Aftermarket steering wheels and the new MOT?

Removing an airbag from a MX5 may not render that car inton the same state as a factory non-airbagged car without further modification.

 

  1. The seatbelts maybe different; some markets use seatbelts that use tear away sections. When removing the airbag, the stituching needs to be unpicked, or the belt replaced.

  2. Airbagged cars have a different steering column from pre-1996 non-airbagged cars. All MX5s have a collapsible steering column. As far as I can make out, the steering column has a welded bracket that secures it to the dashboard bar, and which must break after a certain amount of movement. On airbagged cars, a pin engages with a slotted hole on a shim, which would seem to cause the dash bar to bend during an impact, causing a slight delay until the steering column support brackets break.

A Miata with the dash removed, showing the shim plate and the pin:

From 1996, non-airbagged cars incorporated the same dog-legged stalk controls as airbagged cars. These cars included the shim. Because the shim spaced the steering column down about a quarter of an inch, the steering wheels in these cars had an eccentric boss; the centre of the wheel wasn’t centred, in order to create more space between the legs and the rim of the wheel. I assume the same is true of airbagged wheels. So when you come to fit an aftermarket wheel, with a normal centred boss, the wheel can actually rub on the legs. The solution is to remove the shim plate; the pin doesn’t stop the support brackets from fitting properly against the dash bar.

What I did on my 1996 Roadster, replacing the factory Momo with a Nardi wheel fitted with a 1994 factory Nardi boss.

Eccentric factory boss

 

Steering column with shim in place

Shim removed

The testers manual says “drivers seat fore and aft mechanism not functioning as intended”. If it’s a bucket seat that’s bolted to the floor then it has no adjustment mechanism and therefore is not intended to adjust.

 

Not always the case, only testable items are testable (those refered to in the Inspection Manual). A rear wiper, to use your example can be fitted and defective but the car will most likely still pass, same with front fog lamps.

 

And reversing lamps.

 I think that, just to be on the safe side, we shall be well advised to keep our old airbag steering wheels ready to be re-fitted for MOT purposes if necessary!  I used to do the same with my front number plate Wink