Steering Knuckles, Spindles & Parts

The steering knuckles are where the suspension and steering systems and the front wheels converge. They provide the attachment points for the upper and lower control arms or struts and lower arms, the tie-rod ends, and the spindle and/or hubs to which the wheels are mounted. The steering knuckles allow the wheels to move vertically as the suspension reacts to road irregularities and horizontally in response to steering input. Steering knuckles and spindles are generally very durable components, but if one of yours requires replacement you’ll find what you need right here.

As you can see from the many variations on the page before you, steering knuckles have numerous configurations, but they can generally be divided according to whether the vehicle is rear-wheel drive or front wheel/all-wheel/four-wheel drive. On RWD vehicles the spindle may be an integral part of the knuckle, to which a hub with tapered roller bearings is installed, or a hub with sealed bearings may be bolted to the knuckle. The drive axle on FWD/AWD/4WD vehicles extends through the knuckle and is attached to a hub that is bolted to or pressed into the knuckle. Certain 4WD trucks have a hollow spindle that bolts to the knuckle, through which the drive axle extends and on which the hub rotates.

The precursor of the modern steering knuckle and spindle was the kingpin. Based on designs originally used on horse-drawn wagons, kingpins were commonly found on early leaf spring suspended beam axles. The center part of the pin is retained at the axle end, while the spindle rotates about the top and bottom of the pin on replaceable bushings. When independent front suspension began to replace solid axles, some cars continued to use kingpins that were now mounted in the steering knuckles, but most car makers switched to ball joints. The last cars to use kingpins were manufactured in the 1960s, but kingpins were common on trucks for many years because of their weight bearing capability, and can still be found on some late model heavy-duty trucks.

Steering knuckles and spindles are long-wearing components that usually only require replacement if damaged in a collision. However, whenever suspension ball joints or tie-rod ends are replaced, the knuckle stud bores should be inspected. If a stud was loose and not seated properly in the stud bore, the taper in the bore could be out of round or deformed, which requires knuckle replacement. Spindles should be inspected for damage to the hub retaining nut threads and for galling on the bearing contact surfaces caused by failed bearings. Either condition warrants spindle replacement. The bushings are the common kingpin wear points, and wear here can be checked by supporting the vehicle so the front wheels are off the ground and grasping the tire at the top and bottom to check for play.

Although steering knuckles and spindles don’t usually require replacement, many related components occasionally do, and you’ll find them all right here on our digital shelves. We have the knuckle bearings and seals used with press-fit steering knuckles and hubs, as well as the spindle nuts, washers and hub dust caps used with RWD vehicle spindles and tapered roller bearing hubs. We offer an extensive selection of kingpin sets for early cars and older and late model trucks. These sets provide everything needed to complete the job including kingpins, kingpin locking pins, bushings, bearings, shims, and caps, and some kits even include new grease fittings. Kingpins and related kingpin components are also available separately.