saturnhr

Question as above, in paticular 1 inch threaded track fork which is long enough for steel track frame . Upper threaded fork part would sit in stem. Are there safety concerns? (the question is not about what looks better!)
Thanks

AEO

snap and fail.

there is a $10 threaded to threadless adaptor for this.

LarDasse74

Barracuda bikes had a whole whack made like this in the mid nineties... I always thought it was a disaster waiting to happen, but I did not see a single one break. That being said, I still think it is a disaster waiting to happen.

saturnhr

My question was not about the adapter. The threaded fork is long enough sticking out of the frame so that the threadless stem can go directly on it. Isn't a steel fork tube (even if threaded outside) much stronger than any non-threaded aluminum tube in a similar setup?

Thanks for reconsidering

AEO

well, I won't say I'm an expert on this.

the threaded portion is weaker.
the outer spacers are there to increase the outer diameter for increased stiffness.
quill stems are supposed to go below the threaded portion of a steerer tube.
you have uneven spread of force from the threadless stem due to the threads.
threadless steerers, even 1" steel, have thicker walls compared to the threaded steerers, which are 22.2mm ID.

LarDasse74

No. Aluminum has more strength per unit weight than steel, and cutting threads into something greatly decreases its strength - especially if the part is subjected to a load for which it was not designed.

Coomer

I wanted to do the same thing at one point but did some research and found that it was a bad idea. The threaded area would be the weakest link in the system, and if that broke at speed you'd almost-surely crash.

HillRider

I assume you aren't conversant with the term "stress raiser". The threads are just that. The threads are intended to take a stress in the direction along the length of the steerer, not at right angles to it the way a threadless stem would apply it. Bad idea.

Cannondaler

The threads are CUT into the steer tube, so the tube is about 1/2 as thick in the threaded area. Massively bad idea.

LesterOfPuppets

How many dozen to the whack?

operator

No.

DaveSSS 

The critical question to answer is where do the threads end? If they end well above the top of the headset, then there is probably no issue, but if they extend below the headset, then you will have a weaker area potentially seeing a large force. The OD in the threaded area will also be a little less than 1" in diameter, since threads don't extend to a totally sharp crest.

JohnDThompson 

The fork is threaded -- why not just use a threaded headset?

DannoXYZ 

I tried this about 15-years ago and there are some problems. Aside from the safety issue raised earlier (although i've snapped a couple Modolo stems and SR bars without serious repercussions), the functionality simply isn't there.

What happens is the stem will clamp onto the threads and the harder steel threads on the steerer will cut matching threads into the stem. Over time with bearing-wear, parts wearing, cups bending, etc., the headset will need to be adjusted. Due to the threads inside the stem-clamp, you can no longer slide the stem up & down to adjust the bearing-preload on the headset. The threads on the stem will "index" into fixed positions on the steerer and you end up with too tight or too loose of a headset adjustment; nothing in between.

So in short, no, there aren't any safety concerns, but yes, there are problems that's darn annoying and impossible to overcome without wasting a tonne of time. Like brazing a layer of brass over the threads and spinning the fork on a lathe to get a smooth unthreaded steerer.