I want to determine how old the tires on my car are. I understand there is an age code on each tire. But what if the age code is on the inner side? Is there some code I can use on both sides of the tire?
The age code is only on one sidewall. There is no requirement that it be installed facing out. I have used a mirror to read the code when installed on inside. Tirerack.com has a good article on how to interpret the codes. There is no regulation concerning how many years should be left on a vehicle in the US. Some say 6 yrs max other say 10 years. I have heard that the UK has a 6 year max installed life limit.
You can see this question on how to decode the age of a tire.
Regarding how to read the code if it is on the inside of the wheel, Fred Wilson's answer should be adequate: use a small mirror and flashlight to locate the code and determine the age.
One thing which I have noticed is that some tire manufacturers (especially the less-reputable ones) will not print the manufacturing code on the tire, especially if there is no local legislation mandating them to do so. This is why it is a good idea to insist on seeing the code at the time of purchase.