As most of our old trucks have king pins, I thought this article from Skinned Knuckles magazine was a treasure trove of how-to information. I hope you enjoy it as much as I did.  You can click on any of the images to view a larger image. My thanks again to Neil Maken, the editor of Skinned Knuckles, for providing permission for us to reprint it here for you folks.  If you get a chance, be sure to check out Skinned Knuckles magazine – the information is at the end of the article. — John (Jupes) Hansen.

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REPLACING (Front Wheel) KING PINS

On modern cars – that is from the 1920s or so up to contemporary – two types of suspensions were used: ball joints and king pins. Let’s limit this discussion to the king pins.

We have discussed in the past (June 2007, My Perspective – A Primer on Wheel Alignment) the fact that the wheels have to be oriented in a certain way with relation to the car’s frame, the road, the front end, and that there has to be a certain amount of flexibility in the orientation to allow for turns, road cresting and irregularity, tire wear, and a number of other variables. One of the front-end measurements that has to be allowed for is ‘camber’. Viewed from the front of the car, the wheels are not perfectly vertical. They are slightly offset. This is engineered into the design of the car for optimum performance. This off-vertical tilt is known as camber. (Your little red wagon, when you were a kid, didn’t have any camber to the wheels. They were perfectly vertical, but then again, your little red wagon wasn’t asked to perform the way an automobile is.)

The amount of tilt (in or out) is determined by the factory for each particular car. Most cars from the 1920s, ’30s and ’40s had a fixed degree of camber determined by the angle of the king pin. It was not a variable, and unless the axle was bent (pot holes were a major cause of bent axles) or otherwise damaged, the angle was set and then left alone. The ends of the front axle attaches to the wheels. A spindle (the part that holds the wheel) attaches to the axle by a steel rod that goes through this spindle, and through a hole in the end of the axle to keep the wheel at the correct angle to the axle. This steel rod is known as the king pin. The holes in the spindles are lined with an inner lining made of brass or bronze. This lining is known as the king pin bushing, and it prevents steel-on-steel wear between the spindle and king pin.

Not a whole lot of consideration is given to the king pins. For most of the life of the car they do their job efficiently, quietly, and give trouble-free service. But don’t be fooled. Those king pins are doing a lot of work. They are carrying the weight of the front of the car (including the engine), and are subject to an immense amount of torque and twisting from the movement of the car on the road. They are often the first part to feel the tremendous jolt of a wheel dropping into a pothole. Enough hard work and the king pin assemblies begin to suffer. First, the bushings, made of a softer material than the spindles or king pins begin to wear. And as they wear they allow the king pin to ‘wiggle’. And as it wiggles the wear becomes greater, and eventually the king pin itself is liable to begin to wear, get out of round, and can even crack and break. But as the king pins and bushings wear, even though they may not break, they allow the wheel to lose the set amount of inclination designed into the car. As the front end becomes loose, other parts can begin to wear and exacerbate the ‘sloppiness’ in the front end.

To check for looseness in the king pin, jack up the front end of the car and place it on jack stands (for safety). Grasp the tire at the very top and the very bottom and wiggle the wheel. If a looseness or movement is felt, enlist the aid of a friend to wiggle the wheel while you watch the spindle/axle connection. If you see any movement at the juncture of the spindle and axle, chances are the king pin (or bushing) is worn. It is not a very difficult job to change them, but before you start ripping things apart, be sure that replacement parts are available. Often a search through a Hollander’s Interchange Guide will help locate king pins from another application that might be easier to find than for your car. If you have a really rare or unusual marque, you may have to call on a machinist to make replacement bushings for you. Be sure that he has the old bushings to use as models so that he can match grease grooves, grease fitting holes, inside diameter and outside diameter.

