mraeryceos

Is there a conversion headset that will fit the old frames (normally with a 25.4 inch steerer tube), that will accommodate a 28.6 inch steerer tube (threadless).
So, the point being that the headset seats into the old frame, but provides clearance for a 28.6 inch new steerer tube.

I can't measure the inside of the head tube, because I don't have something with which to remove the headset cup. I guess I could try a screwdriver and hammer. Nope, won't budge, but I think the inside diameter of the head tube may be right around 28.6, and if a little more, there is theoretical space for a 28.6 steerer tube. The head tube flanges out a little bit where the headset seats.

mraeryceos

Here it is being done with a BMX:
How To Convert 1inch Threaded To 1 1/8 Threadless - BMXmuseum.com Forums

dsaul

There is just not enough room inside the head tube for a 28.6 steerer and the bearing cups. The pressed in portion of the bearing cup would have to be about .6mm to allow clearance for the steerer. People have made cups that are pressed onto the outside of the head tube, but I don't know of any commercially available headsets like that.

That BMX bike already had an 1 1/8" head tube and the user simply changed the headsets from a 1" to an 1 1/8".

JohnDThompson 

If your goal is to able to use modern stems designed for 1-1/8" steer tubes, there are adapters for this, e.g.:



https://www.amazon.com/Profile-Desig.../dp/B0028N14GQ

fietsbob

If you were starting from scratch .. the headtube could include the bearing races, if it were machined in one piece.*

but a pressed in insert redices the ID Available.

Agree with JDT, leave the headset/fork just get the stem converter.


*Frame builder and headset manufacturer Chris King has done this. for the cosmetics of a thinner headtube on a custom steel frame..

mraeryceos

I wrote: "The head tube flanges out a little bit where the headset seats." The current headset is pretty thick, so it reduces the opening to less than 28.6. Because it the head tube flanges out, I don't think what dsaul wrote: "The pressed in portion of the bearing cup would have to be about .6mm" is applicable. But I can't verify anything, unless I am able to get the pressed-in-portion-of-the-bearing-cup out of the head tube.

exmechanic89

Take it to a shop and they'll remove the cup/s. They'll probably charge you a few bux but you'll have them out.