What size nut is this?

Well, it converts fairly closely to 22mm; did you have a 22mm spanner to try?

Also Chris

Yes, I tried a 22mm which was (far) too big and a 21mm, which was too small. I found an exotic Whitworth size that came out at 21.5mm and I thought, "yay cracked it!" but that turned out to be too small, too. I couldn't believe it. :(

Have you checked that your 22mm is actually 22? This is a standard size on nearly every car I come across

It was a Siegen spanner, so I assume so (I can't check as I've returned it to the shop because they overcharged me on it and a bunch of sockets I bought at the same time). Siegen is a good make AFAIK. But your point is a valid one. I've just converted the AF size of the mystery nut to metric and it comes out at 21.9202mm. Given that that spanner was way too big for the nut, it would seem there is some merit in what you say. The clearance would be less than one-tenth of a millimetre if that spanner had been made correctly and that doesn't sound unreasonable at all. But I was getting something like 20 degrees of arc!

0.863 inches = 21.9mm 22mm shouldn't have been slack. Does nut mic up the same on all sides? What does your 22mm spanner jaw measure? For 22mm page 5 shows DIN 3110 there can be over 0.3mm slack. Only 2 sizes are close, 22mm and 7/8 AF. The sizes are bolt head for mm, A/F and bolt shank for Whitworth, some older spanners can be made very slack tolerances. 0.813 inches = 13/16 inch AF 0.820 inches = 7/16 Whitworth or 1/2 BSF (20.83mm) 0.827 inches = 21mm 0.866 inches = 22mm 0.875 inches = 7/8 inch AF (22.2mm) 0.920 inches = 1/2 Whitworth or 9/16 BSF (23.368mm)

There are no AF / whit spanners sized in 32nds at this size.

I'm pleased to hear it.

That is the next thing I will check tomorrow, but it didn't appear to be damaged in any way so I would imagine so.

Sadly no longer available to test (returned to the store).

The nut comes out at 55/64" according to some website, but that sounds more like a drill size than a spanner! Thanks for the links, btw.

Being an old design, I'd expect most things on it to be Unified threads. Ie, AF spanner sizes. Cars designed after about the mid 70s were usually metric - although if using an older design of engine etc, that could still be unified, while the new bits like chassis bolts etc metric.

It sounds like a job for a 21mm spanner 'tickled' with grinding wheel or an angle-grinder (so beloved of uk.d-i-y posters).

That's not a stock AF spanner size - and I'd be most surprised if Jag used a special for this. Given they don't make the steering rack.

Looking at a Jag specialist, there are different track rod ends fitted to early and late cars. So it's also possible the thread changed from unified to metric during the long production run. And it is possible the early and late racks can be swapped complete too. So as with any old car you can never be 100% sure it's original.

There's a very useful chart of spanner sizes here:-

Yes, it does, within 1.5 thou all round so it would seem it's a perfectly normal, nominally 22mm jam nut. What a *damn shame* I no longer have that Siegen spanner to check.. :(