Guide: Bottom Bracket Standards on Road Bikes and Mountain Bikes

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Bottom Bracket Standards

This video will talk about the new bottom bracket standards that have been occurring on both mountains bikes and road bikes.

The first standard is one that was introduced primarily by Shimano. It is called PressFit BB86 when used for road bikes and PressFit BB91 when used for Mountain Bikes. This standard can be identified by a smooth bore bottom bracket that goes all the way through. The width of the frame shell is going to be the same as on a english thread bottom bracket with cups threaded in it. The cup for this bottom bracket is going to be plastic and have a 24mm pass through, and pressing it in is going to be pretty easy with park tools. The compatibility with the bottom bracket is going to be exclusive, but will work with many familiar cranks. The difference we got between mountain bikes and road bikes is additional width.

Smooth bore bottom bracket frame shell for PressFit BB86/91

Very similar to the PressFit BB86/91 is Trek’s BB90 and BB95. The 90mm wide bottom bracket is used exclusively for road bikes and the 95mm wide for mountain bikes. The notable difference between the PressFit 86 and the BB90 is that instead of using cups, there is a shoulder for the bearing, and the bearing is going to drop in directly against that shoulder. There are no cups and the race is built directly into the frame. This standard hasn’t been adopted very widely, and will be seen primarily on Trek and Gary Fisher bicycles. The tools used to install and remove this bottom bracket type are shared with park tools for BB86/91. It is called a Park BBT 90.3. The removal tool slides through the bearing and is used to knock the opposing cup out the other side with soft blows from a hammer and rotating the tool as you go. Installation will require a pair of special adapters that rest against the bearing with a Park Tool headset press.

Frame shell for BB90/95 with shoulder for bearing

The PressFit BB30 bottom bracket is going to be larger in diameter as well as narrower, however it’s going to be very similar. We still use plastic cups with a bearing encased and we press them into the frame in order to get the bottom bracket in. The spindle required for this is 30mm in diameter, and BB30 cranks will work with this standard. However, because it is larger in diameter and narrower, we can get a number of adapters to use standard 24 mm cranks in this PressFit 30 frame. The opposite is not true with the previously mentioned bottom bracket standards.

PressFit BB30 bottom bracket frame shell

The BB30 bottom bracket has a 42 mm inside diameter and there is a thin ridge 7 mm inside for a snap ring. The snap ring, when inserted, will allow you to press the bearings right in there. Similar to the PressFit BB30, adapters are available if you choose to use 24 mm cranks. For the installation and removal of BB30 and PressFit 30 bottom bracket frames, we recommend park tool’s new BBT 30.3. The removal tool is like an oversized bearing punch. In order to get this to remove, we would pass it through one of the bearings, and strike it with a hammer while rotating to knock the opposing bearing off. Installation is similar to the other bottom brackets.

BB30 bottom bracket frame shell with installed snap ring

One easy way to keep these standards straight in your head is to think of two separate attributes which are unique to each of the standards. The first would be bottom bracket spindle type (24mm, 30mm). The second attribute to cross reference that with is whether or not the bottom bracket takes internal cups or is the race integrated into the frame.

Differentiate bottom bracket standards with spindle types and internal cup use