Thanks for coming online and sticking your neck out 
Iâm happy we take whatâs on the tyre as minimum and max - hard to argue against that. 
If weâre looking for optimal performance (getting faster) though - One of the points above is that silca uses a âmeasuredâ width, giant doesnât state explicitly. Giant course 700x25s are a measured 28.
Giants calculator gives you a âstarting pointâ but silca is aiming for optimal.
To further support @Wheatstraw53 s point, this review says the SLR2 50s have a max of 125psi:
Thanks so much. You made it very clear and itâs good to know. Iâll run the Gavias at 80psi as Silca suggests and eventually replace them when they wear out with some 30mm ones.
Iâd personally ignore what the dealer said in this thread, and stick below 73psi. I suspect many others here are of that same opinion tooâŚ!
I think theyâre confused, and I think itâs very dangerous advice.
Here is Giantâs recommendation for a 23c on 19.4mm internal hookless rims with a max 129 kg rider. Hmm. Giant has it wrong then?
Link to Giants tire pressure calculator: Tire Pressure | Giant Bicycles US
The dealers words match Giants official marketing. As long as you stay with these tyres or other approved tyres, you can exceed the 73psi for hookless as long as you donât exceed tyre psi limits or that of the rimtape.
Giants hookless tech write up and tyre compatibility chart here
And for your other confusions, psi from a tyre safety standard is as the 700 x 25 printed measurment. For optimal tyre pressure, it is based on its current measurement that you do with calipers, the ~28mm.
I must admit that Iâm a bit surprised by @Wheatstraw53 information, and he seems correct. As long as you are using the Giant combo, youâre safe to exceed the famous 73.3/72.5 PSI.
Seems odd. Especially since that review mentions how easily the tyre goes on with a single lever. Whatâs their secret sauce? 
I think a lot of it is just that theyâve done the testing with those specific combinations to be confident that the setups are safe. Giant is traditionally a conservative company when it comes to safety so it gives me a lot of confidence in them.
For their own tires, they use a combination of Kevlar and carbon material that is supposed to be less susceptible to stretching than other the beads of other tires.
To your earlier point, they certainly are in conflict with ETRTO guidelines, so each individual should take all that into account and do what they feel comfortable with. I personally prefer to run a larger tire at a lower pressure, but I have run 700x25 Giant tires on SLR1 wheels at 90psi for thousands of miles without incident.
The 25mm tyres arrived closer to 29mm wide, although I donât know what pressure is in them. Anyway, canât wait to give it a ride after years riding old steel frames.
Well, one thing is true, itâs a beautiful bike indeed! Congrats.
Thanks. I found a good deal. Last yearâs model (which was the exact same) in red was even more heavily discounted and it was hard decision. Hopefully, Iâll have it for many years, so itâll be worth the extra money. I do love the look of it.
I love fresh bike pjorn in the morning. 
welcome to the propel family ⌠that black is stunning!
Thanks. Going on a the maiden ride today between my sonâs football training and taking the other son to a friendâs birthday party. With a dream bike I need to somehow find the time to ride more.
have a great one! really beautiful. this oneâs mine:
Great colour. Looks like a nice place to ride too.
Indeed, itâs the land of Pogi.
