what could possibly be wrong?
 

I recently realized that my fork seems to be rotating in increments.
What I mean by that is basically that if i hold the bike up, the fork won't rotate smoothly. It basically snaps to random points (straight, about 45 degrees, almost 90 degrees, and 90 degrees). I realized it couple of days ago when i carried my bike up the stairs to my apartment and found instead of needing to hold the front wheel like i used to do (its a really narrow staircase) the wheel basically snaps in position and wont budge unless u manually move it with ur hand. Then it'll rotate and snaps to the next increment.

I tried loosing everything there is except the headset on the fork to no avail. What could possibly be wrong that this is happening?

pitted headset?

would that be noticable on the outside or not necesarily? Coz everything looks fine on the outside.

Would not be visible from the outside. The pitting would be on the cups, causing the bearings to experience less than smooth travel. Can happen from overtightening or just age. Probably needs to be replaced :(

This definitely sounds like a headset issue. Have you tightened it/adjusted it yourself? It sounds to me like it is either massively overtightened or badly worn, as suggested above, although my headset knowledge is limited to modern threadless setups. What kind of bike is it, and what kind of headset?

The good news is they aren't expensive.

its the kilo tt with the stock headset, cane creek threadless. I didnt touch the headset at all since I got the bike. I dont think my bike is old enough for it to be an aged worn issue. Could it be from running my bike head on into a car's rear bumper? That's about a month ago. But the accident wasnt bad at all.

Brakeless?

crashing can do it, pitting the headset I mean.
soft aluminum races getting pitted by hard steel bearings.

This condition has been termed "indexed steering" by Sheldon. The bearings in your headset probably "brinnelled" the cups when you crashed, which causes the steering to click into place.

There's a short explanation here, under the entry "brinnelling."

tl;dr: Replace your headset, keep it lubed and adjusted.

I would guess BD may have overtightened the top bolt if you've never touched it; more likely than the small accident. That top cap pre-load bolt is meant to be tightened only enough to eliminate play in the headset/fork, it's defintely not meant to hold the stem in place, that's what the stem bolts are for. Riding for an extended period with top bolt too tight would cause pitting. Also fyi, top bolt should only be adjusted when the stem bolts are loose.

See
http://www.parktool.com/repair/readhowto.asp?id=65
and

naw, I run a front brake. Thats why it wasnt a serious accident. A car made a sudden switch to my lane and stopped. I braked, just not quite in time.

Ahhhhh damn. Aiite, thanks guys. Looks like I cant fix this by today :(

It's probably not adjusted properly from the factory. Adjustment is best performed with the front wheel removed and the bike held by the frame off the floor as in a bike stand. Loosen the top bolt, then loosen the stem pinch bolts. Slide the stem up a few millimeters so the fork is loose, then tighten the top bolt until you feel no play in the fork when you grab it by the dropouts and push it forward and back. Center the stem and tighten its pinch bolt(s). Turn the bars side to side and see that the fork turns easily with no tight spots. Tighten the top bolt and re-check that the fork has no front/back play. If it does, loosen the stem pinch bolts and turn the top bolt another 1/4 turn, then re-tighten the stem and top bolt.

Edit: I guess that video was posted while I was posting this.

aha! Thanks! wasnn't quite sure what to search for before. Now i know

Depending on how bad the pits in the cups are, you might be able to save the headset by replacing the caged set of ball bearings with loose ones. That lets you get in more balls so they're spaced closer together and no longer line up with the pits that have formed. Worth a try anyway since it's much easier to put in the loose ball bearings than to replace the headset.

Did you recently have the cabling redone?

my kilo stock HS does the same thing, as well as the ritchey logic HS on another bike. i actually like how it "snaps" back straight. it's pretty subtle, only noticeable if the bike is hanging from a stand or suspended somehow. i always thought it was by design haha.

edit: only noticed this on threadless HS btw. threaded HS seems to swing about much more, which i dislike.

Good question. He should try it with the cable disconnected.

^
i dismounted the front brakes and cables hoping that would be the issue, but no. So I came here.
I also lent my repair stand to a friend and I can't get it back until thursday. I guess i could check my headset without a repair stand, it's just kinda a PITA.

Just curious if you have anything else that hasn't been adjusted out of the box?

BD bikes require assembly and adjustment out of the box. It seems that ~90% of the issues that people have with these bikes is due to failure to actually adjust and tune it up out of the box.

i have not touched the cranks and BB. that's it.

A bent fork can definitely be a possibility. One of the bikes I've bought had a sliiiightly bent fork and it would do exactly what you described, but in a very subtle manner.

While I agree with most of your post, I'm fairly confident in saying that the star nut would be stripped out long before the adverse tension would cause the pitting. I say this because in my infinite wisdom, I've pulled the threading straight out of the star nut before.

It's not that the extra preload would create the pits directly. But it can squeeze the normal lubricant out of the interface between the ball bearings and the race. When riding down a straight section of road you can then get vibration at this interface that causes rapid wear and results in the pitting.