First—a test: When you put tires on your bike, the tires have PSI specs molded into the sidewall. However, these numbers will probably differ from what the manufacturer’s specs are. Which set of specifications do you use?
I took my cycle into the shop for service. When I picked it up he looked at his notes and asked me if I preferred a bumpy bouncy ride or if I often had overweight passengers? I had no idea what he was talking about. Answering no to both I then asked “Why?” Because you had 42 pounds in your front tire and 46 pounds in your rear tire. The front tire was seven pounds over manufacturer’s recommendations (the bike manufacturer, NOT the tire maker) and the rear was nine pounds over. I recall another time when I took one of my bikes in and I got chastised for not checking the tire pressure: It was so low that if I’d hit a major chuckhole I might’ve busted the bead on the front tire and had an immediate flat to deal with, horribly dangerous at any speed.
If I asked the members of this club, seated around the table, “What is the manufacturer’s recommended P.S.I. for your front and rear tires?” I suspect most of you, other than the V.P., would not know. Then I’d ask, “How would you find out?” I’d probably be told “It’s on the side of the tire.” True enough, there is a maximum recommended PSI level there. But, how does the tire know what bike it’s going onto? How does it take into effect the weight of passenger and/or gear? It doesn’t and that’s why we don’t use the tire manufacturer’s recommendation. When your bike was designed there was considerable testing to determine what type of tire, tread pattern, size, etc., was best suited for the weight, the distribution of that weight, the design of the frame and engine configuration (and much more) that were considered before they decided what tire to put on the bike as the stock tire. But, erroneously, most of us use the PSI on the treadwall to identify the proper amount of air to put in the tire--completely ignoring the results of all of this testing. Yes, that’s right—the owner’s manual is where you want to find the PSI rating. It gives you the results of all of their testing, all correlated to the bike’s design, weight, etc. So, how does the bike consider what brand/type/style of tire you’re putting on the bike if you don’t go back to the stock tire? It doesn’t because it simply cannot. It’s more important that you have the correct tire pressure based on the manufacturer’s testing and study than any information about tread type, temperature rating, or whether it’s a Michelin Pilot IV or a Pilot II or a Continental or a Shinko. (But, by the way, the arrow on the sidewall showing the rotation direction does matter—it makes a major difference in how the tire behaves and properly works or doesn’t work). And, yes, you have to have the tire remounted. I pointed this out to a friend recently and he was none too happy that the shop actually mounted his tire backwards!
Whether you air up at a gas station or via a compressor at home, there are some realities that are always true: 1) gas station air chuck PSI measurements are generally grossly incorrect and (2) the pencil sized, chromed, pocket air pressure devices aren’t much better. I’ve seen a difference of eight pounds between the stations’s measuring device and my own pencil-type unit. The question is “Which was is right?” A question that shouldn’t have to be answered would be “Does it make a difference?”
I’ll answer the second question first: You bet it matters and the issue is far more than just tread wear (although by keeping my tires properly inflated to the manufacturer’s specifications I pushed a set of Michelin Pilot II’s from an expected life of 8,000 miles to 10,000 miles. I don’t accelerate away from stop signs as if I had my most treasured possession bungee-corded to the backrest and I get on it hard pretty often). Tread wear is secondary to the true critical issue of how the bike handles as a result of the proper ‘relationship’ between the rider, the bike’s frame and everything bolted to it and proper amount of air pressure in the tires.
I chose a digital measuring device over an analog as they tend to be far more accurate over the entire range. Analog gauges tend to be the most accurate at mid-range, so get one that measures 0-60 pounds. Most $19.95 air pressure gauges are worthless if they hit the concrete a single time. The gauge I bought can take some knocking around and has a rubber bumper around the circumference. Digital gauges can generally handle a bit more bumps than an analog, but one should be careful regardless. It also has an air release (bleed valve) button so I can pump the tire up and then bring it down to where it belongs with no resetting required—saves a lot of time. The brand I chose is one used for motorcycle racing where accuracy in measurement is critical to the race and to the safety of the rider. The dial is filled with a fluid to prevent any outside interference with its measurement and cushion if it strikes something.
I carry a cheapo pencil gauge but having checked it against my higher quality unit; I know it’s nearly six pounds off. Using an indelible marker I wrote -6 on the tool to remind me.
MOTION PRO AIR PRESSURE TOOL
High precision accurate to +/- 0.6 psi
Precise digital readout to 0.1 psi; 0-60 PSI measurement
Continuous pressure reading, no need to reset when activating bleed valve
Four selectable scales (PSI, BAR, KG-CM2, kPa)
Large easy to read display with back light for low light applications
Billet aluminum trapezoid body
High flow push button bleeder valve for precise pressure adjustment
18 inch long high pressure hose with dual swivels and brass ball type air chuck
Heavy duty anti-shock protective rubber boot on gauge
Battery powered (1000 tests) with battery strength indicator
Auto off to extend the battery life
One year limited warranty
Now, what kind of idiot would spend $96 on an air pressure tester? At least one—me. You can even buy a holder that Velcro’s the plastic see through bag to the inside of your bag. Actually, clubs only needs one---before a ride, or periodically you could check everyone’s tires.
I hope this collection of 1117 words has at least created some dialogue about each Knight’s habits regarding air pressure check and whether or not you should use the tire indicator or the manufacturer’s specs when airing up.
Now, let’s talk about how often you check your bike’s engine oil level—that one is going to get ugly!
Adam 12, VP (retired), Peacemaker Posse