RoyIII

I have a GIOS Compact Pro with a threadless fork that I would like to replace with a threaded/quill stem set up


I read that converting the thread less is not a good idea because of thin walls of the steering tube. Is that correct? If I have to buy a new threadless fork, what dimensions are important to duplicate the height of the bar, length of the stem, and the headset. Thanks in advance.

fietsbob

Yes it cuts the fork tube thinner in half. the thickness.. but I have seen Some bikes
that mixed a threadless 9/8 fork and a 7/8" quill stem with specially made parts.
these were Koga Miyata touring trekking bikes not a Italian Race bike..

threadless forks come in 1" and 1_1/8", threadless stems are all 1_1/8 with a shim back to 1".

what is the OD of the fork you have?
it looks like a threaded one with a conversion and a threadless stem.

benefit of thereadless setups is the spacers can go above and below the stem.
so you can ride the bike for a long time , before making the final decision
as to where to saw the fork steerer tube off.

I thought Excel in Colorado had Gios stuff, maybe they will sell you a threaded fork.

demoncyclist

If you are not trying to change any of the dimensions of your position, why would you go through this costly exercise? You will have to change the fork- the steerer tube of a threadless fork cannot be properly threaded for a traditional headset. All of the dimensions of the existing fork will have to be maintained for handling purposes, and then you will have to figure out the stack height of your new headset to make sure you get the proper length steerer on the new fork. The new stem will have to be the same extension as your existing threadless one, and then you need to make sure it is the proper diameter to match your existing handlebar, unless you plan to replace that too.

IthaDan 

Just swapping on a new stem with out a faceplate and all the necessary unwrapping/rewrapping would be enough to dissuade me on this one. Let alone sourcing a new fork, stem and headset. Why are you thinking about doing this? Just for looks?

Got some better pictures? Are you sure this isn't threaded already with one of those quill adapters for a threadless stem?

CACycling

+1 A quick search shows that your bike has a threaded fork so it would just be a matter of removing the existing adapter and stem then replacing with quill stem.

RoyIII

Actually it is a thread less - I built up the bike myself. On reflection, I'd do this for appearance, and it's a lot of trouble and expense. Y'all talked me out of it. I will do better riding it!

IthaDan 

Ha, waxahachie. I lived in a tent at the Renn faire a long time ago. Cool town as I remember. I worked for the copper sculptor guy with all the dragons and butterflies and Rennaissance faire stuff. You ever make it across 35E and up the hill?

FBinNY 

It's a fairly straightforward job for a skilled mechanic, and poses no safety issues of any type if you have a 1" steel steerer with a 7/8" ID. The ID is critical for two reasons. First it confirms that the steerer is of the same type as used on threaded forks and has enough wall thickness. Second you'll need the 7/8" ID to fit the stem.

First remove the top cap and confirm the ID. Then check around for a shop that has a good reputation for skilled mechanics and get a quote for the job. As I said it's straightforward for someone who knows how, but it's also a job which is very easy to botch, and thereby destroy the fork.

One other consideration, based on a 2nd look at the photo. Steel fork columns typically have a 2" high swage (butt) reducing the ID at the base. You have a very short frame and there may not be enough height above the swage for a stem to fit into. This was a common issue on small road frames when quill stems were the norm, and on many the stem could barely be inserted to the min. insertion line. Whatever tou do, do not cut this fork until you've confirmed that there's enough full diameter depth for the stem. This isn't something you ant to discover after the fact.

40 years ago, when I spec'd bikes from Italy, we had some "zero headtube" 48cm bikes built. Not only did they have to modify the lugs to make clearance, we also had to have them trim 1" from the bottom of the steerers (usually a strict no-no) to have enough depth of of 7/8" ID to accept a stem, and have any adjustability (almost 3/4").

HillRider

Interesting thought. I was under the impression that threadlsss steel steerers had thinner walls then threaded ones since they didn't have to allow for thread depth. However, I just measured a steel steerer cut-off from a Kestrel EMS Pro threadless fork and the ID is indeed 0.875" (22.2 mm) so the wall thickness is the same as a threaded one. I wonder if this is typical.

I agree that it is a job for a skilled mechanic using good sharp threading dies. Extending existing threads on a threaded sterer is relatively straightforward but starting from scratch is a lot more difficult to do right.

FBinNY 

Yes it's fairly typical, especially for brazed forks, which simply used standard steerers. However many non brazed forks designed from the ground up for threadless used a bulge formed steerer, and these did indeed have thinner walls, and cannot be threaded, or in any case won't fit a quill stem.

As I said in my first post, I suspect the OP's biggest barrier to threading his fork is the remaining depth of the 7/8" ID zone after cutting.

fietsbob

If the Black stem is part of your aesthetics discomfort,
Velo Orange is into selling polished stuff.