Fork steerer diameter

[ChristinaJL]

A friend kindly gave me a carbon fork with carbon steerer for my road bike which I took into my LBS to cut etc. However, they've run up against a problem. The internal diameter of the fork seems to be 21mm (I think) and it won't take either a 1" or 1-1/8" expander bung in the carbon steerer tube as it's too narrow. The mechanic has tried filing down stuff they already have but to no avail.

Anyone got any suggestions as to what we can do? They've tried looking online and can't find anything that might fit. Or should I just give up and splash out on a new fork, which I was hoping to avoid doing this side of Xmas.

Thanks.

 

[RecordAceFromNew]

Are you sure it is a 21mm outside diameter? This table lists what are generally used.

 

[andrew_s]

Try a headlock in place of a bung?
A 1 1/8 version should be easier to trim down than a bung if you can't find 1"

 

[ChristinaJL]

Are you sure it is a 21mm outside diameter? This table lists what are generally used.

Actually, the LBS told me the wrong thing, the 21mm is the internal diameter, external diameter of the tube is 23mm or so they told me.

 

[ChristinaJL]

Try a headlock in place of a bung?
A 1 1/8 version should be easier to trim down than a bung if you can't find 1"

I'm not that technical but would that be ok for a threadless internal headset?

 

[andrew_s]

It should be OK as the headset is all on the outside of the steerer, apart from the bung or starnut.
It does depend on the bottom of the steerer tube being open. Basically, instead of a short top cap bolt going into the bung or starnut, you have a long bolt going to a cap/nut on the bottom end of the steerer.

If it's 21mm inside, the 1" version of the Deda expander bung claims to go down to 20mm. 1" threadless is fairly rare, so you may have to put an order in and wait