I have a 1" threaded Shimano DX headset with slight even spaced dimples in the lower bearing race surfaces and am wondering at what point you folks would suggest replacing a headset. The top is fine and the set has been kept clean without other major wear or jagged pitting. I assume this is from having it adjusted too tight as some point and the balls pressed into the races. Any other ideas on what would cause this? Could it be from head tube surfaces not being exactly parallel?

It is for an old Schwinn Voyageur that I am trying to build up on a budget so I'd rather not spring for a new one at this point. I'm probably going to use it with the thought that down the road I will have the frame powder coated and replace it at that time. I never noticed any roughness or locking into certain positions on the bike it came off of.

Any major concerns if I continue to use it - as in will they likely get deeper or will it eventually wear to an even surface again?
Thanks,

over tightening is a cause of this but if the bike was ridden hard offroad that is the bigger cause (IMHO). if the HS is a good shape otherwise and you are keeping the bike I would put new loose balls in it. that will change the spacing and keep them out of the dimples.

The headset was most likely set too lose and repeated impacts eventually dimpled the lower cup. It's a common headset issue. I would be surprised if you were able to get a satisfactory adjustment out of the headset with it in that condition, but if you can there's nothing dangerous about using the bike in that condition. Eventually, the headset will start ratcheting or will either be too loose or too tight not matter what you do due to the wear. At that point, you'll want to replace it. The contact surfaces won't fix themselves, though you'd make millions if you could figure out how to make that happen (cheaply).

Either one can cause it. It also happens when the headset is adjusted correctly. The repeated impacts with the bearings sitting in the same places when the wheel is facing forward over time causes the dimples. To my knowledge, it's unavoidable over enough miles. In my experience, it is better to just ever-so-slightly overtighten it if you have to choose, because riding around on a loose headset can ovalize the headtube--a problem that is a pain in the tail to work around. Overtightening just slightly may damage the headset over a few years, but that's all it will do.

Changing the bearing cartridge for lose ball bearings is the cheapest solution as biachigirll suggested. But many bike shops can swap out headsets for a reasonable price. It is by no means a major repair, just one that needs a special tool and know-how.

I agree with 'Bianchigirll" - I've only experienced this problem when the headset was adjusted a little too tight. I think that results in all the lubricant being squeezed out of the contact region under vibration from the road and then there's rapid wear on the bearing surface. Replacing a caged set of bearings with loose balls changes the spacing and can frequently result in good operation of the headset for many years and 10s of thousands of miles. Our tandem is one example of that after the headset got pronounced indexing when it was adjusted too tight about 30 years ago. It still has the same headset now, but with loose balls and the steering is nice and smooth.

There's a couple of fixes that will prolong the life of a headset damaged in this fashion. The quickest temporary fix is to replace caged balls with loose balls, you'll be able to fit one more ball, the spacing will change, and the headset won't index quite so badly.

A better fix, for all but the worst indexed headsets, is to pop off the crown race (or the lower cup, I can't remember if it matters which) and rotate it 90 degrees and reinstall. The wear is usually on the front and back of the races, this moves them out of phase.

Of course, the best thing to do is to get a new headset.

prathmann has it as to the cause.

Impact does not do that at all.

https://www.sheldonbrown.com/brandt/i...-steering.html

In fact it is the opposite of what you describe:

OP: I suggest reading the above link for answers to your question.

You have all posted very good and interesting information - much appreciated!

One additional question - is there an advantage to a headset with larger diameter balls than smaller? The DX headset has approx 1/4" balls vs. the original Tange SE-II sealed with balls about half that size. The original set is in good shape but I was thinking the larger size would be an improvement. Maybe I should stick with what I had?

The problem is a design one. https://draco.acs.uci.edu/rbfaq/FAQ/8f.13.html

I've seen this more on road bikes that go on long descents (lots of small impacts, little steering change to bring in fresh lubrication) and cheap bikes with not enough grease in the headset. Less on off road bikes (more impacts, but much more steering to replenish lubrication). Setting things off by a number of degrees not equal to 360*/number of bearings will help hide it a bit, but replacing the headset is the only cure. The good news is that like bottom bracket bearings, worn parts (in this case) won't further hurt anything that doesn't need to be replaced already. So long as you can handle the bike safely I'd leave it.