Steerer extenders?

I've used one it's good so far, here's the original write up.

http://www.retrobike.co.uk/forum/viewtopic.php?f=1&t=235105

@senri:

I had a BBB extender in a Fox fork once. The problem I found was that the steerer tube on the fox fork is tapered on the inside. (so on the top it has a larger inside diameter then on the bottom). The extender was designed for a straight inside steerer tube.
This meant I had to cut down the extender to get it in deep enough; also file of the bottom part of the extender so it would match better with the tapered inside; and finally I decided to add a long bolt and cap to secure the whole thing from the bottom.
I added that last step because it was an all mountain type of bike that I also used in bike parks, so didn't want to take any chances. It never failed on me, headset (cane creek) never came loose. I used it for about 3 years like that.
But now I got a different fork (with full steerer) for the All Mountain frame and the Fox fork has moved on to a frame where it just fits.

Hi Wytze,

That are some good tips! I didn't think that the steerer was tapered, but I didn't really check it either, so that will be the first thing I will do. I have used only a few rings on top, so I guess the big bolt will stick out the bottom, which is a good place to attach another bolt from the bottom. Was that that also how you secured it from below?

Can't remember anymore. But I do remember that the aluminium 'nut' on the bottom of the extender wasn't good enough either; the thread comes out if you try to really tighten things up even though I greased it up properly. So I had replaced it with something else, probably something from a different stem.

Does anyone has an extender at hand? I like to make a provision from the bottom so it doesn't loosen anymore, but my bike is in Italy at the moment. What is the size of the big bolt? M8? Thanks!

the BBB version is M8, BUT not sure about other extenders, AND not sure if the BBB ones are different from other years.

Thanks! Mine is a BBB and it is what I already guessed.