I've tried to search this but all that comes up are the 1" to 1 1/8" quill replacement adapter. Is it possible to switch to 1" threadless by just replacing the adjustable race with a threadless version while keeping the rest of the threaded headset? My bike has a shimano 600 headset that I am happy with and would like to avoid pressing new cups in if possible. Am I missing something or is the only difference between yhreaded and threadless headsets the adjustable race?

You can certainly keep the bottom half of the headset, but it's unlikely you'll find a threadless bearing/top assembly to match your existing Shimano 600 adjustable race.

You realize you're going to need a threadless fork with a significantly longer steerer tube for this, right? Give this a look: Servicing Bicycle Headsets

I don't know the answer, off the top of my head. If you have a local shop that has a lot of spare parts or an older mechanic you might be able to ask. Otherwise you may need to speak with the mfg. it may vary, model to model.

Threadless stem adapters are available from a number of sources. Profile is one of them. They go into your existing fork/headset like a quill one and allow you to use a threadless stem. They are available in both 1" amd 1 1/8" sizes for the threadless stem. I keep a couple around so I can fit stems for people. Roger

The concern here is that the top assemble of a threadless headset isn't meant to be positioned on the threaded section of the steerer. So as Fast Jake said, a replacement fork will be needed.

This makes me ask why does the OP want to change his bike's headset? Is there a problem he's trying to fix? he says he's happy with his 600 headset so, again. what's driving this want of a different one?

I sure hope it's not to then be able to use a threadless stem. because that's where the danger will start. The threaded portion of the steerer is full of stress risers that reduce the strength and increase the probability of the stem breaking off the top of the steerer. With a quill stem the quill extends below this threaded section (of the steerer) and much of the stress is then contained by the unthreaded section. Andy.

A Reynolds ozou comp 1" threadless fork came up on my local Craigslist. The bike it is for is my litespeed ultimate. While the current carbon fork woks fine, it's an ugly green and has always bothered me a little. That's why I'm curious if I could keep my original headset. I looked at ebay and decent 1" threadless headsets are pretty pricy. There are some cheap ones but I didn't want to downgrade the headset just to fit the fork. I thought of I could just replace the adjustable race, I could get a fork upgrade without breaking the bank.

It's possible to machine the threads out of the upper adjustable race of your 600 headset to clear a 1" threadless steerer but it's a tricky job to do properly and the resulting headset lacks a centering cone to maintain alignment. I recommend either paying for a decent 1" threadless headset for the replacement fork or painting your current fork a color you like.

This makes more sense. Short answer: no, I don't think so. To repeat what I said above, it's unlikely you'll find a threadless bearing/top assembly to match your existing Shimano 600 adjustable race. Either way, you'll still need at least a couple bits of a threadless headset to make this work. So you might as well get the whole thing.

The "complete" way to do this is to replace the whole headset. But there is certainly nothing wrong with keeping the bottom half of your current headset and just replacing the top pieces including the pressed in cup.

If you can swallow your pride I have used these Ritchey Logic threadless headsets a number of times and they work just fine. But I admit they are quite ugly. Ritchey Logic Threadless 1" Headset 1 inch Starnut | eBay

One caveat. If the Reynolds fork is all carbon, including the steerer, DO NOT use the starnut that comes with this Ritchey and most other threadless headsets. Along with the headset, buy a suitable compression plug for the steerer and remember they come in sizes to fit either carbon or metal steerers so get the correct one.

Incidentally, FSA still sells a 1" threadless headset, the Orbit X, that has sealed cartridge bearings and is a good quality headset at a moderate price. Here is the link:

https://www.fullspeedahead.com/produc...dless-headset/

I have a 1-1/4" version of this headset on one of my Litespeeds and it has held up beautifully for 32,000 miles so far.

if you are hesitant to replace the headset due to lack od experience, consult a bike shop.

if a threaded replacement fork is so long that you have plenty of length to grip the unthreaded Portion with your new threadless stem

Then you can saw off the threaded portion (a saw guide at the bike shop gets the cut square)..

NB: the NL BBB BHP 20 BHP-20 - Headset parts - BBB is a quill based stem raiser.

It Can reinforce the portion that the threads were cut from and potentially take the new threadless stem.
by gripping the upper 22.2 to 25,4 keyed shims, with the stem itself gripping a shim out to the 1.125".

I have used the BHP-21 version in my 9/8" threadless steerer as a stem raiser .. it works well, has for 6+ years.

Short answer ----- NO.

A threadless system requires a fork steerer roughly 2" longer than the threaded one it replaces. That's because you need the 2" for the threadless stem.

There are some hybrid headset systems that offer some features of threadless in terms of adjustment, but the real issue remains whether you wish a quill or threadless stem.

I decided to stay with the setup I have. The fork was long enough to fit my litespeed frame but short enough to drop my handlebar position below where it is with the quill. I'm surveillance could have fixed it by getting a different stem but I like the position it's set at now and don't want to risk messing with it. Thanks for all the help