I installed a Heidenau K69 front tire. The Cdn dist for Heidenau asked me to try it out and give them feedback.
Needless to say it's a very open and aggressive dirt tire. The casing isn't heavy duty either so I set them at 35psi and kept them there (don't need to add any more dings to the rim
) and they still did well off-road.
I suspect it wasn't designed with 500lb adv bikes in mind it never did anything unpredictable even on cold damp pavement (didn't push it too hard on that knowing what it's designed for). There was a little bit of a light feeling and only a little wander/ squirm.
In the dirt the tracking was great and braking grip was great too. Cornering grip was also good. Terrain was a variety of dirt, rocks (all sizes and with shale) and some sticky mud.
Didn't get any sand but I imagine they would be good there. Being a soft conditions tire I don't expect long life and I haven't had it on long enough to speculate.
If you're looking for a good soft conditions tire I think it's worth a look.
The rear would also be an option but sadly they don't make it in big sizes yet.
I'd like to see a Heidenau in between this and the K60s.