Forum Discussion
CapriRacer
May 09, 2023Explorer II
Here's the reason I don't like the chalk test.
It's quite possible to design a tire to have a footprint that isn't even across the tread face at the proper inflation pressure. Why do that? Rubber costs money and one way to reduce the amount of rubber is to use less in strategic parts of the tread.
Further, a well-designed tire will have a fairly even footprint for a wide range of loads and inflation pressures. How are you supposed to pick out the proper pressure when they all look good?
I prefer the Tire Pressure Build-up Test:
Before starting out on an extended tow (at least an hour!), measure and record both the inflation pressures and the ambient temperature.
It's also a good idea to inspect the tires by rubbing a GLOVED hand over the entire tread surface. You are looking for bulges. If you find any, replace the tire immediately!
After an hour or so into the trip, stop and measure the inflation pressure and note how much pressure has built up.
You don't want more than a 10% buildup - excluding ambient temperature effects:
Ambient temperature effect = 2% per every 10°F change in ambient temperature.
If you get more than 10% pressure buildup (excluding temperature effects), you need more load carrying capacity in your tires - either more inflation pressure or a bigger tire size.
Needless to say, you want to be aware of how heavily you are loading your trailer. More Load = More Pressure build up!
It's quite possible to design a tire to have a footprint that isn't even across the tread face at the proper inflation pressure. Why do that? Rubber costs money and one way to reduce the amount of rubber is to use less in strategic parts of the tread.
Further, a well-designed tire will have a fairly even footprint for a wide range of loads and inflation pressures. How are you supposed to pick out the proper pressure when they all look good?
I prefer the Tire Pressure Build-up Test:
Before starting out on an extended tow (at least an hour!), measure and record both the inflation pressures and the ambient temperature.
It's also a good idea to inspect the tires by rubbing a GLOVED hand over the entire tread surface. You are looking for bulges. If you find any, replace the tire immediately!
After an hour or so into the trip, stop and measure the inflation pressure and note how much pressure has built up.
You don't want more than a 10% buildup - excluding ambient temperature effects:
Ambient temperature effect = 2% per every 10°F change in ambient temperature.
If you get more than 10% pressure buildup (excluding temperature effects), you need more load carrying capacity in your tires - either more inflation pressure or a bigger tire size.
Needless to say, you want to be aware of how heavily you are loading your trailer. More Load = More Pressure build up!
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