I Weigh about 130. I run 100 fr / 105-110 rr

Wow! That gets me down to about 65 PSI. Can't get my brain around that.

Dan

It seems like you'd have to adjust for whether the tire is on the front or the rear. My front tires don't usually show much wear while the rear wears at a slant due to the curvature of the road on the shoulder.

For example, one of the charts above says that I only need 90 psi on the 28 in the rear (instead of the 110 that I always use). However, the chart also says that I should run 105 on the 25 in the front. I'm not sure that makes sense.

Good thread. I think I'll just drop down to 100 psi all-around

I have a Trek Pilot 5.2. I weigh 180. After using 25mm tires, I experimented with 23mm running at 110 to 115. The ride quality definitely deteriorated. I found much more road buzz coming through. I finally gave up on the 23mm tires, and put 25mm tires back on, at 95 to 100. In both cases the tires were Conti GP4000s. The only differnece was the size and pressure. The bike feels much more comfortable again.

But did you notice a difference in performance?

Dan

Since I do not race, the way I measure performance when I try different things is to ride a particular ride. It is 36.5 miles with several thousand feet of climbing, and a lot of twists and turns. I time the ride with each setup, adn repeat the setup a few differnet days. Then I note the elapsed ride time, and the overall ride comfort. Since most of my rides are of this length or longer, being more comfortable probably has more of an effect on performance than it would on a flat out full speed short ride. On my rides, the times were on average the same with either tire setup. The biggest difference for me is that with the 25mm tires at the lower air pressure, I feel like I could continue on for much further, while with the 23mm tires at the higher pressure, I feel more tired and certainly more beat up.

Tire psi and comfort also depends on the specific tire. At 165 I run tire PSIs of 95/105 on Vitoria Rubino pro and 110/115 on Vitoria open corsa. The open corsas are more comfortable and run slightly faster but this is true for all pressures I've tried them at. Experiment for yourself, worst case is you pinch flat.

I run 100 lbs in my 28s and, the ride is sublime. At 110 I start picking up hint of harshness on some surfaces. 100 lbs seems nearly perfect though.

For two years I was the victum of cycling hype and ran 23s. What a revelation the 28s were. I could never go back to 23s.

I been pumping my new contis with a no psi meter pump, It was only at around 60!! felt like it was getting close to 100psi. Not even that! I got a wrenchforce psi meter stand pump and got them to around 110psi. Must say they're quite hard but at 165lb cornering feels better and rolling pick up greatly improved. average speed I don't think has changed too much but acceleration and de-acceleration is a lot faster. Ride feels stiffer also, canning it now on easy cogs. *chuckle*

By "de-acceleration" do you mean heavy breaking?

I find that with my Contis up at 115-120psi, they don't break well. I seem to go from decelerating to skidding in the blink of an eye.