I couldn't find a replacement steerer, my forks were OK so I didn't want to replace them so I looked up extenders.
The BBB - BHP 21. These have been mentioned a few times so I thought I'd give one a try.
Steerer too short, It only caught the first bolt of the stem.
I rode it like this around Cannock but it was always in the back of my mind, not good.
Also I do like to have a spacer below the stem onto the headset, I have no idea why.
The BBB BHP-21.
Advertised as 25.4/28.6. This is the 1 1/8 size. 25.4mm internal dia of the steerer tube (the diameter of the BBB quill stem extender), 28.6 external diameter of steerer (the ext diameter of the BBB spacer/shims).
Whack out the star nut, with a cloth on the front tyre so it doesn't fly across the garage.
The bottom nut of the BBB is keyed? into the wedge to stop rotation? or make a lighter wedge?
The BBB spacer/shims have a key to stop rotation and are split to tighten to the extender. They fit quite tight to the BBB, flip'n'slide 'em off with a screwdriver.
A bit of grease on the wedge, fits nicely into the fork steerer.
The through bolt to the wedge is tightened, then the stem cap bolt tightens into that.
Judging the height with the stem. I kept the quill/wedge tightish to stop it dropping into the steerer.
With the BBB spacer/shims in place. A finger up the fork steerer to hold the BBB at the right height helped.
This bit was as fiddly as Jimmy Saville. Getting the height right to pre-load the headset was a pain in the ass. The supplied stem cap bolt just wasn't long enough, no matter how I tried to rearrange spacers and the BBB. I ended up finding a longer bolt.
All done, I popped a spacer on top of the stem when getting the height right, I didn't feel the need to change it.
I did wonder about sitting the stem on top of the h-set and bolting as much stem as possible to the fork steerer. The BBB is well made though and with the wedge/quill bit tightened nicely it seems solid enough.
I do wonder if the steerer was way short and the whole stem clamped to the BBB would it be solid enough. The instructions show it as fine to do so.
I guess it would even be OK if the fork steerer didn't make it through the headset top, but you'd be relying on the quill/wedge tightness to hold it. But then that'd bee the same as the olden days. Well aparty from your forks falling out too.