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?
That is interesting. I’ll have to ponder putting a 25 mm on the back for next season. I’m ~195 lbs, plus ~20 lbs for bike, 60% rear load would put me at about 140 psi for a 23mm tire and 120 for a 25mm…
Interesting. I am also worried about pinch flats on the front if you drop it to where it says you should be.
I pump my tires as hard as I feel like. In summer ,with all the clubs out in the week end, it is usually in the 7.5bar/110 psi range (I weight around 59kg/130lbs). The ride is HARSH, but I feel fast (and after “serious” test, I am actually a bit faster). In the winter, when I want more comfort and there is nobody to chase and nobody chasing me, I am around 6bar/90 psi. I use 25mm tires, and the speed is exactly the same with 23mm tires. Since i began to ride seriously, two years ago, I never had any pinch flat, even when I used the 23mm.
In relation to the article about tire drop, i am so far to the left of the chart that it does not means much. I should pump my 25mm front tire to 3.5bars/50 psi… I made some test at 5 bars, but the speed drop was noticeable.
I mostly ride a commuter bike w/ 28mm tires, and for my weight plus bike weight it looks like i should then be riding with about 75 psi rear, 65 psi front. That seems a little bit squishy to me… I prefer about 5 psi more on each. I’ve been riding with the rear more inflated than the front, and that part of it does make sense to me.
I’ll note that while the article discusses comfort and efficiency, it says nothing about flats (pinch or otherwise).
I always put my front tire 5-15 psi lower pressure than the rear. On my touring bike, I have 700×37 tires and run about 60/70. On my mountain bike, I have 26×2.1″ tires and run about 40/45. Could go lower on the front, on the mountain bike, and I probably will try that soon.
But, this all varies depending on the conditions, and what kind of riding I’ll be doing.
I have gone with lower tire pressures as well only to get pinch flats. I have settled between 110-115psi and have had good results. This is on Gatorskinz 700×23 tires. Ride seems comfortable as well.
Charles Cushman says
Bicycle Magazine just had an article on this as well. Based on my weight (160) my tire pressure should be 100 psi. I actuality I fill them to maybe 105ish. I actually have never been that attentive to how much air I have in them as long as it is above the minimum. Maybe I should care more…