XK120 front stub axle carrier

I have a question regarding the front suspension uprights, or stub axle carriers on my XK120. When I converted my car back to drum brakes from discs at the front, I noticed that the bolts securing the drum brake backplates (which had previously located the caliper brackets) were of a larger diameter than the holes in the (early manual-adjusting) backplates, so I had to open the holes out a bit to take these larger diameter bolts. This leads me to wonder if XK150 uprights may have been fitted when it was converted to disc brakes? Does anyone know if XK150 and XK120 uprights differed in any way? Were the casting numbers different, for instance?
Also (and this may or may not be a characteristic of XK120 steering) when the car is on full lock, the front tyres scrub alarmingly. The lock is surprisingly good. In fact, when reversing it almost feels like the front wheels are being dragged sideways… Is this normal? Otherwise, the car seems to steer and track well enough, except when approaching full lock. I haven’t measured camber and castor yet. It does appear to have some slight positive camber when viewed with the wheels pointing straight ahead.
I’m hoping someone hasn’t fitted Mk IX front uprights, which I understand have different geometry. Is there a way to tell if they are Mk IX…?
Another thought - are XK and Mk IX steering arms different - if so, does anyone have the casting numbers to help identify what I’ve got?

All of the XK150 caliper mounts that have passed through my hands used the same size bolts as the XK120 drum brake backing plates. If this was a disc wheel car, it may have used Mk9 disc brakes. The Mk9 mounting bracket did use larger bolts than the XK120. That was from a two car sample size, 67202? and a loose pair of indeterminate heritage.

Mk9 on the left, XK on the right.

Mk9 upright and caliper mounting bracket.

Thanks for these very helpful pictures, Mike! It should be easy enough to tell if I have XK or Mk IX uprights - I’ll check tomorrow. It looks like the boss with the tapered hole for the top ball joint extends a bit further inboard on the Mk IX ones, which would increase the positive camber, of course. I think I recognize those caliper brackets - maybe they’re still around somewhere…
It was on disc wheels when the disc brakes were fitted in 1998, according to my old bills. Wire wheels weren’t fitted until about 2013. Back on disc wheels again now.
I’m wondering if the Mk IX steering arms might be shorter than the XK ones? If so, that might explain why the full lock seems so extreme. It would quicken the steering rsponse a bit, too, I imagine. Plus make it a bit heavier, perhaps. If someone had acquired a Mk IX front suspension, it would be easier to stick with the Mk IX arms, rather than open out the holes in the XK ones to accommodate the larger bolts.

Yes, that is correct.

I’ve discovered that XK120 and XK150 share the same stub axle carrier parts nos. - C3009, and C3606. However, the steering arms have different nos. - XK120 C3045/1 and C3046/1; XK150 C8467 and C8468. So there must be some differences there. I don’t know what the Mk IX numbers are - maybe someone has a Mk IX SPC they could look up for me?

Had a look at it again today, and the good news is that it appears to be an XK stub axle carrier (upright) not a Mk IX. The steering arm also looks to be XK, though I’d still like to see the casting numbers of both XK120 and XK150 side by side, if anyone can oblige?
I think what must have happened is that someone has drilled the 4 holes in the upright by which the backplates are mounted to a larger size so the Mk IX caliper brackets could be used. That would have also required the steering arms to have their holes similarly enlarged.
I still can’t explain the excessive scrubbing of the front tyres on full lock, unless that is normal?

I’m certain I don’t have a pair of XK150 arms, but I might have a pair from the Mk9.

I think I’ve got to the bottom of the scrubbing on full lock. At an XK Club / E-Type Club lunch today held at Denbies Winery, Dorking, I asked one of the Winspeed mechanics (they were one of the event’s sponsors) to have a look at it for me. He worked out immediately what was wrong. I had a much better left hand lock than the right hand one, which he reckons is probably due to someone fitting the steering box drop-arm one spline out. The LH lock is made more extreme because whatever bit bears against the lock-stop is riding up over it, because the lock stop itself is bent. That bit should be an easy fix, the steering box problem may be impossible to fix in situ, depending on how tight the arm is on the splined taper.

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It’s been a long time, so I could be wrong, but my recollection is that there is an alignment groove across the face of shaft that lines up with a mark on the pitman arm.

So I understand, Mike. My guess is it’s not quite aligned, but it may only be visible with the box out, which I’m not inclined to do anytime soon.

I’m back, after being off line for a week dealing with computer problems.

Yes, Mike is correct, there is a pair of alignment marks on the shaft and arm.
You could fix it by removing the bolts and jacking up the steering column an inch or two to get the nut off.

I might give it a go some time, Rob, but it looks a pig of a job!
I can also see (with a helper waggling the steering wheel) that the idler arm is moving up and down at the outer end, so I suspect that the idler itself may be seized and the the arm is turning on the taper. I won’t know for sure until I take it off, but I’m hoping the taper is not worn on the shaft or arm. I don’t know how long it’s been going on. Once I can free it off, I can check for wear on the bush and maybe I can get away with cleaning and lubrication. I suspect the bottom seal has worn and let the lubricant escape, causing the shaft to seize. I believe I am right that the steering idler arm C.3885 is the same for RHD and LHD cars?
Good to have you back, Rob!