I have the K44 3.25-19 front and the K36 4.00-18 rear on my K1 750, the tyres recommended for this model by Heidenau's site, replacing a Continental 100/90 front and ditto 120/90 rear. The small print on the Heidenau sidewalls says the correct rim widths are 2.15 and 2.50, so the 750's rims at 1.85 and 2.15 are strictly speaking too narrow. The tyres were wider than I expected, like a 90/90 and a 110/90. The good news was that I could fit the front without dismantling the mudguard bolts or deflating the tyre, and the rear was free of the ground when on the center stand - great when you're greasing or adjusting the chain, and neither of which was the case with the tyres I replaced.
Visually the tyres are good quality, the front being a rib pattern and the rear a block, both of which to me look right on this type of bike. So far I've put about 3500 km's on them, mainly commuting to work. The rear seems to lock up easily when braking in the wet, not what I expected. Turning into corners I lack confidence, but when it's leaned over, it's rock steady with neutral steering, neither trying to rise up or fall into the corner, unlike the Continentals I replaced which were downright unpleasant.
I'm happy with the tyres so far but am not ready to give a blank recommendation. The vague feeling I have when entering corners can be down to the rims not having been trued for a looong time, the ding in the front rim, bad front wheel bearings or the slightly bent front forks. It has new tapered steering bearings, bronze swingarm bushings and new collar, plus new Hagon rear shocks (to my defence).
