From time to time, I’ve fiddled with tire pressure settings on my bike, but have settled in at a psi that I think works for me.

The 23 mm tires that came with the bike listed a max pressure of 115 pounds. I used to pump them to 105, for no particular reason, except that 115 seemed like it would give me a really hard ride — just a guess on my part. When I switched to 25 mm tires, I reduced the pressure to 100 pounds for awhile, but lately I’m back at 105 again.

I was influenced by the Sheldon Brown post which says the load tires must support dictates the pressure. Since I weigh roughly 210, the 105 psi per tire made sense to me.

But now, I’ve come across something else. An article from Bicycle Quarterly says the optimum tire pressure is that which results in a “tire drop” of 15 percent. Tire drop is the amount of compression in a tire when it bears weight. According to the article, anything more than 15 percent reduces your speed. If your tire drop is less than 15 percent, your ride will be less comfortable.

A graph accompanying the article shows tire pressures for different rider weights and different width tires. Turns out that I’m pretty close to where I ought to be, but there’s a wrinkle: the tires are supposed to be pumped to different pressures. On a road bike, the weigh distribution is 40 percent front, 60 percent rear. Yipes! In my case, that means my front tire would be inflated to only about 85 pounds, and the rear to 125.

I’ve gone with lower pressures on the front before, and wound up with a pinch flat for my trouble. So while I find the tire drop article interesting, I don’t think I’ll be making any drastic changes in my tire pressure any time soon. What’s your take?

A few weeks ago, I mentioned that I had a warped rear tire that may have been responsible for my broken front derailleur. At least, the tire — because of its bent shape — rubbed against the derailleur.

The derailleur was fixed, and the tire replaced. But now, here’s what the front tire looks like:

Remember, the other warped tire was on the rear. This is on the front. The warp is more obvious when it’s next to the brake.

I haven’t noticed any ill effects from riding on this thing. Last Sunday, it went on a 30-mile ride with no issues. It turns out that this was the tire I did the time trial on two weeks ago, too.

I suppose I should replace it, but there doesn’t seem to be any urgency to it.

So I’m trying to figure out what caused it.

The wheel appears to be true — it’s the tire itself that’s bent.

Some folks have suggested that it’s the way I mounted the tire on the wheel — but this tire has been on the wheel for quite awhile now, since February. The warp didn’t become obvious until quite recently.

Because of all the 100°+F (38°C) days we’ve had this summer, the garage where I keep the bike has been a broiler. I’m guessing late afternoon temperatures inside the closed-up garage were in the 120°F (48°C) range. I wonder if that had anything to do with it? The badly warped rear tire had been hanging from two hooks in the garage most of the summer, until I got it down to replace a tire that had a screw puncture it. I assume the hooks in the heat could have softened the rubber enough to warp it.

Maybe it’s the brand. These are Hutchinson Top Speed Pro Tech Kevlar (whew!) tires. The Hutchinsons are the only tires that have warped. Specialized, Vittoria, and Continentals have been fine.

So what do you think? Have you ever experienced this kind of thing? Should I replace the tire right away, even though it isn’t causing me any problems?

Oh, and before the snarky comments come in — I took the picture after our club ride last Sunday, and washed the bike later that evening.