I love my Sun EZ-1, but the 16x1.75 front tire needs air before every ride, and 3/4 through today's three-hour ride it needed air again. It has the stock 40psi-max tire in front right now. Will I see improvement a 16x2.00 or 16x1.75 with 60psi? Almost all of the 16x1.75's I've seen advertised are rated to 65psi, and the wider is attractive too, Topeka surfaces have their gaps.

Sounds as though you might have a slow leak in the tube or a loose core in the valve stem.

Another tire won’t do squat for your air loss situation.
Ignoring the possibility of a leak due to a physical conduit, e.g. puncture, leaky valve etc. the easiest fix to try is to shop around for the heaviest tube you can find in that dimension. Thicker tube = less air lost through the rubber.
If you feel up to the task, you can try a Tubeless conversion. On tires with thick sidewalls, you may lose less air through the tire than through the tube.

Losing air between rides is pretty normal, I check mine "before" every ride but going down in 3 hrs. that's gota be a slow leak in the tube. I'd take off the tube pump it up put it in tub of water and look for leak, then patch it. If the tube has been in there a long time you might just need a new tube and I'd recommend some sort of tire/tube sealer (Flat Attack, Blu Goo, Slime, etc. ) or the "tire liners" which ever you prefer! Jmho, Ymmv! Have a most excellent day!

This sounds like a leak to me as well. That needs to be fixed first. You can get cheap replacement tubes at wally mart for this tire. I have a bikeE with a 16x1.75 in the front and I prefer to inflate them not that much. With this tiny wheel potholes have become a lot bigger. Therefore I prefer to dampen it it a bit with a lower tire pressure. Plus the front wheel on a recumbent like the Sun EZ-1 or my bikeE hardly carries any weight.

Thorn Resistant inner tubes.. thicker rubber..

Dismount the tube, inflate it enough to expand it a bit, and then hold it underwater in a sink. You've probably got a small hole, which can be easily patched. Of if you don't want to futz with it, just get a new tube. Holes have causes, and noting where the hole is may give you a clue as to what caused it. If the hole is on the 'outside' of the tube, run a rag around the inside of the tire to make sure there's nothing sharp poking through the tire. And if it was on the 'inside' toward the rim, inspect the rim tape to ensure none of the spoke holes are exposed.

I have an EZ-1 that had Kenda 1.75 tires on it with max pressure of 65psi and just replaced them with Kenda 1.5 inch high pressure tires, each at 100psi. I just put the tires on this evening, but just rolling it around the garage you could feel less resistance. I also looked up the tire size on the owners manual, and it called for 1.50 inch tires on all of the models. This one is an early 2000's model with the ladder frame, red. Fun to ride!

Ah, now that is fascinating. I will keep that as a note for whenever I am ready to replace both!

J.E.B.

We finally got out for a ride earlier today so I got a feel for the high pressure tires. They make for easier pedaling with the lack of surface contact and make a difference on coasting speed too. Going downhill, the speed picked up by about 3 mph from the same hill that had been ridden before. I have the heavier innertubes in them too, so they do not lose the air as fast. Waiting to get out after work some day and see how the speed goes.