How do they work?
A cup and cone hub makes use of loose ball bearings and allows you to easily adjust bearing tension, unlike most sealed bearing hubs that don't allow for any adjustment. They consist of the "cup" that acts as the bearing's outer race, which is pressed into the hub shell and not replaceable, and the "cone" that serves as the inner race and threads onto the axle. The hub bearings, which are usually 1/4" in rear hubs and 3/16" in front hubs, spin between the cup and cone. Bearing tension is adjusted be threading the cone down on the axle, and then locking its position in place with the locknut (a spacer between the cone and locknut allows you to tighten the two against each other easily
). Front cup and cone hubs are usually symmetrical, although the hub will be offset slightly to compensate for its rotor disc rotor mounting. Rear hubs use a freehub (the clutch mechanism that allows you to coast
) and the driveside cone and locknut can be found set within, sometimes hidden from view.
Why cup and cone?
From left to right: the cone (notice the wrench flats), spacer and locknut, with the axle in the background.
Because the majority of high-end aftermarket hubs use sealed bearings it's common to think of a cup and cone hub as lower quality, but that isn't always the case - Shimano's top tier XTR hubs are an example - and there are actually some advantages to going with a loose ball hub set. Not only are they easier to service (if you're into that sort of thing
) once you know how to do it, not requiring any bearing press tools and a vice or hammer, but because bearing tension is adjustable you can dial in the perfect amount tension. On top of that, a well setup cup and cone hub that has been put together with proper grease will usually offer lower rolling resistance that sealed bearing hubs can only dream of. It has also been said that a cup and cone system offers far more lateral bearing support than sealed bearings, although most riders would be hard pressed to notice the difference.
Most cup and cone hubs use a rubber dust shield (left) to help keep the elements out. Remove it to expose the hub's locknut and cone wrench flats (right)
Where do they lose points to sealed bearing hubs? Cup and cone systems often require more maintenance and can be prone to loosening up under hard riders, especially from sideways landings. This can be an especially big issue because the hub's outer bearing race - the cup - and the inner race - the cone - can be easily damaged when ridden lose. The cup itself is pressed into the hub shell and is not replaceable, meaning that the entire hub can quickly be turned to scrap metal if it becomes pitted, whereas it is quite rare to damage a sealed bearing hub's bearing bore from riding it loose. Worn out and lose sealed bearings? Simply pop them out, press in news ones and call it a day.
Some helpful pointers before you begin:
The cone and locknut are tightened up against each other, with a thin spacer in between, to lock them in place.
• Always use the smallest cone wrenches the fit. Most front hubs will accept either 13, 15 or 17mm sizes, while rear hubs often take 15, 17 and 19mm size wrenches. A crescent wrench can be used on the outer locknut.
• Turning the axle with your fingers will give you much better indication of if it is too tight than spinning it in the frame or fork. But rocking the wheel laterally while it is still in the bike will allow you to easily feel if it is too loose.
• It is important to note that adjusting the hub bearings tighter than required will not in any way keep them from coming loose sooner, but will actually increase wear on all components. A loose ball hub that has been ridden with too much bearing tension will likely have damaged both the cone and cup, possibly requiring the hub to be replaced. The same will result from riding a hub that is too loose. Your goal should be to adjust the hub so that it has the least amount of bearing tension without being loose.
The hub's loose ball bearings roll on the cup, a concave and pressed in piece that acts as the outer bearing race. Both the cup and the cone's bearing surface must be in good shape in order for the wheel to turn smoothly, with even the smallest amount of pitting causing a noticeable amount of roughness. Different grade hubs also use differing qualities of bearing surfaces - XTR hubs will turn smoother than lower level product.
• Cone wrenches
(13, 15, 17 and 19mm are all common sizes
• Adjustable wrench
Step 1 - Checking Bearing Tension: While the wheel is still in the frame or fork, hold the tire and rock it back and forth laterally. Tthe hub may be loose by only the slightest amount, but this is exaggerated by the time the movement reaches the rim and tire. Your hub bearings will need to be adjusted if you feel any slop. Remove the wheel from the bike if you don't feel any play, pull out the quick release and turn the axle slowly with your fingers. Any roughness that is felt will mean that the bearing tension is too high and will need to be backed off, or that a rebuild must be performed (to be covered in an upcoming Tech Tuesday). Check to be sure that both sides' locknut and cone are tight against each other before moving on to the next step - if not, all of your work will be for nothing.
Step 2: To adjust bearing tension you'll first need to break the locknut and cone free from each other. Do this on the non-disc side if working on a front hub, or the disc side if working on a rear hub. Position the two cone wrenches so that squeezing them together will turn the locknut to the left (as shown above), but try to keep the inner wrench's position the same. Once the locknut is loose, turn the cone wrench clockwise to tighten, or anti-clockwise to loosen, a few degrees and hold it in place as you tighten the locknut back down onto it. Check for play by trying to rock the axle with your fingers. It should turn smoothly, but have close to zero free play. Repeat as necessary.
Stay tuned for full rebuild instruction in an upcoming Tech Tuesday. Do you have any pointers on how to adjust cup and cone hub bearings? Share them below!
Step 3: If the hub is close to being perfect, but still needs a slight adjustment, you can do so without loosening the locknut once again. If it needs to be tightened, place a cone wrench on each locknut (not the cones!) and give them the slightest clockwise turn - only a degree or two - and recheck. If bearing tension needs to be back off slightly you can turn the cones out against each other by simply putting a cone wrench on each one and turning anti-clockwise.
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