How do I measure tire pressure with Presta valves?
Current guage is built for Shrader and the adaptor I use with my pump does not allow pressure measurement – is there a bespoke guage?

I've got the oxford one from CRC that does both. However, before that, I used an adaptor and a cheap halfords press on type digital guage.

Makes a difference when you start using one. I didn't realise just how firm lower pressures felt. Quite often the 40 psi minimum on some tyres is way way too much.

Must be the style of adaptor I have; sort of a hollow tube that relies on greater pressure at pump end to push the pin in

have you screwed it on far enough? If you do, the presta pin should protrude enough to act like the core of a schrader valve. Does your pressure guage have a pin or cross within the push the pin?

Track pump with gauge is accurate enough

The adaptor has a very positive 'end' to how far it will screw on, the pin is then about 4mm below the top of the adaptor. Guage has a round pin to pish onto valve, but nowhere near long enough to reach

I use a track pump or a compressor with a schrader head or a presta head. The presta head is spot on but the other two are not. Besides, I've found that with some tyre, 5 psi can make all the difference.

You could try filing a few mm off the adaptor so the guage plunger reaches deeper in, but it's probably easier to get a presta compatible guage

Easy vs £19……..
Sounds like easy and then grumble about the cost 😕