One of the biggest changes for frames in the last decade has been the move towards unthreaded bottom bracket shells. The move was as much to make the process of of frame production simpler and cheaper as it was to offer the end user benefits like stiffer, lighter bottom bracket axles with the Cannondale BB30 system. This style of bottom bracket is referred to as PressFit or PF30. There are a number of other versions for different threadless bottom bracket shell specifications, though they all install the same way. Here's how.
Our guide below shows you what we believe is the best method to fit a Pressfit (BB30) bottom bracket. We've included a list of the tools and materials that you will need to complete the job and in some cases where you can buy them. If there are others that you prefer then feel free to let everybody know in the comments.
Threadless bottom bracket shells are nothing new in cycling, though until a few years ago they were only found on BMX bikes. Cannondale developed the BB30 30mm crank axle design and offered it to the cycling industry as an open source technology for mid to high end frames. The design promises quicker, easier fitting, wth no delicate fine pitch threads in the bottom bracket shell to damage or cross thread.
For a home mechanic, the reality is that it is easy to fit a press fit bottom bracket: it takes less than ten minutes but it's easier than fitting a threaded bottom bracket. You still have to follow procedure and take care not get the cups presented at an angle to the bottom bracket shell.
You'll still need some specialist tools, too; a bearing press is pretty much essential. Sure, pieces of soft wood and mallet can get the job done, but it's ugly and doesn't deliver the control required to guarantee a perfect fit. A good press can do both bottom bracket and headset, so if you're a keen home mechanic, the cost can be worth bearing.
1 Prepare the bottom bracket shell. As with any bottom bracket installation the most important part is the preparation. Making sure the bottom bracket shell is perfectly round and because the BB30 specification is without threads, the inside surface must be smooth and free from burrs, swarf or in the case of carbon frames, excess resin or lacquer. If in doubt about your bottom bracket shell's readiness for action, consult your local bke shop who will be able to check it in their workshop. We're adding a layer of copper based anti-seize by Finish Line. This helps guard against metal to metal corrosion and cold welding.
2 Ready to fit. Give the bottom bracket shell an even coat. About three quarters of an inch into the shell should be about right for most bottom bracket cups.
3 Check to see that you have the correct size circular drift for your press. Here you can see the reverse (inner) side of the cup and bearing (the black ring), with the step sided drift seated on the bearing lip.
4 Another view, showing the circular bearing drift being dropped into position in the outer face of the PressFit cup. It should just drop in. Occasionally it might need a finger pressure to seat it.
5 We're fitting a Chris King PressFit bottom bracket. These follow the same size and shape as any other BB30 cups. Chris King does recommend that their alloy bearing sleeve is used. It's a simple push fit onto either of the cups. The orange O-ring holds it in position.
6 Position the bearing cup. There is no left and right cups with BB30 as there are no threads. With the installation press tool in position from the opposite side and the threaded shaft through the centre of the shell, bring the first bearing in and over the threaded end of the press shaft. The first millimetres of the cup's leading edge should slide into the bottom bracket shell without the use of the tool.
7 the bearing going in. We've slid the press tool back through the shell for clarity to show how much of the cup fits with finger pressure. Why not just push it straight in with the tool? Sometimes the cup and the shell need to find their initial position to ensure as straight a fit into the bottom bracket shell as possible. If it's really off it makes fitting difficult and runs the risk of permanently damaging the frame's bottom bracket shell and the bottom bracket itself. With fingers you have more control and feel to squarely align the cup into the shell. This one is OK, if a fraction over on the top of the cup.
8 With the cup presented and ready to be pressed home, slide the bearing drift onto the threaded press shaft. Make sure it's seated squarely.
9 Spin the handle on to the threaded press tool shaft. As it closes up on the face of the bearing drift give the cup a final visual check to ensure it has remained squarely located in the bottom bracket shell. Keep turning the handle and you will feel the cup sliding into position. It can feel quite tight, this is quite normal (its actually a good thing, we don't want sloppy fitting cups as they cause noise, misalignment and premature bearing wear). When it reaches the point where the cup feels fully home, stop and remove the tool.
10 The cup in place. With the tool carefully removed from the bottom bracket shell you should be left with the bearing cup installed like this one. Only the lip of the cup is exposed and there are no gaps between the back of the lip and the face of the frames bottom bracket shell.
11 This side of the bearing is fitted and ready. The second side of the PressFit bottom bracket install is the same process you've just done, repeated on the other side of the bottom bracket shell. Just remember to use the same size bearing drift in the static end of the press tool to keep it centered in the cup you've already fitted.