Using 1" Threaded as a 1" 'A' head pair of forks + a shim to 31.8mm

[TheCyclingRooster]

Hi to you all out there. Is there any reason why I cannot cut down the steerer and use a perfectly good pair of 1" threaded forks as 1" 'A' head and then add a shim to achieve upgrade to an inch & an eighth stem with the advantages of the open front access ?

I have been looking for a pair of 1" 'A' head chrome forks with a sloping shoulder (Coat-hanger style) but cannot find any BUT I do have a pair of 1" threaded available that I would use if my above intentions are feasible.

 

[boydj]

It's unlikely you would need to cut down threaded forks, since they are usually cut to the top of the head tube. The fork steerer may well be too short for your needs, but there are adaptors available (see below) which convert from quill to a-head if you have to use a threaded headset. If it is long enough then you can get 1" stem or a shim which will allow you to use a 1 1/8 stem.
e.g.
http://www.wiggle.co.uk/deda-quill-stem-adapter/

 

[fossyant]

You really need a standard 1" headset, then use an adapter as an aheadset needs the correct sized stem to load the bearings correctly. If you fit a standard 1" headset, then pop in a quill adapter, you can use a 1 1/8th stem.

 

[TheCyclingRooster]

Hi to both boydj & fossyant. The fork and fork steerer are steel,the steerer is 250mm including the depth of the crown seat. I only need 165mm. It needs reducing regardless.
The internal bore diameter is the same as an existing pair of Non-Threaded 'A' head forks that are currently on the frame.

In principle and to all intent and purposes the only real difference is that one has a threaded steerer and the other is plain and was originally for a 1" 'A' head set-up.

 

[fossyant]

It will need cutting down, but the only secure way to use a 1 1/8 stem is to get a traditional headset, then fit an adapter. It works well. Unless you can find a 1" ahead stem ? Most are 1 1/8th so need the adapter.

 

[TheCyclingRooster]

It will need cutting down, but the only secure way to use a 1 1/8 stem is to get a traditional headset, then fit an adapter. It works well. Unless you can find a 1" ahead stem ? Most are 1 1/8th so need the adapter.

Hi again fossyant. Why would the fork fitments be insecure? The security surely relies upon the single or double 'Star' washer being inserted into the internal bore and then the bolt and cap being used as it would with any regular 'A' head. The use of a shim/converter sleeve to bring it to 1&1/8th would then permit the modern front loading stem to be used.

 

[TheDoctor]

I think it's tightening the stem onto a threaded section that might be insecure, especially if there's a shim involved. Might be perfectly OK, but it it's not then it could get very messy...

 

[TheCyclingRooster]

I think it's tightening the stem onto a threaded section that might be insecure, especially if there's a shim involved. Might be perfectly OK, but it it's not then it could get very messy...

Hi TheDoctor. I am truly sorry to be a little slow here (onset of dementia fever) but the external diameter is all but a whisker the same diameter all of the way down to the Crown Race position.
I currently have a pair of 1" 'A' head thread-less forks with a Campagnolo Chorus headset secured with the standard star washer,cap and bolt along with a shim fitted for a stem.
I cannot see what difference a portion of thread would make because the whole assembly relies upon the downward force of the bolt and washer biting into the internal bore. The shim would cover the threaded portion ready to accept the 1&1/18th 'A' head stem.

 

[fossyant]

I wouldn't be using a shim on a steering component. Potential for loss of control.

 

[RecordAceFromNew]

Hi TheDoctor. I am truly sorry to be a little slow here (onset of dementia fever) but the external diameter is all but a whisker the same diameter all of the way down to the Crown Race position.
I currently have a pair of 1" 'A' head thread-less forks with a Campagnolo Chorus headset secured with the standard star washer,cap and bolt along with a shim fitted for a stem.
I cannot see what difference a portion of thread would make because the whole assembly relies upon the downward force of the bolt and washer biting into the internal bore. The shim would cover the threaded portion ready to accept the 1&1/18th 'A' head stem.

