Overhauling cup-and-cone hubs

Many people these days prefer their hubs (and therefore, wheels) to roll on sealed cartridge bearings. You know these by their ring-like form factor, which is actually a pair of rings that act as races for the ball bearings that they keep captive. In cartridge bearing hubs, the hub shell is effectively just an anchor for them to stay in place, and has no real mechanical role other than to resist the tension of the spokes threaded through its flanges.

The other major design of hubs makes use of angular contact bearings. These are also called “loose bearing” or cup-and-cone bearing hubs. While these are easily pooh-poohed as the poor man’s option, the majority of Shimano’s hubs, and a fair number of Campagnolo’s hubs, still use the cup-and-cone design – even at the higher product tiers.

As the name suggests, these hubs use ball bearings that are kept captive by a bearing cup on the hub, as well as a special nut called a cone, which is threaded along the hub’s axle. The cups and cones act as the bearing races, and can then be used to set the preload on the bearings. As per Shimano, the angular contact design braces the ball bearings better under cornering loads compared to the radial contact of cartridge bearings.

Today I attempt to overhaul the cup-and-cone hubs on Hyro’s stock Giant S-X2 wheelset. We will need the following tools:

• Brake rotor removal tools: T25 Torx key, Hollowtech II bottom bracket wrench, or cassette lockring tool – select appropriately
• Chain whip and cassette lockring tool for the rear hub
• Cone wrench(es) – get the one sized for your hub
• Adjustable wrench
• Grease
• Degreaser
• Rags or paper towels
• New ball bearings: 3/16-inch for the front hub, 1/4-inch for the rear hub

Removing the brake rotor with a T25 Torx key.

We start off by removing the QR skewer and brake rotor. On a rear hub, we also remove the cassette. These parts will just get in the way of accessing the bearings. Given that the procedure also involves a fair bit of dirt and grease, this isn’t the stuff you want to find smeared on your brake rotors anyway.

Next, we remove the rubber dust seals on the axle. This is one of the few times a flat-tip screwdriver becomes handy.

Non-drive side of the rear hub with the brake rotor removed. The notched nut is the lock nut, and the rubber dust seal goes around it.

Removing the dust seals should reveal the ends of the axle, which contains the lock nut and cone. These are jammed against each other to lock in the bearing preload adjustment. You will need a suitably sized cone wrench (a 14 mm unit for my hubs) and an adjustable wrench to break them loose.

The thin yellow wrench is a Pedro’s 14 mm cone wrench, which holds the cone nut in place while the adjustable wrench breaks it free from the lock nut.

(L-R) Washer, lock nut, cone nut. The washer goes in between lock nut and cone nut.

With the lock nut loosened, undo the lock nut, any spacers, and the cone nut. Take them off the axle, taking note of the order they came out, and you should be able to remove the axle entirely from the hub. Do so carefully, as removing the axle introduces the chance of the ball bearings falling out in an uncontrolled manner.

The axle coming out of the hub. Note the gray plastic dust shield covering the ball bearings; on this hub, that is a pressed-in piece that can be carefully pried off for easier access.

Axle removed from the rear hub. On this unit, one of the cones is fixed to one end.

Once the axle is successfully removed, use a magnet-tipped screwdriver to pick the ball bearings out of the hub.

Rear hub bearings still covered by the gray plastic dust shield.

The drive-side end of the rear hub contains the freehub. Here, the ball bearings have already fallen out of the cup. There is another, slightly narrower plastic dust shield here.

All eighteen of the old 1/4″ ball bearings in the rear hub.

Your hub is now disassembled and ready for cleaning. For front hubs, you can spray degreaser pretty liberally into the hub shell to clean out the old, dirty grease. More care is needed with rear hubs, however, as going crazy with the degreaser may result in drying out the oil in your freehub, so it’s better to spray degreaser into a rag or paper towel and use that to clean out the old grease.

A cleaned-out freehub bearing cup, rid of its dirty grease.

With the hub dismantled, this is the perfect opportunity to inspect the bearing cups and cones. The point of overhauling your hubs every so often is to ensure that their bearing races remain smooth and free of pitting. Over time, water and dirt may make their way into the bearings, push out the grease, and start corrosion, which will wear the bearing races…and end your hub’s useful life.

Fixed cone on the axle after cleaning. Still pretty shiny, with no pitting.

On my rear hub, there is a small spot of pitting on the cone, but my front hub is in much worse shape. Practically half the cone’s circumference has pitting. This wheelset has lived a pretty hard life, so at this point I should start considering replacing these hubs in the next few months.

Rear hub cone nut. Mostly smooth, but it’s got a tiny spot of rough pitting.

Front hub cone nut. Pretty dire. Half the cone is pitted.

For now, I will be replacing the bearings and reassembling the hub, as due to the ongoing pandemic, most of my riding is done indoors.

Why replace the bearings? Unlike with the bearing races, it’s almost impossible to check individual ball bearings for wear, so the prudent practice is to replace them with each overhaul.

Wheels Manufacturing sells these “bottles o’ bearings.”

Once the hub shells are clean, repack the bearing cups with fresh grease. This will act as protective lubrication and help keep the ball bearings in place while reassembling the hub.

Repacking the cups with fresh grease.

Place new ball bearings into the bearing cups, making sure that they form an uninterrupted circle around the cup. Start with the drive side first. The size and number of ball bearings will differ between front and rear hubs. On the front hub, you typically use ten 3/16-inch bearings per cup, for a total of twenty accounting for both sides. On the rear hub, meanwhile, there are nine 1/4-inch bearings per cup, making a total of eighteen.

The useful thing about grease is it helps keep ball bearings in place.

Once the bearings have been installed in their grease bath, smear the axle with a coat of grease and reinsert it into the hub from the drive side. The fixed cone on the axle will help retain the bearings you just put in and prevent them from falling over. Turn the wheel over and repeat placing the ball bearings into the other cup.

Inserting the axle fills in the gap and helps keep the greased bearings from falling in.

When all the bearings are installed on both sides of the hub, screw the cone nut onto the axle from the non-drive side. Follow this up with any spacers, then the lock nut. Thread them on just enough so that the cone contacts the ball bearings, then have the lock nut follow closely.

Threading the cone nut onto the axle. Ideally this should be on the other, non-drive side, as it can be harder to set bearing preload with the freehub in the way of your cone wrench.

The final step in cup-and-cone hub reassembly is setting the bearing preload. This process is done by feel. You want the cone nut screwed in snugly enough so that there is almost no up-and-down play in the axle, but you also want it loose enough to turn freely. If the axle binds and resists spinning, loosen the cone a bit. If there is too much play in the axle, tighten the cone a bit. Eventually you will get to a happy medium.

(For hollow-axle quick-release hubs like this, leaving a millimeter or two of play in the axle is fine, as the clamping action of the closed quick-release skewer will take up the final bit of slack once the wheel is mounted into the dropouts. Thanks for the reminder, Matt!)

At this point, you take your cone wrench and hold the cone nut in place. With your other hand, take the adjustable wrench and tighten the lock nut against the cone nut to lock in the bearing preload. Recheck after tightening to see if the axle still spins freely without play.

Reusing this picture because this is the final step. After dialing in your bearing preload, tighten the lock nut against the cone.

Once done, reinstall the brake rotor, cassette, and QR skewers. You’re done! This procedure is best done at least once a year, or more frequently if you ride often in wet conditions.

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