Felt like I was biking through sand.

CJ pretty much covered the possibilities there - if there was not any sort of mechanical issue.

Assuming you mean nothing physical and I did not see anywhere where you refered to that, I would also check my bottom bracket by pulling the chain off and spinning the crank arms to make sure it is also spinning freely. Just another thought.

It wasnt a flat.  I did increase my PSI and it was somewhat humid.
I actually felt pretty good physically - best all month really.  So it wasnt the way I felt, just the bike felt slow.
It was noticeable on the down  hills too.
Sorry for bike maintenance 101 question, but could it be my hub needs lubricant?  could that be a cause?

Thanks, I will try that.

This happened to me twice recently.  Once I knew the cause immediately (and presumably this was not your problem) -- I had just biked through fresh (as in, steaming) asphalt (I had little choice).  It felt like I was riding with glue on my tires for a while after that (and I guess I sort of was).

The second time (and I suppose this could be happening to you) I finally discovered that the master link in my chain was quite stiff.  (One more reason why I will NEVER go back to that bike shop....)  I replaced the chain and then all was right with the world.

But yeah, often when I get this feeling, it's because of physical issues with me, not mechanical issues with the bike.

are you hearing any sort of creaking, clanking, rubbing or scraping? Was the tire seated properly in the dropouts? Not an expert but if you are hearing anything strange when riding that could help narrow things down, if not your guess is as good as mine!

Thanks, I didn't hear anything too strange, maybe a creaking from time to time, like when going up hill, but nothing too regular, and not while in 'slow mode' going down hill.  I'll check the dropouts and make sure the tire is in properly.

Stay off the beach next time. Should help?

Road surface?

I have been on rides that it suddenly feels like I'm riding through quicksand, to the point I actaully look down at my rear tire several times checking for a flat.  Then it goes as quickly as it came.

I think it has to do with a stretch of rougher and softer asphalt.

Another thought is grade.  Did the grade tilt up a bit that was not noticable?   On my typical ride, there is a section that tilts from about 2% to 3%.  It's not very noticable by eye, but it creeps up on my and I realize I'm going a couple MPH slower and slogging through using the same gear...

Funny, these are the two things I was thinking! That very slight uphill sneaks up on me. We've got freshly paved roads (THANK YOU, STIMULUS!!!!!), but they are still soft and while the ride is much smoother, there's definitely a bit of lag.

I noticed that each time I rode for about a week it was taking more power to keep the same speed. Also noticed increased rolling resistance when coasting...turned out to be broken free hub in the rear wheel. Replaced the free hub and all is great again. There was a slight noise, almost sand-like, that was hard to determine where it was coming from. That was it...free hub.

Possibly bearings in the hub need to be checked out?.....

I had mine done recently when I also felt like the wheel wasn't spinning as freely and the LBS did a good job of fixing the issue.