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INFLATION PRESSURE
TIRE GROWTH
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INFLATION PRESSURE
The first thing that a mechanic is going to do, after mounting a new tire, is to turn the tire and make sure it doesn't rub anything. But this may not be enough of a test because in the first 100 to 200 miles of use, a tire is going to go through a break in period. During this time, all tires will grow or enlarge slightly, anywhere from 3 to 7%. So, if you start out by mounting a tire and notice that it's just barely going to clear the drive shaft or the fender mounts or whatever, keep in mind it's actually going to grow a little during the break in period.
There's also another good reason to take note of this growth. It has to do with air pressure. Every rider should know that during a new tire's 200 mile break in period, the tire will grow by as much as 7%, causing air pressure to decrease by as much as 7%. If you have a fully loaded Gold Wing, and your mechanic is putting 40 pounds of air in its new tires, 200 miles down the road, the air pressure could be as low as 37 pounds. That's going to detract from the tires' mileage and certainly from its load carrying capacity. So in the first 100 to 200 miles, the rider should be checking the tires' cold pressure frequently, with an accurate gauge.
On the sidewall of every tire, it will tell you what the maximum inflation pressure of that tire should be. Now keep in mind, these are cold pressures. We say cold, as in before you've ridden the bike. As the tire starts to heat up, tire pressure will naturally increase. The difference between cold and hot tire pressures should be about 4 to 6 pounds, or approximately 10%. Another factor relating to inflation pressure is load. Obviously, a Kawasaki Voyager with two 300 pound riders is going to require more inflation pressure than the same motorcycle with one 150 pound rider. But the owner's manual doesn't account for that. The owner's manual just makes one general recommendation. You should adjust the pressure of your tires to accommodate for your particular riding style and load. Here's how:
After a 200 mile break in period, load the bike the way it's normally going to be loaded. If you usually ride two up with a lot of camping gear and so on, load the bike that way. Now set the cold inflation pressure at the recommended level and ride it for 45 minutes to an hour. Then measure the pressure hot. If the pressure has increased more that 4 to 6 pounds, the tire is doing too much work. It's flexing too much and overheating. Let it cool down (minimum 3 hours) and then increase the pressure about two pounds and repeat the process until the hot tire pressure increase is into that 4 to 6 pound range.
Whatever the outcome, I would suggest keeping the cold pressure no lower than the owner's manual inflation pressure recommendation, and no higher than the maximum pressure listed on the sidewall. If you get to the maximum pressure on the sidewall and you're still getting more than a 4 to 6 pound increase after heating up the tire, then you've got to remove some weight or slow down. Under no circumstances should you exceed the maximum pressure on the sidewall while cold, because to do so will distort the profile of the tire, and reduce its overall performance. High inflation pressures also increase the risk of damaging the tire if you should hit a pothole or similar such hazard.
I should also mention here that most tire pressure gauges are not accurate. I've seen them off by as much as seven pounds so use an accurate pressure gauge. The digital gauges now available are the most accurate & portable.
RIDE SAFE