What’s involved with changing king pins? Not much. Remove the tire/wheel to allow maximum working space. The king pins are protected from dust and dirt by caps at the top and bottom of the spindle. They have to be removed. Remove the grease fittings, remove the locking or retainer pin (held in place with a nut). Then the king pins themselves have to be driven out using a large drift or a piece of steel rod. Before you begin, make sure that there is adequate clearance above to allow the length of the king pin to come out of the top. If not, you may have to drive the pin out from the top so that it drops out the bottom. The bushings have to be removed, bearings removed, and spacers removed (make a notation of how many spacers were used at each joint, and be sure to replace them when reassembling). The axle and the spindles should be reamed to be certain that the holes are perfectly round. If not, you may experience premature wear of the king pins/bushings in the future. Reassemble in reverse, and you are set. Now let’s talk about specifics.

Jack the car up and place jack stands under the axle, well out of the way of the axle ends so they don’t interfere with your work. Remove the center nut and remove thewheel. The dust caps generally can be drilled and pried off. Remove the grease fittings (Zerk or Alemite) with an open end wrench. They should be cleaned and the old grease removed before reinstallation. There will be a nut that holds a tapered retaining pin and steering stop. Remove the retaining pin. Often the easiest way to get the old king pin out is to drive it out with a piece of steel rod, a bit smaller in diameter than the king pin itself. Examine the old king pin for obvious wear. This can tell you whether serious damage has occurred to the spindles.

At this point you may find it easiest to remove the spindle from the axle and work in a vise. As you remove the spindle make careful note of the placement of the thrust bearings and spacers. Be sure to write this information down so that upon reassembly you can put the correct number of spacers into the correct positions.

With the spindle off, you can generally use a socket to drive out the bushings. Try not to damage the bushings. You would like to examine them for wear patterns. There is one bushing in the upper spindle arm and one in the lower spindle arm. Thoroughly clean the spindles and spindle holes so that you can examine them for wear, for burrs or other signs of damage. Check with auto-repair friends for a reamer kit. It is not a common tool. It may make sense to rent a reamer kit. Bring the bushing with you to the tool rental store so that you get the correct one. Use a rat-tail file to remove burrs and light damage to the spindle.

Remove all metal filings. Sometimes, but not all of the time, the upper and lower bushings are of different sizes. Unless you have a hydraulic press, you would be well advised to take the spindles and the new bushings to a machine shop and have them pressed into place. This will assure that they go in straight and will not be damaged during installation. The machine shop can generally ream the bushings to that there is approximately 0.001″-0.015″ clearance between the king pin and the bushing (when fitted to the spindle). The king pin should just ‘grab’ when pushed through the dry bushings.

Be sure that the work area is clean so that you do not contaminate the new assembly during installation. Set the thrust bearing in place on the lower spindle, coat the parts with a little white grease, and slip the spindle over the axle. Before you go any further, examine the new king pin and the position of the locking notch. It may not be equidistant, and you do not want to install the new king pin upside down – see the picture of the kingpins on the bottom of this page. Note the notches are not in the center of the pin. Make sure that the locking notch in the new king pin aligns with the locking pin hole. Put a coating of grease on the new king pin and slip it into place. It should be a snug fit, but not too tight. Use a brass hammer or wooden mallet to tap it into place in the lower spindle. Make sure that the holes are aligned, and place the spacers (if any) into position. Make sure the locking notch on the pin is in the right position to line up with the locking pin hole. You can then drive the king pin the rest of the
way in. Put the retaining pin in place and put the lock washer and nut onto the thread hand-tight only at this point. Install the dust caps (they look like freeze plugs) in both the top and bottom of the spindle. Use a socket to align them and then to tap them into place securely. Replace the clean grease fitting retaining pin nut to about 55-to-65 foot pounds.

Replace the wheel (this is a good time to repack the front wheel bearings with grease {Restoration Supply Company stocks the automatic grease bearing press pictured below}) and you are done. S.K.

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This article originally appeared in the April 2009 issue of Skinned Knuckles magazine. Skinned Knuckles is dedicated to the authentic restoration of cars and light trucks and to the preservation of vehicles from the brass era through the early 1970s. It is available by subscription. Articles are copyrighted and all rights reserved. Reprinting authorized by written permission of the publisher only.

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Skinned Knuckles may be reached on-line at www.skinnedknuckles.net. Their mailing address is P.O. Box 6983, Huntington Beach, CA 92615.

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