A Pressing Issue

 In 1885, John Kemp Starley completed his design of the "safety bicycle" - a bike with two equal-sized wheels and a chain drive - and about a week later the first official complaint about a creaking bottom bracket was recorded. Since then the situation does not seem to have improved much. Persistent BB creaks that resist attempts from bike mechanics, manufacturers and exorcists to cure them are the bane of many an otherwise happy cyclist.

Part of the reason these shudder-inducing groans can be so tricky to get rid of is the challenge of accurately diagnosing them in the first place: there are simply so many possible causes. It's easy to immediately suspect the BB itself, but it could just as easily be an over-tight or under-greased pedal bearing, a worn or innacurately torqued crank / axle interface or even something completely different. (Hint: if the mysterious noise stops when you stand up then give your saddle a good wobble and see what happens.)

But let's assume for the moment that the pedals don't creak when you swap them onto another bike, that you've stripped, cleaned and properly tightened your cranks, and that you are now as sure as sure can be that it's definitely the BB. Before you hurl your bike off a cliff in a fit of rage, it's worth sparing a thought for your poor bottom bracket, and what it has to put up with. 

Landing heavily off drops, "schralping" berms, battering through fields of loose rocks and even pedalling back up to the top again all put a lot of stress on the bottom bracket area. Just standing up on the cranks puts your whole body weight through two pretty small bearings, as well as applying a massive amount of torque to the axle itself. The poor thing is suspended a few inches off the floor, right behind your front tyre, as you plough your way through water, mud and sand. And to top it all off nobody will buy it if it weighs more than 95g, even if pro DH riders nowadays are stuffing their crank axles with lead to make their bikes more stable. No wonder it complains occasionally.

The several different bottom bracket standards currently available fall into two camps based on how they fit into the frame: threaded and press fit. There are certainly people out there who are believers in the one true bottom bracket standard, whichever side of the divide they are on, but as usual the truth is that both of these approaches have pluses and minuses. 

Threaded bottom brackets are less likely to creak. The press-fit interface between the bearing and BB cup can be permanently installed by the manufacturer, and the threaded interface between BB and frame should keep itself tight as you pedal. It is also normally easier for a home mechanic to remove and reinstall threaded BBs, as long as they have the correct BB-specific spanner on hand. Press fit BBs on the other hand can be a bit lighter, and allow for a stiffer and stronger frame design in the BB area, all while being cheaper to manufacture and simpler to build into a carbon frame. You can also install them with a hammer in an emergency, or if you have a BMX.

So is one better? That of course depends on your perspective and requirements. I can only tell you that I haven't had any problems with press fit or threaded BBs in the last 20 years, and yes that includes several well-used and never maintained BMX BBs that were installed with a hammer. Square tapered axles on the other hand are a different story, and the quicker they are consigned to the bin of history the better.