Originally Posted by
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.
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").