Alu Steerer Tube - Bung or Star Nut

[токамак]

OK, but when the top cap was no longer providing compression because the bung had slipped in the tube, in this case - play eventually developed in the headset. The stem was tightened up as much as I dared, but every couple of weeks the whole thing needed resetting.

[Rhys W]

Worn bearings?

[Sergeant Pluck]

I had an issue similar to this in the past. I couldn't get things to stay put. To begin with I assumed it had to be a problem with the star nut (not sure why - I'm fully aware that the top cap should be redundant once the stem is tight) and eventually tried a bung. Needless to say this did not resolve the issue.

It turned out that the issue was the fork crown race not fitting correctly - I can't remember why, it may have been damaged or just not seated correctly. Once that was replaced all was fine.

[токамак]

It's a Chris King Devolution headset in a Principia frame which has a 1 1/4" head tube, I was quite careful to order from the US a base plate (CK term for crown race) that is specific for this design, being 1 1/4" with internal diameter for 1 /18" steerer. The bearings are not worn. The fork is a Columbus Tusk Air Chrono with alu steerer. The stem is a Thomson Elite X2. Quite simply, the stem alone was not sufficient to hold the arrangement tight and free of play - compression from the top cap was also required.

I completely accept that a stem should hold a front end together 100% - I've even seen people riding A-head setups with no top cap installed. In this instance, the bung I used was just about OK for a while, but needed regular adjustment, if I had installed the star nut at the beginning these adjustments would not have been necessary.

I will be disassembling the bike soon, and hope to have a full carbon frame and fork for next year, which will be bungtastic! For my new winter bike that I'm about to build, the star nut will be going into the steerer tube post haste...

Thanks, everyone, for your input.

[MacB]

I've got Hope headsets on both bikes and have had none of these issues, the Hope Head Doctor can be bought seperately for not too much.

Though I've since been told it's a pointless exercise and has no basis in reality I've always followed advice from a bike shop mechanic. He told me to get the headset sorted, tighten up the stem and then back the star nut off by half a turn. You can also see some of Sheldons experiments where he use an old seatpost collar at the base of a steerer tube to allow him to move an ahead stem at will.

[токамак]

I've got a Hope Head Doctor in one of my other bikes (carbon steerer) and they're great. Unfortunately, the internal diameter of this particular alu steerer wouldn't accommodate a Head Doctor - it was the first thing I tried!

[MacB]

I've got a Hope Head Doctor in one of my other bikes (carbon steerer) and they're great. Unfortunately, the internal diameter of this particular alu steerer wouldn't accommodate a Head Doctor - it was the first thing I tried!

Doh, missed the bit about the bigger diameter steerer...sorry

[токамак]

That's the annoying thing about steerer tubes - although 1 1/8" is standard external diameter, the internal can vary slightly, meaning that a bung that works well in one fork may not be effective for another.

[Biggsy]

Re: headset going out of adjustment:  I've not found the model of bung or star nut, or its tightness or bolt tightness, makes any difference when I've had this problem.  If the stem is liable to slipping, it will slip.  It only takes a tiny weeny bit of movement to cause headset play when the headset preload is set "just so".

That's the annoying thing about steerer tubes - although 1 1/8" is standard external diameter, the internal can vary slightly, meaning that a bung that works well in one fork may not be effective for another.

That's right.  The bung naturally works with a range of sizes, but your steerer ID might be outside of that range.

This can be a problem for star nuts as well.

[frankly frankie]

... a bike shop mechanic. He told me to get the headset sorted, tighten up the stem and then back the star nut off by half a turn.

Exactly.  This demonstrates that the top cap exerts no significant pressure.  Some of them are made of plastic for gawd's sake.

[токамак]

If the stem is liable to slipping, it will slip.  It only takes a tiny weeny bit of movement to cause headset play when the headset preload is set "just so".

Absolutely, I did suspect that the issue was peculiar to my particular set up. I also knew it only had to keep going for a year before upgrade. If I was keeping this bike going I would look at a more permanent solution.  An interesting follow up to all this will be how I get on with the winter bike. I'm aiming for perfection, there. 

[rafletcher]

Star nuts are fit and forget...

Yes, but if you ever need to get one out (not that I have, yet), you're screwed.

Really? I just bashed mine right through and out of the bottom of the steerer - and re-used it.