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Discussion Starter · #1 ·
I just picked up a carbon rigid fork from what I believe is a 2017/2018 Fatboy second hand. It doesn't say FACT on it, but the cable routing is exactly like what I have found in all of the pictures of a newer specialized carbon fork, it has the Specialized steer tube plug as well as a Specialized axle. I previously had the 2015 carbon fork but I updated to the Bluto so now my front wheels (fat and 29) have a 150mm hub. I wanted to go back to a full rigid setup for grins so here we are.

On my original 2015 carbon fork, there was a machined metal collar built into the fork where the lower bearing sat and there was little to no play between the OD of the steering shaft and the ID of the bearing (same story for the Bluto). With this new fork, there is no metal collar, just carbon but it is tapered so I believe the bearing should just sit directly on the carbon. I've included pictures of the fork for reference, the bearing I'm using is a standard 52/40 IS lower bearing from the 2015 Fatboy frame. When the lower race of the bearing sits on the fork, it appears to match up with the 45 degree 'machined' bearing surface but the inner race of the bearing is 40mm whereas the steer tube at that point is 38.5mm. If I put the whole thing together on the bike, it doesn't have any play (it is centered by the 45 degree tapered portion of the fork where the bearing sits) but something is unsettling about the .75mm gap around the ID of the bearing and the steering shaft.

Can someone confirm what bearing they are running with a newer FACT carbon fork?
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I was able to find a lower headset bearing for those when i put a Specialized chisel carbon fork on my wife's fatbike. Pretty sure it was an FSA that I found on the FSA website for a Specialized integrated crown race fork. They're made to run on the fork with no crown race.
 

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Discussion Starter · #4 ·
I checked mine and it doesn't seem to have a crown race, so a bearing designed for direct mount onto the fork sounds right. It would be an FSA one, as stock.
Thanks so much for the responses! Can you verify which bearing you are using? Also, does the ID of the bearing sit tight up against the steer tube or is there a small amount of play? On mine, the steer tube is 38.5mm but the ID of the bearing is 40mm.
 

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To be clear, the one I mounted is a Specialized Chisel Fact carbon 150/15 TA fork. No idea the year or vintage, bought used off eBay. Searched my email, pretty sure the bearing is this one:
FSA Bearing SL TH-070E ACB 45°x45° 1.5" MR128R
The bearing sits right on the carbon fork with no race, fork fits up flush against the frame. Looks good with no play at all in the fit.
 
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