TallRider

These days it's difficult to find long, up-angled quill stems for road bars. I'm mostly limited to single-bolt clamps with wide clamping area, designed for flat bars. There's no faceplate to remove, and the clamp area is too wide to slide a curved road bar through.
But I wondered about taking a dremel to the clamp area of such a stem, to get a narrower area so I can slide curved bars through. Traditional forged single-bolt road stems typically have a 27mm narrowed area to accomodate sliding the curved bar through.

Attached are two pictures showing a welded-aluminum stem with clamp designed for 25.4 mm flat bar, and traditional forged-aluminum road stem with narrower clamp designed for 25.4mm curved drop bar. The former, of course, is what I'd use the dremel on.
Does anyone have experience with this sort of task? It seems safe enough to me, although maybe welded aluminum isn't a good material to get narrow enough for road bars installation on single-bolt clamp.

Le Mechanic

I'd suggest getting a quill stem adapter. If you get one that fits the ID of your fork steerer and a 1 1/8" top section, you can use any current 1 1/8" threadless stem and 31.8mm diameter handlebar. Much more options than older quill stems/26mm bars.

TallRider

I've considered that option, and as you say, it may be the best solution.
I'm still interested in the viability of adapting a wider-clamp (flat-bar) quill stem, though.

3alarmer 

...it's probably not the best idea. I wouldn't encourage it, exactly for safety reasons. There are shims for this purpose made and sold, or you can make your own.
I think the suggestion to go to a threadless stem is a good one, and there's less chance of maxillofacial surgery involved.

Troul 

Wouldn't be hard to take both of those to make one final piece. Sleeving the mating butt joints & welding them would rely on the type of material it is & skillset of the welder.

70sSanO

Litespud

TallRider

I agree that threadless adapter is a known quantity, and safe.
What do you think is the risk with what I am proposing? I mean, what paths do you see that might potentially lead to failure?
Also, what kind of shims are you referring to? I'm planning to put a 25.4mm bar in a stem with a 25.4mm clamp.

You've got me thinking. A steep angled rise like the Dirt Drop isn't exactly what I was looking for, but I wasn't clear about this in my original post. I have a Dirt Drop style stem with mustache bar on my commuter, with 130mm extension. But even with such a long extension, most of it isn't going forward because of the up angle, so it wouldn't help me get my desired forward reach reach.
See the two attached photos to compare a 130mm Dirt Drop-(ish) stem to a 140mm stem that's only slightly up-angled. Note that the photos aren't exactly to scale, so the Dirt Drop looks larger than it actually is.

TallRider

The screwdriver-spread is part of my plan, if needed, but it wouldn't work by itself because the clamp area of a single-bolt mtb bar is so much wider (41mm) than the narrowest section of the clamp area of a single-bolt road bar (27mm).
I plan to shave off an angle of material on each side of the clamp, so I have a narrower gap to allow the curved parts of a drop bar to get through. I should have put a picture of this originally.
I think that if I file and buff and the cut area so there isn't a spot for stress risers to develop, this should be as safe as the unmodified stem.

Jeff Wills

IMO, cutting away the marked portion of the clamp should be OK. Those sections aren't particularly stressed and don't really contribute to the clamping force on the handlebar.

Of course if I'm wrong... they're your teeth you're risking.

70sSanO

3alarmer 

....I'm uncomfortable with your idea of modifying a stem that has been originally constructed by welding the aluminum clamp (which may be cast or forged, I'm uncertain which), to the aluminum tubing that is the stem extension. I presume that the whole thing has been heat treated after construction to relieve the hardening/stresses that were set up in the welding process. But again, that's a presumption.

Finally, you had originally stated that the clamp diameter is for a 25 mm bar, and you want to insert a 25.4 bar into it. I know that .4 mm does not sound like much, but in this instance ( a stem clamp diameter) it will result in some increased chance of cracking somewhere on the clamp area.....this is based on personal observation. Certainly people do worse things to stems and do not end up breaking their faces. I'm just telling you that I have learned over the years to match bar diameter and stem diameter. They made both 26.4 bars and 26 bars for road use for quite a while, and the stems were also made specific for those diameters.

Best mechanical practice is to use something that you don't need to pry on a whole lot when dealing with forged or cast aluminum alloy.

TallRider

Thank you. very helpful. My mistake, I'd written 25.mm when I meant to write 25.4 in the original post. Edited now.
I hadn't thought of how cutting would interact with the heat treating and/or internal tension/stress leftover within the metal. If the metal was under some degree of internal stress (like frames that, when you cut the tubes, they don't stay lined up) then cutting out an apparent non-load-bearing section could offset the balance. My understanding is that heat treating neutralizes such internal tension in the metal. But I don't know for sure the construction history here, or whether it was heat treated after production, and this question introduces a greater degree of uncertainty and thus limits my ability to project risk. That said, the part I'm proposing to cut off doesn't seem at all likely to contain or reinforce internal tension or stress, since it's effectively a hanging corner.

Stormy Archer

I think it's worth taking into account rider weight and riding style.

However, I will also say I don't think you've dug through quite enough parts bins, or don't have enough in your area. I think these types of stems exists in 2 bolt styles. I've also seen a lot of long 0 degree road stems that might have enough quill to get enough height. As a matter of fact, I haven't really seen all too many stems like the one you have pictured - most of the 1 bolt long MTB bar stems I see are steel, not alloy.

Speaking of which, you could also try using a steel one. It might be OK to open up the clamp more since steel can take that kind of bending stress better.

Next time I'm at the bike kitchen I'll dig through the stems and see if I can find any better suited for you.

HillRider

One way to spread the bar clamp opening in a controlled manner is to remove the clamp bolt and thread it in from the other side. Place a penny or other small metal disk in the opening and tighten the bolt against it. That will spread the gap and not require three hands or gouge the metal like a screwdriver can.

Now, whether you can widen the gap enough to feed the bars through without over-stressing the clamp metal is not certain.

TallRider

It turns out the cro-mo stem that was on my flat-bar commuter (painted black, pictured above next to the dirt drop-ish stem for comparison) has a narrowed section on the underside of the clamp area, so it can take road bars. I'd thought it was 43mm clamp the entire way around. This stem has the same extension and rise as the aluminum stem that I'd considered cutting. So, I will use the steel.

Perhaps this thread will turn up and be helpful to someone considering shaving metal off the clamp area of a single-bolt stem in the future.

squirtdad

google search "nitto dirt drop stem"


https://www.benscycle.com/nitto-dirt...10_870/product

https://velo-orange.com/collections/.../vo-quill-stem

wheelreason

That's the best way to do it. If the threaded section doesn't go all the way through, you can do it with a longer bolt and a nut from the open side.