Threading 1" steerers...

[Cooper Cycles]

So, here is the jam. I've worked at many a shop where we added threads to steel fork steerers so that a replacement fork would fit a frame/headset. I also worked for another builder who would add threads to uncut steerers for new bikes. I've never really given it a second thought. Except when I spend like half an hour and a burrito's worth of energy on threading a steerer tube. But... I recently had a shop mate who thought it might be A Bad Idea because there is enough material lost when cutting threads that it significantly weakens the steerer tube. I still don't think it's A Big Deal. But hey... whats the consensus out there?

Wahoo!
Travis Cooper
Cooper Cycles
cyclescooper.com

PS On another note; does anyone know a source of lightweight 1" threaded (or not) steerer tubes?

[bencooper]

If it's a threaded steerer, then no harm at all in extending the thread. If it's unthreaded, then cutting a thread could be a bad idea as unthreaded steerers can have thinner walls than threaded steerers.

[Curt Goodrich]

If starting out with a threadless steerer and adding threads, done correctly, it's non-issue. Provided the ID is correct for a quill stem, the wall thickness will be the same as a factory made threaded steerer. Given the tools that I have, Campy steerer die, I turn the steerer on the lathe to remove a little bit from the OD. Then the die does an good job of cutting new threads. Otherwise cutting new threads involves pushing a lot of material and the OD increases. Then the die tears off this material and greatly increases the chance of tearing threads out.

[blasdelf]

If it's unthreaded, then cutting a thread could be a bad idea as unthreaded steerers can have thinner walls than threaded steerers.

Unfortunately for all of us, that's rarely true. You have to specifically get a fancy heat-treated steerer tube to get thin threadless-specific walls.

True Temper makes them in 28.6, but the 25.4 ones are long out of production and unlikely to ever come back.