I have an old 10-speed bike (likely 80's vintage) with a threaded fork. Can I replace it with a modern threadless fork with the style of stem that slides over the top of the fork and clamps on? I know I'd need to replace the stem and handlebars too and am happy to do that.
What do I need to look for? Is the diameter of the head tube different with newer bikes?
The technical term is "threaded fork". That is, the steering tube has threads on top for the headset to screw onto. The newer design is called "threadless" - that's the one where the stem clamps onto the steering tube with pinch bolts.
You can switch from one to the other as long as the diameter of the steering tube is the same. (You'll obviously have to use a headset and stem designed for the type of fork you have.) The problem is, the diameter is often not the same. Around the same time as the threadless forks were introduced, they started making the steering tubes and head tubes thicker. The old ones were typically 1 inch (that's the steering tube outer diameter). The new ones are 1.125", sometimes 1.5".
You should measure just to be sure, but I bet you have a 1". It's possible to get a 1" threadless fork, stem and headset, but the choices will be pretty limited.
Not sure the reason for your need to change but,at Nashbar.com they have an adaptor that allows you to use modern threadless headsets with the threaded quill design the cost is under $15 part #NS-TSA.Measure you current quill to order the correct size,note that the one inch quill is actually closer to 7/8".If your quill measures one inch order the 1 1/8" size.This adapter allows you to use the larger variety of stems and bars that clamp on to the steerer tube while reusing your old fork.
possible if you will change the steerer (1 1/4")of the new fork into 1" and you will just use spacers for it to get fit..
