Hey I’m new into frame building and cycling in general, I’ve encountered some problems trying to build up my fixed frame.

I have a I803 Fork that wobbles (toward the bottom) inside my 2011 Felt brougham. Same diameter and length as stock. The stock fork has a built on crownrace without a detachable piece.

Is it the same case with the I803 fork? What’s the next step? if possible what measurments do i need to take for the right fit for whatever i need.

This is probably more appropriate for a mechanics forum.

Framebuilders forum is primarily for people who make bicycle frames, not building a bicycle from an already made frame. You likely need a crown race for the fork that matches your lower headset bearing. Any bike shop will be able to help you with what you need.

I'll add that if I understood the OP's data need/question all the answers are already in hand, the actual fork. Does it look/measure as the same as the old one?

Headsets want a certain shape to interface with the fork crown. Some forks have this shape molded into them, it was common to not do this and instead have a removeable piece (fork crown race seat) that gets transferred to the new (and needing it) replacement fork. It sounds like the OP has one of each... A lack of proper bearing/frame interface certainly might cause wobbling about, but there's a bunch of other possibilities that can cause a poor fit up. But with the poor description/lack of visuals I really can't say what's going on. Andy.