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Trying to get these carbon forks right and no matter what i do i get a little free play in the headset.
I bought this to go in the top.
So i fitted the forks, first using the supplied 'cut' crown race, then also with the correct one that was fitted to the forks previously. So i fit and leave 4mm of spacer above the steerer as usual, then stick in the bung and tighten it... i'd guess 10Nm to start, but holding the fork bottoms i can feel a small wobble. (This is not present when i fit the standard alu steerer forks and usual start nut). I try another 2mm spacer and still the same, same levels of play.
So the question is, am i missing something here when doing the carbon bung thing ? It can't be that complex can it ?
All the fork bung does is allow you to adjust bearing load - it is the steerer clamped in place that holds everything together. If there is some movement in your forks, suggests you might not have the correct crown race for your forks or the headset is assembled incorrectly?
That looks pretty short for a carbon steerer bung - they usually go in for the whole depth of the stem to stop the stem clamp crushing the steerer tube.
In my experience there's two internal diameters of steerer tubes - carbon sometimes need a larger diameter bung. Perhaps this one's not tightening inough inside the tube despite the bolt being fully tight?
Certainly seems to be, if i remove it and then tighten it just half a turn more when off the bike, i can't actually then get it to insert into the steerer as it's then too big, so deffo seems to be the right diameter for the steerer from what i can make out.
it is the steerer clamped in place that holds everything together. If there is some movement in your forks, suggests you might not have the correct crown race for your forks or the headset is assembled incorrectly?
Crown race came with the bike, which was bought brand new. When i fit the same crown race to the revelations, same headset, same spacers etc, all stays 100% snug an nice. The only difference is the forks and the star nut/bung setup. I suppose i could try the carbon bung in the alu forks and see if i still get play, as we know that fork is solid when it has a start nut 🙂
Only time I have an issue is when the top cap hits the top of the bung before the slack is out of the headset - ie. the bolt feels 'tight' but because it's bottomed out on the bung rather than because the whole headset is tight. Try adding more spacers above the stem.
Those M-Part steer bungs work really well so can only assume a fitting issue. You do realise that fitting the bung into the steerer and then tensioning the headset are 2 different operations?
Are you taking the top-cap off the bung and then adjusting the preload?
Just in case you don't know...
Use a 4mm allen key to remove top cap & bolt
Put bung in steerer and tighten with a 6mm allen key
Fit top cap & bolt, tension as you would any other headset. If you still have play then the top cap is probably hitting the top of the steerer so either add a small spacer or chop the steerer down a bit.
This is slghtly different than that type, my bolt on the top cap goes straight through, i don't have a 2nd bolt below it. The spacer below the cap is drilled and threaded, so my tension bolt is the one and the same as the top cap bolt, single bolt action.
Only time I have an issue is when the top cap hits the top of the bung before the slack is out of the headset – ie. the bolt feels ‘tight’ but because it’s bottomed out on the bung rather than because the whole headset is tight. Try adding more spacers above the stem.
This may be it... just may... but my other spacers are too tall really to make me 100% on that answer. If i fit a 2nd spacer it's just too tall.. So i'll need to find/pick up a 2mm spacer.
This is slghtly different than that type, my bolt on the top cap goes straight through, i don’t have a 2nd bolt below it. The spacer below the cap is drilled and threaded, so my tension bolt is the one and the same as the top cap bolt, single bolt action.
I have never seen one like that and the one in my hand looks identical to the one you have posted above. Can you post a pic with the top cap and bolt removed?
Argghhhhhh I'm a numpty... now i get you lot.
Removed it all, removed the cap and there's a 6mm allen bolt head that does the preloading 🙂
Sorted... Thanks all... Apologies. First time doing a non-star-nut.
Make sure the bung will be where the stem bolts compress the steerer when you tighten that 6mm bolt.
there’s a 6mm allen bolt head that does the preloading
Well strictly speaking it tightens the bung in the steerer. The 4mm bolt does the pre-loading.
Glad you're sorted. I see this sort of thing every few days so you're not alone 🙂
So i fitted the forks, first using the supplied ‘cut’ crown race, then also with the correct one that was fitted to the forks previously
Happy to be told I'm out of the loop here, but I've never heard of fitting 2 "crown races". Is this some new feature?
Happy to be told I’m out of the loop here, but I’ve never heard of fitting 2 “crown races”. Is this some new feature?
It wasn't at the same time 🙂 2 separate fittings, for testing. Just to make sure it wasn't down to an incompatible crown race supplied by Chinese. But it seems perfectly fine now we've got the correct procedure on the bung