Bicycle Mechanics - Threded to Threadless conversion on MTB.. possible?

Heya'll...

I have an old GT Outback from about 11 years ago that has a rigid threaded front fork. Today at work a guy gave me a slightly used Judy XL Threadless Suspension fork, since I was complaing about having no suspension, and wanting to do a little offroading.

Is it possible to just replace the headset and install the fork? Are there any sizing issues I should know about?

my guess is that there might be, and I know I'll have to buy a stem and possibly new handlebars.

Lemme know

Jeff

What's the size of the steerer and what's the size of your headtube? That's the biggest issue. If you've got a 1" headtube and the steerer is 1-1/8" or 1-1/4" then you can't make it work. If it's the other way around then you can get reducers. You'll of course need to change your headset and stem to match.

Also the steerer tube must be high enough to clamp the stem for the threadless.

Like if you have a long steer tube and the new steerer was from a bike with a short tube (common later, down and toptube meet @ the steerer, no space between).

Being later and GT, I imagine a 1 1\8 steerer. You may just be good to go!
Ritchey makes some nice stems.

Calipers, or get that stem bolt out and compare the tube diameters.

Remember that the bike very likely was not built to compensate for the added loft of a suspension fork. I ran a shock on a Giant frame that I got in '92 and while the head tube diameter is 1 1/8", running a suspension fork jacked the front end up a bit and made the handling, well, not great. And, even if the bike was suspension corrected in terms of frame geometry, it was probably corrected for a 63mm travel fork. Not a deal breaker, but something to keep in mind.

Tragedy...

Took the old fork apart this morning before work. 1"!! Bastard.... ok...

The guy who gave me the fork yesterday told me that if the headtube was 1", there was a possiblitity that a bike shop could switch out the steering tube on the new fork to a 1". This didn;t sound right to me... but then, on looking at the for this morning, it didn't appear to be welded in.. I'll have to look at it later tonite..

If anything.., maybe it is an excuse to buy a new frame :-)

Jeff

If it's 1" then it's most likely not suspension corrected. Granted there were some suspension forks with 1" steer tubes on them, but they were very low travel compared to today's forks.

If I were you, I'd probably stick a decent rigid fork on the bike and call it a day. You can definately ride rigid off road. There was a time when that was all you could do. You know what I'd really do? Convert it to a singlespeed, rigid, and ride it like I stole it.

Edit: You can probably find a 1" threadless headset to put on it as well. It will probably take a bit of looking, but they're still around. If you find one there might be a decent shot that it'll be cheap, too. I put a cro-mo rigid fork back on the aforementioned Giant recently. The fork was threaded, but the steer tube was long enough to cut it down and set a star nut in the steer tube just fine. This is where a LBS with a good spare parts bin can be a lot of help!

Howdy, I don't want to start a new thread, came accross this one in a search, so I'll see if someone can help me out.

How are headsets measured? It's never come up before in my various fixin' and tinkering. Do 1' and 1 1/8' refer to the inner diameter of the headset tube? Something else?

Thanks,
Adam

[edit]
never mind, I found the answer at http://sheldonbrown.com/gloss_ha-i.html#headset
Thanks again, Sheldon
Adam

The outer diameter of the steerer tube of the fork. 1" headtube means "headtube designed to a take a 1" steerer.

The headset is the bearing the fork rotates on, BTW. Its size is also given referring to the steerer size.