king pins: worn bushes or pin loose in upright?

[ardiesse]

A simple handbrake adjustment on Boxing Day led to a wheel-truing project (as you might expect).  To true the wheel rims up I needed an old upright, front brake assembly and hub which I could mount in the vice and bolt the wheel rim to . . .

. . . once I pulled the tyres off the rims, that is.

Four trued wheel rims later, and the FC no longer feels like it's riding on square wheels.  Bonus.

Before taking the front wheels off to true the rims up I did the wobble-the-front-wheels thing, and it wasn't good.  Both sides were loose, the driver's side much worse than the passenger's.  The upright and brake assembly I used to true the rims had less play in the king pin than the ones on the car, so I pulled it apart.  The pin was in perfect condition, but the bushes were worn.

And then, in the pile of parts I got with the FC, I found a pair of new bushes and a king pin bush drift.  Last June, I bought a king pin bush reamer from a bloke in Wagga Wagga.

It wasn't too much trouble to drive the old bushes out and the new ones in.  I worked out how to set the reamer (use a micrometer, set to the smallest diameter of the pin), and snuck up on the right size bit by bit - free fit with minimum clearance.  If I held onto the king pin too much, it would expand and turn the free fit into an interference fit.  All the parts have to be at the same temperature.

So far, so good.  I assembled all the parts, put the taper pin in, picked up the flat on the king pin with the taper of the lock pin as you should, tightened the nut, and . . . the stub axle wobbled, like the king pin's worn.  Can't be.  I've just replaced the bushes.

It turns out that the hole in the upright is slightly bigger than the king pin.  In the shop manual it says, "insert lock pin and tighten nut securely."  There's a bit more to it than that.  Lubricate lock pin with oil, insert, and tighten nut securely.  Then give the lock pin a few decent hits with a pin punch to drive it in further, and tighten the nut securely.  Repeat a few times more, until the nut stays tight.  Each time I did this, the free play in the stub axle got less, until it went away.

OK, so that was a learning experience.  I then thought I'd replace my driver's side upright and stub axle with the one I'd just rebuilt, only to discover after disassembling the front suspension that I'd just reconditioned a passenger's side.  Who's a bit naive then?

The FC's RHF stub axle was loose, not only in camber, but in caster (that is, in the direction the wheel rotates).  Funny, that's how the reconditioned one felt when the lock pin wasn't tight enough.  I gave the lock pin a few hits with a hammer and pin punch, and the nut came loose.  The king pin was loose in the upright . . .  With the king pin properly secured, there was no play when I tried rotating the backing plate (good), but still a little up-and-down looseness (you can't have everything).  Way better than it was, though.

And the car steers way better.  It always used to "remember" the last corner it went around and pull in that direction, until the next bump in the road, when it'd "forget" and take off in a different direction.

I found the driver's side king pin assembly to match the passenger's side I'd just reconditioned.  But when I looked at it, the lock pin didn't seem to be driven in far enough.  I drove the lock pin out, filed the burrs off, cleaned and oiled it, installed it, got a pin punch behind it, and tightened the nut.  And it took a few goes, driving the pin in further each time, until the lock nut wouldn't tighten any more.  And what I thought was a worn-out king pin assembly is perfect.

This seems to be a trap for the unwary.  You think your king pins are worn out and go to all the trouble of replacing them, when it's just the king pin which is loose in the upright.

Rob

[mcl1959]

Great story Rob, the one time I did replace king pin bushes myself I remember that the lock pin was troublesome and I probably didn't do it right.
The bushes seemed to become loose not long after I did the job and I'd always assumed that I had over reamed them. More likely it was the lock pin as you describe.
I ended up swapping out the front end for a HR one in that car (my first FC) and problem was solved ::)
Never tried king pin bushes again, just bought changeover kits.
Good on you for persevering and writing your experiences down.

Ken

[hsv-001]

Is there a hole in the bush that has to align with the grease nipple ? I seem to recall having a stub seize on me years ago . If you have access to the kitchen oven and freezer you can use temperature to fit these really well, just don't over do it  .

[ardiesse]

Haydn,

Yes, there is.  I lined the hole in the bush up with the grease fitting before I drove the new bushes in.

I imagine you'd put the stub axle in the oven and the bushes in the freezer, and then work quickly.  On the other hand, I've got access to liquid nitrogen at work.  But the bushes are not that tight a fit, so a hammer and drift work well.

Rob

[RET]

Great story, Rob, thanks for taking the time to document it.

But I have to ask... Is there any vehicle maintenance at your house that doesn't involve messing with the ambient temperature of things? It's like Game of Thrones in your garage: an epic battle between Fire and Ice ;D

[ardiesse]

Richard,

Let me review what I've done in the last couple of months . . .

an engine rebuild: shrink-fitting early-series rocker pedestals onto the shafts.  Yep.  That took heat.
the wheel-truing project: freeing up stuck brake adjusters.  That took heat, and even after that, the thread in one adjuster "galled", so it's bin-worthy.
the king-pin rebush: I tried heating up the stub axle to make it easier to slip the shims in between stub axle and upright.  Briefly thought about soldering the expansion plugs into the stub axle, but decided that grease and solder don't like each other.

No, you're right.

Rob