Eight point V bar. From the moment I bought my first set of high quality road clinchers, I’ve ridden at that pressure. I started with that number because that’s the pressure the sidewall told me to pump them up to; I didn’t yet understand much about balancing the benefits of high and low pressures to optimize comfort and friction; I just pumped them up as instructed and off I went merrily down the road.
I’m not as thin as I’d like to be, which is the same thing as saying I’m fatter than I should be, though I certainly hope I climb well for my weight, especially as my third (and hopefully charmed) ascent up Haleakala is looming large in Vajanuary. The point is, I’m not a whippet and even if I starved myself for the next five months and subsist exclusively on IPAs (I draw the line at cutting beer out of my theoretical diet; I might get desperate, but I’m no savage) I’d still be an Eros Poli at best. Being a big guy, the only factor that mattered to me when it came to tire pressure was avoiding the pinch flats that plagued me during my time riding cheaper tires and that meant maximum pressure, no questions asked.
We always dialed our pressure in for Mountain biking and would pull a few pounds out of our road tires when riding in the rain, but by and large, tire pressure was tire pressure, and as far as I was concerned, more was better. I even had a set of 20mm tires on a makeshift TT bike I had that I blew up to a whopping 10 bar. In the last few years, however, the Cycling world has become obsessed with doing the limbo and seeing how low they can go on tire pressure. It all began with an article in Bicycle Quarterly which conducted an extensive and flawed study on the effects of tire pressure and tire width, and concluded that lower pressure and wider tires are faster and more comfortable than high pressure, narrow tires; the idea is that lower pressure allows small bumps to be absorbed by the tire rather than bouncing the bicycle (and rider) in the air, and that wide tires flex more efficiently than narrow tires resulting in lower rolling resistance. Its important to remember that this gain in comfort and efficiency also comes with an increased risk of pinch flats.
This is all well and good, of course, though we always have to be careful to remember the basic principles of such a compromise; lower pressure and wider tires also mean an enlarged surface area which necessarily means more friction; a perfectly hard, narrow tire on a perfectly smooth surface would have almost zero friction, to the point that you’d be unable to gain enough traction to actually move the bicycle at all. What we’re after, in a practical sense, is a balance between the two extremes which optimizes comfort and tire efficiency against reduced surface area and the risk of pinch flats.
I became infected with Tire Pressure Fever myself as the Cycling world became increasingly obsessed with tire pressure. Down went the pressure in my tires and immediately I felt sluggish and lethargic on the bike. Climbing out of the saddle, I could feel the tires flex as I unleashed the Awesome Devastation of the Toothpicks of Navarone. Cornering was like steering in molasses; turn the bars, weight the pedals and then wait a few moments while the bike got round to responding.
These observations first had me reaching for the pump and then got me theorizing about what is really going on with tire pressure and what pressure is right for a given rider. I say “theorizing”, but most other people would use something closer to “guessing assertively”. But that doesn’t mean I’m wrong.
Basically, it comes down to finding the highest pressure and narrowest tire you can that gives a rider of your weight the right amount of tire flex such that your bike isn’t bouncing as it rolls over the tarmac and allows it to roll efficiently, all while minimizing surface area, risk of punctures, and sidewall deformation when accelerating (cornering and climbing are basically the same as accelerating; the acceleration vector is just in some other direction than forward.) This means that each rider at each weight with different preferences on the sliding scale between the above compromises will find a different optimal pressure. Impressed by Tom Boonen’s tire pressure at Roubaix? Tread carefully; that pressure was dialed in based on very specific criteria and unless you’re eating the same cobbles and weigh the same as he does, you’ll need a different pressure to find the same balance. Bicycle Quarterly has a chart that shows what they believe to be the ideal pressure by rider weight, though I don’t believe a word of it; I do however entertain the possibility that I could be missing something based on the fact that I didn’t actually read the article.
Me? I’m still happily riding at 8 point V. I’m comfortable, I’m not flatting, and I’ve got good control. Besides, it just has a nice ring to it.
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What's with the obsessing over 5 to 10 psi here or there? I have two floor pumps, one an SKS and one a Bontrager. They each give different readings. The Bontrager produces a much harder tyre for any given reading. Therefore I am firmly in the camp of 'if it feels right, it is right', but I can't necessarily put a guaranteed number on it.
I've always been happiest at 120psi which is near as damn it 8.V Bar. I've found that with anything less I start to notice the tyre moving about and a little voice in the back of my mind starts telling me that I can only feel the movement because I'm losing air.
I suspect that this has come from spending too much time on the rollers where the bike tends to bob when I'm down below 110psi and working really hard in the middle of a 2 x 20 or full on ten when you really don't need little voices questioning your ability to finish at your current pace - extra voices telling you your're losing air really screw with you as do the ones that tell you that your failure to achieve the principle of silence is bleeding watts all over the place.
The combination of my Dura Ace hubs and tubs is also feels beautiful fast at 8.5V without allowing too much vibration through.
@the Engine It always amazes me just how much he moves his body around in that clip. Classic.
@Fronk,
it's a v. inneresting piece. However, you don't say how tall/weighty you are to get an idea. I used to run 20mm rubino pro's at 130psi until they exploded-frightened the shit out of the girls at the lights-and I had to walk 7K home. I'm 1.88m and much heavier than I should be. I also run the same pressure as you 120psi on all my tyres; tubs and clinchers which gives a silky ride. I've been doing it for so long my cheeks can tell if the tyre pressure is low.
You boys are running some serious pressure......I sit around the 6 and V bar mark or 95 psi in old money. I'm about 81 kg so not that light.
@Nate
Hey, whatever gets you there in your head. Personally, I'm above such trickery like farting to lower my BMI before a climb.
I fart for propulsion and weight loss. Much more rational and a double-whammy to boot.
@unversio
Ah, yes the low TPI count casing and the kevlar belt most likely makes for a pretty stiff tire - surely durable though.
@Monty
I can certainly notice a difference of 5-10psi on chip seal roads. On my aluminum Ridley that can make the difference between finishing a long ride fairly fresh and praying that its close to being over halfway in. So much is made of the difference in ride quality between frame materials (e.g., aluminum is harsh, steel is like butter, carbon absorbs road buzz) but then people throw stiff tires on and pump them up until they feel like granite. Ride quality can be dramatically enhanced/altered by careful tire and tire pressure selection.
@Dan_R
FMB also has a pile of other tires which I assume are as supple. The only problem with FMB is that they realize they have a quality tire and they charge accordingly. When I say "They" I mean "Francois" as I don't think there is anyone else working for him.
@piwakawaka
This is a beautiful viewpoint: use your ideal tire pressure to decide what your ideal riding weight is. It's so backwards its forwards!