I have fitted a pair of the above to my cross bike and tbh they are little better than old skool cantis. Pulling the lever back to the bars results in a feeble amount of grip on the rotor and stopping (even on the road) is unpredictable.

I have cleaned the rotors with disc brake cleaner, so there is no grease on them. All I can think is that the pads are pants or I need to adjust them – though I can see no way of getting any more tension on the cables.

Has anyone else had this problem and if so, any hints on set up to save me piling into the back of a car/lorry/van/rider next time I am out?

They need frequent adjustment!

There’s a dial on the wheel side for moving the non moving pad in towards the disc. With the moving “outside” pad you just need to slide the gripping screw further up the cable to move the pad in towards the disc at rest.

I think there are better systems out there!

Hope that makes sense

if they’re the CX77s, I set mine up with the cable tight while the brake levers are released (as in released to allow the wheel to be removed with rim brakes). Then after centering the caliper, wind in the spoke-side pad till it’s one click off skimming the disc, and tension the other side with the little screw on the outside of the caliper. Once set up they’re mint, and rarely need adjusting. I also found the OEM pads got grippier after they’d bedded in.
EDIT – as above!

Have you used compressionless outer?

I once wired up some cable disc brakes with some nondescript outer I found in my spares pile and the front was poor but the rear (which had full outer) simply didn’t work at all. Couldn’t even lock the wheel while pushing the bike. Replaced it with compressionless stuff and bingo, proper brakes.

Fettling time coming up!

The outer is standard Shimano outer I think, though I did ask for compressionless. I’ll have a gander later.

As above, I’ve found they perform pretty well once they are set up properly. I’ve just replaced the oem pads after a year of mixed on and off road use

As above my mechanical disc brakes (BB7s) took a lot of getting before I got a good level of performance out of them. Makes me wonder how much more I could get out of my hydraulic brakes if I did the same!