Steer Tube to Crown Adapter - Titanium Tube to Ultimate Machine Co

[MuchAlohaNui]

A bit of a conundrum and above my pay grade at the moment. Please see attached this high-res CAD drawing of what I am dealing with.

The steer tube is 28.6 mm (1-1/8") O.D. the entire length, titanium.
The crown press-fit hole is 30.0 mm I.D., anodized aluminum.

In most all cases, the steer tube flares at the bottom to press into the crown, done deal. I am looking for a machined spacer (like picture related and NLA from this specific person online) to mate the steer tube to the crown...all by press fit, non-knurled.

I have spoken with a few people via IM and their advice has given me a general direction. This thread is seeking a bit more spatial resolution to solutions located in the EU or specific items that can be purchased online and mailed. My German sucks, so I don't even know what this is called anyways. Thank you!

 

[rigidftw]

You are looking for an 'Adapterhülse'

 

[benjabbi]

Crown race adaptor, similar thing is used on Pace, Bontrager and Tange Switchblade forks, although they are all flanged not just a ring.

 

[Spankyfart]

I can get you an address that can machine this for you.
He also did machine my steerer for the Switchblade, it's in NL.

 

[benjabbi]

Sorry, just re read this and I got the wrong end of the stick.
The adaptor I mentioned will only allow you to fit the 30mm crown race on the 28.6 tube. A straight tube would go in a 28.6 crown hole then this adaptor goes on top to fit the crown race.
A 30mm crown hole would have a flared tube with the bottom being 30 tapering to 28.6 the flared part extending about 5mm out of the crown to fit the race.

It sounds like what you need is a sleeve, 30mm O.D, 28.6 I.D approximately 5mm taller than the crown. I think you'll struggle without getting something made unfortunately.

 

[MuchAlohaNui]

Sorry, just re read this and I got the wrong end of the stick.
The adaptor I mentioned will only allow you to fit the 30mm crown race on the 28.6 tube. A straight tube would go in a 28.6 crown hole then this adaptor goes on top to fit the crown race.
A 30mm crown hole would have a flared tube with the bottom being 30 tapering to 28.6 the flared part extending about 5mm out of the crown to fit the race.

It sounds like what you need is a sleeve, 30mm O.D, 28.6 I.D approximately 5mm taller than the crown. I think you'll struggle without getting something made unfortunately.

Riddle me this... as you bring up a good point: the installation of the headset lower race...

How rigid does the lower race need to be? If I were to find a solution off the shelf, what is stopping me from using this Adapterhülse to mate the steer tube to the crown, then ANOTHER slid down the steer tube, let this bottom out, then install the 1-1/8" race as usual? I then get a "pressed/static friction" bond of the steer tube through to the race (in theory). Could work?

I am looking for the cheaper, DIY solution. I don't mind paying a machinist to turn this out, however. I understand that having this Adapterhülse extend the entire crown and up high enough to accomodate the race would be the 'safer' approach.

 

[benjabbi]

I can't see why that wouldn't work.
I have a Bontrager fork, you can pull the crown race and adaptor off the steerer tube by hand, hasn't caused any creaks or other problems.

 

[klunkrider]

A purely pressfit seems like a real bad idea in this situation. Like a real, real bad idea!

When you preload the bearings you're going to be pushing the crown off the end of the steerer. Or pulling the steerer out the crown. Either way it's the same outcome, you're about to get pretty familiar with your dentist.

I'm about 99 and a half percent sure that any fork that has a crown without pinchbolts is designed to go with a steerer which is flared or has a machined step on the end. And probably about 95% that even with pinchbolts you still want the flare/step.

 

[benjabbi]

The Pace, Bontrager and Tange straight steerers have a groove machined at the bottom with a spring clip to prevent pull through. They are all bolted though not press fit.
I had assumed the Ti steerer was the same?
Yes, pure press fit with no flange or clip seems like a pretty bad idea.