thundercleese

Let me start by saying I'm an experienced home mechanic, have done about a dozen headset installations in the past. Ran into something new last week that freaked me out: metal shavings that squeezed out as the cups seated.

The bike is a brand new frame, retro steel randonneur with 1" head tube, reputable brand manufactured in Taiwan. Working with the Park HHP-3 headset press, installing a 1" FSA Duron X headset (aluminum external cups), also new, with both surfaces thoroughly lubed with Park Polylube. Each cup went on a little crooked but straightened themselves out eventually, nothing out of the ordinary. Was a little tougher than normal getting the cups to go in, but I continued (foolishly?). When the cups seated, out came a couple long, thin scraped-off bits of metal. The largest grabbed a small bit of the head tube paint and lifted it up, which made my stomach sink, ughh.

Checked to see if the metal bits were magnetic and, thankfully, they seemed to be aluminum from the cups, not steel. That gave me the slightest bit of relief.

I put the frame aside and got back to it today. I removed the headset cups and inspected. No damage or marring inside the head tube, thankfully, but the aluminum cups seem to have been lightly scraped by the head tube. One cup had a bunch of shavings jammed around the 90 degree angle where the frame seats; I gently removed these with a utility knife and cleaned up all surfaces in anticipation of re-installing.

So my question is.... is this normal? Never experienced this before. Should I have had a shop check tolerances and ream the head tube? I'm expecting the re-installation to go smoother, but should I swallow my pride and have a pro take a look?

Crankycrank

Could be you have an ISO headset-(30.2mm) in a JIS-(30.0mm) headtube. Usually not an issue though but your fit could be extra tight. If you have some calipers measure them. I wouldn't ream the headtube unless it's out of round or has some rough edges as it's not necessary but take some sandpaper to smooth out the gouges in the cup.

grizzly59

I use some ~=220 grit auto body sandpaper to break the sharp edge around the circumference of the head tube before pressing the cups. Then grease and shove.

thundercleese

Wow, I think the ISO / JIS difference might actually be the issue. FSA lists 30.2 for the cups. Can't immediately find detailed specs for the frame (Crust Romanceur) but I did get the calipers out. They're a cheap plastic analog set but the head tube seems pretty spot-on at 30mm. Meanwhile there's a teeny tiny part of one cup's wall that wasn't scraped and it's a hair wider, probably 30.2. Seems like my head tube "machined" the cups down for me, yikes.

Think I should look for a proper JIS set or roll with what I've got? I honestly had no idea these two standards were out there and didn't expect to encounter them on a bike manufactured in 2020 (with disc brakes and thru axles, no less...). Now wondering if I should worry about the crown race spec too!

Looking at other manufacturers' 1" offerings, the cups are listed 30.1 (Cane Creek), 30.15 (Chris King) etc.

HillRider

Just reinstall the cups and forget about it. No harm done. Did the crown race seat normally or was it too easy to seat? If you really have a JIS headset (27.0 mm) the crown race would be oversize if the fork is ISO (26.4mm).

thundercleese

EDIT: misread your reply. Haven't installed the race yet, but will be checking measurements first thanks.

Andrew R Stewart 

I generally deburr/chamfer the HT faces' inner edge so that the cups will both initially fit easier and not do what yours did. A fine tooth rat tail file and/or sand paper. Andy