I've had a Topeak digital gauge since my first tour 17 years ago. At the time I got it because I didn't have a gauge on my pump and I'd learned not to trust my 'feel' for pressure on the Schwalbes I was using. Even though I now have a pump with a built in gauge I find it's a bit crude and still carry the Topeak. I check tyre pressure every morning before hitting the road and I reckon it's saved me quite a few punctures. The 1.75 Schwalbes need to be between 45 and 75 psi, and I generally keep them between 50 and 65.