Under Pressure

Air gauges 1

I’ve been busy lately with work and family but I have been riding! I’ve been posting pictures on Instagram; it’s quicker and more fun to snap a picture and ‘gram- it than it is to blog about it. Every ride does not need its own written summary when a picture can paint a thousand words.

The picture above needs some explanation, however. For the past year or so, I’ve been trying different tire and pressure combinations in order to find that “magic carpet” ride on my bikes. My mountain bike is the easiest of the three. It gets 29 psi in the front tire and 32 out back, running a Stan’s Tubeless set up. The road bikes, on the other hand, require more experimentation.

I tried using a formula to find my optimal tire pressure, taking into account the weight of the bike, my weight and the amount the tire compresses with me on the bike. The formula consistently gave an answer of 160 psi for 28c tires, a preposterous number and well above the manufacturer’s suggested maximum pressure. So it’s back to old school methods: using a tire pressure gauge and tweaking the pressure based on ride characteristics.

Tire pressure in cycling is an often overlooked data point. Too much pressure and the tire will ride like a brick and you’ll lose some valuable contact patch needed for handling. Too little pressure and you’ll bottom out or pinch flat. Most people think they can assess tire pressure using the gauge on the tire pump, but that gauge is measuring air pressure in the pump’s hose. It is not an accurate measurement of the tire pressure. You want tire pressure, use a tire pressure gauge.

Air gauges 3

I’ve been using this gauge for several years and it works. It fits on my Presta valves with little fuss and produces a measurement. My issue with the gauge is its size and precision. I’ve reached the age where I need reading glasses and, even with the glasses, the dial is difficult to see. The dial precision doesn’t suit my needs either. I want to see pressure in individual units; in other words, I want to know if the tire is at 78 or 79 psi. I know, I’m fussy.

Two weeks ago I was watching behind the scenes coverage of some bike races and I noticed that a lot of the wrenches were using digital tire gauges.  The two mostly commonly used were the SKS Airchecker and a model by Topeak.  The Topeak model consistently garnered complaints about causing air to bleed from the tire, so I ordered the SKS device pictured above. At $25, I figured it was worth a try.

I’ve been using the Airchecker for two weeks now and I can say that it is serviceable. I won’t go any higher on the rating scale because it could be better. Most of the negative reviews on the Airchecker say that it is fussy. If you don’t put it on exactly “right” it will produce a nonsensical reading. I concur.

The first three times I used it, I got ridiculous readings of 8 psi, 57 psi and 37 psi on a tire that was mostly inflated (my thumb test suggested it was at 55 psi, while the analog gauge read 60 psi.). I very nearly packaged it up and sent it back, but instead decided to hang onto it for awhile. Here’s what I learned:

  • You must hold the valve stem steady with one hand and slide the gauge on with the other. See picture below.
  • For Presta valves, do not unscrew the valve all the way. I found unscrewing about 90% of the way works best. Going all the way seems to provoke crazy readings…maybe the gauge cannot engage the valve properly with the nub fully unscrewed
  • Put it on deliberately. Hold the valve and firmly affix the gauge and push it onto the valve in one motion. When you hear the beep, remove it and read the number. No beep means it did not take a reading.
  • If your Presta valve core is even slightly bent, it will leak a little air and mess up the reading
  • If you hear air leaking, expect the reading to be wonky
  • Evaluate the reading with your common sense

Air gauges 2

The last item seems to be most important from a practical standpoint. You should know what your tires feel like within a couple of pounds. The Airchecker ain’t perfect but it works if you have patience and can be methodical. If your fingers tell you that your tire is mostly at the correct pressure and the gauge tells you something completely different, you have a choice to make:

  1. Go riding
  2. Spend the rest of the day taking serial measurements, create a log and complain to the manufacturer

I’d go with Choice #1. The Airchecker takes some practice. More practice than it should, really. I cannot understand why it’s so difficult to make a good digital gauge; in other words, one with the head of that analog model and the digital guts of the Airchecker. Maybe the folks at DARPA could get on this mission for us! But seriously, it takes some practice, but don’t expect to get it perfect the first couple of times you use it. And don’t spend the whole day fussing with it if you get frustrated because you’ll only get more frustrated. Ask me how I know.

After a few sessions of using the Airchecker, I’m reasonably confident that it gives accurate readings as long as you get it on and off the valve without leaking any air. I’m cognizant that my complaints might be entirely related to the Presta valves on my tires, but the complaints pop up from time to time on bike forums and Amazon so I’m not the only one with these observations.

“So what!” you say, “who cares about a 4 or 5 PSI difference?” You should. A few pounds in either direction can make the difference between a supple tire and comfy ride, or needless pinch flats because you under-inflated the tire. Whether you choose analog or digital, get a tire pressure gauge and use it.

Advertisements

About robertkerner

Educator, registered nurse, attorney, inquisitive mind
This entry was posted in Uncategorized. Bookmark the permalink.

One Response to Under Pressure

  1. Pingback: VSalon Tire Gauge of Choice?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s