Tires for 28' city bike (622x19C) to reduce rolling resistance? I've got a simple city bike that needs some new tires. The bike has been fairly hard to ride lately, and I would like to speed it up a bit. The rims are 28' 622x19C, the current tires are 47mm or 1.75' according to the imprint (although 47mm = 1.85').

It feels like the rolling resistance is too high, compared to similar bikes with thinner tires. Now I've read that thinner tires should have a higher resistance in theory (because there is a larger contact area in rolling direction). But my feeling from comparing several bikes (not MTB or racing, but very similar ones with differnt tires) is that thinner tires feel faster and seem to have less resistance (probably because thick tires have a larger contact area perpendicular to the rolling direction - think of a car tire as the extreme case). Note when I say "thinner", I don't mean like a racing bike, but 37 or 40 mm instead of 47.

So, how to decide what tires to put on the bike? Will thinner tires (optimally inflated) reduce or increase the percieved resistance?

Or do you think I've just been riding with too low pressure all the time, and the current tire size is fine? If thicker really = faster at optimal pressure as they say, maybe the thicker tires also tempt people to use not enough pressure? Otherwise I can't explain my gut experience that the thick tires feel slow.
I have replaced 2.0 (50mm) Schwalbe Marathons for 1.35 ones, and that made an ABSURD difference in my roling resistence. I was feeling burnt out by commuting, and since then I started to feel "exercised", getting to destination much faster and/or with less effort.

Then I got a bike with 700x23 tires, and THAT is good, concerning speed and low effort.

The only thing I think is very important: these skinny tires work fine, even with not-ideal road condition, if the bike has a more performance-oriented position (a firmer grasp on the handlebar - which is lower - , less weight on the saddle). If you take a more upright citybike (the first bike I described), the extra speed gained from thinner (not skinny) tires can make the bike too uncomfortable if road condition is not good.

I have also heard those theories about "balloon is the new fast", but that seems very non-scientific, since the "studies" never describe the parameters that varied versus those that remained constant, not to say other methodologic steps. As for me, narrower is obviously always faster (which doesn't mean always better).

Hope this helps!

(by the way, I think 32mm is a good number to try)