Having got Mrs B some carbon forks for her mtb, i need a steerer bung in order to fit them.

Are they all the same? Any recommendations? Is it correct that the bung has to extend to the area the stem clamps?

Thanks

Ian

This is all you need they work very well

https://www.planetx.co.uk/i/q/FSPXFBUMK2/planet-x-carbon-steerer-fork-bung-mk-2

This is all you need they work very well

That one won’t probably won’t fit an mtb steerer.

it doesn’t ‘have to’ but unless you are a weenie then it’s a good idea to have a longer one, to offer some support.

I prefer the ones with springs around the wedge part. Gives more adjustability than a fixed central shim (like the one above). Something like this:

https://www.ebay.co.uk/itm/New-Packaged-BBB-Powerhead-Road-Bike-Fork-Bung-Top-Cap-For-Carbon-Steerer-1-1/323684778529

Something like this:

That won’t work either.

OP – you need one designed for MTB steerer’s – they have a different internal diameter.

I’ve used the Exotic bung with no problems.

https://www.carboncycles.cc/index.php?s=0&c=70&p=637

That won’t work either.

OP – you need one designed for MTB steerer’s – they have a different internal diameter.

Do they do MTB specific ones? Not obvious in the CRC listings.
This one is what I’d think would be right, and one of the reviewers says “Perfect for my MTB”
https://www.chainreactioncycles.com/bbb-powerhead-compressor-adjuster-bap03/rp-prod29884

I prefer the more knurled ones – one I had like the PX above kept coming loose (An FSA IIRC)

I don’t think they do have a different internal diameter. It’s just that Hope (and others) do a Head Doctor style plug that’s designed for aluminium forks which have a slightly larger diameter. For carbon forks, you usually find that the steerer wall thickness is a little thicker than Aluminium, so the Head Doctor is a tight fit at best. But in Carbon, they should be the same and work the same. Certainly, I’ve used expanders like the above for both MTB, Road and Gravel carbon forks from 2007-2020.

Do they do MTB specific ones? Not obvious in the CRC listings.

From the P-X listing linked above;

Please choose the Silver fork bung for MTB forks

I couldn;t see one but several carbon bungs I’ve had have come with a spacer that you fit/don’t fit (maybe that’s for carbon or alu though.

I’m just aware that there is a difference, not quite sure what it is and don’t want the OP buying the wrong thing and it going pear shaped.

Please choose the Silver fork bung for MTB forks

Very helpful of Planet X to advise you choose something they don’t have! 😆

Yes they do come in different diameters, find the spec for your fork, google “carbon fork stearer bung 2x.xmm” and buy whatever comes up.

I think mine’s from brand-x.

You could probably get away with over tightening a smaller one, but I assumed the segments were profiled to fit a certain diameter, better it pushes out evenly than just having 4 points of contact.

Road or mtb an 1/8th fork(all are at steerer end) Apart from Giants overdrive 2. it’s same diameter bung.

Thanks all! Ordered from Exotic 🙂

the outer diameter is 1 1/8. Fine. But bungs go inside, not outside….

So …carbon steerers have slightly smaller internal diameters than aluminium, as the wall thickness is greater. Hence why Hope bungs fit alu but not carbon.