Minimum Insertion to Bar Height Ratio
 

Hello all!

My wife rides a 1984 Trek 660 road bike. She's not a fan of drop bars despite my attempts, so we switched her to mustache bars. The consensus seems that you have to get mustache bars up high (and she agrees). This is where we're running into a problem.

I had a Nitto Technomic Deluxe stem laying around, but it bottoms out in the steerer tube butting on her very small frame. I'm looking for a quills stem that minimizes the minimum insertion but maximizes the height of the bars.

Basically, the ratio of minimum insertion to bar height should be small.

Any recommendations, noting that the Technomic Deluxe is a failure? Any hard numbers (maybe from stems laying around) would be useful.

Interesting. What size is the frame? How much insertion are you getting before it bottoms out? How far above the headset is the min insertion line?

I suppose the additional leverage of the technomic demands a deeper insertion. If you could figure out a safe ratio of insertion to exposed quill (which I suppose you can derive by measuring the stem you have), you could always cut the Technomic down slightly. I don't know if you'd have enough threading on the bolt that way, so you'd possibly need a different bolt, or a means of cutting more threads. Maybe more trouble than it's worth.

It is a 19 inch (48 cm) frame. I'll get you the relevant measurements when I get home from work (how much insertion, headset, etc).

Ideally, I wouldn't cut the Nitto stem simply because I can easily sell it if I'd like. If not, I'll just save it for a future build.

I'd think a dirt drop would be the solution, but then you probably already own 26.0 mustache bars, so that's out.

What about a stem extender?

I'm almost certain the bars are 25.4. Anyone know the insertion on the dirt drop?

I don't think this is a problem unless the stem is simply too high for her. The minimum insertion line is intended to keep people from not putting enough quill into the steer tube. If you're going all of the way down into the bottom of the steer tube, clearly you have enough insertion. If it goes in 65mm or more, you should be fine.

Well, these things certainly have liberal safety factors, but I would hate to do anything but abide by the minimum insertion and have something happen to her.

What do others think?

After some measuring, it seems I need the bottom of the stem to minimum insertion line to be approximately 2.5 inches instead of the 3 inches that are pretty common on stems.

I have a old Nitto Periscopa (I think?!) laying around from a vintage mountain bike that is 2.5 inches and that seems to work fine. Are there any modern stems with only 2.5 inches that will get the bars up high enough?

I think he's probably right.

What is the min insertion about anyway? Is it there to protect the rider or the frame? Can anyone explain? Breaking a quill seems like quite a feat; deforming a steerer from too little insertion seems much more plausible. I guess I've never really thought about it all that much.

How hard will your wife be pushing this bike?

[edit] Also some of this might be helpful:
http://www.bikeforums.net/classic-vi...guid-stem.html

Minimum insertion on a quill stem is to assure the wedge is NOT expanding at a point where the steerer is threaded.
Severe damage and failure to the steerer tube can occur.

+1 to rccardr's comments on the amount....2.5" is sufficient.

Thanks, everyone. I'll probably grab a Nitto Periscopa (which has sub-2.5" minimum insertion line), but it is good to know that others generally think it will be okay.