Steerer tube extension

[Sir Neil d'Menture]

I have a c1990 Reynolds 531 frame and forks.
Steerer tube has been previously cut but is too short for the headset I wish to use.
I'm reluctant to go down the welding route in case of damage to the paint which cannot be replicated.
I wondered if I could fit a length of steerer tube that has been threaded on the inside and outside.
This will thread onto the existing tube and headset can then be fitted in normal way.
Fixing will have to be thought about but there is little likeliehood of extension piece unscrewing so maybe some epoxy would provide enough grip.
Is this a sensible idea, or are there insuperable problems?

 

[Ralph_the_Rohan]

Wouldn’t the new piece of tube need to be a larger diameter than the original steerer tube?

In which case a headset will not fit it. Or am I missing something?

 

[Sir Neil d'Menture]

Dunno.
In my ignorance I thought that the internal threading would increase the internal diameter by the same amount that the external threading has reduced the existing one.
Not being an engineer I am not clear on threading tubes.

 

[pigman]

Threading doesn't reduce the diameter, the raised bits on the thread are still the diameter of the original tube, if that makes sense. By threading, all that's happening is a groove is cut into the tube.
To reduce the diameter, youd have to step the diameter down with a lathe first, and there just isnt enough meat on a steerer to do that.

Also cutting an internal thread into a steerer sounds like a specialist (expensive) job

 

[Midlife]

Lots of nice short stack head sets, about

 

[fguki]

Just weld an extension on! its a common fix. I have done that to about 10 bikes now. Superb problem solving.
Make sure you put a piece of extension where you will not collide with the stem going into the tube! Rather to the bottom side where the crown race sits. After welding and grinding, the diameter will be the exact same as the tube so you can still put your crown races on!

You can also put extra bolts ("bolts" is not the correct word) through both parts of the old steerer. Hard to explain in English for me.

I will look for pictures of my fixes for you

 

[fguki]

Here is an alloy example I found. The extension had been welded on.

Make sure you place it low enough! You dont want your stem inserting into the steerer tube to collide with it!

 

[Sir Neil d'Menture]

Here is an alloy example I found. The extension had been welded on.

Make sure you place it low enough! You dont want your stem inserting into the steerer tube to collide with it!

View attachment 695767

@fguki Now that looks interesting. Have you got a link?
I'm coming to the conclusion that my original idea was a bit (make that a lot) daft.

 

[Sir Neil d'Menture]

Threading doesn't reduce the diameter, the raised bits on the thread are still the diameter of the original tube, if that makes sense. By threading, all that's happening is a groove is cut into the tube.
To reduce the diameter, youd have to step the diameter down with a lathe first, and there just isnt enough meat on a steerer to do that.

Also cutting an internal thread into a steerer sounds like a specialist (expensive) job

Thank you. I've had one of my saner moments and realised that. Daft idea!!!

 

[fguki]

Which link? I machined the extension and had it welded on. And grinded everything back to flush with a tube grinder attachement. Done!