Originally Posted by Morelock

There are minor adjustments you can make to the SILCA Hiro, specifically the gasket preload. To do this you need the "arm" in the open position, then slightly (small amounts) turn the "face" of the chuck, likely clockwise.

Most issues I see people have are either ^^^ or by ramming the Hiro down on the valve as hard as they can, which has the potential to damage the gasket. There is a big red "button" on the back of the chuck that looks like it's just begging people to press down on it... it's much better to press down firmly closer to where it screws onto the schrader, then turning the lock lever.

It takes a little bit of finess and playing with it to get it right, but you should definitely have no problem getting well over 160+ psi once it's installed correctly on the valve.

Troubleshooting
- if air is leaking from the Chuck - check the preload, check the gasket for damage
- if air is leaking further back - check the pump, check the connection from hose to chuck
- if Hiro is popping off the valve as you're inflating, you are not getting a firm enough "grip on the valve with the chuck... check preload, check lever arm tightness, check press down force to establish connection (too much or too little) check valve - test on different valve.

failing all that, contact Silca customer support, they should be able to better diagnose the issue.