Originally Posted by
Soil_Sampler
Take the bolt out and put the expander into your steerer, then tighten it with the correct size allen.
Then use a 1-1/8" top cap with your stem.
Some expanders(I believe FSA is one make) are configured so the top cap has an internally threaded sleeve projecting down from it that screws on over male threads on the expander body and tightens down to preload the headset. These cannot be replaced with a regular top cap.