Krov9

So I got this old bike, and found out the steerer I.D. is out of round!

Fearing that you're gonna tell me to scrap the fork or get a new steerer brazed in, I'm asking how likely this is to cause issues?

The wall thickness seems to even out deeper down the tube, so it might just be from removing a stuck quill stem perhaps?

There are no signs of collision, bending, fracture etc. The headset threads in just fine. The flatyou can notice in the outside diameter is filed purposefully for the French kind of lockring washer.

Unfortunately the steerer isn't long enough to just saw off the damaged portion. It's a small frame, so the quill will be inserted pretty deep, propably not wedging on the damaged portion(?)


The difference is about 0,5 mm at the brim

Chuck M 

Is there any visible distortion on the outside indicating damage from over-tightening?

smd4

And the problem is…?

Andrew R Stewart 

I might speculate that this fork has been service tested and has passed.

At first I thought the steerer had been squeezed (like in a vise) to ovalize the top/open end. But reading that the wall thickness is what is inconsistent makes me think a production issue when the steerer was made.

Next thought is whether the walls have been actually measured (w/ a caliper) to confirm there's a variation in wall thickness and not you're not just seeing the decreasing thread crest at the very top.

As to this fork's continuing use- if this new knowledge will bother you, you won't be able to get past the possibility of something bad happening, then you need to do something about it. Like a new fork or do find a builder who will replace the steerer. Otherwise I stand by my first comment. Andy

Iride01 

Threaded steerer tube. You are seeing the change in the cross-section thickness of the tube as the helical thread's min and max diameter pass through it.

You are talking about just the thickness seen on the end cut aren't you?

grumpus

That would be about the same as the depth of the thread, no?

FBinNY 

Usually this is only an optical illusion because of the helix of the first thread.

In one place the fork ends at the crest of the thread, and exactly opposite it ends at the root, appearing thinner there.

Unless there's an actual, functional problem, accept that it's OK and move on.

Dan Burkhart 

Is the washer also out of round? Most threaded steerers have a key slot for a tabbed washer, but some older ones had a flat milled on one side for a matching washer to prevent rotation. I don't see a key slot here, and from the photo it looks more like it is the OD that is out of round.

Krov9

Yes there is a flat for the washer. I took a caliper to the steerer to confirm it isn't just that, neither only the thread starting nor an optical illusion.

Measured outside the filed flat, the wall thickness varies <0,5 mm. That difference should be negligible, right?

Guess I just eventually freaked out that my steerer could split in half at any moment

Iride01 

Find some other threaded somewhat thin wall tubing and cut it through the threads. I think you'll see the same thing. I say to cut it, because if the cut end was previously well dressed, then the illusion might go away. Most threaded steerer tubes I've seen never have the cut end dressed up well if any was even attempted.

FBinNY 

Accepting the worst case, that it really Is off that much, think.....

Steerer tubes are produced to tight tolerances of ID, OD, and concentricity. However, it's possible that the threading tool started off a bit. Cutting forces would steer it back to center, so any error would be limited to the end. Plus, we know there's plenty of strength since steerers are routinely keyed to below the root of the threads.

Moreover, the stress imposed by the stem is that caused by the wedge, which is well below the last thread. Lastly the top is buttressed by the headset's cone and locknut.

All in all, this is another example of how knowing what's in the stew can spoil enjoyment of a good meal.