I'm posting this in Singlespeed & Fixed Gear because this is for a fixed gear bike. I've also posted in Bike Mechanics.

I have a new Jamis Sputnik fixed gear bike. When ever I go over a larger bump the headset (or at least it sounds like the headset) makes a vibrating sound. It doesn't make the sound on smaller bumps, but I have a fairly bumpy commute and it's driving me crazy! I've checked the headset (twice) and it's tight, there is no play in it at all. If I lift the bike up and drop the front wheel it will bounce and recreate the noise. I've never had a bike make this noise, and don't think it's normal, nor does it sound good. Could the headset be set wrong? Cheap headset? Is it normal? What's up! Any help appreciated.

*I found one other post which sounds like the exact same problem, I thought it interesting they also had the problem with a fixed gear.

your headsets loose

could be your brake lever clanking around.

Grab your front brake (you have one, right?) tight and rock the bike back and forth to check for loose headset play. Turn the bars 90 degrees and rock the bike fore and aft also. If you detect any play your headset needs adjusting. Adjust it.

Tried that and no play at all. I tried tightening the stem and top cap even more and no help. I don't want to crank it down too much.

Check all other possible noise makers and nothing...

it's a sputnik, but how old is it? did you buy it new? who assembled it?

from the sounds of it your topcap is tightened a lot. this is probably a bad thing. whenever you 'adjust' the headset you should unscrew the top cap until the headset can reseat itself before tightening it more. it's very important to loosen the topcap bolt before tightening it.

i'm going to guess that you or someone before you either
-ovalized the headtube and the headset can no longer sit straight
-overtightened the topcap bolt and damaged the headset bearings and/or races
-are tightening the stem before the topcap so any tightening you do to the topcap bolt is simply pulling the starnut out of the steerer tube instead of preloading the headset.

i'm actually convincing myself as i write these out that it's the last one. did you undo the bolts on the stem's steering tube clamp mechanism before adjusting the top cap bolt?

basically, if you're adjusting the headset properly and it's still making a noise, something is broken or bent or pitted.

3 week old 2010 Sputnik, from LBS. Each time I have completely removed top cap loosened stem bolts. Put top cap back on until it's snug (I've over tightened in the past). Tighten up stem bolts. Bike still makes noise. I loosen stem bolts, turn top cap 1/8 turn tighter. Tighten stem back up, same thing.

Could the headset be put together wrong? I'm at a loss!

take it back to the LBS if it's only been 3 weeks.

is it the fork that has the play? kinda sounds like it. Maybe yer spacer height doesn't match the fork steerer and thus can't tighten it down properly?

My Pinarello does this. 1"headset. It is not the headset that makes the vibrating noise. I have checked and checked and installed a different headset and still have the sound. It doesnt bother me cause when im riding it doesnt happen. Only when im off the bike. I believe the noise was coming from the bb region.

in his post he clearly states it does happen while riding, which means forces are acting that can damage the frame or headset.