Chances are that, unless you have been very lucky, you’ve heard that annoying click. It can start at any time. It gets into your ear and can ruin a ride faster than you can say ‘I might need to re-grease that’.
That annoying click has a source, it’s not always the bottom bracket, but the humble BB usually takes the flack. Generally this is because there are many BB standards, with several ways of converting between them and different cranksets after that. To be honest, it’s a bit of a mess.
With that said, clicks and creaks can originate at chainring bolts, pedals, headsets, saddles, stems and cleats. It’s worth checking that these are all correctly torqued with the appropriate compound applied before we go blaming a possible innocent bottom bracket.
Let’s run through the most notorious clickers, the reasons they go wrong and how you can fix them.
BB30/BB30a & BB90/BB95
Used by Cannondale and Trek respectively, these systems improved both stiffness and weight, but did lead to a few issues. Bearings are pressed directly into the frame.
BB30 - 30mm axle diameter, 68mm shell width,
BB30a -30mm axle diameter, 73mm shell width with an asymmetrical design (5mm wider on NDS).
BB90 - 24mm axle diameter, 90.5mm shell width, 37mm internal diameter
BB95 - 24 mm axle diameter, 95.5mm shell width, 37mm internal diameter
Tight manufacturing tolerances means that is the frame mould is wrong, every bike that comes out will have a faulty bottom bracket. That’s not ideal for smaller manufacturers looking for as few returns as possible.
Clicks and Creaks
With bearings pressed directly into the frame, WheelsMFG suggest that “if your frame’s ID is slightly out of tolerance” even their crank adapters won’t fix the problem.
Park tool have recently released their new AP-1 Adhesive Primer and RC-1 Retaining Compound. When I spoke to Cavlin Jones, Park Tool’s Director of Education, he told me that securing the bearing in place is key to preventing creaks. He also made it clear that you need to use the AP-1, or the bearing will be stuck in there so tight, removal force could damage the carbon shell.
This widely used system is similar to BB30 with a 68mm shell width and 30mm axle. However, there’s an extra layer between with aluminium cups pressed into a 46mm frame shell and then the 42mm bearing pressed into that.
30mm axle diameter, 68mm shell width, 46mm shell internal diameter, 42mm bearing external diameter
The majority of these systems use aluminium cups pressed into a carbon shell. Eliminating any slipping from here is key to keeping the system quiet. Just like the BB30 and BB90 systems, using Park Tool’s AP-1 and RC-1 will take up any space left through manufacturing intolerances.
But what if you have a BB30 or PF30 frame and want to run a Shimano crank, with a 24mm axle? Well, chances are, WheelsMFG have an adapter for that.
Clicks and Creaks
With another layer comes the potential for more things to click. Depending on frame material, different compounds are needed. If you’re pressing aluminium cups into a carbon frame, use the Park Tool compounds as above. Aluminium cups into an aluminium frame requires a high quality grease.
Bearing preload can also be an issue. Make sure your cranks are torqued to the correct setting, my Cannondale Si cranks being a whopping 40Nm.
Cervelo’s hybrid system aimed to take the best from pressfit and threaded to make a stiff, reliable and lightweight system. It’s essentially a wider BB30 which takes the 30mm axel and puts it in a 79mm frame shell. The super wide profile adds a fair bit of stiffness, but also allows for more clearance at the chainstays.
30mm axel diameter, 79mm shell width, 46mm shell internal diameter, 42mm bearing external diameter
Clicks and Creaks
The wider shell puts a little less pressure on the bearings, but they will still click inside the frame if either the frame or bearing diameter tolerance is out. Use the ParkTool AC-1 and RC-1 to secure the bearing in place.
With all that said, proper maintenance can help to prevent clicks. So keep powerful pressure washers away from sensitive bearings and remember to fully service the bottom bracket throughout the year, especially if you ride in harsh weather.