This article will discuss the removal and installation of the common cartridge bottom brackets of the three-piece cranksets. Most cartridge bottom brackets are held by retaining rings or cups on either side. See Adjustable-Type Bottom Brackets.
This article deals with the older type of bottom bracket, which consists of:. Do not think that you don't need a bottom bracket sleeve just because you have a closed seatpost! Although open seatposts on bikes without mudguards are the leading cause of dirty bottom brackets, even the cleanest, most carefully made bike is likely to have leftover brazing flux, paint chips, or other debris inside its frame tubes.
Nowadays, bottom brackets have disposable sealed cartridge bearings and, as frames have got beefier, bearings have increased in diameter to allow for lighter, stiffer chainsets using larger axles. And so goes the irresistible march of technological progress. However, while a traditional bottom bracket sits inside the frame and includes the axle in a single unit, Hollowtech bearings sit outside the frame and the axle is integrated into the crank. To check if your BB needs replacing, drop the chain off of the smallest chainring and spin the cranks.
The bottom bracket on a bicycle connects the crankset chainset to the bicycle and allows the crankset to rotate freely. It contains a spindle that the crankset attaches to, and the bearings that allow the spindle and cranks to rotate. The chainrings and pedals attach to the cranks.
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Bottom bracket service falls into one of two categories: you either change them with a new one or exchange bearings. Other brands do sell replacement bearings or seals to get the job done. Bikes with threadless bottom brackets PF30 or similar require you to punch out your old bearings using a BBT
Begin by removing the cranks. Watch the cotterless crank removal tutorial for a more detailed procedure. Once the cranks are removed, loosen and remove the lock ring on the non-drive or left side of the bike by turning counter-clockwise.
By George Ramelkamp. BB30 bottom bracket systems have very large bearings that press straight into the frame. Note that BB90 is a separate, Trek-specific standard which falls outside the scope of this article.