Indexing headset: toast?
 

I rebuilt the headset on my Shogun 650B conversion at the time that I built up the bike. It's the alloy version of the Tange Levin, and it was smooth as silk when I built up the bike. After clocking in about about 400-500 miles total, with about 50-75 of those being fire trails (some quite rough), I've noticed that my headset is indexing in the center position. It's quite noticeable. Once off-center, it's smooth. Backing off the upper race reduces it, but if I back off enough to eliminate it completely, slight play can be felt. When rebuilding the headset, I kept the original ball retainers but swapped in new grade 25 balls, and also had the head tube professionally faced. Would swapping out the retainers for loose balls cure it? Or does this generally indicate the cups are toast?

I have a theory behind why this happened after so few miles, but I'll wait to hear what others say first.

I have had good luck extending the life of headsets by loose balling them. It should hold a couple more balls without the cages. Since there are more balls they wont line up in the divots in the cups that cause the indexing. It wont be as smooth as a new headset but it will be a lot better than it was.
You need to figure out what caused the problem in the first place. You are probably over tightening your headset. A properly greased headset should last many thousands of miles.

The HS is definitely well greased, but I actually think I may have pounded on the headset on some of the trails while being under-tightened. This may have caused undue pressure on just a couple of balls rather than distributing the pressure over all 16. I noticed after the first 100 or so miles that the headset was a tiny bit loose, but I chaulked it up to the races seating more into the headtube after the initial pressing (which was done with a HS press). I tightened it until it felt right again, then called it good. I didn't pay any attention to it again until yesterday when I noticed the indexing.

+1 to Dan's reply above. Getting rid of the retainers may be enough to cure the problem and is easy to try. I've also had a headset become indexed very quickly as a result of over tightening. Got rid of the retainers and it's been fine ever since. I doubt that the fire roads had anything to do with the problem.

Loose balls may help, the number you use needs to be different from the number with retainer. The need for precision fit (Grade 25 versus 100) may be debateable, but for the moderate cost of 25's, and the need for good diagnostics (Is this installation REALLY parallel?), and the $40 minimum cost of a new HS, I'd go for the better balls. You've already faced and line-bored the head tube, so the bearing circles should be actually perpendicular to the axis and hence, perfectly parallel without added ride loads. This means you can torque the headset based on feel, which will equalize ball pressure as much as can be done (flex over bumps and landings cannot be eliminated). Conventional wisdom is to tighten ONLY as much as will eliminate play, but I think with a perfect installation it can be tighter. If it's tighter, it would take more ride load (forces of weight combined with impact loads) to cause the balls/races to separate due to head tube flexing. And it the grease layers have high integrity and the bearing is free of dirt (overhauled with enough frequency and perfectly clean), the good bearing surfaces should not wear visibly for a long time.

What I don't know is, how do you tell what the maximum allowable headset drag is? But it's not a wheel bearing or a BB.

I'd also take the bottom fixed cup loose, rotate it 90 degrees, and re-press it. One final thing is when it's apart, give the lower fixed cup and crown race a real good visual (bright light and a magnifier) and tactile (point of a ball pen or similar probe) inspection to verify the surfaces are perfect. If they're not, ball bearing tricks may help for a little while, but I'd think the case-hardened layers of the races and cones are already failing. In that case, the bearing surfaces are at the end.

Does the fork require a JIS race?

Rogh fire roads? Its toast.

Get a cartridge bearing headset as a replacement or roller bearing.

I disagree. See
http://www.sheldonbrown.com/brandt/i...-steering.html
for a discussion of the fretting oscillations that can result in an indexed headset. Having it tighter than necessary would displace lubricant from the bearing surfaces and also inhibit free motion of the balls within the bearing while going straight. That increases the chance of such fretting damage. A little tighter is fine for a bearing that is normally rotating, such as in a hub or pedal, but not for the headset that is subject to vibration while stationary.

