Just buy the teeny little presta to schraeder adaptor - usually about 3.00 at most LBSes.
Loosen the presta nut 1-2 turns and tap the presta nut once, install the adaptor. Then use your pencil guage as you would with a regular schraeder valved tube.
When done, you can store the adaptor in your bag or take the adaptor off - close the presta nut - and then put the adaptor back on.
But it might get stolen...
=8-)
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5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life