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Road Bike Tire Pressure: A New Trick for an Aging Horse

October 2014
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The other day I wrote a post about my experience with tire pressure. As a summation, I’ve always maxed out the pressure figuring I was getting the best of rolling resistance though at the cost of decreased comfort. One of the mechanics at the local shop suggest that because I’m not heavy, opting for 120 psi (or even 115) would be better on my wheels when it came to bumps. I heeded that suggestion and found that speed wasn’t sacrificed and that the ride was vastly more comfortable.

In the comments from that post a friend who authors PedalWORKS suggested another option and presented this link.  Following it takes you to a calculator that takes your weight, the bike’s weight and the distribution of weight over the tires, mashes them together and kicks out a rear and front tire pressure based on the idea that the front pressure doesn’t need to be as great because weight is distributed unevenly between the front and rear of the bike (60/40 in my case with a race bike on 23 mm tires)… It suggested I inflate the rear to 116 psi and the front to 76 psi.

Now, let’s see, how to put this kindly… Yeah, there’s no way – even rounding up to 80.  I’m not riding a squishy bike, I’m certainly not riding on squishy tires.  You could pull out a superstar mathematician (LOL, yes I did, only in the movies folks) to show me the math that proved beyond a shadow of a doubt I wouldn’t lose any speed and I still wouldn’t buy it.  On the other hand, just for giggles I inflated my rear to the normal 120 and the front to 110 and you know what? It’s more comfortable, by a lot and even if there were a bit more resistance, I know I can muscle through a mere ten pound difference in one tire.

More importantly, if you follow this link, you’ll see that a tire must ride flatter to conform to this method of filling one’s tires…  If you’re rolling on 23 mm tires (as most road cyclists do), imagine what a nice, sharp pebble would do to a tire rolling that flat.  When you’re pushing 110-120 psi the pebble gets shot to one side of the tire.  Rolling over that pebble at 80 psi, the increased chance of a puncture should be obvious.  If that weren’t enough of a reason to modify the 15% drop method of inflating tires, one must also consider pinch flats when rolling over train tracks.  In other words, I won’t be trying 80 psi in my road bikes any time soon.

That said, with the minor change in pressure and the addition of my new carbon handle bar, the ride on my Venge is exceptionally more comfortable to ride than it was just two weeks ago – which is really saying something because it was a decent riding bike to ride in the first place.

So if you’re looking for a little more comfort, try dropping the pressure in your front tire ten pounds or so.  Chances are, you’ll like it.


21 Comments

  1. PedalWORKS says:

    Like you, I don’t follow the 15% method exactly but I do ride with a softer front. On the 23s I am supposed to inflate to 100 rear / 75 front. I usually inflate to 110/90 and , since I have been doing this, have not had a single flat (at least not on that bike).

  2. fastk9dad says:

    I don’t particularly like the 15% drop method. I use this Michelin chart as a guide and then vary the front & rear by 5psi. http://4.bp.blogspot.com/_ZAH-FFk7Ing/TFxxIiEbtQI/AAAAAAAAAFE/2ANzMN6F_Z0/s1600/Michelin+tire+pressures.jpg

  3. Daniel Weise says:

    Ahh to be light enough that lower tire pressure didn’t increase rolling resistance dramatically. I run my larger (32 mm) hybrid just a shade above their max 84 psi just to keep rolling smoothly. when you are putting a heavy load on the tires, every pound of pressure counts. Of course we are not talking about 23 mm tires here so the ride is acceptable at the maximum pressure, but I can tell when I’ve lost even one pound of pressure in terms of the increased rolling resistance. Amazing what 500 lbs of bike and rider will do. 🙂

  4. I came to this conclusion a while back & have been running on 90/110 for a while, nice to know there seems to ba a justification for it.

  5. MJ Ray says:

    Your front carries two thirds the weight of the rear, so why can’t you accept it only needs a fraction of the pressure?

    It’s not completely proportional because you never want to run a tyre flat, plus it varies a bit by tyre stiffness and is constrained by the min and max pressures.

    • bgddyjim says:

      Because the ratio is off first. And it’s 60/40, not 2/3 (66/33). And 80 psi on a 23 mm tire is too squishy IMHO. And if I followed the 60/40 ratio, I’d be inflating my back to 120 and my front to 96.8 pounds (give or take), not 76 pounds to achieve the 15% drop.

      • MJ Ray says:

        60 * 2/3 = 40, or has my arithmetic deserted me completely now?

        But the other bit I was trying to say is it’s not going to be exactly 2/3rds because the minimum isn’t zero, it’s somewhere between zero and the minimum recommended pressure.

        It all varies by tyre anyway, so if 80psi feels wrong on your tyres, go harder, but 110 seems like it’ll be too much unless you’re riding something extremely supple – although as you probably ride full-on race tyres, they’ll be far more supple than my “active” tyres.

      • bgddyjim says:

        Apparently it has. 2/3’s is 66%. 1/3 is 33%

      • bgddyjim says:

        60% is 3/5. 40% is 2/5. Get it?

      • bgddyjim says:

        Oh, and yes I do run racing tires. Riding below 110 makes too much work. I told you right at the beginning of the post this was going to be the most controversial subject I ever covered. I wasn’t kidding.

      • MJ Ray says:

        Oh yeah, this might amuse you: the 28mm front tyre on my weight-carrying hybrid is usually 65psi; the 37mm tyres (ye olde 28×1⅜”) on my comfy roadster are 60psi rear and minimum pressure front (50psi at the moment I think). The roadster still does a decent speed… it just takes a while to accelerate up to it!

      • bgddyjim says:

        Not at all brother, we ride what we like! I was careful to clarify that we’re talking about road bike tires, 23 mm to be exact. They’re rated for 125 psi and the rolling surface is only a quarter of an inch, maybe a half when they’re worn. 25’s are good to 120 psi (my wife rolls on those). Your wider hybrid tires require much less pressure to maintain their shape than do skinny tires. My mountain bike tires (2-1/2″ I think) roll well on 45 psi.

      • MJ Ray says:

        Yes, but if your front tyre carries 40% of total weight and rear carries 60% of total weight, your front is carrying ⅔rds = 66.666…% of what the rear carries. 60% * ⅔ = 40%, or 60% * 66.666…% = 40% if you prefer.

        Maybe my fault for mixing fractions and percentages and confusing the matter but it’s just how it looks to me.

  6. dagowop says:

    Not to stir the hornet’s nest or anything but, I’m with you on this. I like my tires inflated…a lot. Even when I was much lighter I was riding my rear tire at max pressure with the front slightly lower. I never thought much about the science behind it, it just feels faster and more comfortable.

    And isn’t that what the answer to this question of tire pressure be?

  7. xVx cyclist says:

    I fluctuate around 70kg and run 110psi front, 120psi rear on both my beater (cheap 23mm Vittorias) and my GT (25mm Conti GP 4000 S2s). These pressures really suit me, but I can feel a huge difference between the cheap 23mms and the good 25mms. Obviously tyre pressure affects rolling resistance, but tyre choice is a major factor.

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