Cycling UK Forum

3'40" into this video the guy has fitted an A-head stem to a threaded steerer.
To me the way he has done it is not good.

https://www.youtube.com/watch?v=z7HKCGBr5Ks&t=265s

Very likely to slip or even shear the stem ??

There's a possible risk of the fork column breaking as he's clamping on the threaded section which will be thinner from cutting the threads but if the star nut is set below the threaded area it offers a backup if the fork column breaks. It means if this happens he should have some control to come to a safer stop than if it became detached completely as happened to big George Hincapie in Paris Roubaix.
https://images.app.goo.gl/xHnckEHHou6A3fKr6

Don't take advice from You tube!

He tells us its a one inch steerer, which is right. It is as you say a threaded steerer; this means that the original one sixteenth of an inch thick steel has been cut into to make the thread, weakening the steerer and making a pretty good series of stress raisers.

He then has a shim to make up the inch steerer to inch and eighth to "fit" an inch and eighth stem.

I wouldn't ride that bike like that. Much easier to fit the intended inch threaded headset and a quill stem, or a quill to ahead adapter. Inch threadless headsets are getting a bit scarce.

When I saw this I thought definitely a no-no.
With the threaded section there will be very little surface area for the spacer to grip. So a good chance of the A-head stem slipping round.
Also, as said, the threaded section is a weak point due to the reduction in wall thickness of the metal.

As an aside he has lost height adjustment, which may suit him, but not for my aged torso.

Coincidently I have the same frame but with an A-head adapter.

To me, any adaption of 1" threaded to 1 1/8" always looks a bodge and quite ugly.

There are still better ways to raise the handlebars, which is usually the reason for the conversion to 1 1/8"

There are other threads on here about raising handlebars.

If you just want to use oversize bars or have a removable faceplate, quill stems exist to do that. They are not cheap but they are the best solution.

have seen this done to a bike

the fork steerer broke clean off whilst climbing out of the saddle.

That doesn't in any way appear to be good engineering, and certainly is dangerous.

mig wrote: ↑11 Sep 2024, 3:50pm have seen this done to a bike

the fork steerer broke clean off whilst climbing out of the saddle.

Ouch!

if you have a set of forks like that, you probably need an old set of steel mtb handlebars. The centre section of such 'bars usually has a 7/8" to 1" flare, which means you can use it as an extender eg. if you bond it in place using epoxy resin.
A SFN can be set below this, and the top cap can be secured using a length of M6 studding and a modified v-brake block nut. Obviously you need a 1/16" wall thickness spacer (which can also be secured using epoxy resin), if you want to use a 1-1/8" stem. There is no weakness arising from the cut threads, provided the bonded-in length is long enough. The headset cannot be replaced unless the extension is removed (for which heating to about 150C is normally required) but it can be adjusted and serviced, provided the extension is not set too low.

531colin wrote: ↑11 Sep 2024, 5:08pm

mig wrote: ↑11 Sep 2024, 3:50pm have seen this done to a bike

the fork steerer broke clean off whilst climbing out of the saddle.

Ouch!

it wasn't great. a teeny crack in a winter bike's carbon fork had been spotted and an LBS had replaced the fork with a steel one using - they said - an adapter. that wasn't the case! the stem eeked away at the thread on the thin steerer then......all of a sudden.....

I did the threaded to threadless conversion using one of my 1" forks in one of my wife's frames. As she rides 49cm frames and I ride 61cm frames, when I cut the steerer to length for her frame, the cut was below threaded section of the steerer, and the threadless stem bolted to the unthreaded section of the steerer.

An alternative that works well is to use a threadless stem adapter. That's perfectly mechanically sound. e.g. https://velo-orange.com/collections/st ... em-adaptor