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FAQ:Bottom Brackets
Whats different about FSA external bb's

From around 2007 FSA crankset shafts came out that were 24.07mm rather than 24mm. Not all are that size and it isn't easy to pin it down to particular models so...

to be sure you need to measure the bearing seat on your cranks. You will also need to be sure your your measuring tool (Vernier calipers are probably the best idea) is accurate. If you are not sure about the accuracy of your verniers check a shimano crank. These are incredibly consistent at 24.00mm. What ever you measure this is the what you need to match. If your FSA cranks measures more than 24mm (or the Shimano crank measured) then you are looking at an oversized model. If you are lucky some models may even have the size etched into the end of the shaft.

Why is this a problem? Well it only becomes an issue when you want to fit Enduro external BB upgrade bearings. These bearings have a 24mm ID and run directly on the crank. The original FSA setup uses a nylon/plastic spacer/seal which can compensate for the variation. Obviously a steel bearing race doesn't have the same flexibility.

Once you know the size what options do you have?

24mm crank

You can use any of the Enduro External BB upgrade kits.

24.07mm (oversize)

You can use the Enduro FSA External BB kit which has grade 5 ceramic hybrid bearings or

if the original plastic spacer/seal is ok you can replace the bearings with identical sized ones. You will need to know the width of the bearing in your BB cups as this can vary too. It will be either 6 or 7mm. These bearings are available in a variety of levels (6mm wide only available in ceramic hybrids and Zeros)

Cups get stuck in BB Bearing replacement tool

Why do cups get stuck in the Outbooard BB bearing replacement tool?

The cause is burred contacts from your cup removal tool. The flat metal style cup tools tend to marr the contact areas on the cups. The cup holder of the Enduro BB Bearing tool is a neat fit and these burred edges catch.

First solution is to use a cup tool that fits like a socket (like the Enduro Cup tool, but there are others).

Second remove burrs from the cup with a file and/or coarse wet and dry, before placing in the cup holder.

If you have already got the cup stuck in the cup holder, screw the exposed thread into the BB and by wiggling the cup holder it should come free.


Bottom Bracket Facing


When you get a new frame (or bike) the frame is nicely painted and finshed. For various reasons though, the bottom bracket shell faces are often painted and rarely faced.

Facing of a surface provides a flat smooth finish. This is very important for proper operation of external bearing bottom brackets and many of the ISIS style BB's.

We recommend that when installing a new BB it is adviseable to check if your BB shell has been faced. If you are installing ceramic hybrid bearings then this is absolutely required. So if you don't know it has been done, get it checked.

Older BB systems were less affected because of the placement of the bearings in the housings and the axle location. Newer style BB's depend on the correct alignment of the opposing cups and any small misaligment will result in excess load on the bearings.

Unfaced or misalgned BB shells are one of the major cause of bearing failure in external bearing bottom brackets and cartridge bearing style ISIS BB's. Not to forget it also reduces the efficiency of the system. It can also be the source of annoying BB noises.


First you need a tools or tools. When facing a BB it is generally advised to clean and align the threads, also known as chasing.

Park, Cyclus and others make tools for this (the Cyclus tool is pictured).

Because these tools aren't cheap and it should only need doing once per frame this is usually a bike shop job. Expect to pay $25 (facing only)-$50 (chase and face) depending on the frame material etc.

If this save you one BB in the life of the frame you will have more than saved this money.

If you purchase a tool you should get instructions on how to use it.

Below are some pictures of a new frame that we chased and faced recently.


The frame all new and shiny. Notice the paint on the BB shell and even a litlle in the threads.

Chased and partially faced. A bit hard to see clearly because the photo's were taken in the workshop late at night but...

The threads are cleaned and the facing has removed some of the paint and metal from the BB shell.

Notice the paint remaining at the top left as compared to the exposed metal at the bottom. This illustrates the uneven initial finish to the frame.

Finally done. The BB shell face is smooth all around. The BB cups can now fit nicely up against the face and tighten up straight.

When installing a BB this is what your BB shell should look like, if not get it faced.

Now to do the other side.