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This isn’t a problem with the passenger seat, so assume it’s a wear and tear issue.

There’s a just perceptible rocking in the Driver’s seat runners accompanied by a squeak. A bit annoying when getting in the car and driving over speed bumps. Both disappear when I gently push down on the fore / aft adjustment bar under the seat. It feels like a spring has either weakened or possibly broken. It still occurs if I move the seat further backwards or forwards to another position.

Has anyone else come across this before I start taking things apart?

Thanks

Hi, obvious and easy one to check would be the tightness of the four set screws that hold the seat assembly to the floor. Beyond that I would think it’s possibly a little wear in the seat runner mechanism which relies on small ball bearings for smooth operation that need greasing every so often. I have even experienced one of the ball bearings actually coming out of it’s track in the past. Might be best to take the seat out in order to get a better look at what’s going on and allow you to grease the bearings etc.
Cheers,
Rich.

Hi Rich,

The high tensile bolts to the floor are tight. The runner mechanism moves freely. I’ll have to remove the runners from the seat for a closer look.

The only other thing that comes to mind is the seat frame itself, which in my experience can fatigue and crack in the area close to the tilt mechanism. I had this happen on my old fixed head whereby the seat back started to rock slightly before the frame broke on one side and required welding back up.

Yep, happened to my pal’s 1980 FHC

The seat frame crack cab be welded with a gusset so it is stronger than ever. It is caused by, over the years, forgetting the keys in your pocket, then rather than getting out remove them, you straighten out so you have access to them. That puts a strain on the seat back that it wasn't designed for. I've done it myself over the years but always being cognizant of the force that could be placed on the seat back and consciously minimizing that.

I always thought I had a spare pair of seat runners hidden somewhere in the garage. Someone was selling them for a fiver at a car meet before Y2K since they’d fitted MX5 seats.

Well I found them, covered in cobwebs and the like. The springs seem to engage the ratchet teeth far stronger than those currently in the wedge, with no slop, so I’ll be changing them over shortly to see if that’s the cause.

And check the bearing balls in the slide mechanism move freely

Thanks Beans. Yes the balls are moving freely. The change has worked.

The previous release bar wasn’t strongly sprung enough allowing perceptible movement of the runners.