Quill Stems: What Exactly Does the 'Minimum Insertion' Line Mean?
#1
Senior Member
Thread Starter
Quill Stems: What Exactly Does the 'Minimum Insertion' Line Mean?
At the risk of asking the obvious, does the stem's minimum insertion mark indicate how far into the steerer tube the stem should be inserted, even if a section of the steerer is above the headset / outside the headtube, or does it represent the minimum amount the stem should be inserted below the headset's upper race, i.e. seated inside the headtube proper? I am particularly concerned about where the stem's expanding bolt should be in relation to the upper headset bearing race.
I have a bike with a 1" threaded headset, and between the cantilever brake guide, spacers (about 12 cm worth), the upper bearing race and the locknut, I estimate there is about 60 mm of insertion before my stem even enters the headtube. At maximum insertion, i.e. before the stem starts to taper and I can't insert it any further, I measure there is only about 35 mm of stem seated inside the actual headtube, and this is almost entirely the size of the expanding wedge. Is it a problem for my stem to be seated so relatively high inside the headtube? In particular, does it stress the headset if the expanding wedge is pressing up against the inside of the steerer tube at that point?
Thanks for the help,
Mike
I have a bike with a 1" threaded headset, and between the cantilever brake guide, spacers (about 12 cm worth), the upper bearing race and the locknut, I estimate there is about 60 mm of insertion before my stem even enters the headtube. At maximum insertion, i.e. before the stem starts to taper and I can't insert it any further, I measure there is only about 35 mm of stem seated inside the actual headtube, and this is almost entirely the size of the expanding wedge. Is it a problem for my stem to be seated so relatively high inside the headtube? In particular, does it stress the headset if the expanding wedge is pressing up against the inside of the steerer tube at that point?
Thanks for the help,
Mike
#2
Senior Member
Must be the day for stem threads. You should also follow this one. My take on the Min. insertion line is that it's the mfgrs. best guess at how far you need to insert the stem to get the expander past the threaded portion of the steerer tube. That's critical, and you don't mention it in your post. I can't speak with authority on how far down the headtube the expander needs to sit.
#3
Scott
Join Date: Jun 2006
Posts: 2,393
Bikes: Too Many
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
If you can see that line it's set to high. You run the risk of bending the stem and damaging the tube as well if you have the line above the top of the tube.
#4
cab horn
Join Date: Jun 2004
Location: Toronto
Posts: 28,353
Bikes: 1987 Bianchi Campione
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Likes: 0
Liked 25 Times
in
18 Posts
At the risk of asking the obvious, does the stem's minimum insertion mark indicate how far into the steerer tube the stem should be inserted, even if a section of the steerer is above the headset / outside the headtube, or does it represent the minimum amount the stem should be inserted below the headset's upper race, i.e. seated inside the headtube proper? I am particularly concerned about where the stem's expanding bolt should be in relation to the upper headset bearing race.
I have a bike with a 1" threaded headset, and between the cantilever brake guide, spacers (about 12 cm worth), the upper bearing race and the locknut, I estimate there is about 60 mm of insertion before my stem even enters the headtube. At maximum insertion, i.e. before the stem starts to taper and I can't insert it any further, I measure there is only about 35 mm of stem seated inside the actual headtube, and this is almost entirely the size of the expanding wedge. Is it a problem for my stem to be seated so relatively high inside the headtube? In particular, does it stress the headset if the expanding wedge is pressing up against the inside of the steerer tube at that point?
Thanks for the help,
Mike
I have a bike with a 1" threaded headset, and between the cantilever brake guide, spacers (about 12 cm worth), the upper bearing race and the locknut, I estimate there is about 60 mm of insertion before my stem even enters the headtube. At maximum insertion, i.e. before the stem starts to taper and I can't insert it any further, I measure there is only about 35 mm of stem seated inside the actual headtube, and this is almost entirely the size of the expanding wedge. Is it a problem for my stem to be seated so relatively high inside the headtube? In particular, does it stress the headset if the expanding wedge is pressing up against the inside of the steerer tube at that point?
