With certain bikes and certain bike manufacturers Cane Creek headsets require the use of Shim Spacers (1.3) in order to be installed and function correctly. This only occurs with IS (integrated) headsets and is due to a bike's design around a tall headset bearing and/or a different Bearing Cover (1.1.2) design than we use at Cane Creek. In order to account for this difference headset Shim Spacers are required to space out the Compression Ring (1.1.3) and allow it to preload the bearing.

If you have a bike that requires Shim Spacers then the issue will manifest itself during install. If you are attempting to preload the bearing and, no matter how tight you get the preload bolt, there is still movement in the headset then you likely require Shim Spacers. To confirm this it is worth checking to see if your Compression Ring (1.1.3) is contacting the bearing and if the Bearing Cover (1.1.2) is bottoming out on the bike's headtube.

It is difficult to be definitive about how many Shim Spacers you will actually need so it's useful it to have 1-4mm worth on hand--unless you are converting a Specialized Mindset to an IS 41, in which case you may need up to 10 mm of Spacers. The trick is to have just enough so that the Bearing Cover sits off of the headtube just enough so the seal still protects the bearing from debris. We  Shim Spacers in .25mm, .50mm, and 1.25mm and it is safe to assume that you need a couple of each size.

***It is important to note that Shim Spacers are only used for the Top bearing assembly***

Install: If you require 1mm or less of Spacers then you can integrate these in with your Bearing Cover assembly by nesting them in the Bearing Cover (1.1.2) around the blue Compression Ring (1.1.3). Then you can follow the normal procedure for a headset installation. 

If you require more than 1mm of Spacers then you will want to remove your blue Compression Ring (1.1.3) from the Bearing cover and install it into the bearing first (Tip: it helps to have the fork installed for this operation so that you can slide each piece down the steerer tube). Then you will stack the Shim Spacers on top of the Compression Ring (1.1.3). At this point you will need to experiment to figure out how many Shim Spacers you need. Start with the smallest amount (perhaps a 1.25mm Spacer) and work up from there adding a Spacer each time the headset fails to preload properly. Your looking for that "just right" combination of spacers so that there is just enough but not too much.