Nope, standard ISO.

Loose balls will help, and barely discernable indexing on the workstand will be undetectable when riding. At least that has been my experience with MTB's on technical trails.

In that case I think I'd just replace it with a nice sealed bearing headset. It wouldn't hurt to replace the cages with loose balls, though, to see if that remedied the problem.

What I have found to work is this: mark the location of the lower cup and the fork race. Remove, rotate about 90 degrees (cup and race in opposite directions), re-install. You can also do this for the upper cup, but it is not required. It also helps to use loose balls in the lower race.

Another important point: the headset adjustment must be made with the stem installed, but with the front wheel off. Otherwise it's too hard to notice when the adjustment becomes too tight.

This is an extremely good point to bring up - and I'll bet there are many who don't do this.

So how do you feel for a headset that is too loose?

I've gotten used to feeling the knock in a loose hub or bottom bracket, pushing the rims against the stays, or the crank arm against the seat tube.

With a fork, it seems more subtle.

That's what I was going to suggest. It probably doesn't have to be 90 degrees; wouldn't any random amount stand an equally good chance?

Interesting, I haven't done that. I check the headset adjustment by rolling the bike back and forth with the front brake locked; if I feel any play, I tighten it up until I don't. What's the approved method?

I straddle the bike and clamp very firmly on the front brake lever, also grabbing the bar with my other hand. Then putting a lot of weight on the bars, I rock the bike back and forward, keeping the rear of the bike on the ground w/my posterior. If there is any play, you will feel it in the handlebars. This assumes you don't have any play elsewhere in the front assembly, but you quickly determine that if by tightening down headset the play doesn't disappear. I typically tighten slightly beyond where I feel this play disappear. I do this pretty vigorously, using a lot of strength and weight, but is still less stress on the headset than bumping down a road at speed.

I don't know if this is a good or bad idea, I came up w/it years ago & seems to work pretty well. If you are worried that this squeezes out lube from the bearings, just give the forks a couple of full 360 degree turns when you are done.

This is in essence how I determine if a headset is too loose, Rudi. I first try to roll the bike with the front brake locked, pushing down on the bike to prevent the tire from sliding. If there is anything heard or felt through the bars, the headset needs tightening. But then as MetinUz mentioned, it gets sort of tricky-- how does one determine how much pre-load gets put on the bearings? As others have suggested, it helps to have the wheel off, so that there is no large lever effect acting on the steering pivot. If there's a front bag, that should get removed, too. But even then, it's hard to determine how much preload is being dialed in. On a really smooth headset, too much preload may not be felt. On lower-end headsets or headsets with some wear, I can usually feel too much preload as either resistance to movement or irregularities in movement (meaning, not quite indexing, but not glass-like smoothness, either). The point about the stem being installed is a good one; slight bulging of the steerer tube by the wedge may cause a shortening of the steerer by a couple of angstroms. My guess is that tightening the stem after getting the headset dialed in might introduce more headset preload.

I don't worry about this at all. Maybe my physics understanding is off, but once the bearing balls are in full contact with the races, it shouldn't matter whether there's a little or a lot of preload. The grease is going to get displaced along the path of ball/race contact, period. The issue that concerns me is how quickly the displaced grease can migrate its way back into the contact path. This characteristic is determined by viscosity, I suppose. I forgot whether it was Jobst Brandt or Mark Stonich who posed the argument that for bearing surfaces such as headsets, BBs, hubs, etc, oil is actually superior to grease for exactly this reason, but that grease has replaced oil simply because of the convenience of not requiring as much maintenance-- with oil the same characteristic that makes it advantageous to bearings also causes it to spread and drip outside of the bearing assembly and onto other parts of the bike.

The Levin is a nice headset, but the small balls limit the abuse it can handle. If the suggestions above don't help, you need to replace it. Fortunately, the Levin is still widely available and relatively inexpensive, but any ISO headset of the proper stack height should be ok.