Frequently Asked Questions


<<<(FAQ 2 of 5)>>>

How do I get the right bottom bracket for my bike?

There are actually 2 bottom brackets on bicycles. There's the bottom bracket on the frame, and the component that threads into this part of the frame, which is also called the bottom bracket. To help tell the difference, the frame is usually called the bottom bracket shell and the component bottom bracket is called simply the bottom bracket, or sometimes the "BB" for short. 

When you're shopping for a new bottom bracket, you're looking for the bearing component that screws into the frame and which the crankset is bolted to. That's obvious because the frame bottom bracket is built into the structure and is not replaceable (except in rare situations).

If you already have a bottom bracket in your frame and it has worn out, you've probably noticed some grinding or metal-on-metal noises or roughness. It's usually easier to feel this if you lift the chain off the chainring, rest it on the frame and turn the crank slowly by hand feeling for trouble in the bottom bracket or bearings as the crank turns. When all's right the crank will turn smoothly with a slight hydraulic resistance from the grease inside.

Another test is grabbing the crankarms and pulling sideways back and forth to feel for play in the bottom bracket. If you notice play and roughness or grinding noises, there's a good chance it's time to replace it.

Feel free to bring your bike in for us to have a look if you're not sure your BB needs replacing. In general, they wear out over a period of 3 to 5 years if you ride a lot and in all weather conditions, though some can run for much longer without trouble.

Special tools are required to install bottom brackets and cranksets correctly so you may want to leave the job to us. If you like to do your own work and have the tools, bring the old BB in so we can match it up.

If you're upgrading your crankset, you need to ensure that the new bottom bracket is compatible with your frame and the spacing required by the new crankset. We can advise or you can check the manufacturer's specifications. In most cases, it's best to go with the bottom bracket(s) recommended by the manufacturer for the crankset you've selected.

When you come in to buy a replacement bottom bracket, we need to know the following:

  • The brand and model of your bicycle.
  • The brand, model and type of your crankset.
  • The width of your frame's bottom bracket. Use a metric ruler to measure the width between the outside edges of the frame only (do not include any of the BB). It will measure either 73, 70 or 68mm wide.
  • The length of the bottom bracket axle (also called a "spindle") measured from end to end (if it's threaded on the ends to accept bolts, just measure to the ends of the flat portions of the axle, not to the ends of the threaded portions).

If you have any questions at all, just ask and we'll be happy to help!


<<<(FAQ 2 of 5)>>>

Trek Bicycle Store

1209 Battleground Ave
Greensboro, North Carolina 27408

(336) 273-0100


Mon: 10am - 5pm  Monday Mountain Bike rides at 6:30pm
Tue - Fri: 10am - 7pm
Sat: 10am - 6pm  Saturday Road Rides at 10am
Sun: 12pm - 5pm
Call Shop for details on weekly rides.


Join us on Facebook


Follow us on Twitter