone about the size of your thumb, and the seat presses straight back into it for eleven hours whether the ride is glass or gravel.

Smooth pressure for eleven hours is still eleven hours of pressure.

Four at five in the morning. Four at the reset. Some days that is exactly the right call and nobody should feel a thing about it.

But you already know what this is. It's turning down the volume on an alarm without walking over to find out what set it off. Every driver who's been taking them daily for years has a rough idea what his liver makes of that, and would rather not find out precisely.

This is the rung where most people start hunting for something that changes the cause instead of the signal. It's also the rung where most people quit hunting - because the next thing they try is a cushion, and the cushion lets them down.

Hands on the wheel, weight into your legs, hover over the tracks until they're behind you. A driver wrote it under an ad exactly like this: "I used to damn near stand when goin over bumps or train tracks."

Almost everyone does it. Almost nobody thinks about what it is.

It's your body lifting load off one specific spot - because that spot can't take any more of it. You've been protecting the same square inch for years without ever once saying so out loud.

You don't need a diagnosis. You can put a finger on it right now.

Drivers go, and it helps. Nobody here is going to tell you a cushion replaces one.

But run the arithmetic that never makes it into the brochure. $75 to $150 a visit, weekly, is $3,900 to $7,800 a year. And that's before the part nobody mentions to a driver - you have to physically be in a specific building at a specific time on a Tuesday, which is a considerably bigger ask for you than for anyone else in that waiting room.

Here's the real limit, though. A chiropractor is treating what eleven hours a day is doing to you. She isn't in the cab for a single one of them.

Here's what's in the comment threads under cushion ads, in drivers' own words. A spinal fusion. A second spine surgery at 40 years in. Three bulging lumbar discs. A CT scan that turned up a coccyx that had broken and healed at some point, without anyone noticing when.

Those aren't case studies out of a journal. Those are people typing about their own backs on a Tuesday afternoon.

Not everyone ends up here, and a cushion is not the reason someone does or doesn't. But nobody gets to rung eight in a single move. Every one of them spent years standing on the rungs above it, doing the sensible free things, hoping the sensible free things would be enough.

The thing that ends a driving career usually isn't the injury. It's the physical.

A DOT examiner assesses musculoskeletal fitness. Spinal conditions that affect mobility or strength can disqualify. And when a card doesn't get renewed, what's gone isn't a job - it's the license, the equipment, the route, the twenty-eight years, and the one thing you've always been good at.

That is the honest reason to take rung six seriously while it is still a choice instead of a consequence.