I think you are mistaken in that you think the star fangled nut / top stem bolt assembly does anything other than taking play out of the fork/headset/stem assembly and correctly preloading the headset bearings. What actually keep the bars/stem securely attached to the steerer are the two horizontal stem bolts clamping the stem on to the steerer.

And therein lies your potential problem. If the steerer is threaded anywhere above the headtube, your plan has a weakness never designed for because the thread was designed for nothing but to let the top traditional headset nut taking play out (just like the star-fangled nut/top bolt for aheadset). The threading would have significantly weakened the steerer for taking any lateral or clamp load, which would be exerted by everything including the headset, stem and of course handlebars above the headtube. I would certainly not recommend it.

A threaded steerer, as you know, is bound to the stem via the stem bolt and "expanding" wedge assembly inside the steerer tube.

 

[Profpointy]

I wouldn't be using a shim on a steering component. Potential for loss of control.

I think that's plain wrong in engineering terms. If you have the right sized shim then it'll fit. For comparison, a lot of parts, safety critical or not, will have some kind of spacer as part of the design - nothing wrong with that at all.

Though I agree that shiming 1" out to 1-1/8" is a lot of guiness cans to be emptied.

 

[hoski]

... lot of guiness cans to be emptied.

Hence 'loss of control', I guess?

I would be reluctant to shim a steering component, it adds an additional interface (i.e., stem to shim, shim to steerer) rather than just having contact between the stem and steerer..

The best bet for the OP, as @fossyant says, would surely be to use a traditional headset, and then use a 1" threaded to 1-1/8" threadless quill converter... like this: http://www.evanscycles.com/products...-inch-quill-to-1-1-8-inch-threadless-ec038805

 

[TheCyclingRooster]

Hi to all that have contributed to my query. To take the replies in order of posting.

RecordAceFromNE :- I full well know the function of The Star Fangled Nut and Star Washer/Washers with a double and how they are assemble and which order of tightening they are individually done.
I would not have thought that the depth of cut on the tread would cause any significant weakening of the steerer tube - at all. Indeed the depth and length of the groove that goes the full length of the threaded portion take a great deal more material away from the steerer than the relatively shallow depth of the cut of the thread.

Profpointy :- I am inclined to agree with your line of thought and being that the shim is a one piece item that takes the 1" steerer immediately to a 1&1/8th dimension I fail to see where there is any real detriment - other than the fact the the interface is not continual and totally face to face but is effectively on the peak of the cut of the thread.
The shimming with individual and layered up shims (Guinness Cans) is a non starter as I have pointed out - it is a regularly available item on 'Good Old' E'bay.

Hoski :- I understand your comment about the additional interface but as the thread is a very fine spiral and the shim is trapped between the cap and the top race and or spacer and then the whole assembly is clamped with the steerer-stem clamp - I cannot see anything moving or be compromised.

The whole idea of posting my query/question into the forum was in the hope that someone had already carried out the conversion/modification and could give me a resounding YES it works and will be OK - because I have done the same,

OR - No it will fail because I have tried the very same thing.

 

[andrew_s]

You should only cut own a threaded steerer into an unthreaded steerer if you can cut off the whole of the threaded section. If you clamp onto the threads, either with or without a shim, you risk the top of the steerer breaking off in due course, and causing a crash. It's not so much that the steerer is weakened, as that the thread grooves promote fatigue. Having your handlebars come off when you are riding isn't a good thing to happen. When I saw it happen, the chap concerned got a broken cheekbone and a broken kneecap, despite (or because of?) being only going at walking pace at the time (expander cone bearing against the inside of the threaded section, rather than a clamp-on stem)..

[edit]
example failure here
Chris Juden's opinion

 

[fossyant]

I've already given you the safest and best option - traditional headset and an adapter - they work well.

Don't forget, if the shim is a tube and without a cut down it, it may not compress sufficiently to grab the steerer. At best your headset will rattle loose with the road vibration (very likely) at worse you may have a nasty crash.

Do not 'fettle' safety critical parts. I am the only person that works on my bikes. My Fettling only goes so far as fitting lights and stuff.