Supersix Evo headset preload

I had problems with the

I had problems with the headset on my Super Six Evo from the start. The supplied fork steerer “bung” to fit the carbon fibre fork was very poor quality and would not satisfactorily clamp the steerer. I’ve seen this exact design of bung before on other brand bikes, and its never worked properly. 

As soon as I applied slight pressure through the top cap bolt to tighten the headset, this bung would move up the steerer, preventing the headset from being torqued (only 2-3nm). I tried fibre grip (carbon past) and setting torque on the bung using a torque wrench but it made no differentce. 

I then replaced this with a spare bung from a Specialized S-Works, and applied fibre grip paste. This allowed me to tighten the headset properly. 

The second problem was the headset still coming loose whilst riding, and creaking. This was tracked down to the supplied carbon fibre stem spacers which had a very minimalist cut away design with only 3 points of contact.

Similar to the ones above, but with even more cut out leaving three triangular contact points. These barely made contact with the stem body. 

I replaced these with aftermarket spacers of solid carbon fibre (not cut away) and the problem never occured again. 

“Shouldn’t really put spacers

“Shouldn’t really put spacers above the stem but the press review bikes from Cannondale usually do so don’t think that’s the problem”

er, you should always place one spacer above the stem*, because the steerer needs to protrude from the stem, then the spacer is needed so the top cap doesn’t pull down and contact the steerer, instead pulling down on the spacer->stem and then onto the bearing topcap. And so the steerer can’t be pinched by the stem clamp. Anything to not introduce fractures. 

People who insist on cutting their steerers right down to the stem du jour aren’t thinking about ever a: changing stem  or b: selling their bike. Which is OK, of course.

I acknowledge some folks use the top few mm of the stem as a spacer, to separate steerer from topcap. Done carefully, that’s OK – but you are loosing clamping area betwixt stem/steerer. Which especially for carbon is not good.

…and if it’s a carbon steerer, you should use paste. Best practice.

* this from p340, ‘Zinn and the art of road bike maintenance’. Trust Lennard, not Some Guys On Road.CC (including me) 

pablo wrote:

Nixter understand your comments and this is how mine is setup it’s a new frameset so wear isn’t an issue.  Re the last couple of lines of your comment. It seems some frames may not be 100% to spec and require a 0.25-0.5mm shim under the headset upper race. If the bearing sits low in in the cup the upper race will bottom out on the top face of the bearing before it compresses the collet properly and you end up being unable to set the preload.

so I’m going to 

1) check the length of the expander assembly so it meets the drawing.

 

2) Try to buy some micro spacers (fsa make them but I can’t see any stock in the uk) I think this is what steve_williams may be referring to.  Steve if your still watching this thread where did you get them.  

http://www.fullspeedahead.com/products/cyclocross/micro-spacers/

 

I hadn’t encountered the issue with out of tolerance you refer to but (assuming I’m understanding you correctly) you could check this by removing the bearing top cover completely and just using a spacer stack to compress the collet directly.  This wouldn’t be a long term solution (aesthetically at least) but you would have narrowed down the causes/ solutions.  Surprised that the dust cap hasn’t fouled the top of the head tube and stopped the bars turning though?

As above, I had this problem

As above, I had this problem after changing stem and to cure it I had to add a small spacer to allow a slight gap above the steerer tube so it would clamp down properly.