I have an older 25c Vittoria Rubino on the rear with app 3500 miles.
I brought the tube up to 115 this morning, which is what I always run it at.

Along the ride I started to "feel" the rear sag. I hit a small bump and really felt the rim take the shock. I pulled off and checked. Sure enough it was going flat.

I hit it with a CO2 pump and brought it back enough to get to work that was at 8 a.m.

I just checked, 2:50 pm, and it is soft as a baby's butt, but not flat.

This is the second tube in four days. The first one also developed a small slow, painfully slow leak. I thought maybe it was the Bontrager tube, cause I usually use Kenda, but after this little thing I am thinking that some small particles are getting into the tire and abrading the tube enough to cause small, slow leaks.

Would this be a correct assessment?

When I checked the tire and rim during the reinstall of the new tube I ran my fingers backward and forward along the underside of the tire. I checked the rim track and did not find anything on either surface.

I am going to limp home unless it would be worth my time to find the leak and attempt a patch.

BTW, that CO2 pump is fast!!!