I bought a Periscopa stem and 44cm Nitto Grand Randonneur bars for my Bridgestone RB-T, thinking this would give me some room to adjust the bar height some somewhat more upright posture, with plenty of room to fine tune.
However I'm running into a problem: the stem won't descend far enough into the steerer tube, it runs into a kind of ridge. Photo shows it as far in as it'll go; it's below the minimum line but obviously not as far as it's been used in the past.
I guess the problem is that frame is 53, so head tube and fork steerer within it are correspondingly short. But I'd like to get the stem about an inch lower, at which point the wedge bolt would still be within the head tube.
I know stems can be 'chopped' to be shorter, but is reaming out the steerer tube for the quill a (reasonable) option?





If this doesn't work there are alternatives, of course; I have a Sunlite 2-bolt stem that's similar but the reach is shorter, and it's 25.4. The Periscopa only comes in 26.0 clamp size, so that's the bars I bought.

This is common on smaller frames like yours. Steerers are butted - same outer diameter, but down near the fork crown the wall thickness is thicker for strength. DO NOT ream this.

FIFY

That settles it then. Thanks!

Technomic or Soma Sutro will get you in the range you want at 26.0.

I've done this a couple of times using my mitre saw and being careful to maintain the minimum insertion depth. It is a quick and easy solution.

Might have to cut the bolt as well. Cut or no, make sure you have threads that go up high enough for a shorter quill length, and thread the wedge or a nut above the cut so the cut threads get cleaned up when you take the wedge off.

Agreed. Get a shorter stem instead.

There's only so much you can shorten it before you run out of threads on the bolt, so plan your cut with that in mind. Shorter bolts can be found if you need more shortening, but you can't add threads with a cutting die because the existing threads are rolled not cut. So the shaft diameter is too small to have threads cut into it.

Another issue that could bite you in the future is that the stem will still have a minimum insertion line, but it won't be correct anymore. Someone in the future, you or the next owner, may mistakenly raise the stem to an unsafe height , believing the line and words stamped in the quill.

I have shortened a few stems but never came up with an easy solution for that. Maybe stamp a new mini-insert line, and hope the future person sees it and stops there.

These are valid concerns that absolutely need to be considered.

That's exactly what I did.
Number & letter stamps are cheap.

The problem that can arise is that the bolt threading may come up short if more than a certain amount is cut off.

And the diameter of the non-threaded part of the bolt will usually be slightly too small to extend the threading upward using a die.

So finding a different bolt might solve the problem if you can find on that's the correct length.

I once "flipped" a very small Schwinn Circuit where the original Cinelli 1A stem quill could not be lowered enough to get the limit line close to even with the top nut, just because the steerer had the butting step in the way. A previous owner had attempted to taper the end of the quill (using a grinder) in order to get the stem lower, and it pulled out of the steerer when I test-rode it, nearly getting me flung off the bike in the process.
So the moral here is to not mess with the fit of a stem in a steerer unless you're technically qualified. I was really lucky that I was able to stop the bike without getting hurt, as I had just started sprinting from a stop across an intersection (so was able to get my foot/leg out for a motocross-style "save").

Also, you may have a problem with the bolt not having enough thread.

That's two of us now who seem to have missed bulgie's thread, above!

I skim through a thread and miss a few things here and there.

I have a friend who is a savant wrench with seemingly every tool and part in the world, and the idea of 'chopping' the stem came from seeing a few in one of his bins. It goes against my nature to make such a drastic modification to, well, anything. To a fault, really. But I figured if I did that with the Periscopa, I'd want to make sure the bolt still worked, or find a shorter one, first, and figure out how to clearly mark a new minimum insertion point relative to however much material I removed. If I go this route though, and assuming it works, it'll likely stay on the bike and in my possession a long time, as my 'collection' doesn't move much. And it'll never be a problem for me because I am trying to get it lower, not higher.

A knurling tool and a number and letter stamp to mark new minimum insertion.

Geez. A lot of concern about minimum insertion. Isn't that a CPSC thing? Didn't we survive without it, for 100 years? Don't we still make lawyer lips jokes?

Cut it. I have bought many cut stems. Usually Ambrosio because they didn't drill a stress reliever at the ends of their slots. They crack, previous owners extend the slots, trim the excess. It just is, get over it.

No, You and Bulgie didn't read post #7.

Maybe.

But I happen to know that you had a catastrophic crash while riding a bike that had a cut-down stem. It also had filed-off lawyer lips, removed turkey levers, and a tiny spot of rust on the downtube that had eaten away the steel to a thin bit of foil.

And all failed at the exact same time, while you were on a steep Alpine descent.

You skidded across the road in a cloud of dust, launched over the guardrail and into the sky, only barely coming to rest in the top of a spindly pine tree, which you held onto for dear life.

Then the top of the tree began to bend, coming to a 90 degree angle, and dangling you over a yawning abyss, at which point you held out a little sign reading 'HELP.'

Then the tree snapped, and you plummeted downward, hundreds of feet.

You landed in a heap and were just picking your bruised self up when an ominous sound caused you to look up.

Your eyes diminished to pinpricks.

It was an anvil.

So, you know, maybe you're not the best person to talk about safety.

Nice!

But remember that one time. They were riding with all the safety features and gear. Including knee pads too. Then the asteroid hit, destroyed the Yucatan, and killed them all.

I'm curious about the cut Ambrosio stems, having slots and of course a round, tapered wedge.

If one cuts one of these stems down, isn't there a taper on the inside diameter of the cut end that needs to be restored?

And does the quill's wall thickness not increase above the slots, where the expansion strain/flex would tend to incur much higher bending stress, possibly leading to cracking?

I know it's a lot of assumptions on my part with regards to the variety of such stems out there, but shortening a stem other than the slanted-wedge type seems to be fraught with complications.

I only mention this because I tried it once and was left with some doubts about the quality of my un-tested modification.

Yeah, but at least no one got a concussion.

Great questions. I have no answers. Just went for it. Didn't have a problem.