Can I estimate tyre pressures on a road bike? Can I estimate my road bike tyre pressures by pressing my thumb into the tyre? I don't have a tyre pressure gauge, and feel that the tyres on my new Merida Scultura are pumped too hard.
No, not really. It is difficult to get an accurate idea of tyre pressure by pressing it.

Especially for thin, high pressure road bike tyres - they should feel pretty hard. Even if they do feel hard, the pressure may be much lower than it should be.

Best option is to get a good pump, with a built in pressure gauge. Many mini pumps will take a lot of effort to get the pressure high enough, a 'track pump' would be a lot easier.

Tyres do lose air over time - especially thin, high pressure tyres - so it is a good idea to check them regularly, and inflate as required.