|Integrated headset...long post & hopefully clear...||filly|
Dec 14, 2003 7:18 PM
|I purchased a new ride (KHS Flite 2000...pic below) not long ago, and swapping out the stem was a must. It came with a 120mm and I've now got an 80mm. The fit is great. I noticed, however, that the top cap (not stem cap) of the FSA integrated h/s does not seat flush against the head tube, or at least have a consistent gap (less than 1mm is acceptable) wrt the head tube. Instead, there is about a 1mm gap b/w the cap and head tube at the 12 o'clock position (for orientation, imagine riding and looking down at the headset and the top cap was a watch dial). Conversely, the 6 o'clock position shows no gap at all--the top cap rests on top of the head tube. Now, I know why this is the case, but my question is, is this okay, or will I eventually damage the bearings, headtube, both, etc.?
The cause is due to the bottom of the stem (the part that makes contact with the h/s top cap, or spacers) not being perfectly square. As you torque the h/s adjustment bolt and the stem presses down on the top cap, the 6 o'clock portion of the stem contacts the top cap first, as opposed to a square meeting of the stem and top cap. What you have then is full adjustment pressure at the 6, and little to no contact b/w stem and top cap at the 12.
Of course, I could get a new stem, or I could file off some material at the back of the stem to get a flush fit b/w stem and top cap.
I'd appreciate your guys' thoughts. Thanks.
|Here's the pic...||filly|
Dec 14, 2003 7:20 PM
|Do you need...||BowWow|
Dec 14, 2003 7:31 PM
|a small (1 - 2mm) spacer between the stem and top of the headset? From the top down: cap, stem, spacer, headset. Would this help?
|Nah, won't make a difference||filly|
Dec 14, 2003 7:42 PM
|There's actually a 5mm spacer under there already. I might break out the file...|
|Something sounds odd here...||BowWow|
Dec 14, 2003 7:55 PM
|So what you're saying is that the angle between the bottom of the stem and the center (machined inside) of the stem isn't consistant at 90 degrees? I'd find another stem!
Good luck if you choose to file - you won't be able to return/exchange the stem, and getting the bottom of the stem square and 90 degrees could be difficult. Not impossible, and I'd probably give it a try if the stem isn't too expensive...
I once squared a BSA float bowl by putting a sheet of 400 grit sandpaper on a pane of glass and slowly grinding the surface of the floatbowl until it was perfectly flat - worked like a charm, but I wasn't trying to grind perpendicular to another machined surface...
|I knew this might be tough to explain||filly|
Dec 14, 2003 8:05 PM
|I think I know what you're asking, but it's not that it's not consistant. It does have a consistant angle, but it's like 89.5 degrees or something (or 90.5, depending on how you're viewing it). Hopefully my attempt at clarification doesn't confuse the issue.|
|I knew this might be tough to explain||Spiderman|
Dec 14, 2003 8:50 PM
|make sure the star fangled nut is in properly, and that it isn't at an angle inside the steer tube.|
|Have you just tried another stem on the bike?||Swat Dawg|
Dec 14, 2003 8:51 PM
|When I run into situations like this I just try another of the same object. If it is just the stem, and it is a cheap one, try filing it. If more than one stem is off, the problem might not be the stems but the headtube facing. I know that on some bikes I've built up with integrated HS if the frame was not finished very carefully the headtube area including the stem, fork steerer tube, and fork crown flushness to the bottom of the headset will be off. If I understand your issue correctly, I would be concern about that the construction of the frame and headset. I would be very careful if you are riding, because any time there is inconsistent fusion you are creating stress points on the steerer tube that could lead to potential failure. So try swapping the stems and see what happens.|
|After a careful re-read of your first post...||BowWow|
Dec 14, 2003 11:49 PM
|it appears that the top race isn't completely inserted into the headtube - the back of the top race is flush with the top of the headtube, while the front of the race has a gap between the race and the tube. Correct?
If so, I think you should have your LBS remove the fork and apply a bit more pressure with a headset installation tool, to seat the top race completely in the headtube.
Or you can give it a try yourself. I have installed several headsets with the 2X4 method. Purists and paranoids will instantly flame me for this, but this is what I personally would try (if my diagnosis is correct): Remove the fork and headset bearings, leaving the headset races intact in the headtube. You will need an assistant for this. Take a 2' length of 2X4 and center one end under the lower race, race resting on the top of the 2X4, with the other end squarely on the floor. Your assistant will hold the back end of the bike so the headtube is perpendicular to the floor and steady on the lumber. Then take a short piece of 2X4 (maybe 6" long), center it on the upper race, and tap it with a hammer over the front end of the top race (where the gap is). You may need to give it a couple of sharp raps, or it may take only a quick tap. Check after each tap to see if the gap has disappeared, making the race flush with the top tube. A steady hand, and a steady assistant, will get the job done.
FWIW, I have successfully installed headsets in 3 MTB's without assistance using this method, and in my current road bike using my wife as my beautiful assistant - all without incident, all working well (bikes AND wife!) to this day.
If my revised diagnosis is correct this time, you'll be on the road in 1/2 hour! Remember to thoroughly clean your races before reassembling the headset - new grease would be appropriate, too.
If you're not confident with your mechanical skills, definitely take it to the LBS - they can seat the race quickly, and return your bike with the headset properly adjusted.
If I've missed the mark again, post a close-up if you can.
|Oh, this method may not work with integrated headsets...||BowWow|
Dec 15, 2003 12:04 AM
|If the top of the upper race is already flush with or below the top edge of the head tube you'll need a special tool to guarantee complete upper race insertion.
Or, as Swat Dawg indicates, the top of the headtube isn't finished squarely (perpendicularly to the length of the tube - in other words, the tube was cut at a slight angle). If this is the case, you'll need to have your LBS face the tube. This ensures that the top of the headtube is perfectly square, permitting a proper alignment of the top headset race and the fork steer tube. When an integrated headset is inserted in the headtube it will end up being flush with the top of the headtube. If the top of the tube isn't square the top race won't be square.
If the top of the race isn't extending above the top of the headtube, ya gotta go to the trusted, mechanically sound and competent LBS mechanic.
Sorry for the long and somewhat garbled posts - I hope this helps!