King Pins

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Late '31
Posts: 93
Joined: Wed Dec 07, 2011 7:43 pm

King Pins

Post by Late '31 »

Changing King Pins

The heaviest area of wear is usually the bushings in the spindles. It is the bushings of the spindles that wear. New bushings must be pressed into the spindles, and the spindles with the new bushings installed must be "pin hole honed" on a shop machine (preferred) or reamed using the proper sized parallel king pin reamer.

If you are doing it yourself, you are going to need a bushing reamer for the spindles. Just be sure to get the right size (.812). The king pins are only one diameter (.812). Be careful, some reamers may be a little oversize and will cause loose king pins. The key thing is the two spindle bushings need to be perfectly aligned to each other. The reamer needs to reach the second bushing to align with the first bushing when reaming. Likely, the cost of the reamer will pay for the job in a machine shop.

Having a machine shop hone them will have greater accuracy. Some front end shops may use the wrong reamer, being too short. The reamer end MUST reach the second bushing before the main flutes start reaming the first bushing, so you need one with a longer end. The answer is, you must first take your king pins out and measure them.

Kingpins could be loose just from poor fit or reamed bushings. Check your axle ends for snug fit. If the kingpin has some serous movement in the end of the axle, then your axle is bad.

Once you press in the new bushings you are better off having a machine shop align hone the bushings to size.
Reaming works, but will always leave high spots as they do not do a perfect cut. These high spots will hold the kingpin tight at first, but quickly wear to leave a couple of thou of looseness. If they are align honed then they will be round with no high spots and will stay tight much longer.

If you go with the repro kingpins and you have repro brake pins then make sure you do not have any binding action. Just test fit them. Also some repro kingpins do not have the best holes in the center for the pin. It is wise to check all the fits anyway.

Also, micrometer check the diameter of the kingpin for #1. roundness, #2. undersize, and #3. taper. They must come in at .812" in all three categories. If not, send them back - they are not worth installing. Demand the correct dimension pins or hone them. King pins can vary in the same set, not by much, a few tenths but with honing you get them spot on. They also vary some from brand to brand.

Don't leave the bushes too tight hoping that you will get more life out of them. The steering will be stiff and the car will wander all over the road.
Don't over tighten the cotter pins (tapered lock pins) that hold the king pin in the axle eye. I have seen that done and the eye was stretched oval. It's impossible to not have a wobbly wheel if that happens without shrinking the eye again and not many places will even try that.
As for oversized king pins, if they are oversized, they won't fit through the eye of the axle.

Possibly the last comment about reamers, remove only one bushing, then install the new bushing and ream it. If the opposite bushing is removed, the guiding plug at the end of the reamer would be a very sloppy fit for the Alignment Plug that guides the reamer. After reaming the first hole, then replace the second bushing and ream it.

The Sunnen hone sizes both bushings at the same time - perfectly aligned and sized for clearance to match the size of the spindle bolt.

BTW, while you have the car this far apart, are your front brake wedges known to be good and equal or just good used? This is a potential problem area that can be overlooked. The common recommendation is to just file the front wedge smooth and use them. The problem is you can end up with different wedges from side to side. This may give you a problem that is not something you can adjust out. The repro wedges are pretty good and a matched pair might be a good thing.
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