Hi there again mate,
Re the disk from the Dommie front wheel... no it wont fit the TA, however the Africa twin front disk will fit the Dommie wheel, and is the right size for the TA.
Re AT wheels on the TA, as far as I'm aware, yes they will fit, but beware of the fact that AT wheels have duel disks at the front, so unless your Alp is a 97 onwards model (as this is when the TA changed to duel disks at the front), you will strugle a bit.
Alternative to this is as well as the wheel, you could swap the front forks aswell to give the mounting points for the second caliper, although this then means further expense of the forks (although you could get most of this, if not all of it back when you sell your original forks again...

), another caliper, replacing the brake lines and a second set of pads (most of these available of Ebay).
The advantage whould be increased stopping power due to two disks at the front, which isn't really a disavantage compared to a smallish cost layout, is it...
I'm sure that someone else will be along soon to offer another solution, but thats what I'd be looking at doing, if you cant find either a TA front wheel, or a Dommie one.
One further option for you is... As I'm changing my wheels I will have a spare front wheel, with a fairly new disk attached, and front tyre with approx 2-3 mm tread left on it. But firstly, dont get your hopes up for this too much, as first dibs on this wheel have gone to Warthog, but if he doesn't need it anymore than it could be yours (and also the fact that it is still on my bike at the minute, as funds ran out for me to buy a AT disk for the Dommie wheel...

).
Titch.
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