When I first starting racing, I would pump my tires to the maximum PSI on the label. I often would be at 150 PSI. Then on one long hilly road race, my rear tire exploded. I kind of new it was because of the high PSI combined with heat, that made things go BOOM!
I pumped up my tires so high because I thought it made me faster. Heck, I even cut my chain too short once thinking that it would make for less drag on the rear derailleur, but let's not get into that. Back to the PSI, when pumped very high, you tend to feel fast because you feel all of the road buzz. Feels fast, but it's slow.
So, after the big BOOM, I started pumping my tires to about 120 PSI. This seemed fine for years. Then a few years ago I dropped down to around 105-110 PSI. Things felt better but I wasn't sure, perhaps I was losing speed?
Then last year I dropped down to 100 PSI and finally realized, I wasn't going slower, if anything I was moving faster and with more comfort.
This year, I've been on a sharp drop in PSI. First I went to 85 PSI, then 80 PSI and now 75 PSI. I don't worry about pinch flats since I use thorn resistant tubes. While possible, the probability of a pinch flat is low.
I ride a lot of bumpy, chip seal roads. The low PSI makes me more comfortable and also faster. The reason is the tire deflects and absorbs the bad surface, rather than bouncing over the bad surface.
I also now ride 700x25c tires. My next tire will most likely be a 700x27c (Challenge parigi-roubaix) and I expect to run those at about 70 PSI based on some conversations I've had with others using them.
So, although counter-intuitive, if you want to ride fast, try dropping the PSI down, way way down.
