I have a chris king headset that I got secondhand and I want to fit it to one of my bikes.

Info online says that some people, especially with longer forks, have had the steerer tube damaged by the headset because the older headset doesn’t have the compression ring. According to a few websites the top cap oring is supposed to put a groove in the steerer tube. Does anyone know how the damages occurs? Is it just that if the headset isn’t tightened properly the top parts rub on the steerer tube? I want to avoid damaging my new forks if possible so it would be good to know what is really causing the problem.

It doesnt matter of the headset is correctly adjusted or not, it’ll still score the steerer.
Either get the newer bit which doesnt score the steerer or fit another headset.

Do you know why it scores the steerer tube?

…the o-ring just isn’t enough to keep that top cap away from the headtube, load on the fork will compress the o-ring and rub everything together.
Mine used to fill the headtube with ‘iron filings’ and score the fork headtube – but you can get upgrade kits that swap the top cap out for a dia-compe style compression ring, I’d certainly recommend getting one…

@mtbcowboy

the edges of the groove in the top cap (where the o-ring sits) is responsible for scoring the fork steerer, as the headset moves under load

Yes, the price of Chris King headsets obviously wasn’t enough for them to pay to use the (cane creek?) patent on the split-ring, although cheaper headset manufacturers managed it.

Hypocritical of them to start using a split-ring once the patent ran out

As above, CK headsets with the o-ring are a poor design and in the right circumstances will score the steerer as they flex/move against each other.

The current split ring design solves this flaw.

Okay thanks for the info.

I have inspected the headset and I can now see why there can be a problem with this design. The O ring has to be a very tight fit to restrain the top cup cover against the headset cup and relying on the compression of the o ring to restrain it laterally is not good enough. There is however a small male tapered face on the top cup cover and on the top bearing there is a small female tapered face so when the bolt is tightened the load from the bolt with push the two small tapered faces together. However this small tapered face is only about 1-1.5mm long so if there is too much play between the o ring and the steerer tube then the top cover can move causing the creaking etc.

I have found the steer tube tolerances online here:

https://www.canecreek.com/resources/products/headsets/technical-specifications/oe-head-tube-specification-guide.pdf page 10

The steerer tube tolerances are lower = 1.120” nominal 1.125” and upper 1.126”, I.e the tolerance is – 5 thou and + 1 thou. My guess is that if the steerer tube is at the lower tolerance or even below the 1.120” then there will be enough play between the top cup cover and the steerer tube to cause the problem. However if the steerer tube is at or close to the top end of the tolerance range then there may not be any creaking. As the o ring gets old and is compressed the problem may occur. This may be why only some people have had problems with this headset design.

Given the design issue/flaw here I agree it would be best to upgrade the headset even if initially I have no problem as I have measured my steer tube at 1.125”

Does anyone know the cheapest place to get the compression ring upgrade kit?