The covered wagon, also known as the Conestoga wagon or prairie schooner, worked its way across the American frontier powered by such livestock as mules, horses, or oxen. The wheels spun on spindles with iron bearings. The hub design with a spindle and greasy bearings isn’t bad, but maybe it’s time to use a lighter, faster, simpler, and cleaner design. It’s time for unit bearings under your Conastoga buggy or rock buggy or next custom 4x4.
What is a unit bearing and why would you want to try something new if the age-old system works great? A unit bearing isn’t really anything new except that it’s easier to use. On most full-floating axles (front or rear) you have a spindle with a hub and a pair of bearings, and you need to regularly service these by taking them apart, inspecting the bearings, and repacking with grease. The unit bearing is an all-in-one dual bearing assembly that bolts onto your axle end and doesn’t require recurring maintenance. This sounds great, but unit bearings have gotten a bad rap over the years because they do fail and when they do it requires purchasing a whole new unit bearing for high buy-in costs. Plus, most unit bearings require an axleshaft to hold them together, a problem if you ever break an axleshaft and need to limp home.
But the science of unit bearings has changed. Spidertrax offers a high-performance unit bearing that can take a beating, as has been proven by Ultra-Four rock racers who abuse them without fail every race. These can stand up without an axleshaft, and they are easy to use and install. We know we can’t convince everyone that a service-free hub is the way to go (some of us like the greasy job of tearing down and inspecting our hubs, bearings, and spindles) but if you’re ready for a simpler, stress-free, cleaner option then Spidertrax Ultimate Unit Bearings are the ticket.
The Spidertrax Ultimate Unit Bearing consists of a Timken two-bearing pack of the size you would find on a 1-ton truck such as a Ford F-350, but then Spidertrax upgrades it for additional strength. The bearing pack is in the foreground, but in the back is the Spidertrax spindle and wheel mounting flange as well as the locking nut that is installed for assembly. After years of testing with off-the-shelf parts, Spidertrax has developed its own heat-treated chromoly spindle and flange and assembles them in its Colorado facility.
The spindle flange is heat-treated chromoly and performs multiple jobs. The flange has the wheel bolt pattern drilled into it and is available in 5-on-5 1/2, 6-on-5 1/2, 6-on-6 1/2, and 8-on-6 1/2 patterns. Inside the spindle is broached to accept either 35-spline or extra-beefy 40-spline axleshafts. The spindle itself is what the bearing pack spins on and is threaded left- or rightward depending on which side of the 4x4 the unit bearing is being used. This view is actually the back side, or axle side, of the spindle.
The unit bearing comes assembled as shown. It can be ordered with metric or standard wheel studs up to 5/8 inch. The four threaded holes on the back of the bearing pack is where the M14-1.50x50MM sock head cap screws attach the unit bearing to the steering knuckle or to the rear axle mounting cup (no, these are not only for front axles). This complete unit weighs just under 20 pounds. The compact unit is less than 2 1/2 inches from wheel mounting surface to where the unit bearing attaches to the steering knuckle. This reduces scrub radius for steering and stress on the unit bearing from big tires. So far Spidertrax knows of no failures even with many off-road racing miles and a lot of big-tire abuse.
The Spidertrax fabricated housings and steering knuckles have a machined mounting surface for the unit bearings. The design is strong, simple, and lightweight and allows you to remove the unit bearing with just four big bolts. No more looking for the hub socket or dealing with greasy bearings if you need to repair an axleshaft on the trail.
The Spidertrax Ultimate Unit Bearing with Spidertrax brakes is an ultralight hub option but still very strong. Why is light weight important? Because having less unsprung weight allows your axle to move quicker across off-road obstacles and is easier to control, resulting in a faster vehicle. Sure, most of us are not racing, but light and strong racing parts can benefit anyone building a custom 4x4 who is looking to perform better off-road.
If there is one downfall of the Ultimate Unit Bearing it would be the lack of a locking hub option. This may be a detriment to some looking for optimal fuel economy, but others may not care. Sure, it means the front end is spinning all the time, but it also means you don’t need to get out and lock the hubs when you need 4x4.
The unit bearings are custom built in the USA. We’ve had great luck running Ultimate Unit Bearings on our multiple rockcrawling builds. Though maybe not be for everyone, they are topnotch when it comes to strength and simplicity for axle hubs, and we suspect we will be seeing more of them on recreational wheelers on the trail.