Thanks for the help,
Mike
#5
Senior Member
Join Date: Aug 2007
Location: Northampton, MA
Posts: 956
Bikes: Iron Monkey: a junkyard steel 26" slick-tired city bike. Grey Fox: A Trek 7x00 frame, painted, with everything built, from spokes up. Jet Jaguar: A 92 Cannondale R900 frame, powder coated matte black with red and aluminum highlights.
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
There's something amiss here. Can you take some pictures?
#6
Senior Member
Thread Starter
First, let me clarify that the minimum insertion line is not visible when the stem is installed. In fact, very little of the stem is protruding from the top of the steerer tube, something like 2 to 2.5 inches (because the stem tapers at that point, it is inserted to maximum depth).
Sorry, I'm at work so I can't take pictures, but maybe I can use a text illustration in the meantime. Here's the profile of the headset stack, not including the stem:
jbonamici, I did see that other thread, and while it discussed stem insertion relative to the threads on the steerer tube (a good question, and I will need to confirm that the steerer tube is not threaded at the point where I have inserted the stem), there was no mention about where the stem's expanding bolt should be relative to the headset. What you're suggesting is that that discussion should also answer my question because steerer tubes are always threaded up to the pressed race or thereabouts. The solution for me would be to cut the steerer tube to get rid of some of the extra spacers, so that the stem could sit deeper in the headtube. The downside is that I would then need to use a different stem to raise the height of the handlebars.
Anyway, thanks for the help so far,
Mike
Sorry, I'm at work so I can't take pictures, but maybe I can use a text illustration in the meantime. Here's the profile of the headset stack, not including the stem:
Locknut
2mm Spacer
10mm Spacer
Cable Hanger
Washer
Threaded Race
Bearings
Pressed Race
Headtube
The measured distance from the top of the locknut to the bottom of the pressed race, i.e. where the steel headtube begins, is about 60 mm. When I insert the stem into the steerer tube--which you cannot see, of course, with the locknut, spacers and other components installed--I estimate that the stem's expanding wedge sits a few millimeters below the pressed race, which is at the top of the headtube. So the expanding wedge is inside the headtube, but not very far (extending to something like 35mm below the upper edge of the headtube), and the question is whether this is far enough.jbonamici, I did see that other thread, and while it discussed stem insertion relative to the threads on the steerer tube (a good question, and I will need to confirm that the steerer tube is not threaded at the point where I have inserted the stem), there was no mention about where the stem's expanding bolt should be relative to the headset. What you're suggesting is that that discussion should also answer my question because steerer tubes are always threaded up to the pressed race or thereabouts. The solution for me would be to cut the steerer tube to get rid of some of the extra spacers, so that the stem could sit deeper in the headtube. The downside is that I would then need to use a different stem to raise the height of the handlebars.
Anyway, thanks for the help so far,
Mike
#7
Senior Member
Again, I don't see a problem as long as the expander is below the threads. I don't believe that there's any reason to think that it will stress the headset. One might argue that as you raise the handlebars you increase the leverage of the steerer against the headset. If the headset isn't properly adjusted, this leverage can lead to an ovalized headtube. But, at least as I envision it, that's not a function of the stem length, and if the HS is properly adjusted it's a non-issue anyway.
#9
rebmeM roineS
Join Date: Jan 2006
Location: Metro Indy, IN
Posts: 16,216
Bikes: Bacchetta Giro A20, RANS V-Rex, RANS Screamer
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 653 Post(s)
Liked 347 Times
in
226 Posts
I think minimum insertion refers to the steerer tube/threads and not the head tube or headset.
#10
Senior Member
Thread Starter
Anyway, I managed to make time last night to remove the fork and measure how far into the steerer tube the stem is sitting. From my calculations, it appears that the stem's expanding wedge is a few millimeters below threads on the steerer tube, though probably not below the pressed race (assuming my measurements are accurate, the threading on the steerer tube ends somewhere inside the pressed race, which is logical).
That said, it's very close--as I said, within a few millimeters--and if I made any measurement errors then the expanding wedge could be in the threaded section after all. To be on the safe side, I may get a new stem that I can insert deeper into the steerer tube. Probably overkill, but better safe than sorry.
Thanks for the help,
Mike