Do you happen to be running an unsealed bottom bracket in your one- or three-piece cranks?
If so, are you tired and beaten down by constant rattles, adjustments and poor performance? Well, it’s time to quit hanging your head and build that bottom bracket right. There is no reason your unsealed bearings can’t turn as smoothly as the finest-sealed set if you take the time to care for them and tune them up right. After all, some of the highest-end bearings that cycling (road and mountain biking included) has to offer are unsealed. So, for this month’s “Tech Tip,” we gathered up the few simple tools required to do this job right and set about dialing you in with performance you never thought your bike was capable of.
Step one is to make sure your bottom bracket is loose, not your pedals or sprocket. Do this by isolating the arms and feeling for play, or excess drag.
All arms are different, but most apply a similar two-bolt design. Loosen the pinch bolt first, then remove the preload bolt from the end of the spindle.
The arm should now come off easily by hand.
The proper size cone wrench is key for this job, not pliers or a hammer. This lock nut is reverse threaded, so it must be turned clockwise to be removed.
The lock washer can then be removed by aligning the tooth with the groove in the spindle and sliding it off.
The cone nut is also reverse threaded, and once removed, the remaining contents of your bottom bracket can all be taken out by hand.
Unsealed bottom brackets tend to pick up dirt and grime that will eat your bearings, so a thorough cleaning of all the hardware is always a good idea.
Since you probably forgot, we kept our parts in order for you. Conveniently, the drive-side cone remains on the arm, minimizing loose parts.
A light coating of clean grease on all bearing surfaces is all you need. Don’t overdo it, or the resulting mess will be yours to deal with.
A bearing can then be applied on the drive-side cone and the crank arm/spindle run through the bottom bracket.
The opposing bearing can be placed into the shell with the open bearing surface facing inward and the closed side facing out, as shown.
The cone nut can now be threaded snugly into place, and before you beat your head against the wall, remember: It has opposite threads, so turn it counter-clockwise.
Again, align the tooth on the lock washer with the groove in the spindle and slide it into place.
With your lock nut loosely threaded into place, you can now set your bearing tension by tightening or loosening the cone nut with a screwdriver or, ideally, a spanner wrench.
When you have the bearings set to your liking, you can tighten down the lock nut securely to hold your adjustment.
Sometimes the cone will tighten with your lock nut if the lock washer is worn or damaged, so don’t be surprised if the perfect adjustment takes two or three tries. Finger test your adjustment before reinstalling the arm.
The crankarm bolt can then be replaced and tightened snugly.
Tighten the pinch bolt last to secure your adjustment.
Reinstall your chain, tighten your wheel and get back to doing pedal wheelies for the neighborhood kids. Next order of business: sealed bearings.