Hey Everyone,
Getting back to the bike after a few years away, had a few medical issues that required I take some time away. I have a Surly DT, and I've talked my brother into getting a disc trucker for himself. So we're planning some tours for the '26 season, and as my bike is easily 12-13 years old, give or take (I bought it used) I'm looking to make a few upgrades.

My tires currently are Continental Contacts and I suspect they're original. I remember when I bought the bike it was listed as a 56cm however I never did verify that number. I road it when I bought it and felt like it fit me perfectly. So looking at the tires, they look good but again are old. I'm not clear on tire sizes but what I see on the tire is 37-622 and along the white wall it appears to show 28 X 1 3/8 x 1 5/8. Is it safe to assume these are 700cc tires?

Finally I am considering upgrading the tires to Schwalbe Marathons but I'm not sure what size or even which specific tire to get. I ride mostly paved rail trails and roads here in central Florida, That said I am planning on another GAP > C&O canal ride next year and hope to land a RAGBRAI slot next summer as well. Recommendations for great touring tires would be appreciated.

Thanks!

My current old tires

This says 28 x 1 3/8 x 1 5/8?

This was from a GAP and C&O canal ride in 2016