Wrong bolts for spare wheel?

[donkmeister]

Just had to go and change a wheel for a stranded FIL who has been ignoring my repeated warnings to replace his perished tyres and finally come a cropper (fortunately after driving over a kerb in his yard rather than on a road, at speed, with people about)...

Whilst putting on his spare, I noticed that the wheel bolts seem to be the wrong length and profile for the wheel (conical seats for the alloy wheels, but the spare is a steel wheel with the slightly raised edges to the holes). There are no other wheel bolts in the car. Despite visible threads on the wheel bolts the wheel seems to be on well enough, following a drive around the yard through some bumps and with hard cornering. Doesn't seem right to me though. Didn't take pics, unfortunately.
The alloys and bolts are all original equipment from 2003. Citroen Xsara Picasso, owned from new.
He assures me the spare is also original... Has anyone else come across the situation of visible threads when using the spare wheel or is he telling me porkies? The tyre on the spare is the same as the others (all Michelin).

[E-bmw]

There obviously shouldn't be visible threads.

Could be that the alloy wheels fitted as standard need different lengths to the steel spare, not unusual.

[vikingaero]

Mercs and some other cars used to be supplied with different length bolts (and collars) for alloys vs. steel.

You FIL's car may have come with spare bolts which were lost over time.

I've changed plenty of spares and never had a problem in using the standard bolts for either type of wheel.

[donkmeister]

Ok, glad I'm not going mad here then!

I'll ask him to check his user manual to see if that sheds any light. Although TBH if he did end up knackering his wheel bolts / hub into the bargain, the embuggerance and cost might drill home the need to replace tyres before they
crumble to dust...

(Just bitter at having spent my lunch break changing a tyre that I'd repeatedly told him to change, only to be met with "no, it's fine. Look: plenty of tread." )

[SlimJim16v]

I thought all steel wheels used conical wheel nuts/bolts?

[Twig62]

These do use the same bolts for the alloys and the steel spare. There is something in the handbook about using them and how they fit differently when using them on the spare wheel.

[ridds]

Yep, my Peugeot has this.

There is a label on the spare showing that the flat washer section used for the alloy wheel will float when bolting on the conical face steel wheel.

Being a Citroen it's likely the same.

[Smint]

Remember coming across this before, the same bolts for the steel spare as the standard alloys, the bolt looked like it sat proud of the steel wheel when in fact it had the spare firmly clamped, clever design, this should explained in the handbook if its still with the car.

Bit confusing the first time you come across, much better than needing a different set of bolts and hoping that they can still be found with the locking wheel bolt in the pack which after some years might be buried in some obscure cubby hole or worse still someone's got rid of the locking bolts and lost the spare wheelbolts.